The Study On Response Of Pea To Water Stress And Rewater Effect

Soil water is the main biological factor limiting crop production and distribution in dry area. It is essential to reveal crop's response to water stress and rewater effect for breeding and setting up hi-yield and water-saving technology system. The pot experiment, characterized by artificial water control and simulated water stress and rewater condition, was conducted in agronomic experimental base of Gansu Agriculture University from March to August, 2008. Several treatments were designed, covering stage of exerting water stress and rewater, water stress degree and duration. Response to changes of soil water and rewater effect of pea were also analysised in this paper basing on determining its growing shape and relevant physiological and biochemical characters.1. Water stress altered the outer characteristics of pea, and existed hysteresis effect. Rewater made compensation effect. Water stress in each stage resulted in a decrease in the height of plant, the number of branches, the diameter of main stem , main root and leaf area, but an increase in the length of main and lateral roots and the number of lateral root, the serious the water stress and the longer the stress duration, the more obvious the variation. The effect of water stress on outer characters of pea in seedling stage topped the list of all period, followed by that of flowering stage, the effect of filling stage was unnoticeable. Rewater made compensation to changes of outer characters caused by water stress, and the compensation appeared the same intendancy of the effect above. Rewater weakened the effect of water stress on main and lateral roots to some extent.2. Water stress decreased canopy weight, increased root weight as well as raised ratio of root to canopy, and existed hysteresis effect. Rewater improved growth between root and canopy. Water stress didn't change the total intendancy of dry matter accumulation of root and canopy,but increased the number of lateral roots, the length of total lateral roots as well as the mass growth of roots,while decreased the plant height. the number of branch, the diameter of main stem, the leaf area,and the canopy dry weight. In term of ratio of root to canopy under slight stress, rewater made over-compensation effect in seedling stage, and equivalent compensation effect in flowering stage under slight stress for 5d. But equivalent compensation effect in seedling and flowering stage under serious stress and in filling stage under all kinds of stresses, concentrating on the coordination of growth between root and canopy.3. Water stress declined the vitality of root and altered the water retention capacity of leaf and content of chlorophylls. The total root absorption area, active absorption area and the ratio of active absorption area all appeared in declining trend, influencing the growth of root nodule. Rewater produced compensation effect. In any stage,The root vitality showed a decline which rate became larger as water stress enhanced. Rewater made over-compensation effect in seedling stage and equivalent compensation effect in flowering and filling stage. Serious water stress caused significant change in water retention capacity of leaves, and equivalent compensation effect appeared after rewater. The content of chlorophyll showed an intendancy of increase under water stress in seedling and flowering stage, but the content of chlorophyll a and b changed little. In filling stage, water stress led to a decrease in content of chlorophyll a, chlorophyll b and total chlorophyll, and rewater made equivalent compensation or even over-compensation effect. The total root absorption area, active absorption area and the ratio of active absorption area all appeared in a tendency of decrease under water stress, rewater made part-compensation effect. Water stress declined the number of root nodule in each stage, enlarged the diameter of max-root nodule in seedling and flowering stage, and narrowed the max-root nodule diameter in filling stage. Rewater promoted the growth of root nodule diameter.4. Water stress increased the content of ABA and IAA,decreased the content of GA and ZT, and changed the ratio between any two endogenous hormones,rewater induced compensation effect. The impact of water stress on content of each endogenous hormone appeared hysteresis effect. The compensation effect after rewater varied with growing stage, water stress degree and rewater time. For the content of some endogenous hormones, rewater for 5d caused part-compensation effect, and equivalent compensation effect when for 10d. For the change of ratio of any two endogenous hormones, rewater produced part-compensation effect.5. Water stress impacted protective enzymes activity, degree of membrane lipid proximate,and antioxidant capability. Rewater produced compensation to each protective enzyme activity. In seedling and filling stage, water stress resulted in a decline in SOD activity and an increase in CAT and POD activity, which range or rate raised with the stress became more serious and its duration got longer. The stress also had hysteresis effect, and rewater made reasonable compensation to all protective enzymes. Water stress increased the content of MDA and promoted the cell membrane permeability, and the increasing rate of them went up as the stress got more serious and the time got longer. The compensation on MDA and RC emerged within 5d after rewater,thus effectively improving antioxidant capability.6. Water stress caused soluble protein accumulation of pea plant cell decreased and the content of prolin and soluble sugar increased,and appeared hysteresis effect. Rewater made compensation. Water stress caused visible change of soluble protein content in any stage, and rewater produced equivalent compensation effect. Water stress increased the content of prolin in any stage, and the intendancy was kept till to the time after rewater for 5d, and then produced compensation at the time after rewater for 10d. In flowering stage, slight stress for 10d and serious stress treatments firstly showed over-compensation effect after rewater, then the equivalent effect. For soluble sugar in filing stage, 5d stress led to an increase while 10d stress led to a decrease. Rewater induced part-compensation or equivalent compensation effect.7. Under water stress in seedling and flowering stage, grain dry weight changed dynamically in s-like curve. Appropriate degree of water stress was favorite to improving out put. Water stress in seedling and flowering stage declined grain dry substance accumulation rate, and the influencing degree enhanced with the stress time extended and its degree intensified. Serious degree of water stress for long time topped the impact on filling characteristics, followed by that of slight degree for long time. The affection caused by short-time stress was not obvious. A cubic polynomial equation which can give objective demonstration of grain dry substance accumulation in seedling and flowering stage under water stress evolved basing on the grain dry substance accumulation curve. Although appropriate degree of water stress in seedling stage decreased hundred grain weights, the pod number of per hill and grain number of per pod considerably increased, significantly raising the unit yield at last.