Abstract:

It is important in the long term to explore and exploit the potential of plant traits contributing to the nitrogen (N) absorption efficiency of rice. Root is primary organ for rice to explore and utilize N nutrient. However, little knowledge is known about the relationship between N accumulation and rice root traits. A solution culture experiment was conducted in 2001 and 2002, using eighty eight and one hundred and twenty two conventional indica rice varieties, respectively. A total of 13 traits responsible for morphology and physiological activity of rice roots was measured at heading stage while dry matter accumulation and N accumulation were determined both at heading and maturity. The tested rice varieties were classified into 6 types based on their N accumulation at maturity by the MinSSw method, and the differences of root traits between the types were analyzed to investigate the main root traits that significantly affected the N accumulation level. The average N accumulation of different types of rice varieties varied significantly, from 10.40 to 25.13 g·m^-2 in 2001, and from 8.53 to 33.31 g·m^-2 in 2002, respectively. Both whole growth duration and N uptake per day significantly affected N accumulation at maturity with the determinant coefficient ranged from 0.960 to 0.996, and the latter was more important than the former. N accumulation was closely correlated to number of adventitious roots per plant, root dry weight per plant, total length of adventitious roots per plant, total root absorption area per plant, root active absorption area per plant and total α-NA oxidizing amount of roots per plant, other than the traits for single adventitious root or root activity per unit dry weight. Polynomial stepwise regression analysis showed that N accumulation at maturity was significantly influenced by root dry weight per plant, ratio of shoot to root, number of adventitious roots per plant and total length of adventitious roots per plant (R²＝0.429－0.591). Morphological and physiological evidence in this study provided some prospects for improvement of root traits to improve N accumulation in indica rice.

Key words: Indica rice, Varieties, N accumulation, Root morphological and physiological traits