Genotypic difference in rice yield and zinc partitioning in rice grain response to different Zn²⁺ activities

Two rice genotypes which are different in zinc content (Biyuzaonuo and Zhenong 921) were cultivated at different Zn2+ activities(pZn2+ l1.4，l1.0，10.3 and 9.7) in chelator-buffered nutrient solutions. The rice yield, quality and zinc partitioning in grain response to different Zn2+ activities and the genotypic differences were studied. The results show that different Zn2+ activities have significant effects on rice yield per plant through effective panicles per plant, spikelet numbers per panicles, seed setting rate and 1000-grain weight. Effective panicles per plant is mostly affected, spikelet numbers per panicles is less, and the effect on seed setting rate is relatively little, while they are in obvious differences between the two genotypes. Different Zn2+ activities also have significant effects on grain zinc contents. The zinc content in grain is decreased with the decreasing of Zn2+ activity and the decrease is significant when Zn2+ activity is lower than 10.3, and the zinc content in Biyuzaonuo is much higher than that in Zhenong 921 at any Zn2+ activities. From the distribution of grain zinc, the zinc contents in grain hull, brown rice and milled rice are increased with the increase of Zn2+ activity. When pZn2+ is increased from 10.3 to 9.7, the zinc contents in brown rice and milled rice of Biyuzaonuo are decreased, while that in grain hull is increased and much higher than that in brown rice, and for Zhenong 921, the zinc content in grain hull is higher too. The zinc ratio of brown rice to milled rice is from 0.79 to 0.90, and the ratio is the smallest when pZn2+ is 9.7. In conclusion, it is a cost-effective way to improve zinc in rice by selecting zinc-rich rice genotypes, and the improvement of zinc nutrition by increasing Zn2+ activity can also improve zinc content in rice grain.