Study On Photosynthesis Characteristics And Drought Tolerance Of Wheat Cultivar In The Loess Plateau

Winter wheat as the one of main food crops in the Loess plateau, its production has beenlow and instability. With the wheat production and breeding of continuous development,variety is the inexorable trend of change. The study materials with different historical periodof the main cultivated varieties were selected from1940s to the present day in the Loessplateau, and used the field experiment method and laboratory analysis method to study theagronomic characters, photosynthetic characteristics and nutrition characteristic, and otheraspects of the evolution characteristics in the process of varieties replacement, the resultswere as follows:1. Increased nitrogen application will significantly increase production, but with thegradual increase in fertilizer rate, the yield increase or decrease by different varieties. Whennitrogen rates in60kg/hm2, the yield of part varieties increase1times or so, but increased to120kg/hm2or a higher level of nitrogen, yield increase is relatively small, and the productionof some varieties even reduce, Harvest index is the same as yield change.2. During the process of the winter wheat variety improvement in loess plateau, the plantheight and internode height are reduced, and significantly different among varieties. Basic onthe height of Wuzhimai which was the wheat variety in1940s, the wheat plant height in70years reduced30.59%, year on average0.44%lower. The spike length among differentvarieties has been no significant changed, still keeped in6.5~7.2cm or so.3.1000-grain weight with the replacement of wheat varieties were significantlyincreased, the variety after80s was more heavier than before, but biomass yield were nosignificant changed. Grains per spike was not changed and remain kept relatively stable stateduring70years, there was little influence on it after use nitrogen application. The change ofspike numbers per667m2was divided into two stages: as the main dividing line in the1980s,the varieties before it were maintained250000spikes, some varieties were above300000spikes, but after1980s the varieties were generally lower, below250000spikes, when usednitrogen fertilization, different variety had different response, but without obvious change inthe law.4. By analyzing the impact of nitrogen nutrition on leaf photosynthetic characteristics, due to stomatal limitation of Pn decreased only Changhan58, Wuzhimai and Fengchan3haomay be reduced by chloroplast activity、Rubisoo activity and the regeneration capacity ofRuBP carboxylase, thus be inferred that the response mechanisms of the different varieties ofwheat on the photosynthetic rate limiting factor was different. Continue to increase nitrogenapplication, Pn restored an increasing trend, compared with the peak of nitrogen application120kg/hm2,it still decreased. In the Loess Plateau Nitrogen application rate is suitablebetween60~120kg/hm2, When exceed this level, the net photosynthetic rate, stomatalconductance and water use efficiency were reduced to varying degrees, and the transpirationrate was accelerated, these will lead to the crop wilting, leaves ahead of aging, etc., and is notconducive to yield formation.5. Plant nutrient element contents was generally highest in the jointing stage and headingstages, and was lower in turning green stage and maturity. Fertilization can significantlyimprove the contents of plant nitrogen and phosphorus, but the contents of plant potassiumsignificantly reduced in heading and filling stage, different varieties and nitrogen fertilizerreducing the amplitude was different. The vegetative organs contents of N, P and K werehighest in seedlings and the jointing stage, and the lowest in maturity. Fertilization biggestinfluence on the vegetative organs of nitrogen content, and less impact on the phosphorus andpotassium content, different effects on different varieties, some species even appear to reduce.Stem phosphorus content of varieties after80s promotion was higher, but phosphorus contentof the milk stage was low, stem phosphorus output has been improving with the improvementof varieties; Root phosphorus content gradually decreased with the replacement of varieties,the varieties promoted earlier were generally greater than now, Changwu131was lowest,16%and14%lower than Wuzhimai and Bima1hao; leaf nitrogen content in the earlierpromotion varieties increased obviously in the high fertility conditions, leaf potassium contentafter the1970s varieties than before increased significantly, and between different varieties ofleaf phosphorus content was not significantly different, basically no change in70years.