Effects of Drought Stress on Chlorophyll Content of Two Fast-growing Tree Species

Using bamboo willow and Eucalyptus urophylla × E. grandis seedlings as test materials, drought stress experiments were conducted using a pot-culture method to study theories and mechanisms for water-saving fast-growing tree species in southern China.The test trees were analyzed and evaluated by comparing the changes of chlorophyll a, chlorophyll b and chlorophyll(a+b) contents as well as the ratio of chlorophyll(a+b) ratio in the seedlings after being stressed by drought, Results showed that the contents of chlorophyll a from the test trees of both species decreased gradually after drought stress treatment; E. urophylla × E. grandis declined to 70.2%, whereas bamboo willow declined to 55.5%. The content of chlorophyll b and(a+b) increased at first but then decreased; chlorophyll b content changed little compared with that under conditions of normal water availability; the change of chlorophyll(a+b) content was mainly caused by changes that occurred in chlorophyll a. Bamboo willow's chlorophyll(a+b) varied less than that in E. urophylla × E. grandis. Chlorophyll(a/b) showed a trend that first decreased and then increased, the minimum values being on the 9thday of drought stress; the minimum for this parameter in bamboo willow was lower than in E. urophylla × E. grandis. Through comprehensive analyses of every indicator combined with the drought resistance performance of plants, it was concluded that the bamboo willow had better adaptability and drought resistance performance than E. urophylla × E. grandis.