| The experiment with three row distances and two hill distances was conduced with two conventional japonica rice varieties Shendao 47, Shendao 6 and one hybrid Liaoyou 52210 to study the effects of physic and mechanic features, panicle factors under various row-hill spacing on the lodging resistance of japonica rice cultivars. At the same time, the effects of row and hill spacing to Japonica rice on light interception capacity, population light distribution, light conversion efficiency at full heading stage and yield were studied. The results showed that:1. Effects of row-hill spacing on the yields and canopy structure of rice at full heading stageThe leaf area indices at full heading stage, closely related to light interception, were increased first and then decreased with the decrease of transplanting density. The extinction coefficient in one day increased first and then decreased, and the K value was increased with the increase of planting density. Yield was positively correlated with canopy extinction coefficient and inclinations of the upper three leaves. In terms of energy efficiency, the yields were positively correlated to flag leaf stomatal conductance, intercellular CO2 concentration and transpiration rate. At the configuration of high (25 cm×15 cm) and low (30 cm×20 cm and 35 cmx20 cm)density, Japonica rice could increase light interception capability or optical conversion efficiency respectively, but potential lodging and less panicles of per unit area limited obtaining high and stable yields. At the configurations of 30 cm×15 cm and 25 cmx20 cm, it was easy to get adequate panicles, optimize the structure of the canopy, reduce lodging risk, and obtain high yield. Erect panicle type rice cultivar helped improve the population structure and light distribution, and had higher PAR interception rates as well as strong functional leaf photosynthetic capacity, which should be an important parameter for variety breeding in north area.2. Effect of row-hill spacing onlodging resistance of rice with different paniclesRow and hill distances simultaneously impacted the physic and mechanic features of japonica rice plant, thereby enabling different panicle Japonica rice exhibit different lodging capacity. Liaoyou 52210 significantly increased in height and decreased in flexural strength from 20 cm hill distance, which were the main factors of higher lodging index. Some traits of Shendao 47 and Shendao 6 at the configuration of 25 cmx20 cm decreased significantly, including plant height, the length and fresh weight of base N2 section, panicle angle, panicle length, fresh panicle weight and panicle gravity. At the configuration of 35 cm×l5 cm, the cross-sectional area and flexural strength of the three japonica rice cultivars were greater than those of other configurations significantly. From the perspective of panicle type, the adaptabilities of lodging resistance of Shendao 47 and Shendao 6 to the change in the configuration were better than that of Liaoyou 52210. The three japonica rice cultivars in the configuration of 25 cm×15 cm,30 cmx20 cm and 35 cmx20 cm had larger panicle angle significantly than others, and in the later two configurations not only fresh panicle weight and panicle length were higher, but also the height of panicle gravity. Generally, at the configuration of high and low density, potential lodging and less panicles of per unit area limited obtaining high and stable yields respectively. In the configuration of 25 cm×15 cm and 35 cm×20 cm, flexural strength and bending moment were to become the inducible factor of lodging index increased, which indicating that both tense and sparse planting are unfavorable for lodging resistance and the flexural strength in base internode is the main target to increase the lodging resistance. When selecting cultivars with lodging resistance, the suitable base internode bending moment should be considered, in that the greater biomass is guaranteed for lodging resistance. |
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