Mesophyll conductance variability of rice aquaporin knockout lines at different growth stages and growing environments
Xianhong Huang, Zhixin Wang, Jianliang Huang, Shaobing Peng, Dongliang Xiong
Abstract
SUMMARY The plasma membrane subfamily of aquaporins [plasma membrane intrinsic proteins (PIPs)], which facilitates the CO 2 diffusion across membranes, is proposed to play an important role in mesophyll conductance to CO 2 ( g m ), a major limiting factor of photosynthesis. However, recent studies implied no causal relationship between g m and PIPs because they failed to repeat the previous observed differences in g m between PIP knockout lines and their wild‐type. The contrasting results on the role of PIPs in g m were interpreted as the different growth conditions among studies, which has never been tested. Here, we assessed whether the differences in g m between wild‐type and PIP knockout lines, Ospip1;1 , Ospip1;2 and Ospip2;1 , varied with growth condition (field versus pot condition) and growth stages in rice. Under field conditions, no differences were observed in plant performance, photosynthetic rate ( A ) and g m between PIP knockout lines and the wild‐type. However, in agreement with previous studies, two out of three knockout lines showed significant declines in tiller number, plant height, A and g m under pot conditions. Moreover, we found that the differences in A and g m between PIP knockout lines and the wild‐type varied with the growth stage of the plants. Our results showed that the differences in g m between PIP knockout lines and wild‐type were depending on the growth environments and stage of the plants, and further efforts are required to reveal the underlying mechanisms.