Study On Physiological And Biochemical Responses To Cold,Drought, And Saline-alkali Stress In Some Cultivars Of Herbaceous Peony

Herbaceous peony (Paeonia lactiflora Pall.) is China’s traditional flowers. The herbaceous peony is widely used in the landscape architecture with its elegant color and luxuriant flowers. Cold, drought and soil salinization are three important reasons which affect the promotion and application of herbaceous peony ornamental cultivars. In this study, the treatment of six herbaceous peony cultivars under cold stress (seven different temperatures), four herbaceous peony cultivars under drought stress (four different soil water contents), and two herbaceous peony cultivars under saline-alkali stress were used as the experimental materials. The physiological and biochemical responses to cold, drought and soil salinization were assessed by analyzing changes in the above experiment materials, and the comprehensive evaluation and comparison of the resistance of each cultivar were conducted by usingsome statistical methods such as correlation analysis, principal component analysis and subordinate functions. The results showed that:(1) The relative electric conductivityof underground buds of six herbaceous peony cultivars generally took on S-shaped increase as the temperature declined, and the malondialdehyde content of roots of six herbaceous peony cultivars generally increased. Though soluble sugar content and soluble protein content fluctuated, they increased roughly as the temperature declined. With decreasing temperature, the proline content fell firstly and then rose up, while the superoxide dismutase (SOD) activity showed an up-down-up trend. The six cultivars could be ranked, in decreasing levels of cold resistance, as:’Da Fu Gui’m,’Monsieur Jules Elie’,’Kansas’,’Taff’,’Fen Yu Nu’, and’Pink Hawaiian Coral’.(2) With the reduction of soil water content, the leaves of four herbaceous peony cultivars tended to be yellow and withered, and the relative water content decreased gradually. Relative electric conductivity, malondialdehyde content, soluble sugar content, and proline content generally increased assoil water content declined, while the soluble protein content of ’Da Fu Gui’took on a down-up-down trend, and the other three cultivars’soluble protein contents decreased firstly and then rose up. The SOD activities of four cultivars varied from each other but generally increased as the aggravation of drought stress, while the photosynthetic indicators (max net photosynthetic rate, light saturation point, and light compensation point) decreased. The four cultivars could be ranked, in decreasing levels of drought resistance, as:’Karl Rosenfield’,’Duchesse de Nemours’,’Fen Yu Nu’,and ’Da Fu Gui’.(3) With the aggravation of saline-alkali stress, the leaves of two herbaceous peony cultivars tended to be curl, wrinkled and withered, and the chlorophyll content decreased gradually, while the root vitality increased firstly and then fell down. Relative electric conductivity, malondialdehyde content, soluble sugar content, proline content, and soluble protein content generally increased as the aggravation of saline-alkali stress, and the SOD activities of two cultivars rose firstly and then decreased. The saline-alkali resistance of’Da Fu Gui’is stronger than’Fen Yu Nu’.It is the first time to evaluate the resistance of several new foreign cultivars and two common domestic cultivars of herbaceous peony in this study. The initial screening cultivars,’Monsieur Jules Elie’,’Kansas’ and ’Taff’ with strong cold resistance,’Karl Rosenfield’and’Duchesse dc Nemours’ with strong drought resistance, as well as’Da Fu Gui’with strong saline-alkali resistance, can provide references for the promotion and application of herbaceous peony in the future.