Co-effects Of Elevated Temperature And Soil Waterlogging During Flowering And Boll Formation Stage On The Production And Quality Of Cottonseed

Cotton(Gossypium hirsutum L.)is one of the most important commercial crop and textile materials in the world.As its main byproduct,the role of cottonseed in cotton production has become increasingly prominent.With the effect of global warming being gradually exacerbated,high temperature and flood disaster are becoming more frequently.Cotton is more sensitive to the temperature and moisture during flowering and boll formation stage,while the disasters always occur and seriously affect the production and quatity of cotton in summer of the Yangtze River valley.Field experiment was conducted in Nanjing,Jiangsu Province(118°50’E,32°02’N)from 2013 to 2015.The cotton cultivar Siza 3 which has been widely planted in the Yangtze River valley cotton belt since the early 21st century was used.Experimental treatments during flowering and boll development stages were:soil waterlogging treatments(lasting 3 and 6 days)under ambient temperature(WL3,WL6);elevated temperature(ambient temperature plus 2-3°C)and a well-watered control(ET);3 and 6 days soil waterlogging treatments under elevated temperature(TW3,TW6);ambient temperature with a well-watered control(CK).The study explores the physiological mechanism of the relationship between elevated temperature and short-term soil waterlogging on the yield and quality of cottonseed.The main results are as follows:1.Co-effects of elevated temperature and soil waterlogging during the blooming and boll-forming period on cottonseed yield and morphological developmentThrough three years of experiment,it can be found that the coupling of elevated temperature and soil waterlogging can inhibit the growth and development of cotton.There were significant decreases on the bolls numbers,bolls weight and cottonseed yield under the two stress factors.However,the results were difference in three years.In 2013(year of high temperature),a superposition effect on the decrease of cotton bolls numbers by elevated temperature and soil waterlogging,which results in lower yield of cottonseed under coupled treatment than in single factor.However,in 2014 and 2015(years of low temperature),the treatment of lower elevated temperature can increase the number of bolls,compensate for the reduction of bolls weight,and mitigate the negative effects of soil waterlogging on cottonseed yield.The total biomass of bolls,seed numbers per boll,cottonseed rate and the cottonseed volume were decreased obviously,which led to the lower cottonseed index and cotton embryo index.Therefore,elevated temperature and soil waterlogging will make a significantly adverse impact on cottonseed production during the most sensitive period of growth and development.2.Co-effects of elevated temperature and soil waterlogging during the blooming and boll-forming period on sucrose metabolism of cotton embryoThere were significant effect of related substances content of sucrose metabolism under elevated temperature and soil waterlogging.The variation trend both of the content of sucrose and soluble sugar in cotton were similar,which the content of 17-24 DPA decreased rapidly.While cottonseed closed to maturity,those contents were increased so that the carbohydrater and energy were accumulated for the synthesis of fat and protein.The three-year trend was consistent,as well as the coupling effect was significantly.The variation tendency of hexose and starch content consisted with that of sucrose in 2014 and 2015,but those of hexose and starch in high temperature year(2013)was increased.It can be objected that the carbon assimilation was hampered to decrease the the synthesis of fat and protein.3.Co-effects of elevated temperature and soil waterlogging during the blooming and boll-forming period on the formation of cotton embryo main qualityBased on the difference responses of cotton embryo quality under elevated temperature and soil waterlogging,this study explored the accumulation of fat and protein contents and main components contents of amino acids and fatty acids in cotton embryo under the two stress factors.The results showed that the decrease of fat content under coupled treatment(TW3 and TW6)(decreased by 6.7%-10.1%and 12.4%-15.8%)was greater than those under single factor in cotton embryo.The contents of palmitic acid,oleic acid and linoleic acid of the fatty acids component were significantly affected by elevated tempreture and soil waterlogging,which were the main influencing factors of fat content accumulation.Protein content were higher under elevated tempreture than that under the control,however the trend was adverse under soil waterlogging.Compared with that under the two stress factors,the protein content was mainly related to the accumulation of globulin and gluten contents.The elevated tempreture promoted the accumulation of globulin but inhibited the accumulation of gluten,nevertheless it was consistent under soil waterlogging.So the increase of elevated temperatures in protein content was mainly due to the increase of globulin content.The effect of tempreture increase and waterlogging on the free amino acids was significant,such as Glu,Met,Leu and Pro,which were the main influencing factors of protein quality in cotton embryo.