| Spiraea×bumalda 'Goldflame'in Rosaceace is a deciduous shrub which has high ornamental value with flourish flower, long flowering period, colcorful leaves and is well-adapted.This experiment was cnducted with one-year rooted cuttings of Spiraea×bumalda'Gold Flame'which were exposed to dehydrations under different water stress. We aimed to establish a simple water tolerance system of the Spiraea×bumalda'Gold Flame'rooted cuttings, and to lay a foundation for the evaluation of the other plants of the same genus and to breed water tolerant spiraea ground cover plant materials, the changes of the biological characteristics and the physiological indices of the rooted cuttings under different water stress were determined.The primary research results as follows:1. Anatomical structures of leaves of Spiraea×bumalda'Goldflame'before and after water stress were observed, the result was:The thickness of leaves, the size of upper and under epidermis cells and the stomatal length and width were decreased with intensify of drought while the stomatal density and the density of cells of palisade tissue, showed an increased tendency. These results indicate that:As the water stress was intensified and the time was lengthened, the leaves of Spiraea×bumalda'Gold flame'loosing water gradually which presents cells gradually became smaller,stomatal density increased and stomatal size decreased in the internal structure of metarials. So the size of cells and stoma can be the evaluation indicators for water stress tolerance of Spiraea×bumalda 'Goldflame'rooted cuttings.2. Anatomical structures of roots of Spiraea×bumalda'Goldflame'before and after water stress were observed, the result was:Under the water stress in air, the order of the root vascular bundle had been broken gradually with lengthen of stress time, protoxylem and metaxylem vessel cross-sectional areas were significantly smaller and gradually moving to the edge of vascular cylinder edge;Under the PEG stress, the order of the root vascular bundle also had been broken gradually with lengthen of stress time, protoxylem and metaxylem gradually moving to the edge of vascular cylinder edge with the disintegration of the wood cells. These results show that, as the water stress was intensified and the time was lengthened, the roots of Spiraea×bumalda'Gold Flame'loosing water gradually which presents the deformation of the vascular bundle, movment of protoxylem and metaxylem to the edge of vascular cylinder edge and the disintegration of the wood cells. Therefore, the order of the vascular morphological and the morphology of the wood cells can be used as the evaluation indicators for water stress tolerance of Spiraea x bumalda'Goldflame'rooted cuttings. 3. Anatomical structures of stems of Spiraea×bumalda'Goldflame'before and after water stress were observed, the result was:Under water stress, anatomical structure of the stems under different levels of water stress did not change significantly as the water stress was intensified and the time was lengthened, under the mild water stress, the basic structure of the stem had been severely damaged, the cells completely fragmented. Therefore, changes in stem anatomical structure are not suitable for use as the evaluation indicators for water stress tolerance of Spiraea×bumalda 'Goldflame'rooted cuttings.4. According to the morphological feature of the plants under different water stress, the welting index was divided into 5 grades.The changes of the morphology are described as follows: grade 0, young plants growing normally with light green leaves expanded naturally; 1, the apical leaves began curl and the colour of the plant leaves became dark the lower leaves expanded naturally(slight wilting); 2, the apical leaves folded moderately and the upper and lower leaves began curl and the colour of the plant leaves became darker(moderate wilting); 3, all the leaves crimpled slightly and the colour of the plant leaves became celadon(severe wilting); 4, the plantlets withered completely.Therefore, these welting indexes can be used as the morphological evaluation indicators for water stress tolerance of Spiraea×bumalda 'Goldflame'rooted cuttings.5. Under the dehydrations in air, with lengthen of stress time, the leaf relative water content, the SP content, the Pro content, the MDA content,the SS content and the activities of SOD showed an regular tendency, so they were the evaluation indicators for water stress tolerance of Spiraea×bumalda'Goldflame'rooted cuttings. Under the PEG stress, with the lengthen of stress time, the leaf relative water content, the SP content, the MDA content and the SS content showed an regular tendency, so they were the evaluation indicators for PEG stress tolerance of Spiraea×bumalda'Goldflame'rooted cuttings. However, the Pro content and the activities of SOD showed no tendency, so they were only the references for water tolerance evaluation. |
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