Research On The Distribution Of The Photosynthates Of Cotton In "Boll-Leaf System" With Different Water Stress

This experiment was conducted in canopy at West Campus Teaching Experiment Station from 2006 to 2007,in Agricultural University of Hebei.Bt-transgenic genotype XinMian33B was used as the material.The moisture content control was started at full-bud stage.three levels were set up:the serious drought stress(soil relative water capacity 35%～45%),the moderate drought stress(soil relative water capacity 45%～65%)and the comparison(soil relative water capacity 65%～85%).By feeding ¹⁴CO₂ on different leaf position at different stage,the translocation and distribution regularity of photosynthates under different drought stress was researched.The aim was to define the photosynthates assignment of different spot "source" and the allocation of the assimilation products in the "sink" organ.Simultaneously,the seed cotton yield and the cotton fibre quality had been analyzed.The results showed that:The product's assimilation quantity of ¹⁴C photosynthesis(expressed by the total radioactivity,the same below)of the main stem leaf and the fruit-bearing branch leaf and distribution characteristics were different for the water conditions,location and development stages.The ¹⁴C- photosynthates of the main stems and fruit branches were reduced with the arid degree increased and increased as the time postponing and the upper shift on the position,only except that the product's assimilation quantity of the lower part main stalk leaf were smaller at the beginning of florescence stage than at full-bud stage and the product's assimilation quantity of the inside-bottom fruit branch leaves were the biggest at the beginning of florescence stage.Moreover,in the majority times,the source leaves's assimilation quantity had not displayed the remarkable difference in the moderate drought and the comparison treatment.In the full-bud stage,The majority of ¹⁴C- photosynthates of the bottom main stems were detained in the mark leaves under the three water treatments,and only a small portion of photosynthetic products distributed to the tiny bud,and the proportion of photosynthates detained in the feeding leaves were the smallest under the severe drought stress;Moreover, the photosynthesis product ratio transported to the main stalk growing point and root were obviously higher than the moderate arid coercion and comparison treatment. At the beginning of florescence stage,the ¹⁴C- photosynthates detained in the bottom main stem leaves were sharply declined compared with the full-bud stage,the reduced degree increasing along with the drought stress degree enhancement.Under three kinds of moisture content conditions the ¹⁴C- photosynthates ratio assigns to inner encircles boll's ratio to be biggest under the severe drought stress,on the side,though the ¹⁴C photosynthesis product assigned to the main stalk growing point and the root has certain extent reduction under severe drought stress and moderate arid,but the distribution ratio was still obviously higher under the serious drought treatment than the moderate arid treatment and comparison;the photosynthesis product of inner encircles fruit branch leaves mainly assigned to its corresponding boll,next was fruit branch other,the ¹⁴C-photosynthates ratio assigned to the marked leaves increased along with the arid coercion degree increases,the tendency assigned to the fruit-bearing branch other was opposite.In the florescence stage,the lower peripheral boll had a high ¹⁴C- photosynthates ratio allocated to its corresponding boll under the drought stress than the comparison. Moreover,there was a significant high distribution ratio from the lower peripheral boll to the inner encircle boll and the main stalk growing point under moderate arid than comparison,simultaneously,there was a significant high distribution ratio to fruit-branch other under the moderate arid and comparison than severe drought stress;The majority of photosynthesis product assigned to the inner encircles boll and it had a significant high distribution ratio under the severe drought stress than the moderate arid and comparison.At the same time,The majority of photosynthesis product assigned to the inner encircles boll and others were a significant higher under the moderate arid and comparison than severe drought stress,moreover,the ¹⁴C- photosynthates ratio allocated to fruit-branch other were reduced along with the arid coercion degree increased,simultaneously,there was a significant low distribution ratio to the others under the moderate arid than the severe drought stress and comparison.In the flourish boll-forming stage,compared with the moderate arid and comparison, the majority of photosynthesis product assigned to the inner encircles boll but only a little to the corresponding boll under the severe drought stress.In addition,compared with the severe drought stress and comparison,the moderate arid had the largest photosynthesis product's distribution ratio to the fruit-branch other;A majority of photosynthetic products in the upper main stem leaf assigned to the inner encircles boll and others,the former distribution ratio increased with the increasing degree of drought stress but the latter was opposite.At the same time,the distribution ratio to the inner encircles boll was the maximal under severe drought stress and the minimum under comparison;the most photosynthetic products of the upper inner encircles fruit-branch leaves allocated to the corresponding bell,the has the same rule with the upper main stalk leaf,Moreover,there was a significant high distribution ratio to its hypogynous branches under the severe drought stress than moderate arid and comparison.Different water treatments as also affected cotton leaf area index,cotton fiber quality and Seed Cotton Yield.The leaf area index reduced along with the arid stress degree.On the cotton fiber quality and Seed Cotton Yield,the comparison treatments had the highest yield,the most reasonable Yield Components and the best quality;the ultimate yield of the moderate arid was slightly lower than the comparison although its individual location had a better Micronaire value;Compared with the moderate arid and comparison,the cotton fiber quality of the severe drought stress was obvious declined which causing the Seed Cotton Yield to be conspicuous lower than the comparison and the moderate arid.