Wheat Non-structural Carbohydrates Cumulative Distribution And Photosynthetic Physiological Response To Water Stress

Water stress has great hurt on crops, mainly for the re-allocation of water among thevarious parts of crops, membrane damage, photosynthesis decrease, osmotic potentialdecline, and ultimately led to decline in production. In the studies on drought resistance ofcrops, research on the impact of drought stress on production and correlation traits andrelated mechanisms is the focus of attention of crop scientists.Using strong drought-resistant Xihan No.2and Yongliang No.4which isdrought-sensitive and cultivated in water land as materials, combined pot experiments,with different degrees of water stress and re-watering on the two varieties of wheat, theeffects of water stress on enzyme activity and non structural carbohydrate metabolism ofleaf, stem, sheath and grain before wheat anthesis were studied. Then compared the impactof water stress on photosynthetic characteristics and the distribution and accumulation ofdry matter in different growth period of different drought-resistant wheat，and changes ofenzyme activity in antioxidant enzyme system, content of proline and MDA of wheat leaf,sheath and stem and its sensitivity to water stress. Results showed that:1.Water stress significantly influence the matter accumulation of wheat. Water stressreduced the fresh weight of other wheat leaves，dry weight and fresh weight of spike, andto a certain extent, reduced the dry weight and fresh weight of sheath and stem ofdrought-sensitive Yongliang No.4; the fresh weight and dry weight of flag leaf were notsignificantly affected. The fresh weight and dry weight of flag leaf and sheath ofdrought-resistant Xihan No.2and dry weight of other leaves were greater than that ofdrought-sensitive Yongliang No.4; but the fresh weight and dry weight of spike were lessthan that of drought-sensitive Yongliang No.4.2.Water stress significantly influence the non-structural carbohydrates content ofwheat. Water stress reduced the content of starch, reducing sugar, fructose, sucrose in flag leaf, other leaves, sheaths, stems and grains, but increased soluble sugar content.Throughout the trial period, compared with the drought-sensitive Yongliang No.4, starch,sugar, fructose and sucrose content in Xihan No.2were higher.3.Water stress significantly influence the activity of key enzymes of starchmetabolism wheat grains. During grain filling stage of wheat, GBSS enzyme activitygradually decreased, water stress could improve the GBSS enzyme activity; SSS activitydeclined modestly in the early but later rapidly declined, effect of water stress on SSSenzyme was not significant; AGPP and UGPP enzyme activities in filling stage graduallydecreased, water stress significantly improved AGPP and UGPP enzyme activities.4.Water stress had a little effects on drought resistance of wheat varieties ofproduction. Under mild and moderate water stress, the degree of yield reduction of XihanNo.2was less than that of Yongliang No.4, which showed that Xihan No.2had strongerability to resist drought.5. Drought stress and re-watering can significantly affect photosynthetic efficiency inwheat leaves. Xihan No.2under the moderate water stress, Yongliang No.4under mildwater stress, the chloroplast suffered mild injury. Re-watering after water stress,chlorophyll content were back to CK levels after its absorptive capacity, transfer of energyefficiency is raised. Under mild and moderate water stress, Xihan No.2strong ability toadapt, can maintain normal growth, and the water use efficiency is significantly higherthan Yongliang No.4. After mild water stress and re-watering, Pnmaxin Xihan No.2increased; Under mild and moderate water stress, Pnmaxin Yongliang No.4decreased.6.Drought stress and re-watering could influence the kinetics parameters ofchlorophyll fluorescence of wheat leaves in different degree. Under mild water stress, qPand ETR increased in Yongliang No.4; Re-watering after mild water stress, F0decreased,ΦPSII, qP, ETR and Fv/Fm increased in Yongliang No.4. Under moderate water stress, F0 increased but qP, ETR and Fv/Fm decreased in Yongliang No.4; Re-watering aftermoderate water stress, F0in Yongliang No.4was significantly increased, Fv/Fmsignificantly reduced.7.Under water stress, content of proline and MDA were significantly increased, theactivity of SOD, POD and CAT in antioxidant enzyme system were all increased in wheatorgans. With the treatment of re-watering, the recovery effect of Xihan No.2was higherthan that of Yongliang No.4. The wheat organs to water stress was: leaf>sheath> stem.