Light and Water Conditions Co-Regulated Stomata and Leaf Relative Uptake Rate (LRU) during Photosynthesis and COS Assimilation: A Meta-Analysis

As a trace gas involved in hydration during plant photosynthesis, carbonyl sulfide (COS) and its leaf relative uptake rate (LRU) is used to reduce the uncertainties in simulations of gross primary productivity (GPP). In this study, 101 independent observations were collected from 22 studies. We extracted the LRU, stomatal conductance (g(s)), canopy COS and carbon dioxide (CO2) fluxes, and relevant environmental conditions (i.e., light, temperature, and humidity), as well as the atmospheric COS and CO2 concentrations (C-a,C-COS and C-a,C-CO2). Although no evidence was found showing that g(s) regulates LRU, they responded in opposite ways to diurnal variations of environmental conditions in both mixed forests (LRU: Hedges'd = -0.901, LnRR = -0.189; g(s): Hedges'd = 0.785, LnRR = 0.739) and croplands dominated by C3 plants (Hedges'd = -0.491, LnRR = -0.371; g(s): Hedges'd = 1.066, LnRR = 0.322). In this process, the stomata play an important role in COS assimilation (R-2 = 0.340, p = 0.020) and further influence the interrelationship of COS and CO2 fluxes (R-2 = 0.650, p = 0.000). Slight increases in light intensity (R-2 = 1, p = 0.002) and atmospheric drought (R-2 = 0.885, p = 0.005) also decreased the LRU. The LRU saturation points of C-a,C-COS and C-a,C-CO2 were observed when & UDelta;C-a,C-COS & AP; 13 ppt (R-2 = 0.580, p = 0.050) or & UDelta;C-a,C-CO2 & AP; -18 ppm (R-2 = 0.970, p = 0.003). This study concluded that during plant photosynthesis and COS assimilation, light and water conditions co-regulated the stomata and LRU.