Physiological Effects Of Post-drought And Rewatering On Wheat With Different Pliody

Wheat (Tritium aestivum L.) is one of the staple crops grown on most of the dry land areas, while water is the main limiting factors in wheat production. Different wheat genotypes in their evolution have been produced, which differ in their resistance to drought. The effects of drought on plants growth are fairly well known, hundreds of drought-inducible genes have been identified. Nevertheless, a better integration of the molecular and cellular information with whole-plant responses under drought is still needed. In fact, periods of drought alternating with short periods of available water were the common conditions to many semiarid areas of China. Crops have undergone the in turn of drought and wetting in their whole life. Crops response to this water deficit and variable environments is complex and uninsurable, so most of the crops have evolved the mechanism of responding process to water deficit, this process covers– damaging– protecting and repairing- compensating. The primary effect of drying alternating with rewatering on whole-plant is not well understood, however, a better understanding of physiological difference and functional reparation under rewatering conditions may have a more consistent role in providing tolerance, either through protection or repair mechanisms. Besides, studying mutants with altered responses to water deficit is an important approach for the further understanding of molecular basis of plant responses to drought stress, because it allows us to identify genes important for the expression of whole-plant responses underlying drought adaptation. So, we presented a new consideration concerning physiological difference from the origin to evolution system of cultivated wheat under rewatering condition, in order to provide the biological thought and theoretical basis for water-saving agriculture and anti-drought breeding. The major results are as follows:1. Water deficit affected on a series of process from growth, physiology to yield formation. Leaf RWC, water potential, osmotic potential, Pn, Tr, biomass and yield strutures decreased under water stress; the content of proline, K+, soluble protein, MDA, the activities of SOD and APX and the cell membrane permeability had the trend of increase. Under drought conditions, the decrement of RWC and water potential in diploid wheat was most; the capacity of osmotic adjustment was strongest for diploid wheat; from 2n to 6n wheat, antioxidant ability was getting stronger. The effects of drought stress on physiological was various in the wheat with different ploidy and growth stages. At the jointing stage, the decrease of Pn were 2n >6n>4n; while 4n had the biggest decrease at the flowering stage. It is concluded that the damage of drought on wheats with different pliody at jointing stage are stronger than that at flowering stage, which indicated that these wheats developed the process of"from injury to adaptation"under water stress.2. Wheat was sensitive to water deficit at jointing stage. After rewatering in this period, water status, growth, and physiological metabolism recovered significantly to a certain degree, comparing with the contrast to drought treatments, leaf RWC, water potential, Pn, Tr, and cell membrane permeability had better response than that of well-watered plants. The content of proline, K+, soluble protein, MDA, activities of SOD and APX droped. Wild einkorn and XiaoYan No.6 had a high Pn potential after rewatering at this stage.3. When the plants were not rewatered until flowering stage, the physiological influence tended to be unbenificial. Plant recovery ability was significantly lower for rewatering at the flowering stage than jointing stage. The results showed that leaf RWC, water potential, Pn, Tr, and membrane permeability could not reach the level of well-watered. But when the plants were rewatered at both jointing stage and flowering stage, the recovery of Pn, Tr, and membrane permeability was close to well-watered, there were more significantly recovery potential than that of only rewatering at the flowering stage. Different osmotic substances have different responses when the plants were rewatered at flowering stage. And wild wheat had stronger antioxidant abitity with rewatering them at flowering stage.4. Grain yields were significantly decreased under drought. Compared with drought stress, rewatering increased yields. Rewatering at jointing stage promoted plant growth and biomass accumulation, decreased the ratio of root and shoot as well as the harvest index. Meanwhile, Pn increased dramatically so that the plants yielded more. With rewatering at flowering stage, biomass, ear numbers, and the accumulation of dry weight were restricted significantly, but dry weight of root and the weight of thousand seeds as well as the ratio of root and shoot got increasing. In general, Rewatering at flowering stage were not helpful to increase the yields significantly. With regard to rewatering both at jointing stage and flowering stage, there was big compensatory effect on the yields of modern wheat, that increased by 35% in average, which could be attributed to the the different compensatory in yields structure at the different stage. In conclusion, the development of ear number and biomass got promoted when the plants experienced antecedent drought and rewatering at jointing stage, the transport of carbonhydrate to seeds was promoted when the plants were rewatered till flowering stage.