Far-Red Chlorophyll Fluorescence Radiance Tracks Photosynthetic Carbon Assimilation Efficiency of Dark Reactions

Abstract

Solar-induced chlorophyll fluorescence (SIF) observations from space have shown close relationships with terrestrial photosynthesis rates. SIF originates from the light reactions of photosynthesis, whereas carbon fixation takes place during the dark reactions of photosynthesis. Questions remain regarding whether SIF is able to track changes in the efficiency of the dark reactions in photosynthesis. Using concurrent measurements of leaf-scale gas exchange, pulse amplitude-modulated (PAM) fluorescence, and fluorescence spectral radiances, we found that both far-red fluorescence radiances and PAM fluorescence yields responded rapidly to changes in photosynthetic carbon assimilation due to changes in environmental factors or induced stomatal closure under constant light conditions. Uncertainties in outgoing and incoming irradiance mismatch for SIF measurements may very likely obscure the contributions of the dark reactions, thereby causing the inconsistent findings previously reported, which were no change in far-red SIF and PAM fluorescence yields after clear reductions in the photosynthetic carbon assimilation efficiency of dark reactions. Our results confirm that high-quality SIF measurements have the potential to provide insights into the dark reactions of photosynthesis. This study is particularly relevant for better interpreting satellite SIF observations that are obtained under roughly constant overpass times and relatively stable light intensities.

Net Photosynthesis and Biomass Production in Stevia, Eggplant, and Cowpea Can Be Improved by Fertilization with Cyanobacteria (Limnospira maxima)

“…Significant increases in the root, stem, leaf, and total plant dry weights under L. maxima extract applications were evident in V. unguiculata, S. rebaudiana, and S. melongena. These enhancements likely result from the contribution of nutrients present in the L. maxima chemical composition, which is essential for optimizing vital metabolic processes such as gas exchanges, consequently facilitating efficient carbon conversion [46]. Accordingly, A N , a primary physiological indicator, also accounts for the response to treatments, displaying a significant and positive correlation with the dry weights of organs across all three species.…”

Diurnal Change of the Photosynthetic Light-Response Curve of Buckbean (Menyanthes trifoliata), an Emergent Aquatic Plant

“…Photosynthesis of plants greatly affects global [1,2] and regional [3][4][5][6][7][8][9][10][11][12][13][14][15][16] carbon cycles. Since ecosystem-level photosynthesis is the sum of single-leaf photosynthesis [16][17][18][19][20][21][22], understanding of stress responses of leaves to diurnal and seasonal environmental change is necessary to improve ecosystem carbon cycles modeling [6,8,9,11,12,[23][24][25][26][27] and to increase agricultural [22,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] and forestry…”