Root Restriction Affects Growth,Photosynthetic Characteristics And Root Zone Environment Of Nectarine(Prunus Persica Var.Nectarina Maxim) Grown In Gobi Greenhouse

Under the climate and ecological conditions of Hexi Corridor,in order to solve the problem that the construction of greenhouse in Gobi needs"guest soil"backfill,which would damage to the ecological environment of original cultivated land,and ensure the development of peach industry in local solar greenhouse.Using nectarine variety’Zhongnong Jinhui’as experimental material,the row spacing is 0.9 m×2 m,the differences of root restriction volume 135 L,225 L,360 L,576 L and control 1440 L(RV₁₃₅,RV₂₂₅,RV₃₆₀,RV₅₇₆ and CK)were designed.The nectarine tree growth,chlorophyll content,photosynthetic gas exchange parameters,chlorophyll fluorescence parameters,fruit quality and yield in the solar greenhouse were measured at the fruit ripening period（April to May）in the 4th year of root-restricted treatments.Root exudates and soil nutrients were measured during the flower bud formation period（July to August）in the 5th year of root-restricted treatment,simultaneously measure parameters such as soil enzyme activity and soil microbial quantity.To discuss the growth mechanism of nectarine restricted root cultivation in Gobi solar greenhouse,and study the changes in the root zone environment;in order to screen the smallest possible root restricted cultivation volume,which can not only ensure the normal growth of nectarine,but also reduce the amount of foreign soil,so as to protect the ecological environment.The research results of this experiment are as follows:1.Compared with the control CK,the stem diameter and shoots length of RV₁₃₅ and RV₂₂₅treatments are significantly reduced;the stem diameter of RV₃₆₀ treatments was decreased significantly,while the shoots length have no significant effects;both parameters of RV₅₇₆ treatments does not show significant difference.2.Compared with CK,there is no significant difference in chlorophyll content and photosynthetic parameters under RV₃₆₀ and RV₅₇₆ treatments;while the total chlorophyll content of leaves under RV₁₃₅ and RV₂₂₅ treatments decreased by 32.34%and 25.52%respectively.At noon（14:00）,the net photosynthetic rate（Pn）,transpiration rate（Tr）,stomatal conductance（Gs）of RV₁₃₅ and RV₂₂₅ treatments are significantly decreased,and the intercellular CO₂ concentration（Ci）was significantly increased.In the diurnal variations of photosynthesis curve,compared with CK,there is no significant difference in Pn,Tr and Ci under RV₃₆₀ and RV₅₇₆ treatments;while the daily average photosynthetic rate of RV₁₃₅ and RV₂₂₅ are reduced by 17.3%and 13.2%,and the daily average transpiration rate of RV₁₃₅ and RV₂₂₅ are reduced by 18.6%and 10.7%.3.Compared with CK,the J-I phase fluorescence value of OJIP curve of nectarine leaves in root restriction treatments decreases significantly;at 14:00,the relative variable fluorescence difference（ΔV_t）is less than 0 in K phase,and the relative variable fluorescence difference（ΔV_t）of RV₁₃₅ and RV₂₂₅ are decreased significantly.The fluorescence parameters of RV₃₆₀ and RV₅₇₆ are not significantly different from those of CK;while the maximum photochemical efficiency（F_v/F_m）and the quantum yield of PSⅡelectron transfer（φE₀）of RV₁₃₅ and RV₂₂₅ treatment are significantly reduced,and the comprehensive performance index PI_total are decreased by 34.9%and 27.1%.4.Compared with CK,the average single fruit weight,yield and quality of RV₃₆₀ and RV₅₇₆ treatments have no significant difference,and the yield is above 55.7 t ha^-1.However,the average single fruit weight of RV₁₃₅ and RV₂₂₅ are reduced by 31.24%and 18.23%,yield decreased by 23.14%and 14.89%.5.Compared with CK,there is no significant change in root activity and soil enzyme activity in RV₃₆₀ treatment;and the effect of root exudates in RV₃₆₀ treatment was less.However,when the root volume is less than 360 L,allelochemicals such as benzoic acid,vanillic acid and p-coumaric acid increase significantly,while root vitality and soil enzyme activity decrease.6.Compared with CK,the number of bacteria decreases under root restriction treatment.Although the number of actinomycetes and fungi increase,the total number of soil microorganisms decreases,the proportion of beneficial microorganisms decreased,and began to change from"bacterial type"to"fungal type".7.Compared with CK,there is no significant change in soil p H and nutrients under RV₃₆₀treatment.However,under the root restriction treatment of less than 360 L,total nitrogen,total phosphorus,and total potassium are increased significantly,while alkali-hydrolyzed nitrogen,available phosphorus and available potassium are decreased significantly,which decrease by 4.26%～7.70%,15.19%～21.52%and 29.61%～38.74%respectively compared with CK.In summary,360 L is the suitable root Limited cultivation volume.Under the premise of ensuring the normal growth and stable yield of Nectarine in Gobi solar greenhouse,the amount of guest soil can be reduced by 75.0%,so as to protect the local ecological environment.