Study On Photosynthesis Characteristics And Drought Tolerance Of Wheat Cultivar In Shaanxi

Shaanxi located in northern winter wheat growing areas. The guanzhong area and Weibei dry plateau are the main winter wheat growing areas. Study photosynthetic characteristics, agronomic characters, some physiological and biochemical characteristics in winter wheat varieties replacement in guanzhong area and Weibei dry plateau since liberation is very importent. The research can provided extensive information to further varieties seed selection and guide certain significance to the practice of wheat production. This experiment chose the mainly varieties cultivation in each period since early liberation. Using the combining method of field experiment, the pot experiment and laboratory analysis, studied the photosynthetic characteristics, agronomic characters and drought resistance in winter wheat varieties replacement in these two areas. The results were as follows:1. In the process of variety improvement in Guanzhong area, the grain yield,1000- grain weight and harvest index were significantly increased with cultivars improvement while the plant height was decreased to half of it, the height increased by 0.79cm per year. The length per spike, number per spike, spike per plant and grain weight per spike were not increased with the variety improvement. It means the most cause of production increase was the increase of wheat grain weight. The developed harvest index results from the decrease of plant height and the increase of 1000-grain weight. Grain yields were expeditiously increasing with the fertilization. The modern grains have stronger adaptations in barren soil condition, and its 1000-grain weight, plant height and the No.of tillers per plant were generally stands stable in fertilization and no-fertilizer treatment. In fertilization treatment, the main reason yield increase was increase of 1000-grain weight, and the developing harvest index results from the yield increase. In no-fertilizer treatment, decrease plant height, increase harvest index and 1000-grain weight playing important roles to increase yield.2. In the birth later period the flag leaf photosynthesis speed increasing tendency in the process of variety improvement in Guanzhong area, the modern variety was better than the early variety about peak value or the duration obviously. The water use efficiency of modern variety was lower in entire period of duration; it suits the sludge fertilizer condition. The variety Shanxi 889 was the highest in photosynthesis speed value of entire day displays,and its daily average speed of photosynthesizes was 10.08μmol?m-2?s-1, the yearly average increased range was 0.7%. The relationship between the wheat leaf water use efficiency (WUE) and net photosynthesis rate was significant positive correlation((r=0.88468**),with transpiration rate (E) was positive correlation (r=-0.69633*), with stomatal conductance (C) was weak inverse correlation.3. At Weibei dry plateau, in the process of varietal improvement, varieties biological yield and number of spike had fluctuation of decline. In the fertilization conditions, earlier varieties height increased obviously, it is disadvantage to breed grain filling, and it also susceptible to lodging. This was forming adverse effects to yield formation. In the fertilization conditions, the harvest index increased mainly duo to economic yield increased and biological yield declined. While In the non-fertilization conditions, high-stem varieties had been apt to more tillers per, grain number per spike and number of pikelet. Scattered the limited nutrients to grain spike excessively; it is disadvantage to kernel plump. It affected 1000-grain weight, and in this period, the harvest index increased higher than biological yield increased. Yield decreased caused by varietal height affected 1000-grain weight was significant than number of pikelet, grain number per spike increased.4. With wheat varieties replace, for Weibei dry plateau wheat varieties, the net photosynthetic rate gradually increase in filling stage. The flag leaf photosynthetic rate had an increasing trend in later growth period. In the fertilization conditions, for the modern wheat varieties Changwu 131 and Changhan 58, the photosynthetic rate has increased. Water use efficiency had a decreased trend with varieties pushed out period delay. Water use efficiency of modern varieties is generally lower, but Chnaghan 58 showed higher water use efficiency in every growth period. This explained that it had more widely water and fertilizer adaptability. In the critical period of formation grains-filling stage, modern varieties Changhan 58 and Changwu 131, whether peak value or duration time were obviously superior than earlier varieties, Changhan 58 had higher transpiration rate. It was in favor of transporting nutrient and moisture for photosynthesis. At the same time, in filling stage, the flag leaf net photosynthetic rat(ePn)had a very significant positive correlation to stomata conductanc(eC). (r=0.963**)5. With Shaanxi wheat varieties replacement, drought decreased the yield, but had little impact to 1000-grain weight. Drought made the effective tillering number of early varieties obviously decreased. In drought conditions, the difference of water consumption and normal water treatment of modern varieties had less difference compared with earlier varieties. The ability to drought resistance had gradually strengthened. It became an important index to wheat seed selection for Shaanxi wheat varieties nearly 70 years. 6. When in drought stress conditions, the overall performance of four varieties was that SOD enzyme activity has an enhancement trend. The MDA value of every varieties increased.The lipid membrane of modern varieties at the lowest level and the strongest resistance. The soluble sugar content of varieties had the same trend basically. Every varieties in filling stage excessive consumption of nutrition for reproductive growth. And make soluble sugar content decreased. After grouting to maturation period, soluble sugar content of varieties increasing to the maximum value of growth period. With the varieties replace, the maximum value of varieties soluble protein content ahead from filling stage to blooming stage compared with earlier varieties. For recent period varieties, the soluble protein content drop to a larger extent and had higher maximum value in order to resist severe dehydration that caused by drought stress. From the above,varieties replace made the ability and sensitive degree of resistance drought stress had a great improvement.