Effects Of Different Stress On Growth And Apical Meristem Of Chinese Fir Seedlings

Chinese fir is one of the main timber tree species in China.In recent decades,the continuous generation of Chinese fir plantation has led to a decreasing trend in yield of Chinese fir.A large number of studies have shown that continuous planting of Chinese fir can cause the decline of soil pH,the decrease of available phosphorus in soil,and the aggravation of aluminum toxicity,which has become the main factor restricting the growth and yield of Chinese fir plantation.Related studies have shown that plant root apex meristem is most sensitive to stress induction,so it is of great significance to study the effect of adversity stress on the root apex meristem of Chinese fir in Chinese fir.Therefore,in this study,the seedlings of Chinese fir seedlings and Chinese fir seedlings were used as materials to simulate the effects of different stresses,including phosphorus stress,pH stress and aluminum stress,to observe the effects of different stress on the high growth,ground growth and root growth of the seedlings of Chinese fir seedlings,and the paraffin wax was made from the root tips of the seedlings of the Chinese fir seedlings.The effects of different stress on the apical meristem of Chinese fir were observed.This study attempted to analyze the effects of different stress on the growth of Chinese fir seedlings and the response mechanism of Chinese fir meristem under different stress conditions.It provides scientific basis for seedling cultivation and afforestation of Chinese fir under difficult site conditions.The main experimental results are as follows:1)The effects of different stress treatments on the growth indexes of Chinese fir seedlings were significantly different.The number of different phosphorus concentrations had a significant effect on the number of lateral roots of Chinese fir seedlings.The number of lateral roots of medium,severe and high phosphorus supply were 2.3 times,1.9 times and 0.72 times of the control group respectively.Under the conditions of this study,the supply of low phosphorus could inhibit the elongation of the main root and promote the starting of the lateral root;aluminum stress had a great influence on the growth of the lateral root of Chinese fir seedlings.Aluminum toxicity would inhibit the initiation and elongation of the lateral roots.Three stress levels of 0.5mmol/L Al,1.5mmol/L Al and 2.5mmol/L were equal to the lateral root length of the non aluminum control group,respectively.The effect of acid stress on the growth of lateral root of Chinese fir seedlings was significantly reduced by 20%,48%and 85%.The level of pH4.0 was the most unfavorable for the growth of the lateral root of Chinese fir seedlings.Heavy acid could inhibit the initiation and elongation of the lateral roots of Chinese fir seedlings,and the lateral roots of pH5.0 and pH4.5 were 2 times as long as that of the seedlings.2)The effects of different.stress treatments on the growth indexes of seedlings of Chinese fir seedlings were significantly different.Under the moderate phosphorus stress,the root growth of the seedlings of Chinese fir cuttage seedlings was promoted.The effect of different aluminum stress on the growth of the seedlings,the growth of the ground diameter and the root growth of the young seedlings of the Chinese fir cuttage was significant,and the growth of the seedling height,the ground diameter and the root growth slowed down with the aluminum stress,and the root length of the non aluminum control group was 0.5mmol/L A.The three stress levels of L,1.5mmol/LAl and 2.5mmol/L were 1.5 times,1.7 times and 2.2 times,and the different pH levels also affected the growth,growth and root growth of the seedlings of Chinese fir,and the effect of pH on the root growth of the seedlings of Chinese fir seedlings was reduced with the decrease of pH value.3)The effects of different stress on the apical meristem of seedlings of Chinese fir seedlings were significantly different.The area of root tip meristem area and root crown area of Chinese fir seedlings were significantly affected by different phosphorus concentration stress.The area of high phosphorus supply,moderate stress and severe stress was only 68%,70%and 45%of the normal phosphorus supply,and the normal phosphorus supply area was more active.Under aluminum stress,the area of the root apex meristem of Chinese fir decreased gradually with the increase of aluminum toxicity,and the area of the non aluminum control group was 2 times as high as that of 1.5mmol/L A1 and 2.5mmol/L Al.The increase of aluminum toxicity resulted in the decrease of the active degree of the root apex meristem of Chinese fir,thus inhibiting the growth of the root system of Chinese fir.Under acid stress,the level of pH4.0 stress in the root tip meristem area and root crown area decreased sharply compared with the control group,which led to the control group better than the pH4.0 stress level in the root growth potential.