{"id":15473,"date":"2026-05-26T10:29:13","date_gmt":"2026-05-26T10:29:13","guid":{"rendered":"https:\/\/www.proefschriftmaken.nl\/portfolio\/samikshya-shrestha\/"},"modified":"2026-05-26T10:29:27","modified_gmt":"2026-05-26T10:29:27","slug":"samikshya-shrestha","status":"publish","type":"us_portfolio","link":"https:\/\/www.proefschriftmaken.nl\/en\/portfolio\/samikshya-shrestha\/","title":{"rendered":"Samikshya Shrestha"},"content":{"rendered":"","protected":true},"excerpt":{"rendered":"","protected":true},"author":7,"featured_media":15474,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"us_portfolio_category":[45],"class_list":["post-15473","us_portfolio","type-us_portfolio","status-publish","post-password-required","hentry","us_portfolio_category-new-template"],"acf":{"naam_van_het_proefschift":"Unraveling acclimation mechanisms in plants to fluctuating light","samenvatting":"Bladeren in een gewasdak, zowel in het veld als in de kas, ervaren variaties in lichtintensiteit. Deze fluctuaties in lichtintensiteit kunnen de fotosynthetische effici\u00ebntie verlagen, omdat fotosynthetische reacties niet onmiddellijk zijn, wat kan leiden tot een lagere koolstofopname en productiviteit. Langdurige blootstelling (dagen tot weken) van planten aan fluctuerend licht induceert acclimatisatie-aanpassingen in morfologie, anatomie en\/of biochemie om de fotosynthetische effici\u00ebntie en productiviteit te optimaliseren. Dergelijke aanpassingen kunnen de fotosynthetische effici\u00ebntie moduleren en de plantengroei be\u00efnvloeden. Ondanks de relevantie van fluctuerend licht voor fotosynthese en groei, zijn de onderliggende acclimatisatiemechanismen relatief onderbelicht en slechts bij een handvol soorten bestudeerd. Identificatie van acclimatisatiemechanismen die fotosynthese en groei onder fluctuerend licht vergemakkelijken, biedt potentieel voor nieuwe doelen voor gewasverbetering en verhoging van de voedselproductie. Bovendien is de interactie van fluctuerend licht met andere omgevingsfactoren en natuurlijke genetische variatie nog niet veel onderzocht. Daarom was dit proefschrift gericht op: a) onderzoeken hoe de combinatie van verhoogde CO2 en fluctuerend licht de groei, morfologie, anatomie en fotosynthese be\u00efnvloedt; b) begrijpen van het effect van gelijktijdige snelle veranderingen in lichtintensiteit en bladtemperatuur op gasuitwisseling; c) onderzoeken van natuurlijke genetische variatie in fotosynthese- en groeigebonden eigenschappen bij acclimatisatie aan fluctuerend licht.\n\nIn Hoofdstuk 1 werd de prevalentie van lichtfluctuaties in de natuur en kassen ge\u00efntroduceerd. Vervolgens werden de mechanismen besproken die planten op korte en lange termijn gebruiken, met de nadruk op acclimatisatie. De definities van acclimatisatie (ontwikkelingsgericht en dynamisch) werden kort toegelicht. De acclimatisatiemechanismen met betrekking tot bladanatomie, morfologie en biochemie werden samengevat. Twee aspecten werden beschreven: interactie met omgevingsfactoren (CO2 en temperatuur) en natuurlijke genetische variatie. Ten slotte werd de opzet van het proefschrift gepresenteerd.\n\nIn Hoofdstuk 2 werden de effecten van fluctuerend licht en verhoogde [CO2] op komkommerplanten onderzocht. De focus lag op de vraag of acclimatisatie aan de combinatie van deze factoren de negatieve effecten van fluctuerend licht op groei en fotosynthese kan verzachten. Resultaten toonden aan dat bij normale [CO2] planten onder fluctuerend licht grotere aanpassingen vertoonden in stengelhoogte, bladoppervlak en specifiek bladoppervlak (SLA). Verrassend genoeg verklaarde bladdichtheid in plaats van dikte de 70% hogere SLA. Ondanks deze veranderingen was de droge biomassa 25% lager onder fluctuerend licht. Verhoogde [CO2] verzachtte dit effect gedeeltelijk (slechts 11% reductie) door aanpassingen in morfologie en fotosynthetische effici\u00ebntie.\n\nIn Hoofdstuk 3 werd onderzocht hoe acclimatisatie aan fluctuerend licht de kortetermijnreactie op gelijktijdige fluctuaties in licht en bladtemperatuur be\u00efnvloedde. Bladeren die gewend waren aan fluctuerend licht toonden grotere tijdelijke toenames in fotosynthese. Wanneer temperatuur en licht gelijktijdig toenamen, reageerden de huidmondjes en fotosynthese sneller en sterker dan bij licht alleen. Snelle temperatuurstijgingen veroorzaakten een tijdelijke 'wrong-way' reactie van de huidmondjes en een korte afname in fotosynthese door fotorespiratie. Deze bevindingen benadrukken het belang van realistische temperatuurschommelingen voor het voorspellen van plantgedrag.\n\nIn Hoofdstuk 4 werd de natuurlijke genetische variatie in 218 Arabidopsis-genotypes onderzocht. Er werd een grote variatie gevonden in de mate van acclimatisatie. Bijna alle genotypes vertoonden een hogere SLA onder fluctuerend licht. Genotypes die het beste presteerden onder fluctuerend licht (met verhoogde biomassa) deden dit vooral door een groter geprojecteerd bladoppervlak en niet door veranderingen in fotosynthetische effici\u00ebntie. Dit onderstreept het belang van morfologische eigenschappen bij de veredeling van gewassen voor veranderlijke lichtomstandigheden.\n\nIn Hoofdstuk 5 werden de bevindingen samengevat en vergeleken met bestaande literatuur. De interactie tussen fluctuerend licht, CO2 en temperatuur werd besproken, evenals perspectieven voor toekomstig onderzoek.","summary":"Leaves in a crop canopy, both in the field and greenhouse, experience fluctuations in light intensity. These fluctuations in light intensity can lower the photosynthetic efficiency as photosynthetic responses are not instantaneous and this can lower carbon gain and productivity. Long-term exposure (days to weeks) of plants to fluctuating light induces acclimatory adjustments of morphology, anatomy and\/or biochemistry to optimize photosynthetic efficiency and productivity. Such acclimatory adjustments can modulate photosynthetic efficiency and impact plant growth. Despite the relevance of fluctuating light for plant photosynthesis and growth, the underlying acclimatory mechanisms are relatively understudied and has only been studied in a handful of species. Identification of the acclimation mechanisms facilitating photosynthesis and growth under fluctuating light might hold the potential for identification of novel targets for crop improvement and therefore, increasing food production. Furthermore, the interaction of fluctuating light with other environmental factors as well as genetic variation of fluctuating light acclimation has not been explored much. Therefore, this thesis aimed to a) investigate how the combination of elevated CO2 and fluctuating light affect plant growth and leaf morphology, anatomy, and photosynthesis; b) to understand the effect of concurrent rapid changes in light intensity and leaf temperature on leaf-gas exchange and to disentangle their effects; c) to investigate the natural genetic variation in photosynthesis and growth traits to acclimation to fluctuating light.\n\nIn Chapter 1, the prevalence of fluctuations in light intensity in nature and in greenhouses were introduced. Then after, the mechanisms employed by plants in the short and long term were discussed with emphasis on the long-term responses i.e. acclimation. The definition of acclimation and it\u2019s types namely, developmental and dynamic acclimation were briefly introduced. The acclimatory mechanisms to fluctuating light with regards leaf anatomy, morphology, and biochemistry were summarized. Two aspects of fluctuating light: a) interaction with environmental factors such as CO2 and temperature and b) natural genetic variation to fluctuating light acclimation were described. Lastly, the outline of this thesis as well as the research contents of each chapter were introduced. \n\nIn Chapter 2, the combined effects of fluctuating light and elevated [CO2] on morphological, anatomical, photosynthesis, and plant growth traits in cucumber plants were investigated. The aim was to address whether acclimation to the combination of fluctuating light and elevated [CO2] can mitigate the negative effects of fluctuating light acclimation on plant growth and photosynthesis. Cucumber plants were grown under sinusoidal (with gradual changes) or fluctuating light (with random changes) regimes, in combination with ambient or elevated [CO2]. Results showed that at ambient [CO2], fluctuating light grown plants demonstrated larger enhancements of stem height, leaf area, and specific leaf area (SLA). Surprisingly, leaf density instead of thickness explained the 70% higher SLA under fluctuating light\ncompared to sinusoidal light. Despite these changes, dry biomass was 25% lower under fluctuating light than sinusoidal light, presumably due to lower photosynthetic efficiency and consequently lower diurnal photosynthesis under growth conditions.\nElevated [CO2] partially mitigated the negative effect of fluctuating light on plant growth, via large adjustments in plant morphology and photosynthetic efficiency. In contrast to morphology, steady-state and dynamic photosynthesis traits were relatively unaffected by acclimation to either light regime or [CO2]. These results indicate that fast-growing species such as cucumber acclimate to fluctuating light and different [CO2] by changes to leaf anatomy and plant morphology rather than photosynthetic capacity.\n\nIn Chapter 3, how acclimation to fluctuating light affected the short-term response to concurrent fluctuations in light intensity and leaf temperature were studied and the effects of light intensity from those of temperature were disentangled. Cucumber plants were grown under fluctuating or constant light. A novel measurement set-up was built with a LED and an infrared lamp to provide with light and temperature fluctuations for gas exchange measurements. Protocols with constant temperature and light intensity, fluctuations in only temperature or only light intensity, or simultaneous fluctuations in temperature and light intensity were used. Two successive cycles of fluctuations in light and\/or temperature were imposed. Results showed that leaves grown under fluctuating light showed larger transient increases in photosynthesis to light intensity and temperature fluctuations, leading to a higher tendency for time-integrated photosynthesis. When leaf temperature and light intensity increased rapidly and simultaneously, plants exhibited faster and stronger stomatal opening and photosynthetic induction, especially in the second increase, than with light increase alone. Rapid increase in temperature alone impacted the leaf epidermis and stomata causing wrong-way response of stomata with a cumulative response, while photosynthesis exhibited a transient reduction that lasted 15 min and recovered after 30 min, and was likely partly driven by photorespiration. These findings revealed that small (3\u00b0C), rapid temperature shifts, which are common in nature, can significantly alter plant gas exchange dynamics, underscoring the need for realistic environmental fluctuations to better predict plant behavior.\n\nIn Chapter 4, the natural genotypic variation in arabidopsis genotypes to acclimation to fluctuating light was studied. 218 arabidopsis genotypes were grown under fluctuating or sinusoidal light in a climate chamber equipped with a high-throughput chlorophyll fluorescence imaging system. Growth, morphology, and photosynthesis traits were assessed. Results showed large genetic variation in arabidopsis genotypes to fluctuating light acclimation, with morphological and growth traits showing larger variability than photosynthetic efficiency. Strikingly, all fluctuating light grown genotypes tended to show higher SLA compared to sinusoidal grown genotypes, although this was significant only in 17% of all genotypes. In genotypes that showed higher fresh biomass under fluctuating light than sinusoidal light, enhancement in projected leaf area was the contributing factor for enhanced biomass under fluctuating light rather than changes in photosynthetic efficiency. These results highlight the importance of considering the acclimatory adjustments in morphological and anatomical traits and their impact on photosynthetic traits in breeding for crops with improved yield under fluctuating light. \n\nIn Chapter 5, the findings of this thesis were discussed within a general discussion. The insights gained from this thesis was summarized and compared to the existing literature to provide an overview of the current knowledge about acclimation to fluctuating light. Furthermore, how environmental factors such as CO2 and temperature interact with fluctuating light were discussed. Moreover, the perspectives for future research were provided.","auteur":"Samikshya Shrestha","auteur_slug":"samikshya-shrestha","publicatiedatum":"24 juni 2026","taal":"EN","url_flipbook":"https:\/\/ebook.proefschriftmaken.nl\/ebook\/samikshyashrestha?iframe=true","url_download_pdf":"https:\/\/ebook.proefschriftmaken.nl\/download\/1aeed2c6-d8a0-4936-8de9-d274fedd07e4\/optimized","url_epub":"","ordernummer":"18772","isbn":"","doi_nummer":"","naam_universiteit":"Wageningen University","afbeeldingen":15475,"naam_student:":"","binnenwerk":"","universiteit":"Wageningen University","cover":"","afwerking":"","cover_afwerking":"","design":""},"_links":{"self":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15473","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio"}],"about":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/types\/us_portfolio"}],"author":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/comments?post=15473"}],"version-history":[{"count":1,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15473\/revisions"}],"predecessor-version":[{"id":15476,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15473\/revisions\/15476"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media\/15474"}],"wp:attachment":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media?parent=15473"}],"wp:term":[{"taxonomy":"us_portfolio_category","embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio_category?post=15473"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}