Physiological And Hydraulics Response Of Malus Sieversii To Water Stress

This article is study on the seedling roots of Malus sieversii. We will investigate its water metabolism and some changes in osmolyte under drought stress to discuss the mechanism of adapting to arid environment. At the same time, we discuss the influence by drought stress on the seedling roots of Malus sieversii through using the pressure chamber technique and analyze the change of aquaporin activity by HgCl₂ inhibition test. At last, we investigate the response of hydraulic conductivity of seedling roots of Malus sieversii to drought stress and the role and contribution of aquaporin in this process by detecting the expression of plasma membrane aquaporin using the Western blotting technique. All of the conclusions are as follows:1. With the increase in time of drought stress, the normal seedling has maintained a rapid growth, however, the growth of seedlings which were moderate and severe stress treated has significantly inhibited. After 10 days of drought stress, the growth of seedlings which were moderate and severe stress treated has been to slow. especially the severe stress of seedling growth which was almost stagnant. It is illustrate that drought stress can inhibit the growth of seedling roots of Malus sieversii.2. Different drought stress has different effect on the RWC of Malus sieversii leaves. The extent and degree of water stress is proportional. And at the same level of treatment, as the stress time goes by, the leaf relative water content also decreased, especially the severe stress which the was the biggest drop of seedlings. It is illustrate that the more severe stress are, the leaf relative water content falls faster.3. Under water stress, soluble sugar, free proline and soluble protein have different degrees of accumulation. All of the three material in severe stress were higher than normal growth and moderate stress one. And with the stress time increases, the content of these three substances are higher than before. However, the change of soluble sugar was not significant than the change of free proline. It is illustrate that Malus sieversii can adapt to adversity by the osmotic adjustment under the drought stress.4. HgCl₂ test make Jv and Lp of different treatment of drought conditions of seedling roots of Malus sieversii decreased significantly. And the decrease and the concentration of HgCl₂ were proportional. Recovery after treatment with ME, the flow rate of seedling roots was recover to a certain extent. It is suggest that seedling roots of Malus sieversii contained lots of HgCl₂-sensitive aquaporin which play an important role in water transport in roots. Drought stress resulted in decreased root Jv and Lp .It is illustrate that aquaporin activity was inhibited under drought conditions.5. Western blot results showed that plasma membrane aquaporin of Malus sieversii are mostly exist as mixture of dimer and monomer. And under drought stress, the Expression of plasma membrane aquaporin of Malus sieversii can change by Stress-induced.In this research response of water stress of ZmPIP1;2 and ZmPIP2;5 is obviously different.Under water stress,the expression of ZmPIP1;2 is reduced,and ZmPIP2;5 is increased. This implies that the adjustment mechanism of these two proteins in Malus sieversii seeding roots may be different.