Abstract
Six cultivated rice genotypes showing different stomatal conductance (gs) values were used to investigate the influence of leaf vein traits on leaf gas exchange and leaf hydraulics. The results showed that gs was the main determinant of the varietal difference in the net photosynthetic rate (PN), whereas the area-based leaf nitrogen content (Narea) and mesophyll conductance (gm) were not main factors. gs and PN were both positively correlated with leaf hydraulic conductance (Kleaf). A high density of leaf veins (vein length per leaf area, VLA), especially minor leaf veins (VLAminor), was of benefit for improving the Kleaf. The proportion of the minor leaf vein length to the total leaf vein length did not impact the leaf hydraulics or leaf gas exchange. Overall, these findings suggested that a high density of leaf veins, especially minor leaf veins, enhances Kleaf and promotes gs and PN in cultivated rice genotypes and a high VLA can be regarded as a high photosynthetic capacity trait in rice plants.
Highlights
Under the current ambient atmospheric conditions, CO2 diffusional conductance from air to carboxylation sites is regarded as one of the main limiting factors of net photosynthetic rate (PN) in C3 plants (Evans et al, 2009; Li et al, 2009; Yamori et al, 2011; Flexas et al, 2012; Adachi et al, 2013; Gago et al, 2019)
PN ranged from 21.2 to 36.2 μmol/m2/s, and the highest and the lowest values were found in Champa and N22, respectively
Kirmizi Celtik showed the highest Narea of 2.03 g/m2 and N22 showed the lowest Narea of 1.23 g/m2. gs ranged from 0.18 to 0.46 mol/m2/s and the highest and lowest values were found in Champa and N22, respectively. gm showed no significant varietal difference among the six rice genotypes
Summary
Under the current ambient atmospheric conditions, CO2 diffusional conductance from air to carboxylation sites is regarded as one of the main limiting factors of net photosynthetic rate (PN) in C3 plants (Evans et al, 2009; Li et al, 2009; Yamori et al, 2011; Flexas et al, 2012; Adachi et al, 2013; Gago et al, 2019). CO2 in the air must first overcome the air–leaf boundary resistance to reach the surroundings of the stomata, and it enters the stomatal pores to reach the substomatal cavity, diffuses to the surroundings of the cell wall, and successively passes through the cell wall, cell membrane, cytoplasm, chloroplast envelope, and the stroma (Terashima et al, 2011; Tholen et al, 2012). The CO2 diffusional resistance from air to the surface of the leaf is called boundary layer resistance, the CO2 diffusional resistance from air to the substomatal cavity is called stomatal resistance, and the CO2 diffusional resistance from the substomatal cavity to the carboxylation sites is called mesophyll resistance. Mesophyll resistance can be as important as stomatal resistance under many conditions (Terashima et al, 2011), it was ignored in earlier studies (Farquhar et al, 1980; Kodama et al, 2011). Many previous studies have shown that PN is positively correlated with both gs and gm (Giuliani et al, 2013; Carriquí et al, 2015; Liu and Li, 2016)
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