Fluorescence of chlorophyll a and photosynthetic pigments in Atriplex nummularia under abiotic stresses

Abstract

A B S T R A C TChlorophyll a fluorescence is a very useful tool in ecophysiological studies to analyze the photosynthetic performance of plants under biotic and abiotic stresses. This research aimed to evaluate the parameters of the fluorescence of chlorophyll a, contents of chlorophyll a, b and total, and carotenoids in Atriplex nummularia cultivated under water stress (37 and 70% of field capacity) and salt stress (irrigation water with electrical conductivity of 0, 5, 10, 20, 30 and 40 dS m -1 ), besides two sources of salts: NaCl and a mixture of salts of Ca 2+ , Mg +2 , K + , Na + and Cl -, in a 6 x 2 x 2 factorial, with 4 replicates, totaling 96 experimental plots. At 91 days after transplanting, the initial fluorescence (F 0 ), maximum fluorescence (F m ), potential quantum efficiency of photosystem II (F v /F m ), F v /F 0 ratio and the contents of chlorophyll a, b, and total and carotenoids were determined. All assessed parameters decreased as a standard response to salt stress, except F 0 , which had, as a characteristic, the increase in its values under stress conditions. The emission parameters for Atriplex nummularia varied with the type of salt present in the irrigation water.Fluorescência da clorofila a e pigmentos fotossintéticos em Atriplex nummularia sob estresses abióticos R E S U M OA fluorescência da clorofila a é uma ferramenta de grande utilidade em estudos ecofisiológicos para a análise da performance fotossintética de plantas sob estresses bióticos e abióticos. Objetivou-se avaliar os parâmetros da fluorescência da clorofila a, teores de clorofila a, b e total e carotenoides em Atriplex nummularia cultivada sob estresses hídrico (37 e 70% da capacidade de campo) e salino (água de irrigação com condutividade elétrica de 0, 5, 10, 20, 30 e 40 dS m -1 ), além de duas fontes de sais: NaCl e uma mistura com sais de Ca 2+ , Mg 2+ , K + , Na + e Cl -, em fatorial 6 x 2 x 2 com 4 repetições totalizando 96 parcelas experimentais. Aos 91 dias após o transplantio foram determinadas a fluorescência inicial (F 0 ), a fluorescência máxima (F m ), a eficiência quântica potencial do fotossistema II (F v /F m ) e a razão F v /F 0 e os teores de clorofila a, b, total e carotenoides. Os parâmetros de emissão avaliados reduziram como resposta padrão ao estresse salino, com exceção do F 0 que tem, como característica, o aumento de seus valores quando em condições de estresse. Os parâmetros de emissão para a Atriplex nummularia variaram de acordo com o tipo de sal presente na água de irrigação. Key words:photosynthesis water and salt stress halophyte Palavras-chave: fotossíntese estresse salino e hídrico halófita

Chloroplast pigments and photochemical efficiency of West Indian cherry under salt stress and potassium-phosphorus fertilization

“…fluorescence reflects the plant's ability to transfer energy to the formation of the NADPH reducer, ATP, and reduced ferredoxin, consequently affecting CO 2 assimilation in the biochemical phase of photosynthesis (Lima et al, 2019), and increments in Fo values associated with reductions in Fm values can be interpreted as an indication of damage to the PSII lightharvesting complex (Melo et al, 2017), as observed in the present study.…”

“…Regarding the maximum fluorescence of West Indian cherry plants in the first production cycle, a quadratic fit can be observed through the regression equation, with a maximum estimated value for Fm of 3745.76 obtained in plants cultivated under a water salinity of 2.6 dS m -1 ( Figure 4A). The excess of salts in water and/or soil causes damage to the photosynthetic apparatus and the metabolic processes of plants because the contents of pigments that constitute the antenna complex, as observed in this study were reduced (Figures 1 and 2) , leading to a deficit in the capture of light energy and negatively affecting the signals of chlorophyll a fluorescence Melo, Souza, & Cunha, 2017). The reduction in Fm may be related to the photoreduction deficiency in electronacceptor quinone (QA), due to PSII inactivation in the thylakoid membranes from salt stress, which affects the flow of electrons between photosystems as well as photochemical activity in leaves (Lima et al, 2019).…”

Photosynthetic and biochemical traits change in the green‐tide‐forming macroalga Ulva pertusa during sporulation1

“…The reduction in F m might also be due to a decrease in the chlorophyll level observed at S4 (Melo et al. ). In Ulva prolifera , the electron transport chain is involved in regulating the entire sporulation process, including the early activation of the Calvin cycle and sporangium formation.…”

Responses to Water Deficit and Salt Stress in Silver Fir (Abies alba Mill.) Seedlings

“…Photosynthetic pigments can be included in these putative stress markers, as inhibition of photosynthesis is also a common effect of stress [60][61][62], and is accompanied by a reduction of chlorophyll contents, by inhibition of its synthesis combined with activation of its degradation [63]. Previous studies on plants of different conifer species exposed to salt or drought treatments have also reported a decrease in chlorophylls a and b and, in some cases, in total carotenoids [59,64,65].…”