| Effects of different substrates and chemically root-pruned agents on 2-year old Malus micromalus cv.‘Xuanli' container-grown seedlings were examined.The most suitable ratios of substrate components,type of chemical agent and its concentration were chosen based on growth,physiological characters,root structure and function.The results will provide theoretical and technical supports for container-grown seedlings of M.micromalus cv.‘Xuanli'.Nine groups of substrates with different ratios to peat,perlite,green waste compost and soil were obtained using L9?34?orthogonal experiment design.Substrate 1?Peat: Green waste compost: Soil: Perlite = 5: 1.5: 0.5: 3?;Substrate 2?Peat: Green waste compost: Soil: Perlite = 6: 1: 0.5: 2?;Substrate 3?Peat: Green waste compost: Soil: Perlite = 4: 1: 1.5: 3?;Substrate 4?Peat: Green waste compost: Soil: Perlite = 5: 1: 1: 1?;Substrate 5?Peat: Green waste compost: Soil: Perlite = 6: 0.5: 1: 3?;Substrate 6?Peat: Green waste compost: Soil: Perlite = 4: 0.5: 0.5: 1?;Substrate 7?Peat: Green waste compost: Soil: Perlite = 6: 1.5: 1.5: 1?;Substrate 8?Peat: Green waste compost: Soil: Perlite = 4: 1.5: 1: 2?;Substrate 9?Peat: Green waste compost: Soil: Perlite = 5: 0.5: 1.5: 2?.There were no significant differences in plant height and ground diameter among substrates.The average plant height in substrate 1 was the highest,increasing by 18% during the whole growing season.The plant height in substrate 8 was increased by 19%.The ground diameter in substrate 2 was 35.85 mm,higher than other substrates.The ground diameter in substrates 1 and 3 was increased by 8.5%.There was no significant difference in soluble protein content among different substrates,but significant differences in chlorophyll,starch,and soluble sugar concentrations were observed.The chlorophyll concentration ranged from 0.24 to 0.39 mg·g-1 with the highest concentration in the substrate 5.Substrate 9 had the highest soluble sugar concentration of 16.85 mg·g-1.The highest starch concentrations were in substrates 1,3,6 and 9,ranking 1 = 3> 6> 9.There were significant differences in nutrient concentrations of substrate and leaves among different substrates.The concentrations of total N,total P and total K of leaves were the highest in May and decreased by 39.4%,60.2% and 63.8% respectively at the end of the growing season.The substrate 6 had relatively higher nutrient concentrations.The plant height,ground diameter,physical and chemical properties of the substrate,nutrient concentration of the substrate and leaves?N,P,K?,and physiological indicators of leaves?chlorophyll,soluble protein,soluble sugar,starch?were used as evaluation parameters to get optimal substrate ratio for container-grown M.micromalus cv.‘Xuanli' seedlings.The substrate 6 had the highest comprehensive score according to principal component analysis.The ranking was 6> 1> 2> 8> 3> 7> 9> 4> 5.Therefore,the optimal substrate for container-grown M.micromalus cv.‘Xuanli' seedlings was: Peat: Green waste compost: Soil: Perlite = 4: 0.5: 0.5: 1,following by Peat: Green waste compost: Soil: Perlite = 5: 1.5: 0.5: 3.A series of concentrations of Cu?OH?2(40,80,120,160,200g·L-1)were used as root-pruned agents.80g·L-1 and 120g·L-1 Cu?OH?2 stimulated the plant height,ground diameter,germination and growth of lateral roots,and simultaneously inhibited the growth of the taproot.The number of first-order lateral roots was 69 and the root volume was 614.3cm3 under C2(80g·L-1)treatment which resulted in 21% and 28% increase compared to the control.This would benefit the uptake of nutrients of nitrogen,phosphorus,potassium of root system and consequently increasing leaves nutrient concentrations.Therefore,80g·L-1 and 120g·L-1 Cu?OH?2 were the best root-controlling concentrations for M.micromalus cv.‘Xuanli' container-grown seedlings which can control the length of the taproot and increase the growth of lateral roots.A series of concentrations of trifluralin(1,2,3,4,5ml·L-1)were used as root-pruned agents.The plant height and ground diameter of the control were 21.2% and 12.3% higher than the trifluralin treatments.The nutrient concentrations of leaves under 4ml·L-1 trifluralin treatment were higher than other treatments.1ml·L-1 and 2ml·L-1 trifluralin significantly promoted the plant height seedlings,but the length of the taproot and first-order lateral roots were not significantly inhibited.The volume of the root system and the number of first-order lateral roots were lower than those of the control,reducing by 6.8% and 18%,respectively.Therefore,2 ml·L-1 trifluralin was relatively better to control root deformation.Asphalt carrier could significantly increase the plant height of container-grown M.micromalus cv.‘Xuanli' seedlings,but had no significant effects on the root system and other physiological parameters.The results indicated that the carrier could affect the container-grown seedlings whose mechanism and the combination effects with chemical agents should be further studied in the future. |
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