| Scaevola albida is a popular ornamental crop cultivated as a bedding plant or for hanging baskets. Pink Ribbon is one of its cultivated species that originated at Australia. It belongs to a perennial herb, characterized by fan-shaped flowers with a long flowering period, easily cutting propagation. S. albida is firstly introduced by China, so we still do not know its ability of adapting to our environment. High temperature, drought, acid rain, phosphorus nutrition are important factors affecting growth and physiological characteristics of plants, and plants adapt to high temperature stress, drought stress, acid rain stress and phosphorus stress using different strategies during their growth process. In the cultivation process, Elliot discovered that continuous high temperature, soil drought and high phosphorus would generate adverse influence to S. albida's growth. But the damage mechanisms of previous stress and acid rain stress on it have not been revealed yet. S. albida is firstly introduced by China, so we still do not know its ability of adapting to our environment. This research was conducted to determine the effects of high temperature, drought, acid rain and phosphorus nutrition on the appearance shape, physiological and biochemical indices in S. albida cutting seedlings leaves. To reveal physiological adaptation mechanisms of S. albida to previous stress, and provide theoretical basis which are its introduction and cultivation all over the country. Specific conclusions were as follows:(1) This research was conducted to determine the effects of high temperature on the appearance shape, physiological and biochemical indices in Scaevola albida cutting seedlings leaves. The results showed that compared to the control (day/night temperatures of 25/22℃), the injury indices and most of physiological indices of the cutting seedlings were no significant differences under the high temperature stress of 35/27℃for 3 days or 40/30℃for 2 days, and S. albida did not show the symptoms of heat injury. Under the treatment of 40/30℃for 3 days or 45/32℃for 2 days, some serious heat injuries were produced, but the cutting seedlings were still able to recover from the damages. The injury indices, the contents of soluble protein, soluble sugar, Pro and MDA, the activities of SOD and CAT in the treatments were significantly higher than in the control, while the contents of Chlorophyll and Carotenoid were obviously lower, and the activity of POD decreased slightly. Under the treatments of 45/32℃for 3 days, the severe heat injuries were produced and most of the cutting seedlings could not be able to recover from the considerable damages. Each of the physiological and biochemical indices decreased dramatically, and 40% of the examined cutting seedlings were wilted to death. Our studies demonstrated that the contents of Chlorophyll, Pro, MDA and the activity of POD were changed obviously to the high temperature stress, and the four variables had remarkable correlations with the injury indices (the absolute values of the correlation coefficients> 0.88 for each variable) and, therefore, could be used as heat tolerance indices.(2) This research was conducted to determine the effects of soil water stress on the appearance shape, physiological and biochemical indices in the leaves of Scaevola albida cutting seedlings. 120 cutting seedlings with a similar growth were divided into 4 groups:no stress (control), light stress, moderate stress and heavy stress. The results showed that the content of Pro and the injury indices of the cutting seedlings were increased significantly, the content of RWC was decreased significantly, as drought stress intensified and treatment time prolonged. The content of chlorophyll were higher than the control under light stress or the early stages of moderate stress; the activity of SOD increased markedly under light stress, moderate stress or the early stages of heavy stress. Although the activity of SOD decreased, it was still significantly higher than the control. The content of MDA was slightly lower than the control under the early or medium stages of light stress, and then increased significantly as drought stress intensified. Combined with the changes of the injury indices and physiological and biochemical indices, S. albida had a strong adapting ability to drought stress, and there were still 60 percent of cutting seedlings survived under heavy stress (25 percent to 30 percent of the field of saturated water) within 30 days.(3) This research was conducted to determine the effects of simulated acid rain on the appearance shape, the contents of photosynthetic pigments and MDA, and the activity of SOD in S. albida cutting seedlings leaves. The results showed that compared to the control, the average area of leaves decreased gradually, the content of MDA and the foliar damage percent increased significantly, the contents of chlorophyll a and chlorophyll b decreased significantly, the content of carotenoid and the activity of SOD increased firstly and then decreased. Combined with the changes of morphological and physiological and biochemical indexes, S. albida can live with pH value 4.0 and 3.0 of simulated acid rain, but under the treatment of pH value 2.0, it showed serious injury symptoms, the plant couldn't recover. The results of the correlation analysis showed that chlorophyll (total), carotenoid and MDA played the roles of synergy with each other in inhibiting the process of acid rain stress, the internal relations between SOD and other indexes were not closely[142].(4) This research was conducted to determine the effects of phosphorous stress on the appearance shape, rooting rate, the contents of chlorophyll, soluble protein and MDA, and the activities of SOD and APA in S. albida cutting seedlings leaves. The results showed that under the treatment of 0 g/kg in the phosphorus concentration, no plant death, but the growth status (including plant height, leaf width, color and quantity) of S.albida cutting seedlings was the worst in each treatments, rooting rate was significantly lower than control, the contents of chlorophyll and soluble protein were slightly lower than control, the content of MDA, the activities of SOD and APA were significantly higher than control; Under the treatment of 0.02 g/kg in the phosphorus concentration, growth status, the content of chlorophyll, the activities of SOD and APA were basically the same with control, rooting rate was significantly higher than the control, reaching 100%, the content of soluble protein slightly higher than control, the content of MDA slightly lower than control; under the treatments of phosphorus concentration 0.04,0.06 and 0.08 g/kg, the plant survival rate, rooting rate, the content of chlorophyll and the activity of APA have begun a significant decline, the content of soluble protein and MDA, the activity of SOD were all increased significantly. According to the changes of growth and physiological indexes of S.albida cutting seedlings under all treatments of phosphorus concentration,0.02 g/kg was the most suitable for the growth of S.albida cutting seedlings. |
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