The Effection Of Drought Stress On Potentillaa Sericea Of Structure And Physiology

Potentilla sericea in Rosaceae is a kind of cover plant,which have high ornamental value with beautiful flower and long flowering period in early spring and early summer.It can adapt to the cold and dry climate of the north.lt also can put into use in landscaping.This experimental material was Potentilla sericea, that was one-year growth. The experiment was purposed to research the change of anatomical structure of vegetative organ, the ultrastructural, Stomatal characteristics, photosynthesis and physiological indexes of leaves under different water stress.We aimed to establish a simple water tolerance system of Potentilla sericea, and lay a foundation for the evaluation of water tolerant cover plant materials.The primary research results as follows:1. The variation tendency of anatomical structure of leaves,stems and roots were generally consistent under water stress and PEG stress.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. The volume of cortex parenchyma cells were diminished or broken.The order of cells in the vascular bundle were not compacted.The cells on the edge of primary phloem were not clear and disordered or broken.The shape of roots’ transaction were changed.The cells of secondary phloem were flated.Some of wood cells were broken.2. The leaf ultrastructure was complete under control. Granum lamellaes of chloroplasts were distinct. The number of granum were abundant and the structure were 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. With the intensive of water stress,the length and width of stomatal,the rate of stomatal opening were decreased,but stomatal density were increased. The net photosynthetic rate was closely related to the change in chloroplast structure. The Pn,Tr and WUE of leaf decrease with the declining of soil water content and the damage of chloroplast.3. As the time of water stress prolonged, the changes of the leaf relative water content, the content of chlorophyll was gradually decreased, MDA and proline and the activity of SOD and POD were all firstly increased,and then decreased,the content of soluble protein was sharply increased.After rewater only under the sever water stress the correlative physiological indexes can not recover to the normal level.