Response Of Quercus Variabilis Seedlings To Root-cutting And Water Deficit

In the process of vegetation construction,seedling quality is fundamental factors to the seedling survival and growth after forestation,which directly affects the root architecture and the survival rate of transplanting.Root is the most important function organs of seedling.The changes of root architecture could directly affect the growth and nutrition supply for aboveground of seedling,plant photosynthesis,the absorption ability and utilization of moisture as well as the adaptive capacity to environmental stress after transplanting.Therefore,the representative Quercus variabilis seedlings in the Huabei hilly Mountains were selected as research objects.Set up four root cutting treatment groups i.e.integrated root,1/4 root-cutting,1/3 root-cutting and 1/2 root-cutting,observed the difference of Quercus variabilis seedlings’ root morphology and growth status.,As well as five soil moisture gradient,namely,Ⅰ（20.766%）、Ⅱ（18.197%）、Ⅲ（16.967%）、Ⅳ（13.296%）and Ⅴ（10.435%）,were set up.Through comparing the physiological index and chlorophyll fluorescence parameters under different root-cutting treatments and water deficit,we aimed to investigate the responses of Quercus variabilis seedlings to root-cutting and water deficit,finally,providing theoretical basis to improve the seedlings quality of Quercus variabilis during the construction process of vegetation.Some of results are listed as below:（1）Cut off the taproot of Quercus variabilis seedlings had a direct impact on taproot growing,reduce the plant height,ground diameter,the number of root tips,root density,root volume and root activity,but 1/3 and 1/4 root-cutting ratio could induce the occurrence of fibrous roots,increase the average root diameter and the root surface area,as well.And it could also increase the underground biomass,aboveground biomass and root cap ratio.Moreover,1/2 root-cutting ratio could lead to a drop of the seedlings’ quality significantly.（2）The leaf relative water content of Quercus variabilis had an extremely significant correlation to both degree of root-cutting and soil water content.With the increase of root-cutting ratio and water deficit,Quercus variabilis leaf relative water content was decreased.The leaf with higher relative water content was propitious to promote the photosynthesis,water and mineral absorption and transport,and it was also propitious to improve the drought resistance of plants,and so on.In This experiment,the integrated root treatment had better drought resistance to the other treatments,1/3 root-cutting was the most optimal ratio in the three root-cutting ratios,and the difference between integrated root treatment and 1/3 root-cutting treatment was not significant.（3）There had a significant impact to the chlorophyll content of Quercus variabilis seedlings with root cutting,soil water content and the interaction between them.In detail,under the same soil water content,Chlorophyll a,chlorophyll b and total chlorophyll content of 1/3 root-cutting treatment were the highest,the integrated root treatment and 1/4 root-cutting treatment were relatively low,Chlorophyll a/b was maintained at about 3:1.Under the same treatment,chlorophyll content decreased firstly and then increased with the deepening of water deficit.（4）Responses of chlorophyll fluorescence parameters to root-cutting and water deficit were both sensitive.With the deepening of water deficit,F₀ and q N were increased,meanwhile F_m、F_v、F_v/F_m、F_v/F₀、ΦPSII、ETR and q P were decreased.We could identify the degree of their variation of plant drought resistance or endurance ability.The conclusions we get in this paper was that the integrated root treatment and 1/3 root-cutting treatment had better drought resistance or endurance ability.The difference between them was not significant.（5）Due to the seedlings’ taproot cut off,the main root length,root volume,root density and root tips of Quercus variabilis seedlings under the root-cutting treatment was lower than integrated root treatment.But analysis the index of root morphology,biomass,plant physiological indexes and chlorophyll fluorescence parameters and so on in comprehensive,showed that 1/3 root-cutting treatment had better seedling quality.The root surface area,root diameter,underground and aboveground biomass,root cap ratio,chlorophyll content,ETR and F_v/F_m were higher than integrated root treatment.And 1/3 root-cutting treatment also had the same leaf relative water content to integrated root treatment.Illustrate 1/3 root cutting treatment had strong ability of drought resistance and good seedling quality.