Regulation Of Photosynthetic Characteristics In Island Cotton(Gossypium Barbadense) Leaves And Its Relationship With Production

Island cotton,as an important economic crop,has excellent fiber quality but low yield.Under the pressure of continuous shrinking of the island cotton planting area,increasing the production per unit area is the main way to solve the island cotton production.Biomass is the material basis of crop yield,and more than 90% comes from photosynthetic substances formed during photosynthesis.Therefore,improving the photosynthetic efficiency of island cotton leaves is one of the main ways to increase production.The leaves are the main organs for the production of photosynthetic substances,and their photosynthetic characteristics have a certain degree of heterogeneity.There is obvious cupping in the leaves of island cotton,and there are differences in the light energy received by the leaves and leaves of different orientations along both sides of the main vein,which exacerbates the heterogeneity of photosynthetic performance of the leaves.In this study,the differences of light energy in island cotton with different orientation leaves and different parts of the same leaf were firstly studied.The heterogeneity of leaf morphology and photosynthetic characteristics was studied,and the criteria for leaf selection when determining the photosynthetic performance of island cotton leaves were determined.Through simulation experiments,the possible regulatory mechanisms of leaf heterogeneity were explored.On this basis,the photosynthetic characteristics and production capacity of different island cotton resources were studied.The natural genetic variability of photosynthetic characteristics of island cotton was preliminarily clarified,the influencing factors of photosynthetic capacity were revealed,and the relationship between photosynthetic capacity and production of materials was discussed.The research results can lay a theoretical foundation for the cultivation of high-quality and high-yield island cotton varieties.The main research contents and results are as follows:1)The heterogeneity of light energy received by island cotton leaves and its relationship with photosynthetic characteristics were studied.The light energy and photosynthetic characteristics of the leaves with different orientations along the sides of the main vein were measured.The results show that there is heterogeneity in the light energy received by the island cotton in different orientation leaves and the main veins in the same orientation.The southward leaf receives the highest light energy,followed by the eastward and westward leaves and the northward leaf.Cupping Leaf results in strong heterogeneity of the light energy received on both sides of the main vein of the east and west direction,while the heterogeneity of the south and north direction leaves is weak.Under light heterogeneity,the leaf area and specific leaf weight of the eastward and westward leaves in the low-light environment were significantly less than that of the light energy,while the leaf area and specific leaf weight of both sides of the main vein in the south and north direction were not significant difference.Further analysis of photosynthetic pigments showed that the chlorophyll a content,chlorophyll b content,total chlorophyll content,and carotenoid content of the same leaf in the low light environment were significantly higher than the light energy interception side,and the ratio of chlorophyll a/b was significantly lower than that of leaf part can intercept more light.The low light environment of the blade partially improves the ability to capture light energy to adapt to the low-light environment in which it is located.Under the influence of factors such as anatomical structure and pigmentation,the net photosynthetic rate of leaves in the low-light environment on both sides of the main stem of the east-west direction leaves was significantly lower than that of the strong light environment,but there was no significant difference between the two sides of the main vein of the south and north direction.Therefore,in the related research of leaf photosynthetic performance,considering the same leaf position,we must fully consider the difference between the azimuth of the leaf and the different parts of the same azimuth leaf,so as to increase the comparability and reliability of the test results.2)The systematic regulation of photosynthetic characteristics heterogeneity of the same leaf of island cotton was studied.The morphology,anatomical structure and photosynthetic characteristics of the two parts were determined by shading the two sides of the main vein of the same leaf.The results showed that the maximum net photosynthetic rate,light saturation point,light compensation point,leaf thickness,leaf area,and lwaf mass per area of both sides of the main vein of the island cotton leaf were heterogenous under light heterogeneity.By comparing the unshaded leaves measured along the main vein,it was found that the photosynthetic capacity,leaf thickness,and photosynthetic pigments of the unshaded leaves along the main vein were significantly lower than those of the entire unshaded leaf.This shows that the shading part of the leaves of the island cotton has negative regulation on the morphology,anatomical structure and photosynthetic characteristics of the unshaded part.In addition,the photosynthetic apparatus on the side of the low-light environment of the leaves is under the stress of the light environment,which also inhibits the photosynthesis.At the same time,the shading of the leaves of the island cotton has a negative effect on the morphology,anatomical structure and photosynthetic characteristics of the unshaded part.In addition,the effects of different shading methods on the morphology and structure of island cotton leaves were studied.The results showed that: when the island cotton leaves were treated with different shading methods,their system control methods were different.The shaded seaweed leaves of the whole plant become bigger and thinner to capture more light energy to adapt to the low light environment of the whole plant;while the single leaf or leaf part is in the low light environment,and the low light part leaf area becomes smaller and thinner.By reducing the leaf area of the weaker part photosynthetic capacity,the shading of the lower leaves is reduced,which is conducive to maintaining the normal growth of the plants.3)The photosynthetic capacity of the island cotton leaves and the relationship with the production of photosynthetic substances were studied.The gas exchange parameters and biomass of the leaves were determined.The results showed that there was a positive correlation between photosynthetic rate,stomatal conductance and leaf conductance,indicating that stomatal conductance and leaf conductance were both factors affecting the photosynthetic rate among the island cotton varieties(lines).At the same time,there was a significant positive correlation between photorespiration rate and leaf conductance,but there was no significant correlation with stomatal conductance.Further analysis found that there were significant natural genetic variability in photosynthetic capacity and biomass accumulation of leaves,of which the natural variability of photorespiration rate was the largest,and there was a significant positive correlation with biomass accumulation.This may be in a higher temperature and light environment in Xinjiang.Higher photorespiration not only helps reduce photoinhibition,but also promotes nitrogen transformation,which is beneficial to the production of photosynthetic substances and promotes the accumulation of biomass.