Characteristics of Roots Traits in Conventional Indica Rice Cultivars with Large-Panicle

Eighty-eight and one hundred and twenty two conventional indica rice cultivars were solution-cultured in 2001 and 2002, respectively. Dry matter weight (including root system, culm and sheath, leaves, panicle), root traits, root physiological activity, yield and its components were measured. The tested rice cultivars were classified into six types (i.e. A, B, C, D, E, and F, A was the lowest, and F was the highest) based on their panicle weight level by the MinSSw method, to study their differences of root traits, root physiological activity. Difference of panicle weight of the cultivars used in this study was very large (the ratio of the maximal panicle weight to the minimum panicle weight in 2001 and 2002 were 493% and 764%, respectively), the average of panicle weight was 0.99, 1.56, 2.00, 2.54, 3.16, and 4.08 grams per panicle in 2001, and 0.82, 1.38, 1.80, 2.38, 3.04, and 4.29 grams per panicle in 2002, respectively. Root dry weight per plant, total length of adventitious roots per plant, and total root ab- sorption area per plant in large-panicle type cultivars higher than those in small-panicle type cultivars. Number of adventitious roots per panicle, root dry weight per panicle, length of adventitious roots per panicle, total root absorption area per panicle, root active absorption area per panicle, and root activity per panicle in large-panicle type cultivars were higher than those in small-panicle type cultivars. Polynomial regression analysis showed that panicle weight was significantly influenced by length of adventitious roots per panicle, root dry weight per panicle, ratio of shoot to root at heading stage, root activity per panicle, and the determinant coefficient ranged from 0.620 to 0.639. Larger panicle weight could be reached by increasing length of adventitious roots per panicle, root dry weight per panicle, ratio of shoot to root at heading stage, root activity per panicle.