| The higher grain yield is the eternal subject for the breeding and cultivation of rice .At present, to increase the sink capacity and panicle weight per panicle is a key factor in super high-yielding breeding and cultivation of rice. The breeding model of heavy panicle type of rice (HPTR) has been considered as one of the main methods in breeding rice for super-high-yield, and with this model many varieties with heavy panicle and high yield have been bred and utilized widely in rice production. Sixteen to eighteen varieties(oryza sativa subsp . indica ) were used in the experiments conducted both in Wenjiang, Sichuan andYangzhou, Jiangsu in 2000 and 2001 . The morphology and the characteristics of physiology andbiochemistry and high-yielding potential of different panicle weight type of rice were studied to supply theorial and practical directions for the super-high-yielding breeding and cultivation of rice. The major results were as follows:l.Both the grain yield and yield potential of HPTR varieties was 10% higher than those of medium panicle type of rice (MPTR) varieties and the latter were over 15% higher than light panicle type of rice (LPTR) varieties. The HPTR varieties could easily harvest higher grain yield and possessed higher yield potential and had a stable grain yield between different ecological regions. The reason for the high grain yield of HPTR varieties was a little less effective panicle number, larger spikelet number per panicle, larger sink capacity per unit area and stable seed setting in compared with those of MPTR and LPTR varieties. 2.The grain-filling processes of HPTR varieties were obvious asynchronous between the strong and week potential grains, its vigorous filling phase was late, but had the long active grain-filling phase and grain-filling duration. If the growing condition was regular at the later grain-filling stage the grain-filling of HPTR varieties could also reach the normal level of MPTR and LPTR varieties.3.The leaf area index (LAI) of HPTR varieties was a little lower than that of MPTR and LPTR varieties, but its decreasing rate of LAI after heading was slower and had much higher percentage of efficient LAI and grain-leaf area (cm2) ratio in comparison with MPTR and LPTR varieties. The chlorophyll content and SOD activity in leaves of HPTR varieties were higher and decreased slowly after heading than those of MPTR and LPTR varieties. There was a high efficiency of assimilate's transportation to panicle in leaves of HPTR varieties. The net photosynthetic rate (Pn) of HPTR varieties was significantly higher than that of MPTR varieties and the latter was significantly higher than that of LPTR varieties due to the corresponding change of Rubisco activity and chlorophyll content. In comparison with MPTR and LPTR varieties, HPTR varieties had an ability of keeping high level photosynthesis and Pn under high or low light intensity, high temperature and low CO2 concentration. The results showed that HPTR varieties were resistant to poorclimate conditions. For the stomatal characteristics, it was found that higher Pn mainly resulted from its higher total quantity of stomatal opening degrees of HPTR varieties. So, HPTR varieties showed a potential ability of super-high-yield in its supply of source.4.The number of vascular bundle, the area of vascular bundle, phloem, xylem, cross section of stem, culm wall and pith in the first internode and the number and area of vascular bundle in the branches of HPTR varieties were larger than those of MPTR varieties and the latter were larger than those of LPTR varieties. The vascular bundles had the similar load of spikelet number and sink capacity among HPTE, MPTR and LPTR varieties. The characteristics of the conducting tissue in the first internode and the branches were not related to the empty-grain percentage, but played an important role to the grain-filling, and were a basic structural factor to good grain-filling. The number of vascular bundle, the area of vascular bundle andphloem, total sink capacity per...
|
PDF Full Text Request