Basic Characteristics Of Conventional Japonica Rice Cultivars With Different Sink Capacity

To analysis evolution trend and differences of related traits among conventional japonica rice cultivars with different sink capacity and the basic characteristics of related traits in conventional japonica rice cultivars with large sink capacity, and to provide some reference basis for genetic improvement and high yield cultivation of conventional japonica rice cultivars, a total of 94 conventional japonica rice cultivars (lines) were solution-cultured in 2008 and 2009, respectively. Leaf-area-index (LAI), root morphology, root physiological activity, dry matter weight of different rice plant organs, nitrogen content at heading and maturity stages, and grain yield and yield components and panicle traits were measured. Based on sink capacity by the MinSSw method, these tested rice cultivars were clustered into 6 types in the alignment from low to high (A, B, C, D, E and F). Main results were as follows:1. Great differences in sink capacity per unit area were detected among tested rice cultivars. The sink capacity per unit area ranged from 502.926-1790.899 g·m^-2 in 2008 and 524.2-1675.183 g·m^-2 in 2009. The maximum of sink capacity per unit area was increased by 256% and 220%, compared with the minimum of sink capacity per unit area in 2008 and 2009, respectively. The mean value of sink capacity per unit area of A, B, C, D, E and F type was 619.18, 837.95, 983.67, 1165.49, 1328.23 and 1593.10 g·m^-2 in 2008 and 574.16, 694.63, 796.13, 899.61, 995.63 and 1224.21 g·m^-2 in 2009, respectively. The rice numbers of A, B, C, D, E and F type was 13, 15, 19, 15, 17 and 15 in 2008 and 7, 19, 25, 12, 17 and 14 in 2009, respectively. Significant differences in average sink capacity were observed between conventional rice cultivars with different sink capacity.2. Significant differences in the grain yield, the panicle numbers per unit area and spikelets numbers per panicle between conventional rice cultivars with different sink capacity were detected.Sink capacity were significantly correlated with grain yield, panicle numbers per unit area, spikelets numbers per panicle and filled grain percentage and wasn't significantly correlated with 1000-filled grain weight. Path analysis indicated direct path coefficient of spikelets per panicle to sink capacity had highest value, panicle numbers took the second, the 1000-filled grain weight had least value. The rice cultivars with large sink capacity had higher gain yield, panicle numbers per unit area, spikelets numbers per panicle and low filled grain percentage than other rice types.3. There were significant differences in the LAI (e.g. productive and non-productive leave) at heading, LAI at maturity, green leave weight at heading and maturity stages, sink capacity per panicle, sink capacity per unit dry matter weight, sink capacity per unit leave area and sink capacity per unit nitrogen uptake between conventional rice cultivars with different sink capacity. Sink capacity was strongly affected by above source-sink traits. While, there was little difference in the specific leaf weight between conventional japonica rice cultivars with different sink capacity. And, the difference in the grain yield per unit leave area was significant or not depended on years. The rice cultivars with large sink capacity had higher LAI and green leave weight and larger sink capacity per panicle, sink capacity per unit dry matter weight, sink capacity per leave area and sink capacity per nitrogen uptake than other rice types, while, lower specific leaf weight and grain yield per unit leave area than rice cultivars with medium sink capacity.4. The dry matter weight before heading, after heading and at maturity stages in rice cultivars with large sink capacity were significantly higher than those in rice cultivars with small sink capacity, especially dry matter before heading was. The harvest index in rice cultivars with larger sink capacity was greater than rice cultivars with small sink capacity, while that was inferior to rice cultivars with medium sink capacity.5. Japonica rice cultivars with large sink capacity had greatly higher amount of nitrogen uptake before heading, after heading and at maturity stages than japonica rice cultivars with small sink capacity, especially the amount of nitrogen uptake before heading, while, had less nitrogen use efficiency for grain yield than japonica rice cultivars with medium sink capacity. 6. Great differences in adventitious root numbers per plant, root dry weight per plant, adventitious root length per plant, root absorption area per plant, root active absorption area per plant were detected between rice cultivars with different sink capacity. Total adventitious roots length per plant, root dry weight per plant, total root absorption area per plant and root active absorption area per plant were higher in the rice cultivars with large sink capacity than other rice types. The japonica rice cultivars with large sink capacity were of characteristics of higher adventitious root numbers per plant, root dry weight per plant, adventitious root length per plant, root absorption area per plant, root active absorption area per plant.Significant differences in root dry weight per panicle and root active absorption area per panicle were observed between japonica rice cultivars with different sink capacity than other rice types. The difference in total root absorption area per panicle was significant or not depended on years. Japonica rice cultivars with large sink capacity had higher root dry weight per panicle, root active absorption area per panicle, adventitious root length per panicle than japonica rice cultivars with small sink capacity. The total root absorption area in rice cultivars with larger sink capacity was greater than rice cultivars with small sink capacity, while that was inferior to rice cultivars with medium sink capacity.There were significant differences in maximum root length, modal root length, single adventitious root length, single adventitious root weight between rice cultivars with different sink capacity. The difference in adventitious root weight per unit root length was significant or not depended on years. The modal root length, single adventitious root length, single adventitious root weight and root dry weight per unit root length in japonica rice cultivars with large sink capacity was higher than those in other rice types. The maximum root length in rice cultivars with larger sink capacity was greater than rice cultivars with small sink capacity, while that was inferior to rice cultivars with medium sink capacity.Shoot-root ratio was greatly differed between rice cultivars with different sink capacity. This trend was more obvious at maturity than that at heading. The rice cultivars with large sink capacity showed higher shoot-root ratio than other rice types.The correlation analysis indicated that sink capacity were significantly correlated with root traits per plant (including root dry weight per plant, adventitious root length per plant, total root absorption area per plant and root active absorption area per plant) and root trait per panicle (including root dry weight per panicle, total root absorption area per panicle, root active absorption area per panicle and adventitious root length per panicle) and root traits per root (including the maximum root length, modal root length, single adventitious root length, single adventitious root dry weight and adventitious root dry weight per unit root length) and shoot-root ratio at heading and maturity stages.A further analysis showed that the sink capacity per unit area was strongly affected by both panicle numbers and sink capacity per panicle, while, the correlation trend of sink capacity per panicle to sink capacity per unit area was higher than panicle numbers to sink capacity per unit area. There were significantly and positively linear relationships between sink capacity per panicle and root traits per panicle.In summary, root traits per plant, root traits per panicle, single adventitious root traits and shoot-root ratio in japonica rice cultivars with large sink capacity was superior to those in japonica rice cultivars with small sink capacity. View from sink capacity per unit area, the root traits per plant had obvious superiority over other traits. View from sink capacity per panicle, the root traits per panicle had obvious superiority over other traits.