Organic Acids In Rhizosphere Soils Of Larix Gmelini Seedlings And Effects On Phosphorus Uptake And Accumulation Under Nutrient Deficiency

In the northeast of our country,some waste hills and lands of artificial afforestation,and broad mine soil is in urgent need of reclamation,soil nutrient dificiency often exists at these site conditions.Larix gmelini is the main local tree specie,but its growth and survival are still limited at the serious condition of soil depletion.In this paper,different kinds and quantity of organic acids secretion of Larix gmelini root at the condition of nutrient dificiency was studied by HPLC/MS determination method,and stress supplemental organic acids had effects on phosphorus availability in dark brown earth and phosphorus absorption and transportation of larix gmelini seedling,in order to discuss the feasibility mechanism provide theoretic support that organic acids enhance Larix gmelini seedlings resistance to soil nutrient depletion.The main conclusions are as follows:(1)At the condition of nutrient deficiency,the secretion types of Larix gmelini seedlings in root were increased,and the change was varying due to the different time and degree of nutrient deficiency:from the perspective of stress time,the order of newly added kinds of organic acids was 30d>3d>10d;To different stress condition,the more serious nutrient deficiency was,the more kinds of newly added organic acids was.the content of organic acids was increased because of different stress time and degree:in a short time,the more serious nutrient deficiency was,the quicker the growth rate of organic acids content was;and to lighter treatment,the longer time was,the bigger amplification was.The total quantity of organic acids was decreased with the prolongation of treatment time,ie,3d>10d>30d,to majority of organic acids,the growth rate of organic acids content was biggest at 3d.Generally,to different kinds of organic acids,the content of malic acid was bigger,followed by citric acid and oxalic acid.The order remained same,which every organic acid accounted for the proportion of total quantity of organic acids.(2)Comparing to A1 horizon dark brown earth,rapid available P content of A1 and B horizons mixed soil was decreased.After exogenous organic acids treatment,the content of mixed soil was increased,the order of three organic acids effects was on Larix gmelini seedlings was succinic acid>citric acid>oxalic acid,and the best effect was generally 5.0 mmol/L at 20 d.(3)After soil nutrient deficiency treatments,P accumulation and P uptake efficiency of Larix gmelini seedlings root and blade were decreased,while after exogenous organic acids treatments,both of them were increased,and the ascending range was varying with the change of treatment time,organic acids concentration and types:20d and 30d ascending range in roots were higher than those of 10d,however,10d and 20d in leaves were higher than those of 30d,thus,at the earlier stage of organic acids treatments,more P was absorbed and then transferred to leaves,and at the later stage more P was accumulated in roots;The best effect of these three organic acids increasing range were at 10.0 mmol/L;the order of different organic acids amplification was succinic acid>citric acid>oxalic acid.therefore,exogenous organic acids could enhance P accumulation and uptake efficiency of Larix gmelini seedlings at the condition of soil nutrient deficiency,so that the endurance and adaptive capacity of seedlings were increased.(4)P utilization efficiency of Larix gmelini seedlings root and blade were declined by exogenous organic acids,and the variation trend was according with different treatment time,organic acids types and concentrations:In different treatment times,the best effect of decreasing amplitude was at 20d,the second one was at 10d,and the last one was at 30d;the best effect of decreasing amplitude was 5.0 mmol/L,the second one were 10.0 and 1.0 mmol/L,and the last one was 0.2 mmol/L;The order of decreasing amplitude of organic acids was succinic acid>citric acid>oxalic acid.