Characteristics of Dry Matter Accumulation and Translocation in Rice Cultivars with High Yield and High Nitrogen Use Efficiency

Abstract

The difference of dry matter production and translocation characteristics in low-yielding and low N-efficiency, high-yielding and medium N-efficiency, high-yielding and high N-efficiency rice cultivars was investigated using six representative japonica varieties under their optimum N supply levels, respectively. The results indicated that: with the increase of rice productivity, the total dry matter production amount significantly increased by 20.29% on average, and the dry matter accumulation amount and population growth rate increased on average by 15.05%, 27.04%, 24.75% and 15.05%, 28.38%, 23.00%, during the period before N-n (critical stage of productive tillering), from jointing to heading, and from heading to maturing, respectively, and decreased during the period from N-n to the jointing. Among the high-yielding varieties, with the nitrogen use efficiency increased, the tiller number per unit area at each growth stage showed a downward trend, and significantly reduced on average by 5.76%, 11.61%, 7.01%, and 5.70% at N-n, jointing, heading and maturing, respectively, but ratio of productive tillers to total tillers significantly increased. At each growth stage, the dry matter accumulation amount showed a declined tendency, and reduced on average by 12.18%, 10.54%, 8.29%, and 5.01% at N-n, jointing, heading and maturity, respectively, but harvest indexsignificantly increased. During the period from heading to maturing, dry matter accumulation rate increased on average by 5.40%, the population growth rate increased on average by 5.19%. The results above showed that proper control for population growth before heading, maintaining a high growth rate after heading and a higher harvest index were the important dry matter accumulation characteristics of the cultivars with high-yielding and high nitrogen use efficiency.