Abstract
To evaluate the effect of changes in chlorophyll (Chl) composition and fluorescence on final yield formation, early senescence leaf (esl) mutant rice and its wild-type cultivar were employed to investigate the genotype-dependent differences in Chl composition, Chl fluorescence, and yield characteristics during the grain-filling stage. However, the temporal expression patterns of key genes involved in the photosystem II (PSII) reaction center in the leaves of two rice genotypes were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Results showed that the seed-setting rate, 1000-grain weight, and yield per plant remarkably decreased, and the increase in the 1000-grain weight during the grain-filling stage was retarded in esl mutant rice. Chl composition, maximal fluorescence yield (Fm), variable fluorescence (Fv), a maximal quantum yield of PSII photochemistry (Fv/Fm), and net photosynthetic rate (Pn) in esl mutant rice considerably decreased, thereby indicating the weakened abilities of light energy harvesting and transferring in senescent leaves. The esl mutant rice showed an increase in the minimal fluorescence yield (F0) and 1 − Fv/Fm and decreases in the expression levels of light-harvesting Chl a/b binding protein (Cab) and photosystem II binding protein A (PsbA), PsbB, PsbC, and PsbD encoding for the reaction center of the PSII complex during the grain-filling stage. These results indicated the PSII reaction centers were severely damaged in the mesophyll cells of senescent leaves, which resulted in the weakened harvesting quantum photon and transferring light energy to PSI and PSII for carbon dioxide assimilation, leading to enhanced heat dissipation of light energy and a decrease in Pn.
Highlights
As a staple food, rice (Oryza sativa L.) is one of the most important cereal crops in the world because it feeds nearly a half of the world’s population, especially in Asia [1]
To compare the genotype-dependent differences in the yield properties, the seed-setting rate, 1000-grain weight, and grain yield per plant were investigated for the esl mutant rice and its wild-type after harvesting
Samples of esl mutant rice with the early leaf senescence phenotype were obtained from the mature seeds of gamma-irradiated cultivated rice “Fu142” (Oryza sativa L. indica), which was acquired from Institute of Crop and Nuclear Technology Utilization, Zhejiang Academy of Agricultural Sciences in Hangzhou, Zhejiang Province, China
Summary
Rice (Oryza sativa L.) is one of the most important cereal crops in the world because it feeds nearly a half of the world’s population, especially in Asia [1]. Rice grain yield is highly dependent on the photosynthetic assimilation of leaves during the grain-filling stage. Previous studies have shown that 60% to 80% of nutrients required for rice grain filling are contributed by the photosynthesis of source leaves during the grain-filling period [2,3]. The rest of the nutrients are made up of remobilized carbohydrates that are temporarily stored in culms and leaf sheaths before the heading stage [4]. The photosynthetic intensity and durability of the source leaves are essential for grain filling in the rice plant. Maintaining the vitality of functional rice leaves during the grain-filling stage guarantees carbohydrate synthesis and increased yield [5]. The final grain yield can increase by 1% if the leaf lifespan can be prolonged for 1 day during the grain-filling stage for the rice plant [6]
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