The Effect Of Drought Stress On Leaf Structure And Physiology Of Scabiosa Tschiliensis

Scabiosa tschiliensis Grunning is a perennial herb in the family of Dipsacaceae. It is a kind of cover plant, which has high ornamental value with beautiful flower and long flowering period. It can adapt to the cold and dry climate of north. It plays an important role in preventing the grassland degradation and maintaining biodiversity and ecology balance.This experimental material was Scabiosa tschiliensis, which was one-year growth. The experiment was purposed to research the change of anatomical structure of leaves, the ultra structural, Stomatal characteristics, photosynthesis and physiological indexes of leaves under different water stress. We aimed to establish a simple water tolerance system of Scabiosa tschiliensis, and lay a foundation for the evaluation of water tolerant cover plant materials. The primary research results as follows:1. After water stress the thickness of leaf and the upper and lower epidermis were gradually decreased with the increase of water stress gradient. Thickness of palisade tissue and spongy parenchyma were also decreased, while the ratio of palisade tissue and spongy parenchyma was higher than the one that didn’t under water stress.2. The leaf ultrastructure was complete under control. Grana lamellaes of chloroplasts were distinct. The number of granas was abundant and the structure was compact. The thylakoids were compact and the grana stacks of thylakoids were regular. The chloroplasts showed lowly osmiophilic. There were few and small osmiophilic grain in the chloroplasts. With the intensive of water stress, the grana and envelope damaged, the lamella swelled or dissolved and the grana stacks of thylakoids were decreased. Mitochondrial inner and outer membranes swelled or rived and its inclusion effused.3. With the intensive of water stress, the length and width of stomatal, the rate of stomatal opening was decreased, but stomatal density was increased.4. Under light drought stress, the Gs, Pn, Tr,Ci and WUE decreased, which showed that stomata limited photosynthesis; Under moderate and severe drought stresses, the Pn decreased further, Tr, Gs and WUE decreased rapidly and Ci increased slowly. Non-stomatal limitation played a major role in the progress.5. As the time of water stress prolonged, the change of the leaf relative water content, was gradually decreased, the content of chlorophyll, and the activity of SOD and POD were all firstly increased,and then decreased, MDA, proline and the content of soluble protein were sharply increased. After rewatering only under the sever water stress the correlative physiological indexes can not recover to the normal level.