Studies On The Canopy Structure, Photosynthesis And Genetics In Super-High-Yield Hybrid Rice By Two-Line System

Three TGMS lines including peiai64S , 98073S and Kang201S crossedwith 10 restorer lines to produce 15 combinations with super-high-yieldpotential. Taking a high-yield hybrid rice Shanyou 63 as check, all FI hybridsand their parents were grown under field conditions in 2000.The results showedthat 13 combinations had a higher grain weight per plant (GWP) compared withthe check .Among them two combinations increased in GWP significantly at1% level and three significantly at 5% level .In order to understand the- morphological and physiological basis of super-high-yield hybrid rice and toidentity selective criteria for the parents related, the relationships amongmorphological traits, quality criteria of canopy structure photosynthesis andyield components were studied by using correlative analysis and pathanalysis .The offspring-parent relationships of some important traits mentionedabove were also studied .The main results obtained are summarized as follows:1. Increasing spikelets per panicle is a main approach to enhance the sinkcapacity of super-high-yield rice . But in the meantime , it isnecessary to have a coordinative increase in biomass and harvestindex(ffl).2.The combinations with a very significant increase in GWP over the check have advantages in dry matter accumulation before flowering, integrated leaf photosynthesis of the canopy, and harvest index. 3.Among the morphological traits of the canopy , those of the flag leaves have the most important effects on yield. Flag leaf length is positively correlated with biomass , Ffl and GWP at very significant level or significant level .But flag leaf width has no correlation with them . Therefore , to enhance flag leaf length is an effective way to solve the problem of source shortage. Whereas leaf angle and droopy angle of the flag leaves have negative effects on the canopy structure and yieldcomponents.4. The yield increase of the super-high-yield combinations is not from enhancing of LAI but from improving of canopy structure such as lower leaves getting more light resulting from the less light extinction coefficient benefited from the vertical leaf blades.5. Higher single-leaf net photosynthetic rate(Pn) and canopy net photosynthesis(CPn) of the super-high-yield combinations are the major reasons for their significant increase in yield.6. There is obvious advantage of Pn in super-high-yield combinations when photosynthetically active radiation (PAR, 1331.8 ?BS.Sumol.m'V1) is high, but contrarily in lower light intensiry(PAR, 587.8?4.8umol.m~2.s~1) environment.7. As to midday depression of photosynthesis , among 5 combinations tested, there are three types :the first type has little depression;the second type greater depression but recovers at pm.3:00;the third type also greater depression at pm.l:00 but remains the same at pm.3:00.S.Biomass , HI and GWP are positively correlated with CPn which is reduced by greater leaf angle and leaf width and light extinction coefficient but benefited from flag leaf area and flag leaf length.9. [(Pnl+Pn2)/2] x[(LAIl+LAI2)/2] can represents canopy photosynthetic capacity during grain filling period. Pnl, Pn2, LAI1 and LAI2 mean Pn and LAI at the start and the end of grain filling period respectively.10. Spikelets per panicle and 1000-grain weight have greater broad sense heritabilities . But the former presents heterosis in Fl and the latter contrarily. Therefore, it is easy to get sink capacity enhanced, but it is necessary to overcome 1000-grain weight disadvantage in Fl by means of selecting big grain parents.11. To get benefit from the Fl vigor of the dominant morphological traits affecting yield , it is essential to select parents with longer flag leaf. On the contrary, it is important to use parents with smaller leaf angle andsemi-dwarf culm. 12. Most of the Fl hybrids present higher Pn values than the mean of theirparents, and...