| Measuring the agronomic traits and yield,fiber quality and the features of cotton canopy structure, under the increased density and late seed sowing condition, it provide the theory basis for the reason why chemical detopping could instead of manual topping, with C619 (Al) and JX013 (A2)used as experimental materials,at Liuyang in2014. The chemical detopping agent contained mepiquat chloride or flumetralin solution. At the same time,C619 as material,other field experiment was conducted about the effect of four differnt defoliation ripenning methods for the charateristics of the boll opening. The result are as follows:1,There were basically no signficant differences in plant height by the different concentration of chemical detopping solution treatments at the same variety.and the heights of cotton plants by flumetralin(F1,F2and F3)were higher than the contolplants of cotton by DPC(D1and D2). However, it was showed that the number of sympodials among the treaments under the same varity were increased.2,After ripening,the effect of opening bolls of JX013 was better than that of C619, and the remaining treatments were lower than the control, expect that the treamnts of F1and F2 were as well as the control.3,While the single boll weight of A1D1,the lint precentage of A1D2,the boll number per plant and the single boll weight of A2D1 were significantly different with the control,the factors of yield of all treatments were similar to that of the control plant.As a result, the theory of seed cotton yield and lint yield of F1 were equivalent to the control’s,when others were significantly or very significantly lower.4,Except that the uniformity index of A2F2 and the micronaire of A2D1 were significantly higher than the control’s, the chemical detopping treatments had no siginificantly influence on the five indexes of fiber quality.5,It’s obviously that the structure of canopy of Fl was quitely better, providing better photosynthetic environment for the yield formation.While the SPAD of all treatments increasing as the passing of development stage, the change carves of LAI on the middle and bottom of canopy were "w", and the PAR and light transmissivity on the middle canopy were single peak crave with upward opening.From the flowering to boll opening stage, LAI and PAR varied with height of the cotton canopy, listed as middle of cotton canopy> lower of cotton canopy,with the change range of LAI of C619 bigger than that of JX013.6,The results showed that the effect of 40% ethephon 900 g/hm2+20% paraquat 600ml/hm2 was more better.And its defoliantion rate and boll opening rate, the highest of all treatments, were 60.5% and 73.25%,which the theoretical seed yield was signficantly lower than CK. To comparing CK,the influences of the remain treatments to the numbers of boll of a plant,the boll weight,the lint precentage,the seed index and the lint index were not obviously.Meanwhile,the fiber quality of four agents were simliar to CK,except the elongation of T2 obviously lower than CK. |
