Influence Of Nitrogen And Potassium Interaction On Physiological Of Pecan Seedlings

Pecan?Carya illinoensis K.Koch?is one of the world's most efficient economic trees,can provide high quality dried fruit,good wood and other products.However,the farmers in the economic interests of the blind fertilization,especially N and K fertilizer,resulting in many pecan forest fertilization overdose phenomenon,not only reduces the efficiency of fertilizer use,but also cause waste of resources and environmental pollution.In order to find suitable pecan growth nitrogen,potassium nutrient concentration,the biennial pecan grafted seedlings,from growth,enzyme activity and photosynthetic characteristics,nitrogen and potassium of different nutritional levels and different potassium levels?K0,K0.5,K1,K2,K5?on effect of biennial pecan seedlings growth and physiological characteristics,to explore the difference of physiological response of pecan seedlings to different nitrogen and potassium concentration treatment,the main results are as follows:1.Effects of different potassium concentrations on physiological and biochemicalcharacteristics of Pecan Seedlings1)With the increase of potassium concentration,new root length,the new root number,biomass growth,shoot length,root diameter,leaf nitrogen content and leaf potassium carbohydrate?soluble sugar,sucrose,glucose and starch?content,leaf pigment content,soluble protein content,POD and CAT activity were increased first and then decreased,and reached the maximum at K2?2 m M?.;in the leaves of calcium and magnesium content,SOD activity and MDA content decreased gradually,and reached the maximum at the treatment of K0?0 m M?;has little effect on manganese and zinc content in rhizome.2)Pn,Gs and Tr,reached the maximum at 40 days after K2?2m M?treatment,which increased by 122.27%,61.35% and 120.48% respectively compared with potassium deficiency K0?0 m M?.Under the condition of potassium deficiency K0?0m M?and high potassium K5?5m M?decreased,pecan seedlings of NPQ have different amplitude increases,the electron transport efficiency??PSII?of the optical system?PSII?decreases,which is mainly due to the decrease in the excitation efficiency?F'v/F'm?of the PSII.3)The potential CO₂ assimilation rate?Wc?,potential CO₂ assimilation rate?Wj?and apparent carboxylation efficiency?CE?were reduced by treatment with potassium deficiency?0m M?and low potassium?0.5 m M,1 m M?.The levels of Vcmax,Jmax,TPU,LSP,LCP and AQE were decreased in the treatments of low potassium and high potassium?5 m M?,and the six indexes were significantly decreased.The lower the potassium concentration,the stronger the inhibition of Amax in the pecan seedlings.In the treatment of 0-40 d,the lower the potassium concentration,the larger the Rd of the pecan seedling,indicating that the low potassium stress increased the pecan seedling consumption of photosynthetic products.2.Effects of Nitrogen and Potassium on the Growth and Physiological Characteristics ofPecan SeedlingsUnder the condition of K1?0 m M?treatment,the biomass and the root length of the seedlings increased significantly with the increase of nitrogen supply.Under K2 treatment,the content of N in leaves was significantly higher than that in K1 treatment,and the content of N was not significant.With the increase of nitrogen concentration,the leaf Pn increased,and when the nitrogen concentration reached 1.5 m M,the Pn increased and then decreased.The F'v/F'm,?PSII and q P were significantly decreased under the treatment of potassium deficiency and low nitrogen?K2N1,K2N2?,indicating that the efficiency of light harvesting was decreased,and the photosynthetic electron transport was inhibited.