Effects Of Soil Drought On Physiological Growth,yield And Quality Of Aksu Apple Trees

Improving the water use efficiency of plants is one of the important ways to save water in arid areas.In recent years,the frequency and intensity of extreme weather has increased,coupled with the climatic characteristics of scarce precipitation and large evaporation in arid areas,the growth and development of fruit trees mostly rely on irrigation water,and the current irrigation is mostly the experience of fruit farmers.Extensive management and stable production of fruit trees,and high-quality fruit contradictory.The current water-saving methods for fruit trees mainly focus on the analysis of irrigation methods or irrigation amount and frequency of crop growth and development,photosynthesis,yield and quality and other unilateral or several aspects.Red Fuji apples in Aksu area rarely involve systematic analysis.The adjustment of the amount and frequency of irrigation is the easiest and most effective way.The water use efficiency of crops is often the highest under medium water supply conditions.Based on this,during the critical period of water demand for fruit trees,by reducing the frequency of irrigation,that is,carrying out drought treatment,the aim is to enhance the adaptability of fruit trees to water shortage and improve water use efficiency.From June to November 2019,using the national geographic product Aksu apple tree as the test material.Drought stress,half-root irrigation and full-root irrigation were set for comparison,and the growth and development,water consumption characteristics,photosynthetic characteristics and endogenous hormones in flower buds were measured under each treatment,so as to improve water use efficiency on the premise of less impact on yield and quality.Research indicates:(1)Lack of water to a certain extent benefit the efficient use of limited water and the transformation of reproductive growth.Too much water leads to nutrient growth and water consumption.Under drought treatment,the inhibition of branch length is obvious,and the capping time is early,which has little effect on fruit growth and fruit shape index.It improves fruit quality to a certain extent,which is reflected in the content of vitamin C,soluble solids and total sugar.increase.During fruit maturity,fruit longitudinal diameter: full-root irrigation(90.32 cm)> half root water stress(87.16 cm)> drought stress(84.72 cm),fruit transverse diameter: full-root irrigation(90.52 cm)> half root water stress(88.53 cm)> drought stress(85.81 cm).The proportion of fruit diameter ≥75 mm under half root water stress is the highest,and the commodity rate is the highest.(2)Irrigation time in the evening can avoid the influence of irrigation water on stem flow.The stem flow under half root water stress and full-root irrigation varies due to changes in weather conditions and irrigation volume.Sunny > cloudy > overcast.The single-day stem flow has a greater correlation with VPD.Correlation coefficient: half-root zone irrigation,r = 0.783(P < 0.01),whole root zone irrigation,r = 0.477(P > 0.05).Irrigation time is during the day,the single-day stem flow decreases,and the irrigation time is in the evening,the single-day stem flow is less affected.Under drought treatment,the stem flow curve of tree trunk decreased slowly and was less affected by the weather.The correlation between stem flow per day and the water content of 50 cm deep soil layer was high,r = 0.654,and the proportion of stem flow at night increased slightly with the drought.(3)When fruit trees are in water deficit,the photosynthetic characteristic parameters are most related to the moisture content of the-50 cm soil layer.With the increase of drought duration,Pn decreased.The reason for the decline was mainly due to stomatal factors in the early stage and non-stomata factors in the later stage.The average daily WUE under drought treatment was the highest,which was 1.2 times and 1.3 times that under half root water stress and full-root irrigation,respectively.Under drought stress,the WUE order of different types of branches: short branches(1.82 μmol·mol-1)> lateral shoot of bearing part(1.75 μmol·mol-1)> long fruiting branch(1.63 μmol·mol-1)>pruning vertical branch(1.49 μmol·mol-1),short branches and lateral shoot of bearing part have strong adaptability and high water use efficiency.Under drought treatment,the leaf transpiration rate is highly correlated with the stem flow rate.(4)Under drought stress,flower buds endogenous hormones content respond differently.IAA content first decreases and then increases,ABA first increases and then decreases,ZR and ZT decrease,and there is a certain compensation effect after rewatering.Correlation analysis found that the change in IAA/ABA ratio was most correlated with ABA content(P < 0.01),ZR/IAA,ZR/ABA values were significantly correlated with ZR(P < 0.05),and the degree of correlation between IAA/ZT and ZT The highest(P > 0.05).The difference in hormone content between half-root zone irrigation and full-root zone irrigation is small but significant.Flower buds of different branches respond to endogenous hormones,and growing branches are the most sensitive.The ZR content of flower buds decreases with the decrease of water,and the ABA content of flower buds increases with the decrease of water.(5)Fruit trees have the highest water productivity under drought stress,but water shortage seriously affects fruit yield,so it is not recommended in production practice.The water productivity of fruit trees irrigated in the semi-root zone reached 2.95 kg/m3.Although the yield was lower than the control,the commercial fruit yield was the highest,and because the root system was affected by local drought,it produced crisis signals and promoted flower bud differentiation,so its water-saving and yield-increasing effects were obvious.In summary,fruit trees under half-root water stress irrigation can optimally allocate limited water.Irrigation at night is beneficial to apple tree growth and water utilization.Half-root water stress irrigation can be used as a reference during fruit expansion.