Studies on the Density- tolerance Rice Varieties with Different Panicle Types in Two Planting Densities

To study the density-tolerance of semi-erect panicle type in rice,14 Japonica varieties,belonging to 3 spike types,were grown in the two densities level( 30 cm,25 cm). The results show that,in low density,leaf area index( LAI) of the semi-erect panicle type varieties was significantly lower than that in the curved panicle type varieties,efficient leaf area of semi-erect panicle type variety was significantly greater than that of the upright rod spike type and curved panicle type varieties. During increasing the density,LAI in semierect panicle type varieties show little changed,but the high efficient leaf area was increased significantly. In high density,plant height and ear length in semi-erect panicle type varieties were significantly reduced compared with the curved panicle type varieties. Grain density in semi-erect panicle type varieties was significantly lower than that in the upright rod spike type cultivars. In semi-erect panicle type,flag leaf and top 2 leaf length was significantly longer than that in the upright rod spike type cultivars,leaf width was significantly wider than that in the curved panicle type varieties. With increasing the density,individuals of semi-erect panicle type tend to convergence. In high density,semi-erect panicle type show higher lodging resistance than the curved panicle type varieties,higher seed setting rate than the upright rod spike type cultivars,and higher milled rice rate and yield. Taken together,semi-erect panicle type is more density tolerant than two other spike types,which attributed to,suitable ear rise and plant height( 85 cm ~ 90 cm),increasing individuals convergence and effective leaf area,more panicle number per square meters and lodging resistance. Thus,the total yield of semi-erect panicle type is significantly increased in high density,which is the key and base for high density growth cultivation.