Effects of endogenous ascorbic acid on the distribution of photosynthetic electron flow in rice leaves
2019
Zhang, Qilei | Cai, Minling | Lu, Lina | Gao, Hui | Peng, Changlian
Ascorbic acid (Asc) is one of the major antioxidants in plants. l-Galactono-1,4-lactone dehydrogenase (GLDH) is an enzyme that catalyses the last step of Asc biosynthesis in higher plants. In this study the effects of endogenous Asc on the distribution of photosynthetic electron flow were investigated in wild-type (ZH-11) rice (Oryza sativa L.) and in GLDH-overexpressing (GO-2) and GLDH-suppressed (GI-2) transgenic rice. The ratio of photosynthetic electron flow distributed to Rubisco-dependent carboxylation was highest in GO-2, whereas other electron flows in addition to carbon fixation were highest in GI-2 after flowering. Further examination showed that the photosynthetic electron flow, GLDH content and reactive oxygen species-scavenging ability were highest in GO-2 and lowest in GI-2. Therefore, the senescence of leaves was faster in GI-2 but slower in GO-2 compared with ZH-11. In addition, leaves with higher Asc content had more Rubisco content and a superior photosynthetic rate, which increased rice yield. These results suggest that increasing the endogenous Asc content of rice delays senescence, maintains a higher photosynthetic rate and results in more photosynthetic electron flow distributed to Rubisco-dependent carboxylation, ultimately leading to increased rice yield.
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