Effect Of Water Stress On Source-Sink Relation Of Different Boll Weight Genotypes In Cotton

Three cottons genotypes, small-boll genotype CeHengDaMianHua, middle-boll genotype XinMian33B, big-boll genotype SuMian9108, were used to study the harmony of source-sink under water stress. The author scientifically studied the changes of plant morphology, physiological and biochemical characters, yield and fiber quality in different boll-weight genotype cottons. The results were as the follows:1. Under water stress, the growth of cotton was restrained, dry matter weight decreased. The growth stages were advanced under drought conditions, and the growth stage of small-boll genotype advanced most.2. The plant height of each boll-weight genotypes declined and the leaf area decreased under water stress. (After July 17)The LAI of each genotype under water stress was lower than that in normal condition. When it reached the highest under water stress, the LAI was about 46.7%-70.2% of that in normal condition.3. Under water stress, the soluble sugar content of main stem leaf and different branch leaves increased to different level, the starch accumulation were restrained significantly, but the changing trend of soluble sugar and starch of different boll-weight genotypes were the same. After flowering stage (July 5), the change of soluble sugar content of small-boll genotype was more stable than middle-boll and large-boll genotypes, and the starch content in upper branch leaf was more obvious than in middle and lower branch leaves in big-boll and middle-boll genotypes, except the small-boll genotype.4. Under water stress, the proline content increased and the content of soluble protein reduced. The change of soluble protein of middle-boll genotype in stem leaves was not significant, that of middle and lower branch leaves were the same. There was no difference among genotypes in upper branch leaves, the change of soluble protein of seed in lower position was bigger than that of middle and upper position, and that of middle-boll and small-boll was bigger than big-boll genotype in middle and lower branch leaves.5. The cell membrane systems of cotton were harmed and the osmotic capability boosted up under water stress, relative MDA content increased. Different genotypes suffered differently. The changes of MDA content in branches of each position were the same in the two treatments.6. Protective enzyme activities of different cotton genotypes were rising, such as SOD and POD. The contents of SOD and POD were different at different position and fordifferent genotypes.7. The content of chlorophyll, chlorophyll (a/b) ratio, net photosynthetic rate, of every cotton genotype decreased under water stress. The changes of chlorophyll in different branch leaves had different changing tendency.8. Under water stress condition, the yield of big-boll genotype decreased about 19.6%, middle-boll genotype decreased about 16.7% and the small-boll genotype decreased about 24.9%. The quality of each genotype decreased too.9. It was a complex problem of water stress to the harmony of cotton source-sink. The results showed that the harmony of middle-boll genotype XinMian33B was the best, the next was big-boll genotype SuMian9108, the small-boll genotype was the third.