Photosynthesis, Matter Translocation And Water Use In Different Drought Resistance Cultivars Of Winter Wheat

To investigate the characteristics of photosynthetic production, matter translocations, yield formation and water use in different drought tolerance cultivars of winter wheat and its responses to drought stress. Three cultivars, Jinmai47(JM47) with strong drought resistance, Yanzhan4110(YZ4110) with weak drought resistance and Aikang58(AK58) with moderate drought resistance, were planted under rain-proof shelter conditions in2012-2013and2013-2014. In the trial, three moisture treatments, including persistent drought from jointing to maturity(W1), drought from anthesis to maturity(W2) and suitable water supply from jointing to maturity(W3) were conducted on the basis of seeding at sufficient soil moisture for overwintering security. The main results were as following.1)The responses of the characteristics of the photosynthesis and transpiration of different drought resistance cultivars of winter wheat to drought stress were difference during different period after anthesis, and the strong drought resistance cultivar had the photosynthetic superiority in the later filling stage and in the noon. Drought stress decreased the photosynthetic rate and transpiration rate, and the decrease of transpiration rate was higher than that of photosynthetic rate, which led to a significant increase of leaf water use efficiency. The responses to drought stress among the three kind cultivars were difference during different period. Compared to the weak drought resistance cultivar, the leaves chlorophyll content in the later growth stage, the decrease of diurnal or afternoon mean photosynthetic rate and leaves water content in JM47were lower, however, the decrease of transpiration rate and increase of water use efficiency were higher. The sensitivity of leaves photosynthesis, transpiration and water use efficiency to drought stress in the afternoon was higher than that in the morning. When water stress happened, the decrease of leaves water content and photosynthetic rate in the afternoon of strong drought resistance cultivar was lower than that of weak drought resistance cultivar. Therefore, the leaves F, Fm’, Yield, ETR, NPQ and qP keep at a relatively stable level, and the organ-air temperature difference of canopy organs were lower. Further analysis indicated that the F ratio, Fm’ ratio and organ-air temperature difference of severe drought treatment to suitable water treatment of the same variety should be considered as the indices in the selection of drought tolerance wheat cultivars.2) The dry matter accumulation abilities, and reserve matter translocations efficiency of different cultivars and its responses to drought stress were difference. Under water stress conditions, the strong drought resistance cultivar had higher dry matter accumulation advantage and reserve matter translocation abilities. Although drought stress decreased the biomass, however, the decrease of strong drought resistance cultivar was lower than that of weak drought resistance cultivar. Compared to YZ4110, the pre-anthesis and post-anthesis biomass of JM47were significantly higher and post-anthesis biomass of AK58was a little higher, therefore the pre-anthesis dry matter translocation amount and its contribution rate to grain yield of JM47were higher, and those of AK58were significantly higher. For the different water treatments, the order of pre-anthesis dry matter translocation amounts and its contribution rate to grain yield were stem+sheath>leaf>spike, and the pre-anthesis dry matter translocation rate were leaf>stem+sheath>spike. Drought stress significantly increased the pre-anthesis dry matter translocation amounts and its contribution rate to grain yield, dry matter translocation rate of the different organs in JM47and AK58, however, there were no significant effects on those in YZ4110.3) The seminar period and diurnal change tendency of sugar metabolism were found in leaves, stems and spikes, however, the sugar concentration and accumulation in different drought resistance cultivars and different organs existed the significant differences. The strong drought resistance cultivar had the higher sugar concentration in leaves and spikes, and had the higher sugar accumulation and translocation in stem+sheath. The sugar concentration showed the patterns with raising first and then declined, and arrived at the peak about14:00. Although water stress had no effect on the diurnal sugar change tendency, but the concentration were significantly increased when drought stress happened. The sugar concentration in leaves and spikes of JM47were higher than that of YZ4110, however, there was an opposite tendency in stem+sheath. The sugar concentration in the different organs showed a single peak curve with raising first and then declined, indicating the sugar accumulated at the beginning of filling stage and then transferred from source organs to grain among the filling stage. Drought stress advanced the peak time of sugar in the filling stage and enhanced the sugar accumulation and translocation of stem+sheath. All of the sugar accumulation, translocation and the contribution rate to grain yield in the stem+sheaths were AK58>JM47>YZ4110.4) The responses of different drought resistance on yield formation and water use to drought stress existed the significant difference, and the main characteristics of the strong drought resistance variety were the higher effective spike rate, the bigger population sink, the stable kernel weight, the stronger water uptake and growth abilities at earlier stage, and the higher water production efficiency at later stage under drought conditions. There were no significant differences in the grain yield and water use efficiency among different cultivars when the water supply was suitable; however, the grain yield decreased significantly under the drought stress conditions, and the order of decrease was JM47<AK58<YZ4110. Compared to YZ4110, the water consumption and dry matter accumulation increased at the earlier growth stage of JM47, which led to the total kernel numbers per unit area improved. However, in the yield formation stage (anthesis to maturity) of JM47the flag leaf transpiration rate decreased, the water consumption reduced, and the water production efficiency and the contribution of pre-anthesis translocation to grains enhanced. Therefore, the strong drought resistance cultivar JM47gained the higher grain yield and water use efficiency. The cultivar of AK58also obtained higher grain yield due to the higher dry matter production capacity and pre-anthesis translocation contribution when the drought stress took place from anthesis to maturity. The main characteristics of the improved varieties with strong drought resistance and higher water efficiency were the stronger water uptake and growth abilities at earlier stage, the bigger population sink, and the higher pre-anthesis translocation contribution and post-anthesis water production efficiency under drought conditions.The comprehensive research demonstrated that winter wheat with strong drought resistance had the strong regulating capacity and higher adaptability. The strong drought resistance cultivar increased canopy biomass and population sink by enhancing the water uptake to promote vegetative growth in the earlier growth stage, maintained the afternoon photosynthetic function stable and increased the water use efficiency by means of regulating the stoma and osmotic to reduce water consumption of transpiration in the later growth stage, and promote grain filling through increasing the reserve matter efficiency. Therefore, the strong drought resistance cultivar could realize the unity of drought resistance, water saving and high yield.