Studies on the Photosynthesis.Efficiency in High Yielding Colony of Hybrid Rice

The colony growth rate(CGR)of hybrid rice at the yield level of 8～10 t/hm2 was 15.4～18.2 g/(m2·d), while from primary panicle emerging stage to heading stage was 19～28 g/(m2 d). The leaf area index(LAT)of the colony between booting to heading stage was 6.5～7.5,and the leaves in top layer were erect. Thus the sunlight was able to cast onto the deep part of the colony, the light intensity on leaves in the botom of colony was 2～3 times of the light compensa-tion point The averge net assimilation rate(NAR)during field growing period was 3.4～4.4 g/(m2· d); the total energy of solar radiation was 137～150 kJ/cm2 with the daily solar radiation(S)of 1445～1456 J/(cm2·d). The light-energy utilizing rate(EU)of the colony during field growing period was 1.67%～1.96%, While from primary panicle emerging stage to heading stage was 2.15%～2.70% with the highest of 3.75% in a short time. Path analysis showed that, before panicle initiation, LAI and S contributed more to CGR, and NAR and EU contributed rnore to CGK after the panicle initiation, However, S appeared a very significant position correlated to CGR and NAR after heading stage.