Coordinated Diffusional and Biochemical Limitations Underlie Age-Related Decline in Photosynthetic Capacity of Rice Leaves

Coordinated Diffusional and Biochemical Limitations Underlie Age-Related Decline in Photosynthetic Capacity of Rice Leaves | 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 Coordinated Diffusional and Biochemical Limitations Underlie Age-Related Decline in Photosynthetic Capacity of Rice Leaves Haifeng Xiong, Fengshuo Ma, Mengdi Mu, Jingwen Wang, Yunmin Wei This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6897596/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 23 Jul, 2025 Read the published version in Photosynthesis Research → Version 1 posted 7 You are reading this latest preprint version Abstract The net photosynthetic rate ( A ) decreases with leaf aging and senescence, primarily due to reductions in stomatal conductance (g s ), mesophyll conductance (g m ), and the maximum carboxylation rate ( V cmax ). However, the relative contributions of these factors to age-related declines in photosynthesis remain insufficiently understood. In this study, we investigated gas exchange parameters, chlorophyll fluorescence, and biochemical traits in mature and senescing rice leaves. The net photosynthetic rate ( A ) decreased with leaf age, from 22.2 µmol m⁻² s⁻¹ in mature leaves to 15.9 µmol m⁻² s⁻¹ in older leaves. The absolute limitations imposed by g s (LS), g m (LM), and V cmax (LB) were 8.54%, 9.33%, and 11.2%, respectively. The observed reduction in V cmax in senescing leaves was primarily attributed to a decline in Rubisco content, while the in vivo specific activity of Rubisco ( V cmax /Rubisco) remained comparable between mature and older leaves. Similarly, the apparent decrease in Rubisco activity was driven by reduced Rubisco content rather than limited CO 2 availability, as the ratio of chloroplast CO 2 concentration to Rubisco content (C c /Rubisco) was even higher in older leaves, indicating that substrate supply was not a limiting factor for catalysis. Taken together, stomatal conductance, mesophyll conductance, and V cmax imposed comparable limitations on photosynthesis during leaf aging, with the decline in V cmax and Rubisco activity largely attributed to a reduction in Rubisco content. leaf aging maximum carboxylation rate mesophyll conductance Rubisco stomatal conductance Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 23 Jul, 2025 Read the published version in Photosynthesis Research → Version 1 posted Editorial decision: Revision requested 03 Jul, 2025 Reviews received at journal 02 Jul, 2025 Reviewers agreed at journal 23 Jun, 2025 Reviewers invited by journal 23 Jun, 2025 Editor assigned by journal 20 Jun, 2025 Submission checks completed at journal 17 Jun, 2025 First submitted to journal 15 Jun, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-6897596","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":475432284,"identity":"21ac478b-d9d5-400b-b57c-3954dd91d6dc","order_by":0,"name":"Haifeng Xiong","email":"","orcid":"","institution":"Zhoukou Normal University","correspondingAuthor":false,"prefix":"","firstName":"Haifeng","middleName":"","lastName":"Xiong","suffix":""},{"id":475432285,"identity":"dcab6ae4-b768-44ec-a381-d2c870b77909","order_by":1,"name":"Fengshuo Ma","email":"","orcid":"","institution":"Zhoukou Normal 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However, the relative contributions of these factors to age-related declines in photosynthesis remain insufficiently understood. In this study, we investigated gas exchange parameters, chlorophyll fluorescence, and biochemical traits in mature and senescing rice leaves. The net photosynthetic rate (\u003cem\u003eA\u003c/em\u003e) decreased with leaf age, from 22.2 \u0026micro;mol m⁻\u0026sup2; s⁻\u0026sup1; in mature leaves to 15.9 \u0026micro;mol m⁻\u0026sup2; s⁻\u0026sup1; in older leaves. The absolute limitations imposed by g\u003csub\u003es\u003c/sub\u003e (LS), g\u003csub\u003em\u003c/sub\u003e (LM), and \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003ecmax\u003c/em\u003e\u003c/sub\u003e (LB) were 8.54%, 9.33%, and 11.2%, respectively. The observed reduction in \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003ecmax\u003c/em\u003e\u003c/sub\u003e in senescing leaves was primarily attributed to a decline in Rubisco content, while the in vivo specific activity of Rubisco (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003ecmax\u003c/em\u003e\u003c/sub\u003e/Rubisco) remained comparable between mature and older leaves. Similarly, the apparent decrease in Rubisco activity was driven by reduced Rubisco content rather than limited CO\u003csub\u003e2\u003c/sub\u003e availability, as the ratio of chloroplast CO\u003csub\u003e2\u003c/sub\u003e concentration to Rubisco content (C\u003csub\u003ec\u003c/sub\u003e/Rubisco) was even higher in older leaves, indicating that substrate supply was not a limiting factor for catalysis. 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