Effect Of Cold Stress On Physiological Metabolism Of Buxus Sempervirens

Buxus sempervirens (Buxaceae) is an evergreen shrub, which is used for the green fencebecause it has dense branches and leaves, and dose not wither and fall in the winter. The areasof B. sempervirens introduced and cultivated are gradually extended northward. The plants of B.sempervirens are seldom injured at zero or below zero in the north. Therefore, people areinterested in studying the physiological adaptation mechanism of B. sempervirens under thecold stress.In this thesis some methods of studying plant physioecology were used. The effects ofdifferent conditions on the morphological and physiological features of B. sempervirens wereanalyzed, which include the cold stress of different temperatures, 5℃continually cold stress,and the cold stress of different light conditions. The physiological mechanism of B.sempervirens adapting the low temperature conditions was clarified preliminarily. The resultsshowed:(1) The leaf structures of B. sempervirens in the cold stress of different temperatures and5℃continually cold stress dose not have obvious changes.(2) The activities of antiadversity enzymes (SOD, CAT, POD, APX)of B. sempervirensin the cold stress of different temperatures and 5℃continually cold stress are different. Theactivities of antiadversity enzymes are increased in the former condition and vary undulantly inthe latter.(3) When the low temperature and light are used at the same time, B. sempervirens keepsthe high level of SOD activity, which could clean effectively the active oxygen produced byphoto-oxidation of the low temperature induction, and meanwhile B. sempervirens maintain thestable H₂O₂ level in cells through increasing the activity of CAT and POD.(4) In the cold stress of different temperatures and 5℃continually cold stress, B.sempervirens resists the effect of the harmful environment by means of increasing the contentof bound water.(5) In the cold stress of different temperatures and 5℃continually cold stress, B.sempervirens get more soluble sugar through degrading starched of leaves and fit the harmfulenvironment.(6) The soluble protein and praline of B. sempervirens increase markedly in the coldstress of different temperatures. At 5℃continually cold stress the soluble protein increasesfirst and reduces later, and the proline increases undulantly.(7) In the cold stress of different temperatures the respiratory rate and cyanide-resistantrespiration of B. sempervirens showed the trend of increasing-reducing-increasing. The normal respiratory rate had same trend above at continually low temperature stress.(8) In the cold stress of different temperatures, B. sempervirens has the protein induced ofmolecular weight 27kD, and the expressing amount increases with the adding cold stress.When 5d and 5℃continually cold stress were used, the proteins of molecular weight 99.35kD,51.60kD and 14.58kD were not found, the expressing level of 17kD protein is increasedobviously, but there is no new protein induted.Our study showed B.sempervirens resist the harmful environment from the lowtemperature by means of changing the membrane permeability, increasing the content of boundwater, changing the respiratory rate, and resist the expressing of antiadversity protein andincreasing the activity of enzyme. These results provide the basic data for studying thephysiological mechanism of B.sempervirens in antiadversity.