| A field experiment was conducted in Dafeng Basic Seed Farm,Jiangsu(120°34’ E,33°24’N)and the Pailou experimental station of Nanjing Agricultual University(118°50’E,32°02’N)by setting different groundwater depths(1.0,1.4,1.8,2.2,2.6,3.0 m in Dafeng and 0.6,1.0,1.4,1.8,2.2,2.6,3.0,3.4 m in Nanjing)with two cotton cultivars(Dexiamian 1,drought tolerant;Yuzaomian 9110,drought sensitive).The treatments in Dafeng were disposed with water in natural groundwater.In Nanjing site,the water treatments were disposed in a pool and the water depth of the pool was controlled by 0.3 m.The experiment was conducted to study the effects of different groundwater depth variation on pollen viability in cotton,explored the effects of different soil water content on carbon metabolism and antioxidant metabolism of the stamen.The results provided the scientific references for farmland irrigation and water conservancy.The objectives of our research were as follows:1.Optimal groundwater depths were beneficial to maintain high pollen vitality of cotton and increase seed cotton yield.With the groundwater depths increasing,the soil-relative water content displayed a downward trend.In Dafeng,soil showed waterlogged in the depths of 0.7-1.1 m(calibrated actual water depth,the same below)and mild drought in the depths of 1.9-2.7 m.In Nanjing,soil showed waterlogged in the depth of 0.6 m and drought of different degree in the depths of 1.8-3.4 m.With the groundwater depths increasing,pollen viability firstly improved,reaching the maximum in the depths of 1.9 m(Dafeng),2.2 m(Nanjing)and then reduced.The corresponding soil relative water content was 66.3%and 62.1%respectively.The cottonseed yield reached the maximum in the condition of 1.9-2.3 m in Dafeng and 1.8-2.6 m in Nanjing,and the corresponding soil relative water content was 60.2%-66.3%and 58.2%-66.9%respectively.The decrease of cotton yield in other groundwater depths was resulted from,firstly the decline of boll number and then the reduction of boll weight.It is mainly due to the seed weight per boll that the boll weight changes in different conditions.2.The groundwater depths affect the carbon metabolism and active oxygen metabolism of cotton stamens,which affects the pollen viability.The pollen viability reached the maximum in the depth of 1.9 m(Dafeng)and 2.2 m(Nanjing).In other treatments,the activities of sucrose synthase and acid invertase in stamens decreased,resulting in the decrease of sucrose hydrolysis rate and the increase of the sucrose content.However,the hexose content still accumulated.The activity of glucose pyrophosphorylase(AGPase)were limited,which leads to the deficiency of starch synthesis substrate.Compared with Yuzaomian 9110,Dexiamian 1 had higher AGPase activity and could ensure the rate of starch synthesis under water stress,resulting in higher starch content.The enzyme activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)of the stamen reduced in the depths of 1.1-1.5 m,2.3-2.7 m in Dafeng and 0.6-1.8 m,2.6-3.4 m in Nanjing,resulting in the increase of hydrogen peroxide content and superoxide anion production rate in stamens.The imbalance of active oxygen metabolism is also the reason for the decrease of pollen viability.Compared with Yuzaomian 9110,Dexiamian 1 had higher SOD activity.Its SOD and CAT activities were less suppressed by water stress and could accumulate more proline content to maintain cell osmotic potential.To sum up,cotton’s pollen can maintain high viability at the optional groundwater depth(1.9 m in Dafeng,2.2 m in Nanjing),and the soil relative water content is 66.3%and 62.1%.The reason is that the stamens can keep the higher ATP and starch content to provide sufficient energy supply for pollen development and germination,maintain higher active oxygen scavenging ability and accumulate more osmotic adjustment substances to keep the pollen viability.What’s more,Dexiamian 1 had stronger adaptability to excessive or deficient water. |
PDF Full Text Request