Root Morphological and Physiological Characteristics of Rice Cultivars with High Yield and High Nitrogen Use Efficiency

Abstract

The difference of root morphological and physiological characteristics of 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 levels. The results showed that the high-yielding genotypes showed distinct advantages over the low-yielding ones in root dry weight, root volume, total and active absorbing surface areas of root system, root oxidation ability of α-NA, and root bleeding intensity at each growth stage, indicating that the increase of productivity was accompanied by the improvement of root morphological traits and the enhancement of root physiological activities. Cultivars with different N-efficiency displayed diverse root morphological and physiological characteristics, even though they were all on a high-yielding level. Comparing with medium N-efficiency genotypes, the high N-efficiency ones showed lower root dry weight, root volume, root bleeding intensity and root total absorbing surface area for populations, but for single plants, the root dry weight, root volume, root bleeding intensity, active absorbing surface area and α-NA oxidation amount were superior in a significant or extremely sig-nificant degree. The results above suggest that the coordination of high-yielding with high N-efficiency could be achieved through controlling population growth properly, facilitating the concordant development of plant population and individuals, and endeav-oring to improve the single stem root quality after heading.