Effect Of High Molecular Weight γ-PGA On The Ability Of Plants To Absorb Nutrients

Gamma-polyglutamic acid(γ-PGA)is produced by microbial metabolism and has attracted attention at home and abroad due to its broad application scenarios.As a new type of polymer material,γ-PGA has been widely studied and applied in the agricultural field.However,the current researches mostly use low molecular weight γ-PGA as a synergist for root irrigation,while high molecular weight γ-PGA is used in other fields such as medical treatment and environment.In this paper,the laboratory-produced high molecular weight γ-PGA was combined with urea as a foliar fertilizer to grow lettuce to explore the effect of high molecular weight γ-PGA on the ability of plants to absorb nutrients.The main results achieved are as follows:(1)Spraying γ-PGA urea foliar fertilizer can promote the growth of lettuce at an appropriate concentration,but if the concentration is too high,it will inhibit the growth of lettuce.Among them,0.2g/L γ-PGA foliar fertilizer has the best fertilizer effect.In the pot experiment,the yield of 0.2g/L γ-PGA combined with urea foliar fertilizer increased by 15.1% compared with that of urea foliar fertilizer,and the stem and leaf increased by 6.4% and 18.2%respectively.The growth of leaves was faster than that of stems.And the leaf area increased significantly.Under the treatment of 0.2g/L γ-PGA,the chloroplast pigment content of lettuce was significantly increased.(2)0.2g/L γ-PGA combined with urea significantly increased the total nitrogen level of lettuce leaves,indicating that the nitrogen absorbed by lettuce increased.In order to explore the specific way that γ-PGA promotes nitrogen absorption,by measuring the changes of lettuce physiological indexes in a short period of time after spraying foliar fertilizer,it was found that 0.2g/L γ-PGA combined with urea foliar fertilizer had a significant effect on the opening of lettuce leaves’ stomata.The promotion effect can slow down the transpiration of lettuce leaves,but has no significant effect on the photosynthetic rate in a short time.At the same time,γ-PGA at this concentration can prevent the decomposition of nitrogen fertilizer urea,reduce the loss of nitrogen fertilizer,and promote the utilization of nitrogen by leaves.(3)To further explore whether the urea is fully utilized after entering the interior of the leaves,the research on the key enzyme activities of nitrogen metabolism in lettuce leaves sprayed with γ-PGA urea foliar fertilizer found that the enzyme activity was significantly increased after the application of fertilizer,and the use of γ-PGA urea foliar fertilizer The enzyme activity of the-PGA treatment group was significantly higher than that of the non-use treatment group,indicating that γ-PGA can promote the internal nitrogen cycle of lettuce leaves.At the same time,the control of low-concentration nitrogen fertilizer was made.The synergy of 0.2g/L γ-PGA on low-concentration urea made the promotion of enzyme activity reach the level of high-concentration urea,which is of great significance to the reduction and efficiency of nitrogen fertilizer.The above results show that a certain concentration of high molecular weight γ-PGA can promote the nitrogen absorption capacity of lettuce leaves,enhance the nitrogen metabolism of plants,and finally increase the yield of lettuce.