| Indica hybrid rice Xinongyou10 andⅡyou838 as materials, we took field and pot controlling experiments and studied on the photosynthesis characteristics,plant type, grain filling characteristics and effects of density and fertilizer on the experimental field of Southwest University in 2009. The main results are as followings:1. At booting and heading stage, the chlorophyll content decreased after we put detached leaves of Xinongyou10 andⅡyou838 under natural strong light 7 days. At booting stage, compared with CK, the chlorophyll content of XinongyoulO decreased 61.8%, and the chlorophyll content ofⅡyou838 decreased by 51.7%, to reach important significant difference. At heading stage, the chlorophyll content of XinongyoulO decreased by 50.5%, and the chlorophyll content ofⅡyou838 decreased by 37.9%, also to reach important significant difference. Therefore, photooxidation tolerance ofⅡyou838 is stronger than that of Xinongyou10.2. At tillering stage, we put plant into shading conditions 15 days and the plant' dry matter weight decreased. Compared with CK, dry matter weight of Xinongyou10 decreased by 56.3%, and that ofⅡyou838 decreased by 58.2%. Decreased ranges were more than 50%, so they both are poor shade tolerance varieties. The two varieties had different responses on shading conditions, compared with control, the tillers of Xinongyou10 decreased rapider and total top three leaf area ofⅡyou838 decreased faster.3. After shade-grown rice leaves suddenly exposed natural sunlight, the photosynthesis rate and diurnal photosynthesis accumulation both decreased, and photoinhibition happened. In shading treatments, compared with CK, the diurnal photosynthesis accumulation of Xinongyou10 decreased to 89.37%, and the photosynthesis accumulation ofⅡyou838 decreased to 94.93%, to reach significant difference. So the photoinhibition of Xinongyou10 was heavier thanⅡyou838. After 3 days, the photosynthesis accumulation of Xinongyou10 increased by 5.32%, andⅡyou838 increased by 2.74%. Therefore, Xinongyou10 photo recover faster.4. The photosynthesis rate of Xinongyou10 was faster than that ofⅡyou838, and diurnal photosynthesis accumulation of Xinongyou10 was more than that ofⅡyou838.5. At different density and fertilizer levels, the specific leaf weight (SLW) of Xinongyou10 was 4.1 mg/cm2, and SLW ofⅡyou838 was 3.7 mg/cm2 at heading stage, to reach significant difference. This may be reason for Xinongyou10 has faster photosynthesis rate and bigger photosynthesis accumulation. In addition, with the changes of density and fertilizer levels, the change of Xinongyou10 SLW was bigger thanⅡyou838, so the SLW of Xinongyou10 was more sensitive to density and fertilizer.6. With the changes of density and fertilizer levels, the changes of Xinongyou10 top four leaf areas were bigger than those ofⅡyou838. So we thought Xinongyou10 was more sensitive to density and fertilizer. From the top fourth leaf to the flag leaf, the leaf area changed less and less, we called this "Dilution Effect".7. With the changes of density and fertilizer levels, the top second leaf at booting stage, the average leaf basic angle, splay angle and crooked degree of Xinongyou10 was 25.7°,15.3°and 10.4°respectively. That ofⅡyou838 was 17.0°,12.7°and 4.3°respectively. Therefore, the leaf angle of Xinongyou10 was bigger, especially at low fertilizer and low density level, the leaf basic angle and splay angle both were biggest. So the leaf angle of Xinongyou10 is sensitive to density and fertilizer.8. At heading stage, the average sunlight transmittances of Xinongyou10 were lower than those ofⅡyou838 on 60cm,80cm, and 100cm leaf layers. From the ground 20cm,40cm, there were no significant differences in the average sunlight transmittance. The reason is that Xinongyou10 has larger leaf area, thick leaf, big leaf basic angle and splay angle.9. At early filling stage, the filling rate of Xinongyou10 was faster, and the filling rate ofⅡyou838 was slower, but at middle and late filling stage, the filling rate of Xinongyou10 were slower, and those ofⅡyou838 were faster.10. Density-fertilizer response:Variance analysis and multiple comparison on yield at different density and fertilizer levels. We thoughtⅡyou838 is suited for middle fertilizer level and high density. XinongyoulO is suited for low fertilizer or middle fertilizer level middle density. In the shallow topsoil and low fertilizer level paddy field, we adopt N 6～10kg/667m2 and density 13000～15000/667m2 holes, it is good for high and stable yield.Ⅱyou838 is suited for higher fertilizer-density level than Xinongyou10.
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