Effect Of New PGRs Application On Kiwifruit Seedling Growth And Soil Microbial Abundance

Kiwifruit,a deciduous vine of genus Actinidia in the Actinidiaceae family is one of the important emerging fruits with rich nutrition.Kiwifruit roots belong to fleshy shallow roots,which are prone to be stimulated by soil texture and structure and abiotic stresses such as drought,waterlogging and salinity,thus affecting plant growth and yield.Plant growth regulators（PGRs）play an important role in regulating plant growth and root environment.In this study,the effects of three novel PGRs,melatonin（MT）,pollen polysaccharide（SF）and14-brassinosterol（14-HBR）,alone or in combination SF+MT and MT+14-HBR,on seedling growth,soil microbial abundance and mineral nutrient absorption in kiwifruit were studied.The results will provide theoretical reference for improving the healthy growth of kiwifruit.The main results are listed below:1)Application of PGRs significantly increased plant growth parameters and biomass accumulation.Plant height,stem diameter,leaf area,root length,root diameter and root activity were increased in both single and mixed treatments.MT had the best effect in single treatment,and MT+14-HBR had the best effect in combined treatment.Compared with the control,MT and MT+14-HBR treatments increased the dry mass of aboveground part by25.68%and 27.0%,and the dry mass of underground part by 26.05%and 25.55%,respectively.2)Application of PGRs significantly increased photosynthetic pigment content and photosynthetic parameters of leaves.MT and MT+14-HBR treatments significantly increased the contents of chlorophyll a,chlorophyll b,total chlorophyll and carotenoid,and contributed to the increase of stomatal conductance,transpiration rate and intracellular CO₂content,and ultimately increased the net photosynthetic rate.In addition,compared with the control,MT+14-HBR treatment increased SOD enzyme activity by 29.60%,POD enzyme activity by26.75%and CAT enzyme activity by 32.12%,respectively.3)Application of PGRs significantly increased soil enzyme activity.Compared with the control,MT and MT+14-HBR treatment significantly increased the activities of invertase,urease,protease and phosphatasey,which were increased by 49.35%,45.32%,48.72%and25.60%by MT+14-HBR treatment,respectively.4)Application of PGRs significantly increased soil microbial abundance.The main microorganisms in soil were Proteobacteria,Acidobacteria,Gemmatimonadetes,Planctomycetes,Verrucomicrobia,and Chloroflexi,accounting for 80.21%to 82.73%of the total.Compared with the control,the relative abundance of Proteobacteria and acidobacteria was the highest after MT+14-HBR treatment,reaching 38.92%and 24.96%,respectively.5)Application of PGRs increased the uptake of soil mineral nutrients and leaf mineral nutrients.MT treatment increased the available K content in soil.MT+14-HBR treatment significantly increased the contents of N,P and Fe in leaves by 47.21%,68.18%and 23.56%,respectively.In conclusion,MT and MT+14-HBR treatment improved the rhizosphere beneficial bacterial community,thereby improving soil enzyme activity,promoting nutrient cycling,increasing soil fertility,promoting plant nutrient absorption,and ultimately promoting plant growth.