Fluorescence characteristics and photoinhibition in saplings of manwood on clear days and under overcast conditions

Abstract

High irradiance may reduce the productivity of tropical plants by exacerbating photoinhibition of photosynthesis, particularly in the case of shade-adapted plants. The aim of this study was to determine the effect of cloud cover on the fluorescence characteristics and photoinhibition on saplings of manwood (Minquartia guianensis Aubl.). Three-year-old saplings were exposed to full irradiance either on clear days (10, 45 and 90 min) or under overcast conditions (120, 180, and 420 min). Changes in the population of functional photosystem II (PSII), the initial (F o ) and maximum fluorescences (F m ), and the F v /F m ratio (maximum potential quantum yield of PSII) were monitored after plant exposure to full irradiance and during recovery (within 48 h) at low light intensity. Although photoinhibition of PSII (F v /F m ) was determined by the number of photons reaching the leaf surface (photon fluence), cloudiness tended to reduce the photoinhibitory effect of irradiance. F o increased with fluence on cloudy days and was unaffected by irradiance on clear days, except for a sharp rise during the first 10 min of exposure to full sunlight. For a given photon fluence, F m was lower on clear days. Recovery from photoinhibition was similar in both light environments. Although photon fluence is the preponderant factor determining the extent of photoinhibition, cloudiness might alleviate the photoinhibitory effect of irradiance. Key words: Amazonia, functional photosystem II, initial fluorescence, light quality, photon fluence CARACTERÍSTICAS DA FLUORESCÊNCIA E FOTOINIBIÇÃO EM ARVORETAS DE ACARIQUARA EM DIAS NUBLADOS E ENSOLARADOSRESUMO: Alta irradiância pode reduzir a produtividade de plantas tropicais por intensificar a fotoinibição da fotossíntese, particularmente em plantas adaptadas à sombra. O objetivo deste trabalho foi determinar o efeito da nebulosidade nas características da fluorescência e na fotoinibição em arvoretas de acariquara (Minquartia guianensis Aubl.). Plantas jovens de três anos de idade foram expostas à irradiância em dias ensolarados (10, 45 e 90 min) ou nublados (120, 180 e 420 min). Foram monitoradas mudanças na população de fotossistemas II (FSII) funcionais, na fluorescência inicial (F o ) e máxima (F m ) e na relação F v /F m (rendimento quântico potencial do FSII), antes da exposição das plantas à irradiância e durante a recuperação (até 48 h) sob baixa intensidade luminosa. Apesar de a fotoinibição (F v /F m ) ser determinada pelo número de fótons incidentes na superfície da folha (fluência), houve tendência de a nebulosidade reduzir o efeito da irradiância na fotoinibição. F o aumentou com a fluência em dias nublados, mas não em dias ensolarados, exceto pelo aumento nos primeiros 10 min de exposição à luz solar plena. Para uma dada fluência, F m foi menor nos dias ensolarados. A recuperação da fotoinibição foi similar em ambos os ambientes de luz. Apesar de a fluência de fótons ser o fator preponderante na determinação do grau de fotoinibição, a nebulosidade ameniza o efeito fotoin...

Differential photosynthetic plasticity of Amazonian tree species in response to light environments

“…The values of A max found in this study are in close agreement with those of other studies on tropical tree species, especially the higher photosynthesis rates of pioneer species in high irradiance environments (Marenco et al 2001a;Dias & Marenco 2007;Guimarães et al 2018). In all other species investigated, irrespective of successional group, and with exception of C. guianensis and H. brasiliensis, A max decreased about 50% when comparing FS with DS.…”

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Environmental stress - what can we learn from chlorophyll a fluorescence analysis in woody plants? A review

“…Examined species Drought Ögren, 1990;Percival and Fraser, 2002;Percival et al, 2006;Bacelar et al, 2007;Christen et al, 2007;Fini et al, 2009;Bussotti et al, 2010;Faraloni et al, 2011;Wang et al, 2012;Guha et al, 2013;Lee et al, 2016;Falqueto et al, 2017;Banks, 2018;Kalaji et al, 2018;Guadagno et al, 2021;Mihaljevićet al, 2021;Fini et al, 2022 Olea , 1984;Brodribb and Hill, 1997;Hamerlynck, 2001;Gonҫalves et al, 2001;Lichtenthaler et al, 2004;Dias and Marenco, 2007;Cascio et al, 2010;Desotgiu et al, 2012a…”

“…Changes in light conditions alter the performance of the photosynthetic apparatus. Under full sunlight at midday, the maximum quantum efficiency of PSII (F V /F M ) decreases sharply ( Dias and Marenco, 2007 ; Desotgiu et al., 2012a ). The opposite trend was observed for the dissipation rate expressed by F 0 ( Dias and Marenco, 2007 ).…”

“…Under full sunlight at midday, the maximum quantum efficiency of PSII (F V /F M ) decreases sharply ( Dias and Marenco, 2007 ; Desotgiu et al., 2012a ). The opposite trend was observed for the dissipation rate expressed by F 0 ( Dias and Marenco, 2007 ). Indeed, the ChF response in plants reflects their ecophysiological characteristics.…”