The Physiology Mechanism Of Strawberry Antistress Response,Nitrogen Utilization And Fruit Quality Under The Regulation Of Water,Silicon And Light

The shortage of water resource is one of the main restricting factors to the sustainable agriculture development.Deficit irrigation could benefit water conservation and fruit quality improvement at the same time,but the interactive effect between the irrigation,fertilizer application and light treatment to the crop water utilization and fruit quality formation has not been fully illustrated.This project investigated the influence of deficit irrigation,silicon fertilization and supplemental lighting on the greenhouse strawberry water use and fruit quality,and aimed at providing a theoretical basis for the improvement of whole-season strawberry fruit yield and quality,in order to optimize management strategies for water-saving strawberry production.The project firstly studied the effects of rhizosphere treatments and canopy treatments on the strawberry water consumption and the basic plant morphology,including irrigation reduction 30%（with partial rootzone drying and deficit irrigation）,root confinement,different leaf spray(3%kaolin,0.01 mol L^-1sodium silicate and 0.05 g L^-1salicylic acid),and leaf removal.After determining the outstanding effect of deficit irrigation and silicate leaf spray,,the two factors interactive effect was studied since the young plant stage.The second experiment contained two irrigation amount（full irrigation and deficit irrigation）and three silicon application methods（no application,leaf application and root application）,focusing on the further enhancement of pant antistress response and fruit quality.Finally,light supplement（4 h per day）was introduced into the study,the effect of deficit irrigation,silicon application and light supplement since blooming stage on the plant antistress response and numerous nutrition contents in the strawberry fruit were assessed.The third experiment contained two irrigation amounts（full irrigation and deficit irrigation）,two silicon application methods（no silicon and silicate leaf spray）,and two light conditions（natural light and supplemental light）.The whole project achieved valuable outcomes,as summarized below:（1）The partial rootzone drying and deficit irrigation could regulate the plant transpiration and enhanced the plant antistress response through the leaf ABA,exchangeable calcium ion and leaf thickness.The irrigation reduction reduced stomatal conductance by 22.1%and reduced specific leaf area by 15.6%,and its also increased leaf ABA concentration by 19.5%,with a minor increase in leaf calcium concentration;whilst the silicate spray led to a reduction of stomatal conductance and leaf calcium concentration,and also a 14.5%increase of leaf thickness,showing an enhancement of stress tolerance.（2）When the deficit irrigation was started since young plant stage,it would improved the plant stress resistance by thickening the leaf,and both of the silicon and its application methods regulate the plant stress response,which was also reflected on the leaf thickness.The silicate leaf spray would increase the leaf thickness and improve its stress resistance,whilst the silicate root application would relieve the stress,making the leaf thickness recovered to the non-stressed level.（3）When the deficit irrigation started since young plant stage,combination with the silicon foliar application could improve the leaf antioxidant capacity and nitrogen assimilation,enhancing the ROS scavenging and amino acids synthesis,which increased the leaf glutamate and proline concentration by 8.1%and 30.3%.whilst the silicon root application increased the leaf carotenoids concentration,and decreased the MDA concentration,relieving the membrane peroxidation,which benefited plants on the recovery of leaf photosynthesis and the acclimation to drought stress.（4）When the deficit irrigation started since blooming period,it would reduce the fruit size in the late season.But the simultaneously silicate spray increased leaf carotenoids and sucrose concentration,protecting the leaf photosynthesis membrane and maintaining the photosynthates transportation to fruits under the drought stress.In the early season,silicon increased fruit anthocyanins,polyphenols and citrate concentrations by 41.7%,14.7%and 8.2%respectively;in the late season,it increased single fruit mass by 8.8%,and it also enhanced the leaf GOGAT activity and glutamate concentration by 56.3%and 25.8%,respectively.（5）When the deficit irrigation started since the blooming period stage,the combination with light supplement effectively increased the fruit reducing sugars,organic acids,polyphenols and anthocyanins in both early and late season,and the early season fruits had largest improvement on the sugars content and anthocyanins,which were up to 10.9%and25.0%,respectively.（6）When the treatments started since blooming period,if combined with supplemental lighting,at maximum,the deficit irrigation and silicon application could increase the fruit total sugar,anthocyanins and polyphenol concentrations by 21.9%,97.1%and 42.3%,respectively.In the early season,the three factors interaction would reduce the fruit size,but was able to elevate fruit polyphenols by 15.5%,and elevated fruit total sugar;In the late season,the supplemental lighting increased total sugars,glucose and fructose concentrations by 10.0%,10.9%and 10.2%,respectively,without the negative impact on the fruit size.Besides,it slowed down the transformation of sugar to organic acids,reducing the fruit citrate concentration by 18.9%,indicating a slowing down of fruit senescence.In a summary,the projected confirmed the vitally practical meaning of the combined application of deficit irrigation,silicate spray and supplemental lighting on the greenhouse strawberry water-saving production.In the greenhouse strawberry production with non-soil substrates,deficit irrigation with 30%irrigation reduction could increase the fruit quality to a certain level,improving the reducing sugars,glutamate and citrate concentration in the fruits without significant fruit size decrease.Under deficit irrigation,applying silicon fertilizer could relive the plants from the drought stress,recovering the plant photosynthesis and crop productivity,improving the fruit quality.Whilst supplemental light could enhance the positive effect of silicon on the leaf photosynthesis and tissue antioxidation,furtherly improve the fruit total sugar,anthocyanins and polyphenols.Thus,the combination of deficit irrigation,silicon application and supplemental lighting could simultaneously save the irrigation water,improve fruit quality and guarantee the marketable yield,which could be recommended to the growers.