Effects of Potassium Deficiency on Chloroplast Ultrastructure and Chlorophyll Fluorescence in Inefficient and Efficient Genotypes of Rice

Potassium (K) plays important roles in leaf photosynthesis, and the K-efficient rice genotype (HA) could maintain a significantly higher net photosynthetic rate (Pn) and stomatal conductance (Gs) at low K (5 mg K L−1) than the K-inefficient genotype (TLHZ). As compared to K-inefficient genotype (TLHZ), the K-efficient genotype (HA) was found to be able to maintain higher PSII-available photochemical efficiency (Fv/Fm), electron transport rate of PSII (ETR), and photochemical quenching (qP), but a smaller value of the non-photochemical quenching (NPQ) when grown at low K. In addition, better preserved chloroplast ultrastructure was noted in HA than in TLHZ under K deficiency. These results indicate that the K-efficient genotype has greater ability to keep PS reaction center less damaged and maintain stronger photosynthetic ability with high resistance to photoinhibition under K deficiency. The high efficient photochemical capacity in K-efficient genotypes may be a key factor for high K efficiency in rice.