Diffusional conductance to CO₂ is the key limitation to photosynthesis in salt‐stressed leaves of rice (Oryza sativa)

Abstract

Salinity significantly limits leaf photosynthesis but the factors causing the limitation in salt-stressed leaves remain unclear. In the present work, photosynthetic and biochemical traits were investigated in four rice genotypes under two NaCl concentration (0 and 150 mM) to assess the stomatal, mesophyll and biochemical contributions to reduced photosynthetic rate (A) in salt-stressed leaves. Our results indicated that salinity led to a decrease in A, leaf osmotic potential, electron transport rate and CO concentrations in the chloroplasts (C ) of rice leaves. Decreased A in salt-stressed leaves was mainly attributable to low C , which was determined by stomatal and mesophyll conductance. The increased stomatal limitation was mainly related to the low leaf osmotic potential caused by soil salinity. However, the increased mesophyll limitation in salt-stressed leaves was related to both osmotic stress and ion stress. These findings highlight the importance of considering mesophyll conductance when developing salinity-tolerant rice cultivars.

Differential Regulation of Stomatal Conductance as a Strategy to Cope With Ammonium Fertilizer Under Ambient Versus Elevated CO2

“…The regulation of stomata has been described as a process linked to transport and absorption of nutrients (Aranjuelo et al., 2014). This strategy has been reported under abiotic stresses such as salinity (Wang et al., 2017) or high temperature (Aranjuelo et al., 2006; Jauregui et al., 2015), among other factors.…”

“…This process is greatly affected by ammonium nutrition in wheat plants. In parallel with other compounds that impair photosynthetic machinery via stomatal regulation (Aranjuelo et al., 2014) or to the “avoidance mechanism” under saline stress (Wang et al., 2017), ammonium-fertilized plants are able to regulate their stomatal function and thus prevent further ammonium accumulation in leaves via the transpiratory stream, which otherwise could be extremely harmful to cell functions. The counterbalance for the plant is that stomatal closure restricts the entrance of CO 2 , with negative consequences for photosynthesis and biomass productivity.…”

Leaf economics spectrum in rice: leaf anatomical, biochemical, and physiological trait trade-offs

“…Moreover, A was also tightly correlated with V cmax and J max , which supports a biochemical limitation in photosynthesis. In fact, previous studies suggested that the major photosynthetic limiting factors in C 3 plant leaves are modified by slight changes in the growing conditions ( Yamori et al , 2011 ; Wang et al , 2018 ). Therefore, the LES trait trade-offs may relate to the photosynthetic limitations, shifting the cause to leaf anatomy and/or biochemical changes.…”

“…A photosynthetic limitation analysis is a helpful tool to quantify the relative limitation of g s , g m , and the photosynthetic biochemistry on A ( Grassi & Magnani, 2005 ; Buckley & Diaz-Espejo, 2015 ), and it has been widely used recently, especially under stress conditions ( Flexas et al , 2009 ; Galle et al , 2009 ; Tosens et al , 2016 ; Wang et al , 2018 ). In this study, the photosynthetic limitations, including the relative stomatal ( l s ), mesophyll ( l m ), and biochemical ( l b ) limitations at different N a , were calculated using fitted A , g s , g m , and V cmax values according to Grassi and Magnani (2005) :…”

Leaf hydraulic vulnerability triggers the decline in stomatal and mesophyll conductance during drought in rice

“…In C 3 plants, the light-saturated leaf photosynthetic rate ( A ) is limited by stomatal conductance ( g s ), mesophyll conductance to CO 2 ( g m ), and/or the photosynthetic biochemistry related to either carboxylation velocity, V cmax , or the maximum electron transport rate set by photochemical and Calvin cycle activities, J max ( Tosens et al , 2012 ; Tomás et al , 2013 ; Tosens et al , 2016 ; Veromann-Jürgenson et al , 2017 ). Grassi and Magnani (2005) developed a method to estimate the partial contribution of each limiting factor to the overall reduction of photosynthesis; this approach has since been applied to many species under a variety of environmental stresses ( Flexas et al , 2009 ; Galle et al , 2009 ; Galle et al , 2011 ; Galmés et al , 2013 ; Wang et al , 2018 ). Although the limiting effects of g s , g m , and photosynthetic biochemistry on A are dependent on the species, A has been suggested to be first inhibited by a decrease in g s and g m under drought conditions, with the biochemical inhibition occurring later, under more severe drought stress conditions ( Grassi & Magnani, 2005 ; Flexas et al , 2009 ; Galle et al , 2009 ; Galle et al , 2011 ; Galmés et al , 2013 ; Galmés et al , 2017 ).…”