Assessing the Effects of Water Deficit on Photosynthesis Using Parameters Derived from Measurements of Leaf Gas Exchange and of Chlorophyll a Fluorescence

Abstract

Water deficit (WD) is expected to increase in intensity, frequency and duration in many parts of the world as a consequence of global change, with potential negative effects on plant gas exchange and growth. We review here the parameters that can be derived from measurements made on leaves, in the field, and that can be used to assess the effects of WD on the components of plant photosynthetic rate, including stomatal conductance, mesophyll conductance, photosynthetic capacity, light absorbance, and efficiency of absorbed light conversion into photosynthetic electron transport. We also review some of the parameters related to dissipation of excess energy and to rerouting of electron fluxes. Our focus is mainly on the techniques of gas exchange measurements and of measurements of chlorophyll a fluorescence (ChlF), either alone or combined. But we put also emphasis on some of the parameters derived from analysis of the induction phase of maximal ChlF, notably because they could be used to assess damage to photosystem II. Eventually we briefly present the non-destructive methods based on the ChlF excitation ratio method which can be used to evaluate non-destructively leaf contents in anthocyanins and flavonols.

Triploid Citrus Genotypes Have a Better Tolerance to Natural Chilling Conditions of Photosynthetic Capacities and Specific Leaf Volatile Organic Compounds

“…The chlorophyll fluorescence parameters provide insights on the photosynthesis properties under environmental constraints. Under optimal conditions, the F v /F m ratio reaches values about 0.83 in most C3 plants, as do our citrus trees during the warm period (Urban et al, 2017). The decrease in F v /F m we observed during the cold period is usually interpreted as being related to photo-inhibition (Genty et al, 1989).…”

Temperature Impacts the Response of Coffea canephora to Decreasing Soil Water Availability

“…Upon re-watering, A recovered partially, but this occurred in the absence of a significant recovery in g s . This suggests that the recovery of A after a water deficit may be due, in part, to diffusional modifications in CO 2 transport that are independent of g s (Urban et al 2017).…”

Molecular responses to freshwater limitation in the mangrove tree Avicennia germinans (Acanthaceae)

“…Moreover, these roots are photosynthesizing, contributing to carbon gain and enabling respiration in anaerobic soils, using both atmospheric and photosynthetically regenerated oxygen (Kitaya et al, 2002). Being sessile under extreme environmental conditions, PA-arid plants should need to rapidly adjust gene expression to intermittent freshwater availability (Chaves, Flexas, & Pinheiro, 2009;Urban, Aarrouf, & Bidel, 2017). Being sessile under extreme environmental conditions, PA-arid plants should need to rapidly adjust gene expression to intermittent freshwater availability (Chaves, Flexas, & Pinheiro, 2009;Urban, Aarrouf, & Bidel, 2017).…”

“…Interestingly, functional categories associated with the detected transcriptome changes in PA-arid seedlings included various biological processes previously identified to be involved in central aspects of osmotic, heat and UV stress in model and nonmodel plants (Ding et al, 2013;Fan et al, 2018;Zhang et al, 2015). Being sessile under extreme environmental conditions, PA-arid plants should need to rapidly adjust gene expression to intermittent freshwater availability (Chaves, Flexas, & Pinheiro, 2009;Urban, Aarrouf, & Bidel, 2017). Thus, the increased freshwater supply and the restriction in solar irradiance, to which samples from the degraded PA-arid site were subject under the experimental conditions (Figure 2c), probably required seedlings to broadly adjust their photosynthetic machinery.…”