The Adaption Of Epidermal Micromorphology And Physiological Mechanism Of Caragana Fabr. To Drought Stress

A typical plants of Caragana in drought and desert areas extensively are used in wind and sand, soil and water conservation, improving soil properties and drought resistance etc., which are of great significance in ecological restoration and reconstruction in the desert region. Selecting 11 species of caragana leaves and seeds as experiment materials, the study was designed to investigate and compare the drought resistance mechanism of different species of eremophytes in respects of ecological characteristics and physiological metabolism and morphology, and with mathematical membership function method, to convert each index factor data, the results as follows:1. Sorting the ability of drought-resistance of Caragana genus using the membership of fuzzy mathematics, C.intermedia>C.stenophylla>C.microphylla>C.spinosa>C.opulens>C.arborescens>C.pruinosa>C.tibetica>C.roborovskyi>C.korsh-inskii>C.brevifolia. The results quantitatively evaluated drought tolerance of the different Caragana species, so as to provide scientific theoretical basis for vegetation restoration in arid and semi arid climate region.2. Through a comparative study of Caragana leaf epidermis and appendages(such as epidermal cells, cuticle, waxy, stomas, trichomes, etc.) and leaf anatomical structure(such as chloroplast, mitochondria, starch grains and liposomes) changed differently to clarify the adaptability of the plant to drought environment from the aspect of morphology and anatomy. C.intermedia, C.opulens, C.roborovskyi and C.stenophylla, which the leaf epidermis were with thick cuticle and wax layer, cells shape evolving into irregular, and the leaves were covered with long trichomes.Anisocytic stomata with large quantity and sunk existing more on the upper epidermis of leaves showed adaptive characteristics to drought. However, drought resistance of C.pruinosa and C.spinosa affected by water deficit were poor, that leaf anatomical features performed swelling chloroplasts, obvious accumulation of starch grains andlipid globules, decreased or transmutative thylakoids, many mitochondrias, but partly vacuolating. Otherwise, the cells structure tend to be normal.3. The difference in RWC, SLA, chlorophyll, free proline, SOD and MDA contents of Caragana leaf were compared, which revealed the adaptability of the genus to drought from the view of physiological and ecological mechanism.C.stenophylla, C.spinosa, C.microphylla and C.pruinosa mainly adapt to drought environments through physiological and ecological changes, which leaves owned higher content of chlorophyll, free proline, SOD and RWC, but lower SLA and MDA.Further study in C.intermedia, C.korshinskii, C.stenophylla found that the degree of drought stress increased gradually, the leaves SLA increased with no significant, plant growth progressively decreased, while the relative conductivity increased first at the beginning of stress, and then got lower along with the drought degree from moderate to severe, after rewatering, the indexs returned to control levels. Difference in the degree of recovery among species.4. The study showed that germination rate and time related to seeds size, surface layers structure, and further elucidated the breeding strategy of the plant seeds adapting to special habitats. The compact degree of palisade tissue and stereid layers,size of hilums and pores, and amyloplast number. The size of C.korshinskii,C.intermedia and C.microphylla seeds with strong adaptability to drought were big that also had big hilums and pores, which owned loosely arranged palisade layers and funnel cells so that no intercellular space but many amyloids in embryos. The seeds germination rate were high(about 95%) and germinated fast(begining from the 1st day). On the contrast, the germination rate of C.arborescens and C.opulens were low(about 77%) needing more time to germinate(begining from the 3rd day and the2 nd day), and seeds size were relatively smaller, so were the hilums and seed pores.The seeds of palisade layers and funnel cells arranged closely that there were no or small intercellular space. What's more, less number of amyloids in embryos. These architectural features symbolized poor drought adaptability. However, C.stenophylla seeds were small with less amyloids, but their hilums and seed pores were big, the arrangement of palisade layers and funnel cells was loosen, correspondingly, which were with lower germination rate(66.67%) and shorter germination time(germinated on the 1st day).The study was aiming for assessing comprehensively, scientifically and quantitatively on drought resistance ability of plants, for soil and water conservation,vegetation restoration, ecosystem rebuilding choosing advantage species in desert areas.