Effects Of Different Root Storage Capacity On The Growth And Physiological Characteristics Of Paulownia

In the process of revegetation,forest tree is the main source of forestation,forest tree quality is an important factor that is directly related to the success or failure and effect of forestation,and the root is the most important function organs of the forest trees,the changes of root storage capacity could directly affect the growth and nutrition supply for aboveground of forest tree,photosynthesis,the absorption ability and utilization of moisture,which greatly affects the growth and physiological of forest trees.Therefore,this study selects the high quality of Paulownia clones of M(9501)as the material,set up three cultivation treatment groups i.e.retaining stem,transplanting and cutting stem,we aimed to investigate the effects of the root storage capacity of different treatment groups on the growth and physiological characteristics of Paulownia.In order to provide theoretical basis to improve the quality of Paulownia during in the process of revegetation,the cultivation of high quality trees and the construction of fast-growing and high-yielding forests.The study results are listed as below:(1)By transplanting and cutting stem,root storage capacity of Paulownia changed,growth index of each group showed obvious differences.Root storage capacity increased by cutting stem,the tree height,ground diameter and leaf area growth rate increased significantly compared to the other two groups,underground biomass,aboveground biomass and relative root cap ratio are also obviously increased,forest tree was growing well.But root storage capacity of Paulownia by transplanting decreased,and the growth rate of growth indexes were decreased relative to retaining stem,cutting stem,the growth of forest tree was poor.(2)The diurnal variation of photosynthetic rate,transpiration rate and stomatal conductance of Paulownia under different root storage capacity showed a single peak curve in the early and end of the growing season,but double peaks curves were also found in the middle of the growing season,and had the typical "lunch break" phenomenon.And the diurnal variation of intercellular CO2 concentration of Paulownia showed consistent trends and a single peak curve under different growing season,change trend was first decreased and then increased,similar to parabola concave.But the seasonal variation of different root storage capacity of the photosynthetic rate and transpiration rate have no obvious regularity,and they were different.Overall view,the diurnal variation of photosynthetic rate and transpiration rate in each period,stomatal conductance showed significantly correlated,withing intercellular CO2 concentration was negatively correlated.The photosynthesis of Paulownia of cutting stem during the whole growing season are higher than the other two groups,large root capacity plants could show that stronger photosynthetic energy power.(3)The physiological indexes of Paulownia by the cutting stem were optimal in the whole growth season.The chlorophyll a,chlorophyll b and total chlorophyll content of photosynthetic pigments were the highest,and carotenoid content was the highest.Leaf relative water content reached the highest value between groups.And Paulownia physiological indexs by retaining stem and transplanting treatment are relatively low.This indicated that the increase of root storage capacity had a positive effect on the formation of plant photosynthetic pigments and the relative water content of leaves.Through the correlation analysis,it was found that the relative water content and chlorophyll content of the leaves were positively correlated with Pn,Tr and Gs.(4)During the experiment,the variation trend of nitrogen,phosphorus and potassium contents in the leaves of Paulownia under different root storage capacity were consistent,the content of nutrient elements in the growing season were as follows: the early growing season>the middle of growing season>the end of growing season.The three nutrient elements in the leaves of Paulownia by cutting stem were higher than those of the retaining stem,transplanting in the whole growing season.The root storage capacity of the transplanting treatment was lower than that of the retaining stem.The study also found that the nutrient content in the leaves of Paulownia under different root storage capacity were significantly positively correlated with chlorophyll content and photosynthesis.(5)After a lot of studies had show that the cutting stem treatment of Paulownia,short term,the tree height and ground diameter were lower than the retaining stem treatment of Paulownia.However,due to the cutting stem treatment of Paulownia had larger capacity,faster recovery speed,after a period of time,to the middle of growing,the tree height and ground diameter were greater than the retaining stem treatment of Paulownia.Analysis the indexs of growth,physiological and nutrient elements,the results showed that the biomass of Paulownia by cutting stem was the highest among the different groups,and it increased the tree height,the diameter and the leaf area,and increased aboveground,underground biomass and relative root cap ratio,increased photosynthesis capacity and photosynthetic pigment content,had higher leaf relative water content,and also increased the content of nutrient elements in different degrees.These indicate that the Pulownia by cutting stem had a strong ability to grow and a high forest quality due to the increase in root storage capacity.