Diurnal OJIP chlorophyll a fluorescence changes reveal key Photosystem II parameters associated with yield of siliques in rapeseed-mustard under elevated temperatures

Diurnal OJIP chlorophyll a fluorescence changes reveal key Photosystem II parameters associated with yield of siliques in rapeseed-mustard under elevated temperatures | 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 OJIP chlorophyll a fluorescence changes reveal key Photosystem II parameters associated with yield of siliques in rapeseed-mustard under elevated temperatures Krishna M Nair, S. Shanmughapriya, Mahesh Rao, Alexandrina Stirbet, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8876036/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 Our understanding of how winter crops would respond to mean temperature rise and warming events is limited. We selected rapeseed-mustard, a prominent winter crop that will likely experience such conditions in the near future. In a greenhouse experiment, 17 rapeseed-mustard genotypes were grown under a simulated elevated-temperature scenario with diurnal fluctuations. The mean day/night-time air temperatures were ~30/24°C, but increased to ~36.9°C at midday. To study photosynthesis changes, we measured the OJIP chlorophyll (Chl) a fluorescence induction of the dark-adapted top wider leaves, at the flowering stage; this was done during three diurnal timepoints: morning (07:30-08:00 h), afternoon (14:00-14:30 h), and evening (16:30-17:00 h). Transient decline in photosystem-II (PSII) maximum quantum efficiency (inferred from variable to maximum Chl a fluorescence, F V /F M ) and in the performance indices (PI ABS and PI TOT ) was evident in the afternoons, with a higher magnitude of changes in PI ABS and PI TOT . However, the fluorescence data suggested no permanent PSII damage, but a strong increase in photoprotective quenching and restricted electron supply from PSII during the afternoons, which extended till the evenings and took overnight to recover. The IP phase of the OJIP kinetics showed robust correlation with PI TOT but not with F V /F M, and identified genotypes that were less or highly sensitive to diurnal changes. Both F V /F M and PI TOT were positively correlated with the number of branches and the dry silique biomass. Lastly, the afternoon PI TOT displayed better correlation with silique biomass, and it could be used as a trait for identifying potential heat-resilient genotypes with higher yield performance. Plant Physiology and Morphology Agroecology General Cell Biology & Physiology Biophysics Chlorophyll a fluorescence elevated temperature Photosystem-II Rapeseed-mustard Silique Winter crop Full Text Additional Declarations The authors declare no competing interests. Supplementary Files SupplementaryMaterial.docx Supporting Material Cite Share Download PDF Status: Posted Version 1 posted 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. 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\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e fluorescence changes reveal key Photosystem II parameters associated with yield of siliques in rapeseed-mustard under elevated temperatures\u003c/strong\u003e\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[{"identity":"0160d3b2-fccb-4505-bccd-0990094ae5dc","identifier":"10.13039/501100001407","name":"Department of Biotechnology, Ministry of Science and Technology, India","awardNumber":"BT/RLF/Re-entry/08/2021","order_by":0}],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Indian Institute of Science Education and Research, 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We selected rapeseed-mustard, a prominent winter crop that will likely experience such conditions in the near future. In a greenhouse experiment, 17 rapeseed-mustard genotypes were grown under a simulated elevated-temperature scenario with diurnal fluctuations. The mean day/night-time air temperatures were ~30/24°C, but increased to ~36.9°C at midday. To study photosynthesis changes, we measured the OJIP chlorophyll (Chl) \u003cem\u003ea\u003c/em\u003e fluorescence induction of the dark-adapted top wider leaves, at the flowering stage; this was done during three diurnal timepoints: morning (07:30-08:00 h), afternoon (14:00-14:30 h), and evening (16:30-17:00 h). Transient decline in photosystem-II (PSII) maximum quantum efficiency (inferred from variable to maximum Chl \u003cem\u003ea\u003c/em\u003e fluorescence, F\u003csub\u003eV\u003c/sub\u003e/F\u003csub\u003eM\u003c/sub\u003e) and in the performance indices (PI\u003csub\u003eABS\u003c/sub\u003e and PI\u003csub\u003eTOT\u003c/sub\u003e) was evident in the afternoons, with a higher magnitude of changes in PI\u003csub\u003eABS\u003c/sub\u003e and PI\u003csub\u003eTOT\u003c/sub\u003e. However, the fluorescence data suggested no permanent PSII damage, but a strong increase in photoprotective quenching and restricted electron supply from PSII during the afternoons, which extended till the evenings and took overnight to recover. The IP phase of the OJIP kinetics showed robust correlation with PI\u003csub\u003eTOT\u003c/sub\u003e but not with F\u003csub\u003eV\u003c/sub\u003e/F\u003csub\u003eM,\u003c/sub\u003e and identified genotypes that were less or highly sensitive to diurnal changes. Both F\u003csub\u003eV\u003c/sub\u003e/F\u003csub\u003eM \u003c/sub\u003eand PI\u003csub\u003eTOT\u003c/sub\u003e were positively correlated with the number of branches and the dry silique biomass. Lastly, the afternoon PI\u003csub\u003eTOT\u003c/sub\u003e displayed better correlation with silique biomass, and it could be used as a trait for identifying potential heat-resilient genotypes with higher yield performance.\u003c/p\u003e","manuscriptTitle":"Diurnal OJIP chlorophyll a fluorescence changes reveal key Photosystem II parameters associated with yield of siliques in rapeseed-mustard under elevated temperatures","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-17 05:31:42","doi":"10.21203/rs.3.rs-8876036/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":"cca8e2c4-8dd5-4f23-b616-dcd5bf0b3fa9","owner":[],"postedDate":"February 17th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":62913112,"name":"Plant Physiology and Morphology"},{"id":62913113,"name":"Agroecology"},{"id":62913114,"name":"General Cell Biology \u0026 Physiology"},{"id":62913115,"name":"Biophysics"}],"tags":[],"updatedAt":"2026-02-17T05:31:42+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-17 05:31:42","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8876036","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8876036","identity":"rs-8876036","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}