{"id":16777,"date":"2026-08-20T02:42:48","date_gmt":"2026-08-20T00:42:48","guid":{"rendered":"https:\/\/dodo.proefschriftmaken.nl\/portfolio\/keshav-jayasankar\/"},"modified":"2026-08-20T02:42:58","modified_gmt":"2026-08-20T00:42:58","slug":"keshav-jayasankar","status":"publish","type":"us_portfolio","link":"https:\/\/dodo.proefschriftmaken.nl\/en\/portfolio\/keshav-jayasankar\/","title":{"rendered":"Keshav Jayasankar"},"content":{"rendered":"","protected":true},"excerpt":{"rendered":"","protected":true},"author":8,"featured_media":16778,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"us_portfolio_category":[45],"class_list":["post-16777","us_portfolio","type-us_portfolio","status-publish","post-password-required","hentry","us_portfolio_category-new-template"],"acf":{"main_text":"","naam_van_het_proefschift":"In a World of fluctuating light","samenvatting":"Een groeiende wereldbevolking leidt tot een toenemende vraag naar plantaardige producten. De huidige trends in gewasopbrengst schieten echter tekort om aan de voorspelde vraag te voldoen. Daarom is een aanzienlijke verhoging van de opbrengst essentieel. Fotosynthese is aangemerkt als een belangrijk doelwit om de kloof tussen de voorspelde opbrengst en de vraag te dichten. Hoewel onderzoek heeft aangetoond dat een verbetering van de fotosynthese kan leiden tot hogere opbrengsten, is veel kennis gebaseerd op constante omgevingsomstandigheden. Gezien de gevoeligheid van fotosynthese voor veranderingen in de omgeving, moeten inspanningen om de fotosynthese te verbeteren ook dynamische omstandigheden meenemen. Van alle omgevingsfactoren varieert licht het meest. Dit proefschrift onderzoekt hoe fotosynthese reageert op en zich aanpast aan fluctuerend licht om strategie\u00ebn voor verbetering te onderbouwen. Omdat planten genetisch divers zijn, onderzoekt dit werk de fenotypische variatie in fotosynthetische reacties op fluctuerend licht om nuttige strategie\u00ebn en aanpassingen te identificeren.\n\nHoofdstuk 2 onderzocht de variatie tussen tomatensoorten om de fotosynthese te verbeteren. Er werd gekeken naar de correlatie tussen de maximale fotosynthetische capaciteit (Amax) en het vermogen om te reageren op lichttoenames. Er werd vastgesteld dat Amax en de reactiesnelheid onafhankelijk van elkaar zijn, wat betekent dat ze als afzonderlijke eigenschappen moeten worden beschouwd. Desalniettemin bleek een hogere Amax gunstig voor de algehele koolstofvastlegging.\n\nHoofdstuk 3 onderzocht de invloed van koude (chilling) in combinatie met fluctuerend licht. Er werd variatie gevonden in de kinetiek van de fotosynthetische effici\u00ebntie onder suboptimale temperaturen bij de ouderlijnen van een MAGIC-populatie van tomaat. Sommige lijnen vertoonden veerkracht tegen kou, wat kansen biedt voor het kweken van klimaatbestendige gewassen.\n\nHoofdstuk 4 richtte zich op de langetermijneffecten van fluctuerend licht op zes genotypen van vijf verschillende tomatensoorten. Hoewel de effecten op de lichtreacties minimaal waren, werden er genotype-specifieke variaties waargenomen. Een belangrijke bevinding was dat fotosynthetische eigenschappen op basis van bladmassaaanzienlijke variatie vertoonden onder fluctuerend licht, wat pleit voor een herbeoordeling van hoe deze eigenschappen worden ge\u00ebvalueerd. Daarnaast verbeterde de intrinsieke watereffici\u00ebntie (iWUE) bij de meeste genotypen onder fluctuerend licht.\n\nTenslotte brengt Hoofdstuk 5 de inzichten uit de voorgaande hoofdstukken samen en bespreekt de implicaties voor het verbeteren van fotosynthese, inclusief aanbevelingen voor screeningsprotocollen om deze variaties effectief in kaart te brengen.","summary":"An increasing population results in an increase in demand for crop-based products. However, current crop yield trends have been shown to fall short of meeting the predicted demand. Therefore, a substantial increase in crop yield becomes essential. Photosynthesis has been suggested to be a key target by which the gap between predicted crop yield and predicted demand can be closed. In the preceding decade, multiple studies have reported how an increase in photosynthesis has resulted in an increase in crop yield. However, much of what has been understood of photosynthesis is based on photosynthetic responses under constant environmental conditions. Considering the inherent sensitivity of photosynthesis to change in environmental conditions and constantly changing environmental conditions experienced by crops in the field, efforts to improve photosynthesis must incorporate dynamic environments. Of the various environmental conditions that affect photosynthesis, light drives photosynthesis and varies the most. Light, specifically intensity, constantly fluctuating in nature, from the seconds to the hours or days scale. These diverse ranges in fluctuations can give rise to responses and acclimations, understanding of which, will be cruise to improve photosynthesis. Therefore, this thesis investigates how photosynthesis responds and acclimates to fluctuating light, and how these insights can better inform strategies to improve photosynthesis. Importantly, plants are genetically diverse, which can result in diverse physiology and morphology. These genetic variations can lead to a diverse set of photosynthetic responses and acclimations to fluctuating light. Therefore, this thesis explored the phenotypic variation in photosynthetic responses to fluctuating light, to determine strategies and adaptations that can prove useful for efforts to improve photosynthesis.\n\nChapter 1 introduces the scientific background of the thesis. It includes research gaps and approaches that this thesis addresses.\n\nChapter 2 was designed to determine whether photosynthetic variation exists between tomato species that can help improve photosynthesis. In Chapter 2, investigation into the correlation between the amount of carbon assimilation at light saturated conditions (Amax), a key indicator of the photosynthetic capacity, and the ability of photosynthesis to respond to increases in irradiances were carried out. We hypothesized that having a higher Amax can enable photosynthesis to respond faster to short term changes in irradiance. The rationale being that plants that have higher photosynthetic capacity can potentially reach the same rates of photosynthesis by activating a smaller fraction of the photosynthetic apparatus compared to plants that have lesser capacity. This would imply that by selecting for higher Amax, higher rates of photosynthesis along with faster responses to increasing irradiance can be achieved. To determine whether there was variation in photosynthetic responses to short-term fluctuating light and Amax, and if the variations are correlated, investigation was carried out on three genotypes across three species of tomato, namely, Solanum lycopersicum (cv. Money Maker), Solanum pennellii, and Solanum pimpinellifolium. The response of CO2 assimilation to a single step increase, and to five successive step increases in irradiance spanning multiple light-adapted states, was monitored. However, no correlations were observed between Amax and speed of photosynthetic response during single irradiance step increases from light adapted states as well as to multiple step increases from a range of light-adapted states. Therefore, implying that Amax, and rate at which CO2 assimilation responds to an increase in irradiance are independent, and thus, need to be considered as separate traits. Nevertheless, we observed that having a higher Amax, was better than genotypes with faster response and thus can be useful for improving photosynthesis.\n\nChapter 3 follows from Chapter 2 where we investigated whether photosynthetic variation exists within species that is beneficial to improve photosynthesis. In addition to responses to fluctuating light, the effect of chilling on these responses were investigated. The motivation behind this investigation was to understand how a combination of abiotic factors can influence photosynthesis. This investigation provides insights into generating climate-resilient crops, which is a crucial facet in improving photosynthesis. Generating climate resilient crops necessitates identification of genetic markers associated with desirable photosynthetic traits in plant populations. However, the combined effect of chilling and photosynthetic responses to fluctuating light remains unexplored, and there was a lack in populations designed to explore these responses. Thus, exploration needed to be done in pre-existing populations where there is phenotypic variation in photosynthetic responses and in how chilling affects these responses within parental lines. This study examined the variation in photosynthetic responses of the parental lines of a Multi-parent Advanced-Generation Inter-Cross (MAGIC) population of tomato (Solanum lycopersicum) under fluctuating light and suboptimal temperatures. Photosynthetic responses to step increases and step decreases in irradiance were measured using modulated chlorophyll fluorescence and the effect of lowered temperature (14\u00b0C) on these responses was investigated. The results showed variation in the kinetics of the response of quantum efficiency of PSII (\u03a6PSII) to step changes in irradiance under control and chilling conditions. Chilling had a minimal effect on the photosynthetic responses of some parental lines, indicating resilience to chilling. These findings highlight the potential of exploring genetic components to breed climate-resilient crops.\n\nChapter 4 investigates the long-term effect of fluctuating light on short-term photosynthetic responses as well as how these acclimations vary between evolutionarily distinct tomato plants. We investigated the long-term effect of two different fluctuating light regimes on six genotypes spanning five evolutionarily distinct species of tomato. The genotypes used were from Solanum arcanum, Solanum chilense, Solanum lycopersicum (cv. Money Maker), Solanum lycopersicum (cv. Narcalan), Solanum pennellii, and Solanum pimpinellifolium. The effect of fluctuating light on light reactions was minimal, however the certain traits from certain genotypes were observed, which would be desirable to increase photosynthetic efficiency. For instance, NPQ of Solanum pennellii was considerably lower compared to NPQ of the other genotypes across all irradiance steps while \u03a6PSII remained similar across all genotypes. In contrast, we observed significant genotype to genotype variation in the effect of fluctuating light on the potential buffering effect of PSI acceptor side. Importantly, we observed that although irradiance responses of CO2 assimilation per unit area did not vary, CO2 assimilation made on a mass basis exhibited significant variation to fluctuating light. This potentially highlights a need to reevaluate how photosynthetic traits are evaluated for improving photosynthesis. Additionally, responses of CO2 assimilation to step increase in irradiance and intrinsic Water Use Efficiency (iWUE) also revealed specific acclimations to fluctuating light that can be beneficial for improving photosynthesis. For example, we observed that the iWUE of most genotypes increased when grown under fluctuating light, indicating that these genotypes can maintain similar CO2 assimilation rates while losing less water when grown under fluctuating light. Our investigations also revealed key considerations for improving photosynthesis under fluctuating light.\n\nFinally, chapter 5 gathers insights from the previous chapters and discusses their implications for improving photosynthesis. Chapter 5 also discusses key considerations for investigating photosynthetic variation to improve photosynthesis and how best design screening protocols to determine these variations.","auteur":"Keshav Jayasankar","auteur_slug":"keshav-jayasankar","publicatiedatum":"16 september 2026","taal":"EN","url_flipbook":"https:\/\/ebook.proefschriftmaken.nl\/ebook\/keshavjayasankar?iframe=true","url_download_pdf":"https:\/\/ebook.proefschriftmaken.nl\/download\/59d53d00-5fdf-445b-a187-9ddf79bbb8b6\/highres","url_epub":"","ordernummer":"19245","isbn":"","doi_nummer":"","naam_universiteit":"Wageningen University","afbeeldingen":16779,"video_url":"","podcast_url":"","naam_student:":"","binnenwerk":"","universiteit":"Wageningen University","cover":"","afwerking":"","cover_afwerking":"","design":""},"_links":{"self":[{"href":"https:\/\/dodo.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/16777","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dodo.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio"}],"about":[{"href":"https:\/\/dodo.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/types\/us_portfolio"}],"author":[{"embeddable":true,"href":"https:\/\/dodo.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/dodo.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/comments?post=16777"}],"version-history":[{"count":1,"href":"https:\/\/dodo.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/16777\/revisions"}],"predecessor-version":[{"id":16780,"href":"https:\/\/dodo.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/16777\/revisions\/16780"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/dodo.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media\/16778"}],"wp:attachment":[{"href":"https:\/\/dodo.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media?parent=16777"}],"wp:term":[{"taxonomy":"us_portfolio_category","embeddable":true,"href":"https:\/\/dodo.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio_category?post=16777"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}