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Changes of sink source characteristics during the cultivar improvement in rice in China

Huang Yumin 1 Chen Qifeng 2 Li Yizhen 1 ( 1 Rice & Wheat Research Institute of Fujian Academy of Agricultural Sciences, Fuzhou 350001; 2 College of Crop Science, FAU, Fuzhou 350002)  
Main rice cultivars at different historical stages were observed to study the evolution of sink source structure. The results were as follows:(1) In past forty years, the rice cultivars in Fujian had experienced the evolution from long stalk to dwarf and then to hybrid rice, which caused the increase yield by 55%.(2) As the cultivar improvement, the sink storage capacity had increased by 63%, of which about 20% was from the increase in spike number and 80% was from the increase in kernel number per spike. The setting percentage and 1 000 grain weight kept stable. (3) The cultivar improvement in rice raised the photosynthetic product accumulation ( W ) by 40%. The increase in dry matter accumulation was mainly from the extension of leaf area index (LAI) and prolongation of growth duration, but the net assimilation rate (NAR) had decreased. Since the erect leaves of top leaf layer of improved cultivars let much solar radiation transmit into lower layer of rice colony, the NAR didn ′t decrease so much with the increase of LAI. Meanwhile, the accumulation of non structural carbohydrate in vegetative organs and accumulation of dry matter after heading of improved cultivars increased significantly. Therefore, the economic coefficient appeared higher and the sink source structure could keep balance at high yield level.
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