Effects And Mechanism Of ?-poly Glutamic Acid On The Growth And Nutrients Absorption Of Summer Maize

In agricultural production,?-poly glutamic acid??-PGA?,as a fertilizer synergist,has been proved to be of great effects on most vegetable and fruit crops,but lacks of strong data on food crops,especially on summer maize.To find out the regulation and function of?-PGA on growth metabolism and nutrient absorption of summer maize,the pot experiment and the field experiment combined were conducted to study the effects of?-poly glutamic acid under different nitrogen rate on morphological characteristics,yield and nutrient absorption,protective enzyme activity,photosynthesis to confirm the synergy of?-PGA on summer maize and to explore its mechanism preliminarily.The main research results are as follows:1.The results of the pot experiments showed that:1)?-PGA significantly increased the accumulation of dry matter above ground during the vegetative growth stage.Under normal nitrogen,after spraying?-PGA the uptake of nitrogen was significantly increased,and the accumulation of phosphorus at early stage and potassium at latter stage were substantially increased.And especially 0.27 mg?plant^-11 could enhance entirely the absorbtion of NPK,and significantly increase grain-weight per plant by 28.35%,and also 0.54 mg?plant^-1 significantly increased by 18.35%;under the nitrogen 30%reduction,?-PGA 0.27and 1.08 mg?plant^-11 significantly increased the entire uptake of phosphorus and potassium as well as the early nitrogen,which significantly increased grain-weight per plant by19.44%and 23.90%.2)Compared with the control,the treatments with foliar-spraying?-PGA 0.54².16 mg?plant^-1 increased the leaves length or width to expand leaves area and the effects are better at the latter stages;moreover,0.27mg?plant^-11 had some hysteresis effect at the normal nitrogen;3)With spraying?-PGA,the SOD and POD activity enhanced;under nitrogen reduction when it was especially at maturity stage the increasing of activity was drastically soaring;CAT activity of the?-PGA treatments was also significantly increased.4)At the early stage,the total root absorption area increased by 25.80%³8.02%,and with low dosage,the fresh weight of root increased by 18.94%;but there was no difference on the roots growth between?-PGA treatments and control.5)?-PGA could improve the photosynthetic capacity of summer maize,but the increase gradually decreased with the increase of spraying dosage,and the effect was more obvious at low dosage.2.Our study of the field experiment in two years showed that:1)compared with clear water control,both?-PGA treatments had achieved higher yield by increasing the grain number per ear;they had significantly promoted the accumulation of dry matter from flare opening stage to flowering and silking stage and high-dose treatment could also significantly promote the accumulation of flowering and silking to filling stage,which contributed to the increase of total accumulation of dry matter;the accumulation of NPK changing consistent with the dry matter accumulation,also significantly increased.Treatments with glutamic acid,compared with water control,had no significant change in yield,composition,dry matter and nutrient accumulation.2)Under normal nitrogen,compared with clear water control,the treatment with low-dose?-PGA had no obvious effect on yield,but the total dry matter accumulation was significantly increased;while high-dose treatment can significantly increase the yield by 3.43%with spike grain number increasing significantly and the amount of dry matter accumulation increased insignificantly.Both low and high dose treatments made NPK accumulation increasing significantly,and there was no significant difference between the two treatments.Under 30%reduction of nitrogen level,the high-dose?-PGA treatment significantly increased yield by 3.07%by increasing spike grain number while low-dose treatment increased the yield by 4.70%by increasing both the spike grain number and grain weight obviously;for both of treatments,the total accumulation of dry matter and nutrition were increased,and especially low-dose treatment had better effect,but there was no significant difference between the two treatments.There was no significant difference in the all indexes of glutamate treatments under the two nitrogen groups.3)In the high-yielding year?2017?,the high-dose treatment with?-PGA significantly increased the yield by 2.54%.In terms of the total accumulation of dry matter and nitrogen,phosphorus and potassium,both treatments were significantly increased.The difference between the two doses was not significant.In low yield year?2018?,the yield of low-dose?-PGA treatment increased significantly by 4.37%increasing spike grain number and the weight of 100 grains,the high-dose treatment increasing spike grain number increased by 4.14%,and the accumulation of dry matter and nutrient of low dose treatment were significantly higher than the control,and also significantly higher than the high-dose treatment.For glutamic acid treatments,only the low-dose treatment in 2018 significantly increased the yield by increasing the weight of 100 grains,but the effect was lower than?-PGA,and other indicators were slightly higher or lower than the control.Above all,the application of?-PGA can expand the summer maize leaves area,improve the ability of photosynthesis,increase the total amount of dry matter mainly by promoting dry matter accumulation after or before flowering,and also promote the total early root absorbtion area which could improve the nutrient absorption capacity contributing to the nutrition accumulation,which could result in increase of the yield mainly by increasing the grain number per ear of summer maize;while the application of glutamic acid has no obvious effect.It can be seen that it is mainly the?-PGA not the decomposition L-glutamic acid that worked efficiently.Under 30%reduction of nitrogen or in low yield year?-PGA has more great effects than normal conditions;under normal nitrogen the high dose?-PGA treatment has better effects,while under 30%reduction nitrogen low dose treatment has better effects.In addition the effects of spraying the low dose?-PGA with 30%reduction of nitrogen and normal nitrogen control and30%reduction of nitrogen control decreasing sequentially shows that under 30%reduction of nitrogen spraying low dose?-PGA can achieve the normal efficiency while reducing fertilizer rate.