Effects Of Soil Waterlogging On Physiological Charateristics Of The Subtending Leaf During Flowering And Boll-Forming Stage

Flowering and boll-forming stage is the key yield determinant period of upland cotton. Soil waterlogging during this stage can reduc cotton fiber yield and fiber quality. The study on the effects of soil waterlogging on physiological charateristics of subtending leaf in cotton has obvious implication for improving waterlogging resistance and guiding cultural management in cotton. A pool experiment was performed with different waterlogging days (3,6,9and12days of waterlogging) during flowering and boll-forming stage. The study were focused on:(1) effects of soil wterlogging on photosynthesis and chlorophyll fluorescence parameters of the subtending leaf during flowering and boll-forming stage;(2) effects of soil waterlogging on carbon-nitrogen metabolism of subtending leaf and agronomic traits of cotton during flowering and boll-forming stage;(3) effects of soil waterlogging on sucroce metabolism of subtending leaf.1. Effects of soil wterlogging on photosynthesis and chlorophyll fluorescence parameters of the subtending leaf during flowering and boll-forming stageThe photosynthetic charateristics of subtending leaf are affected by soil waterlogging during flowering and boll-forming stage, cased the decrease of the boll weight and fiber qualities. Under less than3days of waterlogging, the photosynthetic charateristics has not significant differences. When under the conditions of more than6days of waterlogging, compared with well-watered control, there were significant differences in the photosynthetic characteristics of subtending leaf under waterlogging treatments. The reduction of photosynthetic charateristics in the subtending leaf under soil waterlogging conditions resulted in the decrease of cotton yield and poor fiber qualities finally. This indicated there is a threshold in the photosynthetic characteristics with different waterlogging days, which is3to6days of waterlogging. 2. Effects of soil waterlogging on carbon-nitrogen metabolism of subtending leaf and agronomic traits of cotton during flowering and boll-forming stageCompared with soil well-watered control, under3days of waterlogging, the C and N metabolism of subtenging leaf is in balance and boll weight had the tendency of decrease, but not significant (P>0.05). However, with waterlogging days, especially the treatments of9days and12days of waterlogging, both the transformation rate of soluble sugar and declining rate of amino acid reduced rapidly in subtending leaf. This resulted in the imbalance of carbon and nitrogen metabolism. Compared with well-watered control, specific leaf weight in subtending leaf decreased under different days of waterlogging because of low soluble sugar content. The imbalance of carbon-nitrogen metabolism in subtending leaf and the changes of agronomic traits of cotton rasulted in low boll weight, low fiber yield and fiber quality. Soluble sugar content, amino acid content and specific leaf weight in subtending leaf, and agronomic traits of cotton of Siza3were higher than those of Simian3.3. Effects of soil waterlogging on sucroce metabolism in subtending leaf of cotton during flowering and boll-forming stageThe results showed that soil waterlogging regulated the synthesis and degradation of sucrose by affecting the activites of sucrose metabolizing enzymes (SPS, SuSy and Inv), which resulted in the decrease of sucrose content. The treatment of3days and6days of waterlogging had no significant effection on enzyme activities in sucrose metabolism. Therefore, there was no significant change on the sucrose content. However, the treatment of9days and12days of waterlogging accelerate the reduction of sucrose metabolism related enzyme activity which resulted in the blocking of sucrose metabolism and sucrose content decreased significantly in subtending leaf.