Effects of reduced chlorophyll content on photosystem functions and photosynthetic electron transport rate in rice leaves

To elucidate the photosynthetic performance of rice mutant with low chlorophyll content, we assessed light energy conversion and photosynthetic electron transport at the flowering stage in rice of yellow-green leaf mutant (ygl) and a control with normal pigment content (IR36) under field conditions. The results showed that the reduced chlorophyll content and high expression levels of chlorophyll-binding protein genes suggested that ygl has smaller light-harvesting chlorophyll antennae. The small chlorophyll antenna size reduced non-photochemical quenching (NPQ) and generation of reactive oxygen species (ROS), and increased PSII efficiency in ygl. Analysis of the chlorophyll a fluorescence transient showed that the higher ratio of reaction-center chlorophylls and the total chlorophyll of PSII (gamma RC) improved excitation energy capture and electron transport efficiency of PSII in ygl. The IP amplitude (delta VIP) and the reduction rates of the pool of end electron acceptors in ygl increased, compared with IR36. These results suggest that the light absorbed by the mutant with reduced chlorophyll content was more efficiently partitioned to photosynthesis and could be used to improve photo-synthetic efficiency.

Automated summary

The study examined a rice mutant with low chlorophyll content and found that it had a smaller light-harvesting chlorophyll antenna, resulting in reduced non-photochemical quenching and generation of reactive oxygen species, and increased PSII efficiency. Analysis of chlorophyll a fluorescence transient showed improved excitation energy capture and electron transport efficiency of PSII in the mutant. These findings indicate that the mutant efficiently partitions light absorbed to photosynthesis, thus improving photosynthetic efficiency.