Studies On The Mechanism Of Response And Adaptation Under Drought Stress In Summer Maize

The main planting areas of maize are focus on the semi-drought and semi-wetness regions in the north of China, where the water which use in agriculture mainly depends on the rain, therefore, the drought stress threaten the every and the whole growth stages inevitably and unpredictably, which can reduce the yield to decrease. This is the important reason why the maize yield is not too high and too stable in our country and the other country in the world. Thus it attach more and more importance to the mechanism of response and adaptation under drought stress in maize. But the former research of field observation and theory discussion is focus on some growth stage, And lack of studying the whole growth stage, what's more the research about adaptation to water stress in the main growth stages and the whole stage in maize is not too deeply, the degree of quantity is relatively low. So, the water content is the single factor in this research, summer maize was selected to study as trial crop, The methods of pool culture in water proof installations and analysis were used to systematic study of effects of the different soil water content (ie. full supply water, a moderate and a severe water stress) on growth and development, yield and it's component, WUB and the mechanism of physiological and biochemical. The main results were indicated as followings:1. Effects of water stress on growth and development, accumulation, translocation and redistribution of photosynthetic product in summer maizeUnder water stress the growth and development of maize was restrained. The plant height declined, stem diameter, LAI, root volume, the growth speed of leaf etc. were restrained in different degree. And the specific leaf area decreased, while selerophyllous index, succulence degree increased. It can prolong the ASI under water stress, and that it postpone the filling stage in some degree. It hindered the growth of spike and cause yield dropped.Although the total mount of accumulation, translocation, redistribution and transfer rates in the different growth stages were much different under drought, the general trend of accumulation, translocation and redistribution of photosynthetic product of summer maize was not significantly influenced by water deficient, Under water stress, the dry matter of different organs was decreased, the ratios of root to shoot, root to stem, leaf to stem, root to leaf of maize plant were changed. And the amount of dry weight transferred, transfer rate and the percentage of ear weigh in the different organs were changed under drought The proper water supply can effectively promote the dry matter accumulation during the prophase growth stages, and it can also stimulate vegetative organs transfer to grain at the evening of growth stages. This suggested that the remained non-structive carbohydrates in vegetative organs were fewer and the redistributed dry matter mainly contributed to higher grain weight, and thus getting higher corn yields, compared with the other two water treatments.2. Effects of water stress on physiological and biochemical index in summer maizeUnder water stress the internal physiological and biochemical of plant changed distinctly. The leave relative water content and roots vitality decreased, the plasma membrane permeability of leave and roots enhanced under drought stress in maize. Furthermore the root plasma-membrane permeability enhanced more sharply than the leaf. Leave water-holding capacity declined apparently but it will get back the intrinsic characteristic of the specific species at the evening growing stage in maize, consequently it indicate the genetic speciality of the species. Photosynthetic rate and transpiration rate also shut down under water stress, what's more the Photosynthetic rate was more sensitively than the transpiration rate. And the middle and bottom PAR was enhanced while the top is no difference.Under water stress, activities of superoxide dismutase(SOD), catalase(CTA),and peoxidase(POD) in leaves and roots increased sharply at prophase and metaphase growth stages such as male tetrad stage, while declined at the evening developmental stages such as milky stage, different strategies of maize for coping with water stress under field conditions were found at different growing stages of plant development. At the stage of male tetrad and the pre-tasselling the mechanism response to drought is active while at the stage of filling and milking is forbearing negatively; The protective enzyme activities in root are lower than that in leaves, but the sensitive degree of these enzymes to water stress is different, SOD activities is not sensitivity under drought stress compared with the other to protective enzymes. The content of malondialdehyde (MDA) is increased following the stronger water stress, and also the content of MDA in roots is lower than that in leaves. Under water stress, the soluble protein in roots and leaves is decreased.The protective enzyme activities and lipid peroxidation in root are positively related to that in leaf, and furthermore the most of correlated coefficients show the significant difference.3. Effects of grain yield and it's components and quality in summer maizeThe water content of soil correlated closely to pod yields,with the decrease of the water content,pod yields declined significantly. The main factors that caused reduction of output were the decreases of the grain number per ear and the drop of weight of 100 grains. Serious water stress can cause postpone the harvest stages, and that become"water corn". At harvest the water content of grain, spike axe, bract were enhanced sharply under drought stress. Severe water stress would enhance about 20%～60% for the water content of grain, grain axes, bract ,filigree compared to the treatment of full- water supply, and resulted in the postponement of its maturation.Water condition can influence grain quality in some degree. Under water stress, the content of grain starch, crude fat were decreased, while the content of soluble sugar, soluble deoxidize sugar,N,P,K and microelements(Ca,Mg,Cu,Zn,Mn) in grain were improved.4. Effects of water consumption character, water use efficiency (WUB) in summer maizeThe amount of water consumption was decreased at the every growth with the decrease of the water supply, but modulus of water consumption was almost the same under different water treatments. The general trend of water consumption intensity at every growth is a parabola shape(single apex curve) under different water treatments, and it is not big at the stages of seedling and autumn, it got to the maximum at the stages of tassseling and spin. The modulus of water consumption increased by the increase of soil water content. WUB in the lea level enhanced by the increase of soil water content except the milky stage, while WUB in the grain level wasn't increased by the increase of the amount of water consumption, it is the largest(1.59 kg·mm-1 )under the light water stress treatment M, it improved 19.32% times compared with the treatment of full-water supply.5. Comprehensive judgment of water benefits under different water treatmentsUnder the condition of this experiment, the result of fuzzy comprehensive Judgment showed that the treatment of light water stress((55±5)% of SWC) was the optimum. In addition, Because of the significant difference between severe water stress treatment and sufficient water supplying treatment above characteristic, and insignificant difference between light water stress treatment and sufficient water supplying treatment. The light water stress ((55±5)%)can be as minimum index for normal growth and development of summer maize.