Effect Of Drought On Grain Filling Of Wheat And The Relationship Of That With Hormones

Water has a significant influence on the growth and development of crops. The crop metabolism vary obviously when subjected to drought stress. Two wheat cultivars, Xinong979 and Changhan343 were planted with different drought treatments in rain proof shed which Xinong979 is sensitive to drought stress and Changhan343 is drought resistance cultivars in the years of 2013 to 2014 in the Northwest Agriculture and Forestry University of Agriculture. The test conducted three water treatments from flowering to mature of wheat, namely:(1) normal supply(soil water potential of-20 ~-30 k Pa, T1),(2) moderate drought soil(soil water potential at-40 ~-50 k Pa, T2),(3) soil severe drought(soil water potential at-70 ~-80 k Pa, T3). To study the influences of water stress on grain filling rate, grain weight, changes of endogenous hormone and antioxidant systems of two winter wheat in order to explore the relationship between wheat grain filling and changes of endogenous hormone, enzyme activity, drought resistance.Study results are as follows:(1) two cultivars have different response to drought on grain filling. Severe drought stress(T3) significantly decreased the maximal grain filling rate,the average filling rate and reduced the grain weight of different grain position of Xinong979 compared to the control group. For Changhan343, severe drought stress(T3) just decreased the maximal grain filling rate, the average filling rate and reduced the grain weight of inferior grains while drought had no significant effect for strong grain filling. However, moderate drought(T2) could dramatically improve the grain filling rate and increased grain weight compared with severe drought stress(T3).(2) Water obviously affected hormone contents of IAA, ABA, Z+ZR, GAs and ETH release rate in grains of wheat. Compared with the control, moderate and severe drought had no significant impact on the superior grain content of IAA, Z+ZR, ABA and GAs of Changhan343,while for inferior grains of Changhan343 and superior and inferior grains of Xinong 979, moderate drought stress significantly increased the content of IAA, Z + ZR and ABA and reduced GAs content of grain. However, heavy drought remarkably reduced the IAA and Z+ZR content and increased the content of ABA and GAs. ETH release rate of two varieties manifested as inferior grains>superior grains, namely R-T3>R-T1>R-T2>Q-T3>QT1>Q-T2. Moderate drought significantly reduced the rate of ETH release. The content of ABA showed Q-T3>Q-T2>Q-T1>R-T3>R-T2>R-T1. With drought enhancing, ABA content increased significantly.(3) The tendency of free state spermidine(Spd) and spermine(Spm) contents performance firstly increased and then decreased. The free state Spd, Spm contents of Xinong979 grains at different positions were expressed as T2>T1>T3 under water deficit stress. Drought treatments have no significant effect for the strong grains of the free state Spd, Spm content of Changhan343, but the free state Spd, Spm contents of inferior grains showed different which manifested as T2>T1>T3. Free Put content of two varieties grains showed a decreasing trend, and inferior grains Put content higher than superior grains. Combined state(soluble and insoluble)Spd, Spm, Put content showed a higher lever at the early state of grain filling and then decreased. IAA, Z+ZR, free state Spd, Spm content of Grains had a significant positive correlation with the final grain weight, maximum filling rate and average filling rate, which had a significant negative correlation to the ETH release rate and free Put content. However, ABA, GAs, combined state(soluble and insoluble)Spd, Spm, Put content was not associated with grain filling. Correlation analysis between hormone showed that IAA, Z+ZR content was positively correlated to free state Spd, Spm content of grains, and IAA, Z+ZR content and free Put content showed significant negatively correlation.(4) Soluble sugar content of two cultivars grains showed high levers at early grain filling stage of winter wheat and then decreased under drought. The soluble sugar content at different drought treatments showed T2>T1>T3. Starch content showed gradually increasing trend and the starch content of different drought treatment performance similar to soluble sugar. Non-carbohydrate(NSC) content of stems showed increased at the first then gradually reduced. The results showed that the moderate drought was benificial to soluble sugars rapidly transport to the grain using for starch synthesis.(5) The different drought had obviously effect to chlorophyll content and antioxidant enzymes of wheat flag leaf. Two cultivars in flag leaf of SOD, POD activity showed a decreasing trend after the first increase, and with the severity of the drought, activity was significantly reduced. CAT activity and chlorophyll content in the overall grain grouting period showed a decreasing trend. CAT activity in six days after flowering is reached high values which indicated that CAT prior to SOD, POD play a role under drought stress. Chlorophyll gradually degraded with the aggravation of drought so that premature aging plants. Membrane Lipid oxidation product of MDA content increased with increasing of drought stress.