Studies On The Drought Resistance Of Some Species Iris L.

Iris L. is a large family, and also an important green landscaping materials. Several species have been applied wildly. In future the plants of Iris L. will be applied more widely. Due to the environmental changes and the characteristics of monsoon climate, in many areas, there are different degrees of drought,which influences the distribution and application, so the researches on drought resistant of Iris L. are important both in their application and breeding.In this paper, the physiological and biochemical factors(including water changes in plants, chlorophyll changes, enzyme activities and osmotic adjustment et al) of 5 Iris species:I.tectorum,I.lactea var.chinensis,I.pseudacorus,I.ensata var.hortensis,I.sanguinea were studies based on pot experiment under drought stress.The main results are follows:1.The changes of water content and chlorophyll content under drought stress. Under drought stress the relative water content of 5 species was decreased. The relative water of I.tectorum was higher than I.lactea var.chinensis, I.pseudacorus,I.ensata var.hortensis , and the relative water of I.sanguinea was the lowest. The organizational water content of I.tectorum was the highest, and there was a little decrease when the other 4 species decreased a lot. The transformation between free water and confined water under the drought stress was evident. The changes of chlorophyll content varied on 5 species, The chlorophyll content of I.tectorum decreased and I.lactea var.chinensis , I.pseudacorus , I.ensata var.hortensis ,I.sanguinea were increased, especially I.sanguinea increased significantly.2.The changes of cell membrance system and enzyme activities under drought stressThe relative electric conductivity of 5 species was increased, among them I.tectorum increased little; I.ensata var. hortensis had the highest relative electric conductivity in 15d. The MDA content of I.tectorum increased at first, then decreased, the other 4 species increased always. The activities of SOD increased at first, then decreased. The SOD activities of I.tectorum,I.lactea var.chinensis were higer than I.pseudacorus,I.ensata var.hortensis and I.sanguinea.3.The changes of osmotic adjustment under drought stressThe changes of soluble protein were different in 5 species. I.tectorum,I.lactea var.chinensis and I.pseudacorus were increased in the beginning, then decreased. The changes of soluble protein of I.ensata var.hortensis,I.sanguinea were slight. The content of proline were increased with the drought days becoming long. I.sanguinea was the earliest increased to the peak value of content proline, and the rang of increase was also the most; I.tectorum had the lowest praline content, I.lactea var.chinensis, I.pseudacorus,I.ensata var.hortensis were middle.4.Comprehensive evaluation of drought resistant11 physiological and biochemical indexes were evaluated comprehensively by principal components analysis and subordinate function analysis. Results show that the drought resistance of Iris species from strongest to the weakest were as follow:I.tectorum, I.lactea var.chinensis , I.pseudacorus , I.ensata var.hortensis ,I.sanguinea。5.11 physiological and biochemical indexes were evaluated comprehensively by cluster analysis, the results show that 5 species can be divided into 3 classes of drought: the drought resistant of I.tectorum, I.lactea var.chinensis were strong; I.pseudacorus,I.ensata var.hortensis were middle; and I.sanguinea was weak. Based on the correlation analysis between D value and 11 physiological and biochemical indexes, the relative water content, organization water content, relative electric conductivity, chlorophyll content, MDA content and praline content can be made as reference indexes in future in the drought research of Iris L.