Effects Of Phosphorus Addition On Photosynthetic And Physiological Characteristics Of Phoebe Bournei Seedlings

Phoebe bournei(Hemsl.)Yang,a secondary key protected tree species in my country,has high ornamental value and unique economic value.However,due to the lack of key protection,coupled with the slow growth of Phoebe bournei,its seedling regeneration ability Due to its weaker characteristics,the distribution of Phoebe bournei natural forests in China has become very scarce,and the artificial cultivation cycle is long,and the protection and development of bournei resources is imminent.Phosphorus is the main limiting factor for the growth of forest trees in southern my country.The traditional method of applying phosphorus is mainly to provide the forest trees with concentrated or periodic nutrient supply,ignoring the allometric growth characteristics of seedlings,resulting in excessive nutrient concentration in the early stage of growth and high nutrient supply in the later stage.The lack of fertilizer restricts the growth potential of seedlings,and there are problems in the cultivation of seedlings,such as poor quality,waste of phosphate fertilizer and environmental pollution.Therefore,how to regulate the nutrition at the seedling stage through a new way of applying phosphorus has become one of the key technologies for cultivating high-quality and strong seedlings of Phoebe bournei.In this study,the annual container seedlings of Jindong were selected as the experimental materials,and there were 9 different phosphorus application treatments with no phosphorus CK,7 groups of index phosphorus application,and 1 group of average phosphorus application.The research on the growth,root morphology,physiological and physiological characteristics of Phoebe bournei seedlings The impact of nutrient loading and other aspects.the result shows:(1)The ground diameter,plant height,and biomass of Phoebe bournei seedlings increased first and then decreased with the increase of phosphorus application level.They all reached the maximum at 2000 mg/plant,while the root-to-shoot ratio decreased first.After increasing,the total root length,total surface area and total volume of the root system all showed a trend of first increasing and then decreasing with the increase of phosphorus application level.The average roots had no obvious regularity.The total root length of root system was 1600～2000 mg/plant when phosphorus was applied.Indexes such as,total surface area and total volume performed the best,while root vitality showed a downward trend.Compared with the average phosphorus application,the exponential phosphorus application had better effect on the growth promotion of Phoebe bournei seedlings’ ground diameter,seedling height,and root system,but there was no significant difference in biomass,but it significantly affected the seedling root-shoot ratio.(2)The soluble sugar content of Phoebe bournei seedlings increased first and then decreased with the level of phosphorus.It reached the maximum when phosphorus was applied at 2000 mg/plant Malondialdehyde showed a rising trend throughout the experimental period.The performance between groups As the phosphorus level increases,it first decreases and then increases.The accumulation of soluble sugar content during exponential phosphorus application was higher than average phosphorus application,and it was slightly lower after stopping phosphorus supply.The performance of soluble protein throughout the experimental period was that exponential phosphorus application was better than average phosphorus application,while the content of malondialdehyde was better than average phosphorus application.The performance is lower than the average phosphorus application in index application.(3)Leaf chlorophyll a,b,and total chlorophyll all increased first and then decreased with the increase of phosphorus level,reaching the highest when phosphorus was applied at 2000 mg/plant;leaf chlorophyll a,b and total amount were greater than average application when phosphorus was applied exponentially.Phosphorus,but the difference is not significant The maximum net photosynthetic rate(Pnmax)first increased and then decreased with the increase of the phosphorus level.The apparent quantum efficiency(α)first increased and then decreased,and the light saturation point(Lsp)showed a trend of increasing with the phosphorus level.In the daily change,the net photosynthetic rate,stomatal conductance and transpiration rate showed an asymmetric bimodal trend.The daily average comprehensive performance between treatments reached the best when phosphorus was applied at 2000 mg/plant.The initial fluorescence(P0)of leaves increases with the increase of phosphorus application level,the maximum fluorescence(Fm),actual maximum quantum yield(Y(Ⅱ)),photochemical quenching coefficient(qP)and relative electron transfer rate(ETR)All of them showed a trend of first increase and then decrease with the increase of phosphorus application level,reaching the maximum at 2000-2400 mg/plant,respectively.There was no significant difference in the maximum quantum yield(Fv/Fm)among the treatments.(4)When phosphorus was applied for 8 weeks,the content of N,P,K,Ca,and Mg in the leaves of Phoebe bournei seedlings showed a trend of increasing with the increase of the phosphorus level.After 16 weeks,they all showed a significant increase first with the increase of the phosphorus level.When phosphorus is applied to 1600～2000 mg/plant,the growth rate slows down or decreases.The overall distribution of N,P,K content is leaf>root>stem,Ca content is leaf>stem>root,and Mg is root>leaf>stem.The accumulation of N,P,K,and Mg all showed the order of leaf>root>stem,and the accumulation of Ca showed the order of leaf>stem>root;the accumulation of N,P,K,Ca,and Mg in a single plant all showed that the accumulation of N,P,K,Ca,and Mg showed an increase in the level of phosphorus application.The trend of increasing first and then decreasing reaches the maximum at the phosphorus level of 2000 mg/plant.The critical value analysis method was used to preliminarily determine the optimum phosphorus level in the range of 1200～2000 mg/plant.(5)There is a significant or extremely significant correlation between the growth,physiology and nutrient content of Phoebe bournei seedlings.The optimal index phosphorus level for seedlings ranges from 1600 to 2000 mg/plant.At this time,the seedling quality of Phoebe bournei seedlings is relatively Best,the exponential fertilization mode is better than average fertilization in promoting the growth,physiology and nutrient carrying capacity of Phoebe bournei seedlings and improving the quality of seedlings.