| The depletion of 03 has been resulting UV-B enhancement and meanwhile the global warming induced by greenhouse effect deteriorates drought-stressed environment. Plants have developed a full set of physiological and molecular mechanisms that confer the plants to adapt the complicated eco-environment which include the extreme environments risking the growth, development and propagation of botany. The research on single stress environmental factor is no longer enough with the more complicated climate changing background. This research considered the enhanced UV-B and drought as stress factors for greenhouse experiment design and examined different physiological indexes of two maize cultivars, drought-sensitive CS and drought-resistant R7. The final research aim was to explore how the two cultivars with different water-sensitive traits would respond to enhanced UV-B radiation and the interactive effects between UV-B and drought, both being speculating the crosstalk between the pathways in which plants respond to different environmental conditions.Through the results, the conclusions are listed as follows:1. Different sensitivity to drought was consistent with that to enhanced UV-B. Drought-resistant cultivar R7 maitained a steady MDA content and membrane permeability and low soluble protein content. CS was in an opposite position. The result verified the cultivar trait: drought-sensivie cultivar was more injured in drought condition. Though UV-B radiation did not imposed the damage as drought, a high SOD, CAT and APX acitivity was maintained in R7 leaves. Meanwhile, Pro was accumulated rapidly in root. These regulations of the anti-drought cultivar in UV-B presented the tolerance of plants to different environment;2. The positive interaction was observed between UV-B and drought but changed with different indexes. In antioxidant system, 24h combined stress pushed up the SOD activity in CS leaves and suppressed 7 times down in root system and presented an antagonium in CAT and APX in leaves and CAT in root of R7. Otherwise, flavonoids increased 1.4 times in sensitive CS cultivar in drought condition and conbined stress. It obviousely accumulated in combined stress but not in each single stress. To sum up, UV-B run a relief in the oxidation. The bright side changed with cultivars. The positive effects were covered in drought-sensitive cultivar while emerged in anti-drought cultivar, which meant plants were more sentive to the water condition and UV-B radiation must be avoiding the drought-induced signal pathway to relieve the drought stress;3. The responses to stress from root and shoot were different. Totally maizes held a higher RWC (water potential as well) and synthesized and transported abundant ABA to regulate the antidative cases in shoot. It manifested the labor division of root and shoot;4. In drought, root system directly sensed the environmental signals and spured ABA accumulation. In 12h drought, ABA was transporting from root to shoot to activate the antioxidative system. Only after 24h UV radiation ABA was obviously accumulated but not in drought-condition amount while the responses of all the indexes were not active as in drought and retarded always. It was deduced that ABA was not the first-hand signal which UV-B excited in the whole stress-induced signal network. Also the relief effects of oxidative hurt UV-B made should practiced through other pathways. A long-term UV-B experiment considering other signals like NO and ethylene is suggested to investigate the the first-hand UV-induced signal. |
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