Diurnal variation in nonstructural carbohydrate storage in leaves of trees and shrubs

Diurnal variation in nonstructural carbohydrate storage in leaves of trees and shrubs | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Diurnal variation in nonstructural carbohydrate storage in leaves of trees and shrubs Ning Wang, Xiao Liu, Hongliang Ji, Hong Li, Pan Wu, Shijie Yi, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5213807/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Non-structural carbohydrates (NSC), including soluble sugars (SS) and starch (ST) are an important material basis for maintaining metabolic activity in plants, and are an important energy response to extreme weather. The differences in biological characteristics of different tree species lead to significant inter-species differences in NSC allocation. In this study, we conducted the field experiments in Xinjiang in August 2023. Sixteen common species (eleven trees and five shrubs) were selected for SS and ST concentration measurements in daytime and nighttime. We found that the NSC and SS concentrations of trees were significantly higher than those of shrubs. Through two-way analysis of variance, NSC concentration, ST concentration, and SS:ST were influenced by life form and time treatments. However, the SS concentration was influenced by life form treatment, but not by time treatment. The results showed that minimum sugar concentrations were necessary to sustain basic cellular functions. ST was a temporary storage substance that accumulated in leaves during the day and was degraded at night before being converted into SS output, thereby regulating the diurnal output of carbon assimilated in leaves. common species diurnal variation non-structural carbohydrates shrubs trees Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1 Introduction Carbohydrates are the main products of plant photosynthesis, typically present in the form of structural carbohydrates (mainly lignin and cellulose) and non-structural carbohydrates (NSC, mainly sugars and starch) within the plant body (Hoch et al., 2003 ). NSC have the function of regulating osmotic pressure, and the mutual transformation between soluble sugars (SS) and starch (ST) can regulate the accumulation and distribution of nutrients, enhancing plant stress resistance (He et al., 2020 ; Natale et al., 2023 ). The accumulation of NSC in plants can to some extent reflect the supply-demand balance of carbon in plants, and plays a crucial role in maintaining plant osmotic regulation, hydraulic transport, and growth and development (Hartmann and Trumbore, 2016 ). Therefore, studying the accumulation patterns of plant NSC and the differences in NSC concentrations among different species is beneficial for revealing the differences in plant physiological and ecological characteristics. NSC in leaves are not only an important material basis for maintaining metabolic activities in plants, but also have significant implications for litter decomposition and soil organic matter formation (Lin et al., 2018 ). Leaves are the most important NSC storage pool in plant bodies, with higher NSC content than other organs (Trumbore et al., 2015 ; Martínez-Vilalta et al., 2016 ). After leaf senescence, it is returned to the soil as litter, while NSC in the litter, as an easily decomposable component, is rapidly released in the early stages of decomposition and is the main contributor to the early quality loss of litter decomposition (Wu et al., 2023 ). Meanwhile, these easily decomposable components can be quickly captured by soil microorganisms and provide them with abundant carbon sources, thereby regulating soil microbial metabolic turnover and soil organic matter formation. Therefore, a deeper understanding of the changes in NSC content in forest leaves is of great significance for revealing plant carbon metabolism. There is a lack of relevant research on the diurnal changes of NSC in woody plants, mainly focusing on herbaceous plants such as Arabidopsis (Liang et al., 2019 ). The main trend of the metabolism of primary products of photosynthetic carbon is the synthesis of ST, which is temporarily stored in the leaves during the day in the form of ST, and then degraded and exported at night, thereby regulating the diurnal output of carbon assimilates in the leaves (Samuel et al., 2007 ). However, whether the daily dynamics of NSC in woody plants are consistent with those in herbaceous plants, and the mechanism of NSC storage dynamics in woody plants are urgent issues that need to be addressed. In addition, some studies suggest that the NSC concentration in tree leaves is higher than that in shrub leaves. While some studies have found that the concentration of SS in the leaves of trees is relatively low, like Acer saccharum , which may be due to the conversion of SS into anthocyanins in leaves, leading to a decrease in SS concentration (Zhao et al., 2018 ). Therefore, further exploration is needed to explore the differences in changes in NSC in leaves between trees and shrubs. To study the diurnal variation in NSC storage in trees and shrubs, we set up field experiments in Xinjiang. Sixteen woody plant species were selected, including 11 tree species and 5 shrub species. The common species are widely distributed sympatric woody species in Xinjiang. We hypothesized that there are differences in carbon allocation strategies between trees and shrubs, and they are influenced by circadian rhythms. 2 Materials and Methods 2.1 Study site and Plant materials This study was conducted at the Turpan Eremophytes Botanic Garden, Xinjiang (42.8° N, 89.2° E), with a temperate continental climate. The average conditions for the entire experimental duration were as follows: mean temperature 28.6℃, relative humidity 19.5%. Sixteen woody plant species were selected, including 11 tree species and 5 shrub species (Table 1 ). Table 1 Life form and taxon of the 16 woody plant species. Life form Species Family Genus Tree Fraxinus chinensis (FC) Oleaceae Fraxinus Populus pruinose (PP) Salicaceae Populus Populus euphratica (PE) Salicaceae Populus Populus przewalskii (PR) Salicaceae Populus Ailanthus altissima (AA) Simaroubaceae Ailanthus Ulmus pumila (UP) Ulmaceae Ulmus Morus nigra (MN) Moraceae Morus Elaeagnus angustifolia (EA) Elaeagnaceae Elaeagnus Broussonetia papyrifera (BP) Moraceae Broussonetia Koelreuteria paniculata (KP) Sapindaceae Koelreuteria Gleditsia triacanthos (GT) Fabaceae Gleditsia Shrub Alhagi camelorum (AC) Fabaceae Alhagi Xanthoceras sorbifolium (XS) Sapindaceae Xanthoceras Apocynum venetum (AV) Apocynaceae Apocynum Euonymus alatus (EL) Celastraceae Euonymus Robinia hispida (RH) Fabaceae Robinia 2.2 Experimental design Our field experiments were carried out in August. Firstly, randomly select 5 standard trees from 16 tree species, with each tree divided into upper, middle, and lower layers for leaf collection. Fresh leaves are taken during the day (14:00) and at night (2:00), and samples are taken from the sunny side of the tree, which is free of pests and diseases and fully unfolded. Bring the obtained samples back to the laboratory in a dark ice bag at 4 ℃. 2.3 Non-structural Carbohydrates Analysis SS were extracted twice with 80% ethanol, and ST content was measured after subjecting the solid residue of each sample to a washing step and hydrolysis. The absorbance of the extracts was measured at 620 nm (UV-9000S, Metash, Shanghai, China) after an anthracenone-sulfuric acid reaction. The concentrations of SS and ST (measured as glucose equivalents) were calculated on dry mass basis (mg g − 1 ). Then, the ratio of SS to ST (SS:ST) was SS concentration divided by ST concentration. 2.4 Statistics Data were checked for normality and homogeneity. Two-way analysis of variance (Two-way ANOVA) followed by Duncan’s multiple comparison was applied to test the differences in life form and time on NSC, SS, ST concentrations, and SS: ST. T-test was applied to compare the significant differences between day and night variation. Statistical analyses were performed in SPSS 26 software package (SPSS Inc., Chicago, IL, United States), and figures were drawn in Origin 2019b (Originlab Co., Northampton, MA, United States). 3 Results The time treatment had a significant impact on ST, NSC, and SS:ST, whereas had no significant impact on SS (Table 2 ). The life form treatment had a significant impact on SS, ST, NSC, and SS:ST (Table 2 ). The interaction between life form and time had a significant impact on SS, ST, NSC, and SS:ST (Table 2 ). Table 2 Two-way ANOVA from life form (tree and shrub), time (day and night), and their interactions on plant carbon allocation. SS, soluble sugars; ST, starch; NSC, non-structural carbohydrates; SS:ST, the ratio of SS to ST. Parameters Life form Time Life form × Time SS (mg g − 1 ) 55.767*** 1.636 12.784*** ST (mg g − 1 ) 10.336** 31.287*** 4.896* NSC (mg g − 1 ) 64.095*** 11.771** 5.293* SS:ST 8.856** 8.551** 9.501** Overall, the SS, ST, and NSC concentrations of trees were higher than those of shrubs without time differences (Table 3 ). In tree species, the SS concentration and NSC concentration of night time in AA, EA, FC, GT, and PP were significantly lower than that of day time (Fig. 1 A, Fig. 3 A). The ST concentration of night time in EA, GT and KP were significantly lower than that of day time (Fig. 2 A). As for SS:ST, we found that in EA, FC, GT, and PP of day time were higher than that of daytime (Fig. 4 A). Table 3 Comparison of leaf carbon allocation between tree and shrub plants, in daytime (D) and nighttime (N). SS, soluble sugars; ST, starch; NSC, non-structural carbohydrates; SS:ST, the ratio of SS to ST. Parameters Life form Species number Mean ± SE P DSS Tree 11 121.30 ± 3.88 < 0.01 Shrub 5 70.56 ± 3.26 NSS Tree 11 98.99 ± 4.20 0.05 Shrub 5 54.16 ± 1.82 NST Tree 11 49.18 ± 1.96 < 0.01 Shrub 5 37.82 ± 1.67 DNSC Tree 11 177.56 ± 4.55 < 0.01 Shrub 5 124.72 ± 3.61 NNSC Tree 11 148.18 ± 4.50 < 0.01 Shrub 5 118.93 ± 4.40 DSS:ST Tree 11 2.26 ± 0.10 0.05 Shrub 5 2.25 ± 0.16 In shrub species, the SS concentration of nighttime in XS was significantly higher than that of daytime (Fig. 1 B). The ST concentration of nighttime in AC, AV, EL, and XS was significantly lower than that of day time (Fig. 2 B). The NSC concentration of night time in AV and EL were significantly higher than that of day time (Fig. 3 B). The SS:ST of night time in AC and XS were significantly higher than that of day time (Fig. 4 B). According to principal component analysis, we found the carbon allocation of tree species was not affected by diurnal changes, but the carbon allocation of shrub species was affected by diurnal changes (Fig. 5 ). 4 Discussion 4.1 the effect of life form on carbon allocation Generally speaking, the NSC in plant leaves not only reflect the carbon supply status of plants but also indicate their adaptation strategies to the external environment (Myers et al., 2007; Wiley et al., 2013 ; Liu et al., 2018 ). In our study, we found that the SS and NSC concentrations in the leaves of tree species were higher than those of shrub species (Table 3 , Fig. 1 , Fig. 3 ). The tree layer is the dominant layer in the forest community, receiving the strongest light and experiencing the most intense photosynthesis (Mensah et al., 2018 ). The carbon assimilation capacity of plant leaves is the highest, and NSC and SS are the primary products of photosynthesis and those that can be reused, respectively. Compared to the tree layer, the shrub layer and herbaceous layer are in the sub-dominant layers (Yang et al., 2017 ). Due to the shading by the tree layer, their absorbed solar radiation is lower, leading to a weaker carbon assimilation capacity in plant leaves, which results in lower SS and NSC concentrations. In addition, we found the ST concentration was not affected by life form treatment during the day (Table 3 ). The results showed that the ST concentration was a carbon sink during the day does not cause consumption, which was consistent with previous research (Gregory et al., 2017 ). 4.2 the effect of time on carbon allocation Carbon allocation plays a dominant role in plant metabolism, which involves intricate and coordinated pathways of primary and secondary metabolism (Dusenge et al., 2019 ). Many plants are constantly exposed to sunlight, and even their photosynthetic organs must adapt to transient environmental disturbances, such as the day-night cycle. According to two-way ANOVA, we found that the concentration of SS was not affected by time treatment, whether in trees or shrubs (Table 2 ). This indicated that the concentration of SS was stable for osmotic regulation. SS are highly sensitive to environmental stresses, which impact the supply of carbohydrates from source organs to sink ones (González et al., 2009 ). SS not only serve as metabolic resources and structural constituents of cells, but also act as signals regulating various processes associated with plant growth and development (Smith and Stitt, 2007 ; Sala et al., 2012 ; Wiley et al., 2013 ). We observed that the ST concentration at night was notably lower than during the day across various species, whereas their SS concentrations show minimal variation (Fig. 2 , Fig. 3 ). This suggests that plants engage in carbon dynamic transformations, whereby ST is degraded into SS during the night, contributing to the plant's physiological functions (Miranda et al., 2020 ; Amico et al., 2021 ). Based on PCA quantification, we have arranged the tree and shrub species on the carbon allocation under day and night (Fig. 5 ). We found that the carbon allocation of tree species was not affected by diurnal changes, but the carbon allocation of shrub species was affected by diurnal changes (Fig. 5 ). This may be related to almost all shrubs at night showed a significant decrease in ST concentration to maintain stable or even increased SS concentration compared with daytime (Fig. 2 ). Previous study showed that minimum sugar concentrations were necessary to sustain basic cellular functions (Rosa et al., 2009 ). Therefore, we found the SS:ST at night was higher than during the day of shrub species Alhagi camelorum and Xanthoceras sorbifolium (Fig. 5 ). This is because increasing the proportion of SS enhances the concentration of cytosolic components, thereby enabling resistance to subsequent low-temperature stress at night and facilitating participation in physiological activities. 5 Conclusion Sixteen common species (eleven trees and five shrubs) were selected for Carbon allocation parameters in Xinjiang. Our results indicate that the NSC and SS concentrations of trees were significantly higher than those of shrubs. Then, we found that the concentration of SS was not affected by time treatment. Because the minimum sugar concentrations were necessary to sustain basic cellular functions. The results showed that the ST concentration was a carbon sink during the day. The ST concentration at night was notably lower than during the day across various species. The results showed that plants engage in carbon dynamic transformations, whereby ST is degraded into SS during the night, contributing to the plant's physiological functions. Declarations Conflict of Interest statement The authors declare that we have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Fundings This work was supported by the National Natural Science Foundation of China (32101255), the Natural Science Foundation of Shandong Province (ZR2023QC238, ZR2023QC253), the Postdoctoral Innovation Project of Shandong (SDCX-ZG-202203031), the Natural Science Foundation of Qingdao (23-2-1-42-zyyd-jch), the Fundamental Research Funds of Weifang University (44124002), and the Fundamental Research Funds of Qilu Normal University (107002001365001). Author Contribution NW, XL, and QL proposed the study and designed the experiment. NW, HL, HJ, PW and SY conducted field and laboratory experiments and analyzed the data. NW, XL, and QL secured funding. NW wrote the manuscript, which was intensively edited by all authors. All authors contributed to the article and approved the submitted version. Acknowledgement We would like to thank Professor Yao Huang from School of Ecology and Environment, Hainan University; and Doctor Yixiang Sun from South China Botanical Garden, Chinese Academy of Sciences for assistance in the field and laboratory measurements. Data Availability The authors confirm that the data supporting the findings of this study are available within the supporting information for review and publication. References Amico RA, Orozco J, Guzmán-Delgado P et al. 2021. Spring phenology is affected by fall non-structural carbohydrate concentration and winter. Dusenge ME, Duarte AG, Way DA. Plant carbon metabolism and climate change: elevated CO 2 and temperature impacts on photosynthesis, photorespiration and respiration. New Phytol. 2019;221:32–49. González JA, Gallardo M, Hilal M, et al. Physiological responses of quinoa ( Chenopodium quinoa Willd.) to drought and waterlogging stresses: dry matter partitioning. Bot Stud. 2009;50:35–42. Gregory JM, Sahar M, Mark AAM, et al. Starch as a source, starch as a sink: the bifunctional role of starch in carbon allocation. J Exp Bot. 2017;68:4433–53. Hartmann H, Trumbore S. Understanding the roles of nonstructural carbohydrates in forest trees – from what we can measure to what we want to know. New Phytol. 2016;211:386–403. He W, Liu H, Qi Y, et al. Patterns in nonstructural carbohydrate contents at the tree organ level in response to drought duration. Glob Change Biol. 2020;26:3627–38. Hoch G, Richter A, Körner C. Non-structural carbon compounds in temperate forest trees. Plant Cell Environ. 2003;26:1067–81. Liang X, Gao Z, Zhang L, et al. Seasonal and diurnal patterns of non-structural carbohydrates in source and sink tissues in field maize. BMC Plant Biol. 2019;19:508. Lin T, Zheng H, Huang Z, et al. Non-Structural Carbohydrate Dynamics in Leaves and Branches of Pinus massoniana (Lamb.) Following 3-Year Rainfall Exclusion. Forests. 2018;9(6):315. Liu W, Su J, Li S, et al. Non-structural carbohydrates regulated by season and species in the subtropical monsoon broad-leaved evergreen forest of Yunnan Province, China. Sci Rep. 2018;8:1083. Martínez-Vilalta J, Sala A, Asensio D, et al. Dynamics of non-structural carbohydrates in terrestrial plants: a global synthesis. Ecol Monogr. 2016;86:495–516. Mensah S, du Toit B, Seifert T. Diversity–biomass relationship across forest layers: implications for niche complementarity and selection effects. Oecologia. 2018;187:783–95. Miranda JC, Rodríguez-Calcerrada J, Pita P, et al. Carbohydrate dynamics in a resprouting species after severe aboveground perturbations. Eur J For Res. 2020;139:841–52. Myers JA, Kitajima K. Carbohydrate storage enhances seedling shade and stress tolerance in a neotropical forest. J Ecol. 2007;95:383–95. Natale S, Tomasella M, Gargiulo S, et al. Stem photosynthesis contributes to non-structural carbohydrate pool and modulates xylem vulnerability to embolism in Fraxinus ornus L. Environ Exp Bot. 2023;210:105315. Rosa M, Prado C, Podazza G, et al. Soluble sugars–metabolism, sensing and abiotic stress: a complex network in the life of plants. Plant Signal Behav. 2009;4:388–493. Sala A, Woodruff DR, Meinzer FC. Carbon dynamics in trees: feast or famine? Tree Physiol. 2012;32:764. Samuel CZ, Steven MS, Alison MS. The diurnal metabolism of leaf starch. Biochem J. 2007;401:13–28. Smith AM, Stitt M. Coordination of carbon supply and plant growth. Plant Cell Environ. 2007;30:1126–49. Trumbore S, Czimczik CI, Sierra CA, et al. Non-structural carbon dynamics and allocation relate to growth rate and leaf habit in California oaks. Tree Physiol. 2015;35:1206–22. Wiley E, Huepenbecker S, Casper BB, et al. The effects of defoliation on carbon allocation: can carbon limitation reduce growth in favour of storage? Tree Physiol. 2013;33:1216. Wu X, Cao Y, Jiang Y, et al. Dynamics of non-structural carbohydrates release in Chinese fir topsoil and canopy litter at different altitudes. Plants. 2023;12:729. Yang B, Li Y, Ding B, et al. Impact of tree diversity and environmental conditions on the survival of shrub species in a forest biodiversity experiment in subtropical China. J Plant Ecol. 2017;10:179–89. Zhao D, Gao Y, Liu J, et al. Changes of pigment and soluble sugar conents in autumn leaves of two ormanrntal maples. Agriclutural Sci J Yanbian Univ. 2018;40:32–7. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5213807","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":365871917,"identity":"41abcf44-3f52-499a-a199-0d3cdcd7a543","order_by":0,"name":"Ning Wang","email":"","orcid":"","institution":"Weifang University","correspondingAuthor":false,"prefix":"","firstName":"Ning","middleName":"","lastName":"Wang","suffix":""},{"id":365871918,"identity":"38578249-a5c8-43e3-8377-59e8541ade80","order_by":1,"name":"Xiao Liu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3UlEQVRIie2QMQrCQBBFNwxMmlHbhATPEEkZ0LNIChtBS0FBRUgaD6B4j1xgQRsPoJ1xwd4LiONaKbJJabGvmd1hHzN/hbBY/hA3dxZcIBTu8vJqULNKIflWiE+RbmC1ogsrXqoVUa0AZGo8SSg6K0c1ht0QBZTXk1Fx8nhzHJC/S6GzLVJeDON4aFB64GRBI5PUCkZ7714AK4SBSSGtPCShL9HrF/O6yoKneIA8RdZSOMues6x1lgMhVGQhN7+p8SxpRwfJP1ZMey13VSqTwiB83uH3M5NisVgsli+ekig47JFDD3AAAAAASUVORK5CYII=","orcid":"","institution":"Qilu Normal University","correspondingAuthor":true,"prefix":"","firstName":"Xiao","middleName":"","lastName":"Liu","suffix":""},{"id":365871919,"identity":"f512ae91-8152-4e05-86da-3cc1cbc040aa","order_by":2,"name":"Hongliang Ji","email":"","orcid":"","institution":"Weifang University","correspondingAuthor":false,"prefix":"","firstName":"Hongliang","middleName":"","lastName":"Ji","suffix":""},{"id":365871920,"identity":"3f4633f1-0ab1-48b6-b1e3-0ebb4223f265","order_by":3,"name":"Hong Li","email":"","orcid":"","institution":"Weifang University","correspondingAuthor":false,"prefix":"","firstName":"Hong","middleName":"","lastName":"Li","suffix":""},{"id":365871921,"identity":"d92e8b37-222e-4d04-a2fc-6641cdaa76fa","order_by":4,"name":"Pan Wu","email":"","orcid":"","institution":"Shandong University","correspondingAuthor":false,"prefix":"","firstName":"Pan","middleName":"","lastName":"Wu","suffix":""},{"id":365871922,"identity":"c5d4881b-f4da-4712-bfeb-1a0f8de68e97","order_by":5,"name":"Shijie Yi","email":"","orcid":"","institution":"Ministry of Natural Resources","correspondingAuthor":false,"prefix":"","firstName":"Shijie","middleName":"","lastName":"Yi","suffix":""},{"id":365871923,"identity":"2efd03fc-cf38-4dd1-9e90-fa450bce1910","order_by":6,"name":"Qiang Li","email":"","orcid":"","institution":"Hainan Medical University","correspondingAuthor":false,"prefix":"","firstName":"Qiang","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2024-10-06 16:23:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5213807/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5213807/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":68253400,"identity":"67a0c7c8-25ff-4136-8607-334631b631aa","added_by":"auto","created_at":"2024-11-05 10:28:36","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":53788,"visible":true,"origin":"","legend":"\u003cp\u003eSoluble sugars concentration of leaves (SS) of tree species (A) and shrub species (B) under different time treatments. The asterisk represents the significant difference (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05) between the day group and the night group.\u003cem\u003e n\u003c/em\u003e = 5.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5213807/v1/fb3da110cfaf10e17b3c4bd7.png"},{"id":68253691,"identity":"7f8f59b7-34da-482c-b14a-c7070fc6f649","added_by":"auto","created_at":"2024-11-05 10:36:36","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":52689,"visible":true,"origin":"","legend":"\u003cp\u003eStarch concentration of leaves (ST) of tree species (A) and shrub species (B) under different time treatments. The asterisk represents the significant difference (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05) between the day group and the night group.\u003cem\u003e n\u003c/em\u003e= 5.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5213807/v1/a2825677f989dac6b404d3d9.png"},{"id":68253403,"identity":"18e54d3a-e1b2-4780-93b6-d777a08325d9","added_by":"auto","created_at":"2024-11-05 10:28:36","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":54188,"visible":true,"origin":"","legend":"\u003cp\u003eNon-structural carbohydrates concentration of leaves (NSC) of tree species (A) and shrub species (B) under different time treatments. The asterisk represents the significant difference (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05) between the day group and the night group.\u003cem\u003e n\u003c/em\u003e = 5.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5213807/v1/acd79de0a3f83b538cbc310f.png"},{"id":68253401,"identity":"d67ecef6-bb81-4f5b-8632-75484c2ce8da","added_by":"auto","created_at":"2024-11-05 10:28:36","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":48180,"visible":true,"origin":"","legend":"\u003cp\u003eSoluble sugar: starch of leaves (SS:ST) of tree species (A) and shrub species (B) under different time treatments. The asterisk represents the significant difference (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05) between the day group and the night group.\u003cem\u003e n\u003c/em\u003e = 5.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5213807/v1/5848f4961a92d2a536f193c1.png"},{"id":68253405,"identity":"9504ecae-4972-4534-bd0a-cd1d4da52d9b","added_by":"auto","created_at":"2024-11-05 10:28:36","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":86612,"visible":true,"origin":"","legend":"\u003cp\u003eThe principal component analysis diagram of carbon allocation for tree and shrub species. In daytime (D) and nighttime (N). SS, soluble sugars; ST, starch; NSC, non-structural carbohydrates; SS:ST, the ratio of SS to ST.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5213807/v1/190e0f9865fa686960010345.png"},{"id":72312095,"identity":"856ddc3c-8f10-4efa-b97b-21c1253b74c3","added_by":"auto","created_at":"2024-12-25 06:46:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":715048,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5213807/v1/028c4c8b-a28f-46af-979c-7f54ce842284.pdf"},{"id":68253404,"identity":"4d519be9-cba2-4825-8493-598f31294588","added_by":"auto","created_at":"2024-11-05 10:28:36","extension":"xlsx","order_by":7,"title":"","display":"","copyAsset":false,"role":"supplement","size":20950,"visible":true,"origin":"","legend":"","description":"","filename":"data.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-5213807/v1/20ba13dd9bca881cb86e124b.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Diurnal variation in nonstructural carbohydrate storage in leaves of trees and shrubs","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eCarbohydrates are the main products of plant photosynthesis, typically present in the form of structural carbohydrates (mainly lignin and cellulose) and non-structural carbohydrates (NSC, mainly sugars and starch) within the plant body (Hoch et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). NSC have the function of regulating osmotic pressure, and the mutual transformation between soluble sugars (SS) and starch (ST) can regulate the accumulation and distribution of nutrients, enhancing plant stress resistance (He et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Natale et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The accumulation of NSC in plants can to some extent reflect the supply-demand balance of carbon in plants, and plays a crucial role in maintaining plant osmotic regulation, hydraulic transport, and growth and development (Hartmann and Trumbore, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Therefore, studying the accumulation patterns of plant NSC and the differences in NSC concentrations among different species is beneficial for revealing the differences in plant physiological and ecological characteristics.\u003c/p\u003e \u003cp\u003eNSC in leaves are not only an important material basis for maintaining metabolic activities in plants, but also have significant implications for litter decomposition and soil organic matter formation (Lin et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Leaves are the most important NSC storage pool in plant bodies, with higher NSC content than other organs (Trumbore et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Mart\u0026iacute;nez-Vilalta et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). After leaf senescence, it is returned to the soil as litter, while NSC in the litter, as an easily decomposable component, is rapidly released in the early stages of decomposition and is the main contributor to the early quality loss of litter decomposition (Wu et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Meanwhile, these easily decomposable components can be quickly captured by soil microorganisms and provide them with abundant carbon sources, thereby regulating soil microbial metabolic turnover and soil organic matter formation. Therefore, a deeper understanding of the changes in NSC content in forest leaves is of great significance for revealing plant carbon metabolism.\u003c/p\u003e \u003cp\u003eThere is a lack of relevant research on the diurnal changes of NSC in woody plants, mainly focusing on herbaceous plants such as Arabidopsis (Liang et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The main trend of the metabolism of primary products of photosynthetic carbon is the synthesis of ST, which is temporarily stored in the leaves during the day in the form of ST, and then degraded and exported at night, thereby regulating the diurnal output of carbon assimilates in the leaves (Samuel et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). However, whether the daily dynamics of NSC in woody plants are consistent with those in herbaceous plants, and the mechanism of NSC storage dynamics in woody plants are urgent issues that need to be addressed. In addition, some studies suggest that the NSC concentration in tree leaves is higher than that in shrub leaves. While some studies have found that the concentration of SS in the leaves of trees is relatively low, like \u003cem\u003eAcer saccharum\u003c/em\u003e, which may be due to the conversion of SS into anthocyanins in leaves, leading to a decrease in SS concentration (Zhao et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Therefore, further exploration is needed to explore the differences in changes in NSC in leaves between trees and shrubs.\u003c/p\u003e \u003cp\u003eTo study the diurnal variation in NSC storage in trees and shrubs, we set up field experiments in Xinjiang. Sixteen woody plant species were selected, including 11 tree species and 5 shrub species. The common species are widely distributed sympatric woody species in Xinjiang. We hypothesized that there are differences in carbon allocation strategies between trees and shrubs, and they are influenced by circadian rhythms.\u003c/p\u003e"},{"header":"2 Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Study site and Plant materials\u003c/h2\u003e \u003cp\u003eThis study was conducted at the Turpan Eremophytes Botanic Garden, Xinjiang (42.8\u0026deg; N, 89.2\u0026deg; E), with a temperate continental climate. The average conditions for the entire experimental duration were as follows: mean temperature 28.6℃, relative humidity 19.5%. Sixteen woody plant species were selected, including 11 tree species and 5 shrub species (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLife form and taxon of the 16 woody plant species.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLife form\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecies\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFamily\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGenus\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"10\" rowspan=\"11\"\u003e \u003cp\u003eTree\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eFraxinus chinensis\u003c/em\u003e (FC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eOleaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eFraxinus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003ePopulus pruinose\u003c/em\u003e (PP)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSalicaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ePopulus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003ePopulus euphratica\u003c/em\u003e (PE)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSalicaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ePopulus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003ePopulus przewalskii\u003c/em\u003e (PR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSalicaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ePopulus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eAilanthus altissima\u003c/em\u003e (AA)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSimaroubaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eAilanthus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eUlmus pumila\u003c/em\u003e (UP)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eUlmaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eUlmus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eMorus nigra\u003c/em\u003e (MN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMoraceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eMorus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eElaeagnus angustifolia\u003c/em\u003e (EA)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eElaeagnaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eElaeagnus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eBroussonetia papyrifera\u003c/em\u003e (BP)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMoraceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eBroussonetia\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eKoelreuteria paniculata\u003c/em\u003e (KP)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSapindaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eKoelreuteria\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eGleditsia triacanthos\u003c/em\u003e (GT)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFabaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eGleditsia\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003eShrub\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eAlhagi camelorum\u003c/em\u003e (AC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFabaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eAlhagi\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eXanthoceras sorbifolium\u003c/em\u003e (XS)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSapindaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eXanthoceras\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eApocynum venetum\u003c/em\u003e (AV)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eApocynaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eApocynum\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eEuonymus alatus\u003c/em\u003e (EL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCelastraceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eEuonymus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eRobinia hispida\u003c/em\u003e (RH)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFabaceae\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eRobinia\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Experimental design\u003c/h2\u003e \u003cp\u003eOur field experiments were carried out in August. Firstly, randomly select 5 standard trees from 16 tree species, with each tree divided into upper, middle, and lower layers for leaf collection. Fresh leaves are taken during the day (14:00) and at night (2:00), and samples are taken from the sunny side of the tree, which is free of pests and diseases and fully unfolded. Bring the obtained samples back to the laboratory in a dark ice bag at 4 ℃.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Non-structural Carbohydrates Analysis\u003c/h2\u003e \u003cp\u003eSS were extracted twice with 80% ethanol, and ST content was measured after subjecting the solid residue of each sample to a washing step and hydrolysis. The absorbance of the extracts was measured at 620 nm (UV-9000S, Metash, Shanghai, China) after an anthracenone-sulfuric acid reaction. The concentrations of SS and ST (measured as glucose equivalents) were calculated on dry mass basis (mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). Then, the ratio of SS to ST (SS:ST) was SS concentration divided by ST concentration.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Statistics\u003c/h2\u003e \u003cp\u003eData were checked for normality and homogeneity. Two-way analysis of variance (Two-way ANOVA) followed by Duncan\u0026rsquo;s multiple comparison was applied to test the differences in life form and time on NSC, SS, ST concentrations, and SS: ST. T-test was applied to compare the significant differences between day and night variation. Statistical analyses were performed in SPSS 26 software package (SPSS Inc., Chicago, IL, United States), and figures were drawn in Origin 2019b (Originlab Co., Northampton, MA, United States).\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results","content":"\u003cp\u003eThe time treatment had a significant impact on ST, NSC, and SS:ST, whereas had no significant impact on SS (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The life form treatment had a significant impact on SS, ST, NSC, and SS:ST (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The interaction between life form and time had a significant impact on SS, ST, NSC, and SS:ST (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTwo-way ANOVA from life form (tree and shrub), time (day and night), and their interactions on plant carbon allocation. SS, soluble sugars; ST, starch; NSC, non-structural carbohydrates; SS:ST, the ratio of SS to ST.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLife form\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTime\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLife form \u0026times; Time\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSS (mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e55.767***\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.636\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e12.784***\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eST (mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e10.336**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e31.287***\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e4.896*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNSC (mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e64.095***\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e11.771**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e5.293*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSS:ST\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e8.856**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e8.551**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e9.501**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eOverall, the SS, ST, and NSC concentrations of trees were higher than those of shrubs without time differences (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In tree species, the SS concentration and NSC concentration of night time in AA, EA, FC, GT, and PP were significantly lower than that of day time (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). The ST concentration of night time in EA, GT and KP were significantly lower than that of day time (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). As for SS:ST, we found that in EA, FC, GT, and PP of day time were higher than that of daytime (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of leaf carbon allocation between tree and shrub plants, in daytime (D) and nighttime (N). SS, soluble sugars; ST, starch; NSC, non-structural carbohydrates; SS:ST, the ratio of SS to ST.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLife form\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSpecies number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDSS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTree\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e121.30\u0026thinsp;\u0026plusmn;\u0026thinsp;3.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShrub\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e70.56\u0026thinsp;\u0026plusmn;\u0026thinsp;3.26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNSS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTree\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e98.99\u0026thinsp;\u0026plusmn;\u0026thinsp;4.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShrub\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e81.11\u0026thinsp;\u0026plusmn;\u0026thinsp;4.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDST\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTree\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e56.26\u0026thinsp;\u0026plusmn;\u0026thinsp;1.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShrub\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e54.16\u0026thinsp;\u0026plusmn;\u0026thinsp;1.82\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNST\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTree\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e49.18\u0026thinsp;\u0026plusmn;\u0026thinsp;1.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShrub\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e37.82\u0026thinsp;\u0026plusmn;\u0026thinsp;1.67\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDNSC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTree\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e177.56\u0026thinsp;\u0026plusmn;\u0026thinsp;4.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShrub\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e124.72\u0026thinsp;\u0026plusmn;\u0026thinsp;3.61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNNSC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTree\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e148.18\u0026thinsp;\u0026plusmn;\u0026thinsp;4.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShrub\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e118.93\u0026thinsp;\u0026plusmn;\u0026thinsp;4.40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDSS:ST\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTree\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e2.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShrub\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e1.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNSS:ST\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTree\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e2.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShrub\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e2.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn shrub species, the SS concentration of nighttime in XS was significantly higher than that of daytime (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). The ST concentration of nighttime in AC, AV, EL, and XS was significantly lower than that of day time (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). The NSC concentration of night time in AV and EL were significantly higher than that of day time (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB). The SS:ST of night time in AC and XS were significantly higher than that of day time (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003eAccording to principal component analysis, we found the carbon allocation of tree species was not affected by diurnal changes, but the carbon allocation of shrub species was affected by diurnal changes (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4 Discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e4.1 the effect of life form on carbon allocation\u003c/h2\u003e \u003cp\u003eGenerally speaking, the NSC in plant leaves not only reflect the carbon supply status of plants but also indicate their adaptation strategies to the external environment (Myers et al., 2007; Wiley et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Liu et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In our study, we found that the SS and NSC concentrations in the leaves of tree species were higher than those of shrub species (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The tree layer is the dominant layer in the forest community, receiving the strongest light and experiencing the most intense photosynthesis (Mensah et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The carbon assimilation capacity of plant leaves is the highest, and NSC and SS are the primary products of photosynthesis and those that can be reused, respectively. Compared to the tree layer, the shrub layer and herbaceous layer are in the sub-dominant layers (Yang et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Due to the shading by the tree layer, their absorbed solar radiation is lower, leading to a weaker carbon assimilation capacity in plant leaves, which results in lower SS and NSC concentrations. In addition, we found the ST concentration was not affected by life form treatment during the day (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The results showed that the ST concentration was a carbon sink during the day does not cause consumption, which was consistent with previous research (Gregory et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e4.2 the effect of time on carbon allocation\u003c/h2\u003e \u003cp\u003eCarbon allocation plays a dominant role in plant metabolism, which involves intricate and coordinated pathways of primary and secondary metabolism (Dusenge et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Many plants are constantly exposed to sunlight, and even their photosynthetic organs must adapt to transient environmental disturbances, such as the day-night cycle. According to two-way ANOVA, we found that the concentration of SS was not affected by time treatment, whether in trees or shrubs (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This indicated that the concentration of SS was stable for osmotic regulation. SS are highly sensitive to environmental stresses, which impact the supply of carbohydrates from source organs to sink ones (Gonz\u0026aacute;lez et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). SS not only serve as metabolic resources and structural constituents of cells, but also act as signals regulating various processes associated with plant growth and development (Smith and Stitt, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Sala et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Wiley et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). We observed that the ST concentration at night was notably lower than during the day across various species, whereas their SS concentrations show minimal variation (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). This suggests that plants engage in carbon dynamic transformations, whereby ST is degraded into SS during the night, contributing to the plant's physiological functions (Miranda et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Amico et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Based on PCA quantification, we have arranged the tree and shrub species on the carbon allocation under day and night (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). We found that the carbon allocation of tree species was not affected by diurnal changes, but the carbon allocation of shrub species was affected by diurnal changes (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). This may be related to almost all shrubs at night showed a significant decrease in ST concentration to maintain stable or even increased SS concentration compared with daytime (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Previous study showed that minimum sugar concentrations were necessary to sustain basic cellular functions (Rosa et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Therefore, we found the SS:ST at night was higher than during the day of shrub species \u003cem\u003eAlhagi camelorum\u003c/em\u003e and \u003cem\u003eXanthoceras sorbifolium\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). This is because increasing the proportion of SS enhances the concentration of cytosolic components, thereby enabling resistance to subsequent low-temperature stress at night and facilitating participation in physiological activities.\u003c/p\u003e \u003c/div\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eSixteen common species (eleven trees and five shrubs) were selected for Carbon allocation parameters in Xinjiang. Our results indicate that the NSC and SS concentrations of trees were significantly higher than those of shrubs. Then, we found that the concentration of SS was not affected by time treatment. Because the minimum sugar concentrations were necessary to sustain basic cellular functions. The results showed that the ST concentration was a carbon sink during the day. The ST concentration at night was notably lower than during the day across various species. The results showed that plants engage in carbon dynamic transformations, whereby ST is degraded into SS during the night, contributing to the plant's physiological functions.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eConflict of Interest statement\u003c/h2\u003e \u003cp\u003eThe authors declare that we have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e \u003ch2\u003eFundings\u003c/h2\u003e \u003cp\u003eThis work was supported by the National Natural Science Foundation of China (32101255), the Natural Science Foundation of Shandong Province (ZR2023QC238, ZR2023QC253), the Postdoctoral Innovation Project of Shandong (SDCX-ZG-202203031), the Natural Science Foundation of Qingdao (23-2-1-42-zyyd-jch), the Fundamental Research Funds of Weifang University (44124002), and the Fundamental Research Funds of Qilu Normal University (107002001365001).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eNW, XL, and QL proposed the study and designed the experiment. NW, HL, HJ, PW and SY conducted field and laboratory experiments and analyzed the data. NW, XL, and QL secured funding. NW wrote the manuscript, which was intensively edited by all authors. All authors contributed to the article and approved the submitted version.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe would like to thank Professor Yao Huang from School of Ecology and Environment, Hainan University; and Doctor Yixiang Sun from South China Botanical Garden, Chinese Academy of Sciences for assistance in the field and laboratory measurements.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe authors confirm that the data supporting the findings of this study are available within the supporting information for review and publication.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAmico RA, Orozco J, Guzm\u0026aacute;n-Delgado P et al. 2021. 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Non-structural carbon dynamics and allocation relate to growth rate and leaf habit in California oaks. Tree Physiol. 2015;35:1206\u0026ndash;22.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWiley E, Huepenbecker S, Casper BB, et al. The effects of defoliation on carbon allocation: can carbon limitation reduce growth in favour of storage? Tree Physiol. 2013;33:1216.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu X, Cao Y, Jiang Y, et al. Dynamics of non-structural carbohydrates release in Chinese fir topsoil and canopy litter at different altitudes. Plants. 2023;12:729.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang B, Li Y, Ding B, et al. Impact of tree diversity and environmental conditions on the survival of shrub species in a forest biodiversity experiment in subtropical China. J Plant Ecol. 2017;10:179\u0026ndash;89.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhao D, Gao Y, Liu J, et al. Changes of pigment and soluble sugar conents in autumn leaves of two ormanrntal maples. Agriclutural Sci J Yanbian Univ. 2018;40:32\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"common species, diurnal variation, non-structural carbohydrates, shrubs, trees","lastPublishedDoi":"10.21203/rs.3.rs-5213807/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5213807/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eNon-structural carbohydrates (NSC), including soluble sugars (SS) and starch (ST) are an important material basis for maintaining metabolic activity in plants, and are an important energy response to extreme weather. The differences in biological characteristics of different tree species lead to significant inter-species differences in NSC allocation. In this study, we conducted the field experiments in Xinjiang in August 2023. Sixteen common species (eleven trees and five shrubs) were selected for SS and ST concentration measurements in daytime and nighttime. We found that the NSC and SS concentrations of trees were significantly higher than those of shrubs. Through two-way analysis of variance, NSC concentration, ST concentration, and SS:ST were influenced by life form and time treatments. However, the SS concentration was influenced by life form treatment, but not by time treatment. The results showed that minimum sugar concentrations were necessary to sustain basic cellular functions. ST was a temporary storage substance that accumulated in leaves during the day and was degraded at night before being converted into SS output, thereby regulating the diurnal output of carbon assimilated in leaves.\u003c/p\u003e","manuscriptTitle":"Diurnal variation in nonstructural carbohydrate storage in leaves of trees and shrubs","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-11-05 10:28:31","doi":"10.21203/rs.3.rs-5213807/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c10eccf9-0199-484e-9274-3e0f716c6a0e","owner":[],"postedDate":"November 5th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-12-25T06:38:37+00:00","versionOfRecord":[],"versionCreatedAt":"2024-11-05 10:28:31","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5213807","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5213807","identity":"rs-5213807","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}