Partitioning of photosynthetic electron flow between CO2 and O2 reduction in a C3 leaf (Phaseolus vulgaris L.) at different CO2 concentrations and during drought stress

Abstract

Photosystem II chlorophyll fluorescence and leaf net gas exchanges (CO2 and H2O) were measured simultaneously on bean leaves (Phaseolus vulgaris L.) submitted either to different ambient CO2 concentrations or to a drought stress. When leaves are under photorespiratory conditions, a simple fluorescence parameter ΔF/ Fm (B. Genty et al. 1989, Biochem. Biophys. Acta 990, 87-92; ΔF = difference between maximum, Fm, and steady-state fluorescence emissions) allows the calculation of the total rate of photosynthetic electron-transport and the rate of electron transport to O2. These rates are in agreement with the measurements of leaf O2 absorption using (18)O2 and the kinetic properties of ribulose-1,5bisphosphate carboxylase/oxygenase. The fluorescence parameter, ΔF/Fm, showed that the allocation of photosynthetic electrons to O2 was increased during the desiccation of a leaf. Decreasing leaf net CO2 uptake, either by decreasing the ambient CO2 concentration or by dehydrating a leaf, had the same effect on the partitioning of photosynthetic electrons between CO2 and O2 reduction. It is concluded that the decline of net CO2 uptake of a leaf under drought stress is only due, at least for a mild reversible stress (causing at most a leaf water deficit of 35%), to stomatal closure which leads to a decrease in leaf internal CO2 concentration. Since, during the dehydration of a leaf, the calculated internal CO2 concentration remained constant or even increased we conclude that this calculation is misleading under such conditions.

Gas Exchange, Photochemical Efficiency, and Leaf Water Potential in Three Salix Species

“…Similar results have been documented in some woody species in analogous environments (Christiane andLudger 1999, Brodribb andField 2000). In addition, photosynthesis is partly limited by reduced intercellular CO 2 concentration due to stomata closure (Cornic andBriantais 1991, Quick et al 1992). Our investigation suggested that the indigenous species would have higher endurance to both air and soil drought than the non-indigenous ones when drought accidents occur.…”

Effect of water stress on carbon isotope discrimination and Rubisco activity in bread and durum wheat genotypes

“…Our results also found support from the work of Cornic and Briantais et al, 1991 who observed that under severe dehydration stress, photosynthesis may be controlled by chloroplast capacity to fix CO 2 rather than diffusion characteristic. It has been shown in sunflower that non-stomatal limitation of photosynthesis may be related to reduced carboxylation efficiency, reduced RUBP regeneration or reduced amount of functional Rubisco.…”

Light Intensity Influences Photosynthesis and Crop Characteristics of Jeffersonia dubia

“…A very good correlation has been observed between photoinhibition and a decreased ratio of variable to maximum fluorescence, i.e., the F v /F m ratio (Bolhar-Nordenkampf and Öquist, 1993). The Fv/Fm parameter has been correlated with the maximum quantum yield of photosynthesis (Björkman and Demmig-Adams, 1987;Bolhar-Nordenkampf and Öquist, 1993;Cornic and Briantais, 1991), reaching a maximum This kind of photoinhibition causes a decrease in photosynthetic efficiency, and may lead to limitations in daily carbon gain with a lower capacity for plant dry mass accumulation (Ögren and Sjöström, 1990). In this study, the dry weight of the shoots and roots under 0% shade was 24% and 22% lower than that under the 50% shade (Table 1).…”