Study On The Shade-tolerance Of Apple Cultivars And 5-ALA Regulation Technique

Apple is suitable for arid or semi-arid regions as a heliophile fruit tree,which is native to Europe,Central Asia and China's western Xinjiang with less precipitation,plenty of sunshine,so can produce bright appearance and rich flavor fruit.However,apple can also grow in our country south humid and semi humid region with a large area and form a China's central and southern apple producing areas,so it made a great contribution to the development of apple industry in China.In recent years,in order to reduce rainwater direct impact on the growth of apple,especially in order to reduce disease transmission,reduce pesticide use,improve the food safety of fruit,apple rain shelter cultivation modes arouse people's attention.Research shows that the use of shelter cultivation techniques helps to reduce the happening of the disease,significantly reduce the number of pesticide spraying and pesticide residues,increasing fruit-bearing rate at the same time.But in some heavy rain or the rainy season concentrated region,plant diseases and insect pests happen seriously,the apple tree grow strong and management cost is higher,so that the increase of the fruit quality is limited.In addition,the of shading facilities covering and skeleton structure and adverse weather conditions including rain and snow in winter and spring,even the cloudy days,the plant in the facilities is always in the weak light environment.Weak light will cause the decline in crop growth,photosynthetic capacity and resistance to diseases and insect pests,which also affect the blossom fruit set and fruit development,eventually lead to the decline in yield and quality.Therefore,it is very necessary for the cultivation of apple to select strong shade-tolerance varieties and relieve the apple trees shading stress.In order to provide theoretical basis for Apple cultivation,this study is based on ten different varieties under three different light treatments as well as the shade tolerance of two varieties of different root irrigation 5-ALA,compare the effects of different treatments on the physiological characteristics.The results are as follows:1.In order to compare the shadow resistance of different apple varieties under the condition of shelter cultivation,the ten different apple cultivars as material in this study,this cultivars were treated under shading?Rain shelter,shelter shed and net?and natural light conditions in a field experiment.The leaf physiological indexes were measured and the result showed that the shading treatment significantly increase leaf length,leaf breadth and Leaf area,leaf chlorophyll b/a content,superoxide anion free radical,MDA content and H₂O₂ content.But the leaf thick,autioxidant enzyme activities in leaves and the activity of PSI,PSII reaction center and photosynthetic capacity index were reduced.However,the high shade-tolerance cultivars are insusceptible.These data suggest that ten cultivars were divided into three shade-tolerance types,which were the strong shade-tolerance type,the middle shade-tolerance type and the low shade-tolerance type.Thus,in practice,strong shade tolerance and middle shade tolerance of varieties were suitable for cultivation of rain-shelter,but the low shade-tolerance type was not suitable for cultivation rain-shelter.2.In order to explore an effective approach of 5-aminolevulinic acid?5-ALA?application in high-quality apple production,twenty apple?Malus x domestica Borkh.cv.'Qinyang'?trees were used in this study.The rhizosphere-applied treatments monthly from the late of April to the late of June included 0.1,1 and 10 mg/L 5-ALA concentration solutions,with clear water as the control.The leaf physiological indexes were measured one month after the last application,and fruit quality was evaluated when fruits were mature.The results showed that 5-ALA applications significantly improved leaf chlorophyll content,increased photosynthetic energy conversion efficiency,and alleviated active oxygen injury.Meanwhile,5-ALA treatments decreased the content of phosphorus,potassium and sodium,but increased calcium,magnesium,iron,copper and zinc content in apple leaves.Furthermore,5-ALA treatments improved the anthocyanin content of the skin and the soluble sugar content of the flesh when they apple fruits were mature.These data suggest that rhizosphere-applied 5-ALA solution was as effective as foliar-applied in improving leaf chlorophyll accumulation and photosynthetic energy conversion,as well as promoting fruit quality.The 5-ALA solutions applied by foliar spray was often blocked by bags covering around fruits,therefore 5-ALA could not be directly absorbed by fruits;however,the 5-ALA solution applied by rhizosphere irrigation can be transferred to leaves as well as fruits,whether fruits were bagged or not,especially those were bagged with plastic bags,which did not debagged until fruits were harvested.Thus,rhizosphere application of 5-ALA solutions can be used in both bagged and unbagged apple production.Additionally,the most effective concentrations of 5-ALA solutions were 0.1-1 mg/L.3.The mitigative effects of Rhizosphere-applied 5-aminolevulinic acid?1 mg/L 5-ALA?in the apple cultivars under different shading stress were explored in the present study.The leaf physiological characteristics indexes were measured and the result showed that 5-ALA increase leaf chlorophyll and b/a content,autioxidant enzyme activities in leaves and the activity of PSII reaction center and photosynthetic capacity index.However,superoxide anion free radical,MDA content and H₂O₂ content were reduced,and the effect of Zhengyou 3 is better.These data suggest that 5-ALA by rooted-application could mitigate the damage effect of shading on apples and therefore improve the shade-tolerance of apple plants.