Relationship between yield formation and leaf nitrogen content and color in rice plant

Relationships between nitrogen contents in leaf at different stages and tiller emergency,spike,grain and yield formation were studied with six middle and late maturity rice varieties.The results indicated that tillering percentage increased with enhancing nitrogen content in leaf,suitable nitrogen contents in leaf for tillering emergency and termination enhanced with the delay of tillering stage.Spikelet number per spike was mainly affected by the nitrogen contents in the first and second leaf from the top,productive grain percentage was related to nitrogen content at heading stage,and suitable nitrogen contents in leaf for spikelet differentiation and productive grain formation were 27?28 g·kg -1 and 25 g·kg -1 in Japonica and Indica rices respectively.Color of four top leaves in main stem at N-n,N- 1 and heading stage was similar with or slightly darker than that of three top leaves,which was a common characteristic for high yield in different rice varieties.In addition,suitable leaf nitrogen content indices for high yield in rice plant were provided.