Rapid responses of mesophyll conductance to changes of CO2 concentration, temperature and irradiance are affected by N supplements in rice

Abstract

Photosynthesis in C3 plants is significantly limited by mesophyll conductance (gm), which can vary with leaf anatomical traits and nitrogen (N) supplements. Several studies have investigated the response of gm to N supplements; however, none examined the implications of N supplements on the response of gm to rapid environmental changes. Here we investigated the effect of N supplement on gm and the response of gm to change of CO2, temperature and irradiance in rice. High N supplement (HN) increased mesophyll cell wall surface area and chloroplast surface area exposed to intercellular airspace per leaf area, and reduced cell wall thickness. These changes resulted in increased gm. The gm of leaves with HN was more sensitive to changes in CO2 concentration, temperature and irradiance. The difference in leaf structural features between low N supplement and HN indicates that a rapid change in gm is related to the regulation of diffusion through biological membranes rather than leaf structural features. These results will contribute to an understanding of the determinants of gm response to rapid changes in environmental factors. The effects of nitrogen supplement on mesophyll conductance and its response to rapid environmental changes are poorly known. This study demonstrated a profound impact of nitrogen supplement on mesophyll conductance and its response to rapidly changing CO2 concentration, temperature and light in rice leaves. The improved mesophyll conductance under high nitrogen supplement condition attributed to the changes of leaf structure and aquaporin. Our results also highlighted the importance role of aquaporin in mesophyll conductance response to environmental changes.