Effect Of Shading In Flowering And Boll-forming Stages On The Development Of Cotton Fibre And Physiological Characteristics Of Cotton Leaves

The experiment was conducted on the research farm of Shandong Agriculture University from 2003 to 2004. Two cotton cultivars, Lumianyan No.18(Lu18) and Zhongmiansuo No.41(Zhong41), which were different in fibre quality , were used to study the development of cotton fibre and physiological characteristics of cotton leaves through two experiment , shading at different intensity and shading at different stages.The main results are as follows: 1.Effect of shading on physiological characteristics of cotton leavesShading at both different intensity and different stages reduced photosynthetic and evaporation rate but increased the intercellular CO2 concentration of cotton leaves. The range of reduction and increase enhanced with the shading intensity increased. Fv/Fm and ΦPS Ⅱ was increased under shading condition. Fv/Fm and OPS Ⅱ in treatment I and treatment Ⅱ were lower slightly than that of CK in the influence of shading .Shading increased the content of chlorophyll a,chlorophyll b and the total content of chlorophyll in both of main-stem and sympodial leaves , but decreased the rate of chlorophyll a and chlorophyll b . The range of increase and reduction enhanced with the shading intensity increased.The content of chlorophyll a, chlorophyll b and the total content of chlorophyll was stillhigher than that of CK ,but the rate of chlorophyll a and chlorophyll b still decreased when the shading were ceased.The content of sugar in both main-stem and sympodial leaves was reduced under shading condition .And the range added with the shading decreased. The content of sugar in cotton leaves was still less than in CK when the shading were ceased, and treatment I has more effect on the accumula-tion of sugar in cotton leaves .The content of SOD and MDA in main-stem and sympodial leaves of cotton was reduced and the reduce range increased when shading intensity increased, but shading has no clear rule in effect of POD. Shading decreased the content of IAA and ABA,but increased the content of ZR and GA3. The content of IAA , ZR and GA3 reduced continued and ABA increased when shading in treatment I and treatment II were release from shading.2. Effect of shading on the accumulation of dry matter of cotton bollsThe accumulation of dry cotton boll weight, dry carpel wall weight and dry fibre weight were reduced under shading condition. And the accumulation falls more when shading intensity added.Dry cotton boll weight, dry carpel wall weight and dry fibre weight were still reduced when the shading ceased.3. Effect of shading on the accumulation and translation of sugar in cotton fibreThe content of soluble sugar and cellulose were reduced, and the range of reduction increased when shading intensity added . The content of soluble sugar and cellulose were less than that of CK in treatment I and treat-ment Ⅱ when shading ceased. Treatment Ⅲ has less effect on the content of soluble sugar and cellulose, which has no significant difference compared to CK. 4.Effect of shading on cotton fibre qualityWith the shading intensity increased,the maximum fibre length of cotton decreased and elongation period increased. Treatment Ⅰ has more effect on fibre length than treatment Ⅱ, and treatment Ⅲ has no effect on fibre length. That shows sunlight within 20 days of boll age has significant effects on the elongation , but shading after 20 days has less effect on the elongation . Treatment Ⅲ has no effect on fibre length .Fibre gauge tenacity of 0 mm and 3.2 mm isolation were decreased under shading condition and the range increased when shading intensity increased . The range in treatment Ⅱ is higher than that of treatment Ⅰ and treatment Ⅲ.Fibre micronaire was decreased under shading condition and the range was larger when shading intensity increased ,but there is no significant difference between different shading. Treatment Ⅱ has more effect on influencing fibre micronaire.Fibre maturation was lower under shading condition, and the range become lager when sunlight dropped . Shading at earlier stage has more effect on fibre maturation than at later stage . Shading at different stages can decrease fibre maturation ,among three treatments treatment Ⅱ has more effect and treatment Ⅰ less,and treatment Ⅲ has the lest effect on influencing cotton fibre maturation.