| Drought is one of the main environmental factors that affects crop growth and development, and is also one of the most important limiting factors for crops. To understand the effects of water deficit on the growth and yield of speckled kidney bean is significant for both the studies of drought stress and the problem solving theoretically and practically.This project was carried out in agronomic experimental base of Heilongjiang Bayi Agricultural University in2012and2013using speckled kidney bean as the subject. PEG-6000(polyethylene glycol6000) of different concentrations was applied to seeds of speckled kidney bean to simulate drought stress. The seed germination and physiological characteristics were measured in this study. Pot experiments were carried out by artificial water control to study the changes of morphological, physiological characteristics and yield of speckled kidney bean under drought stress and rewater in the aspects of stages, severity and duration. According to the study, the dynamic models of dry matter accumulation of speckled kidney bean were established. Regulation of drought was investigated by uniconazole waterless-dressed seed.The main results were shown as follows:1. In the experiment of PEG-6000modifying drought stress, seed germination was not significant suppressed, but enhanced a little under mild drought stress. With the increase of drought stress, the seed germination was inhibited, protective enzyme activities and the content of protein were first increased and then decreased, while the contents of MDA, Pro and soluble sugar were increased in a unimodal curve trend.2. Drought stress in each stage altered the canopy characteristics of speckled kidney bean, and resulted in decreases in the plant height, leaf area, specific leaf weigh, water retention capacity of leaf and main stem diameter. More obvious variations were observed under stricter drought stress and longer stress duration, but there is no significant difference in leaf relative water component. The plant height in the growth period was varied in an ascending order of pod-setting stage, flowering stage and seedling stage. The leaf area was more severely affected by drought stress during growth.The content of chlorophyll a increased under drought stress in seedling stage, and then was observed a decline tendency with the development of the plant. The more serious the drought stress, the greater the decline. The trends of the level of chlorophyll b and total chlorophyll were almost the same as that of chlorophyll a, and the ratio of chlorophyll a to b was random. Canopy morphological and physiological biochemical parameters showed hysteresis effect after rewater, and then were restored to a certain degree by the compensation effect.The plant height had obvious compensation effect in seedling stage under a5-day drought stress and mild drought stress in flowering and pod-setting stage. But compensation effect was relatively poor under severe drought stress. The response of main stem diameter to the changes of drought stress and rewater was not obvious.Leaf area showed priming effect in flowering stage, eventually, the compensation effect of pod-setting stage is the best, followed by that of flowering stage and seedling stage.Specific leaf weight had equivalent compensation effect in seedling and flowering stage under5-day mild drought stress, partial compensation effect in flowering stage under other drought stress, and damage or no compensation effect in pod-setting stage.Water retention capacity of leaf showed equivalent compensation effect in seedling stage, but had no obviously compensation effect in flowering and pod-setting stage. The content of chlorophyll a had equivalent compensation effect in seedling stage under5-day drought stress,10-day flowering stage and5-day pod-setting stage. The content of chlorophyll b showed equivalent compensation effect after a5-day stress in seedling and pod-setting stage. The ratio of chlorophyll a to b had equivalent compensation effect in seedling and pod-setting stage under10-day mild drought stress and5-day flowering stage stress. The content of total chlorophyll had the same trend as that of chlorophyll a.3. Drought stress leaded to an increase of length of main and lateral roots, but resulted in a decrease of the diameter of main root and the vitality of root, the more serious the drought stress, the more obvious the variation. Along with the prolonged period of drought stress, the parameters were not changed in the same way between stages. The total root absorption area was appeared in declining trend. Higher drought stress and longer stress duration will lead to a greater declination.The root active absorption area was increased in seedling stage under mild drought stress. The increment reduced under longer stress duration.The root active absorption area was decreased in seedling stage under severe drought stress. The serious drought stress and the long stress duration resulted in great the declination of absorption area in flowering and pod-setting stages.The ratio of active absorption area had the same tendency as that of the root active absorption area. All of the lengths of main roots, lateral roots and the diameter of main roots showed hysteresis effect after rewater, other parameters were not obvious.Length of main roots was produced equivalent compensation effect in seedling stage, and in5-day flowering stage. The total length of lateral roots was observed equivalent compensation effect in flowering and pod-setting stage. The diameter of main root was observed equivalent compensation effect in seedling stage. The vitality of root had equivalent compensation effect in each stage. The total root absorption area had equivalent compensation effect in seedling stage and in5-day flowering stage, the root active absorption area had equivalent compensation effect in seedling stage under5-day mild drought stress and10-day drought stress. The trend of the ratio of active absorption area was the same as that of the root active absorption area.4. Drought stress resulted in a decline of SOD activity, the more serious the drought stress and the longer the stress duration, the greater the decline. Drought stress leaded to increases of POD activity, CAT activity and content of MDA, the more serious the drought stress and the longer the stress duration, the greater the increase. All of the parameters were affected the most by drought stress in pod-setting stage. POD and CAT activities had priming effect; SOD activity had equivalent compensation effect in seedling and pod-setting stage, and damage compensation effect occurred in flowering stage.POD activity and the content of MDA were produced equivalent compensation effect by and large. Compensation effect was changed irregularly in CAT activity. Rewater produced equivalent compensation effect in seedling stage under5-day drought stress and pod-setting stage, and partial compensation effect in seedling stage for10-day, while produced respectively damage and over compensation effect in5-day and10-day flowering stage.5. Drought stress caused the accumulation of soluble protein decreased in each stage except in10-day pod-setting stage, the more serious the drought stress, the greater the decline; the longer the stress duration, the greater the decline in seedling and pod-setting stage and the smaller the decline in flowering stage. The impact in seedling stage is larger than that in pod-setting stage which is larger than that in flowering stage. Drought stress increased the content of Pro and soluble sugar, the more serious the drought stress, the greater the increase. The longer the stress duration, the greater the decline of the content of Pro in seedling stage under severe drought stress, the later the developmental process, the greater the increase. Drought stress decreased the increment amplitude of the content of soluble sugar in seedling and flowering stage, and increased the content of soluble sugar in pod-setting stage under mild drought stress. There were no obvious variations in severe drought stress.The content of soluble protein had priming effect in each stage after rewater, so did the content of soluble sugar in flowering and pod-setting stage. All of them had equivalent compensation effect, and the content of soluble protein had over compensation effect in seedling for10-day. Rewater raised hysteresis effect to the content of Pro, in the end rewater produced equivalent compensation effect in seedling stage for10-day, and partial or damage compensation effect in other treatments.6. Drought stress decreased canopy dry weight, increased root dry weight as well as ratio of root to canopy. The more serious the drought stress, the greater the decline of canopy dry weight and ratio of root to canopy. Long stress duration leaded to the big declination in seedling and pod-setting stages, and small declination in flowering stage.The root dry weight increased intensely in response to serious drought stress and long stress duration. Rewater leaded hysteresis effect to canopy and root dry weight, and ratio of root to canopy. Final equivalent compensation effect occurred in seedling and flowering stage, while poor compensation effect occurred in pod-setting stage and in the10-day stress treatment especially.7. during harvest period, drought stress decreased pod number and yield of per plant as well as the100-grain weight, the more serious the drought stress and the longer the stress duration, the greater the decline, but there had no significant influence on the grain number per pod. Drought stress let pod number per plant decrease significantly in pod-setting stage, but the100-grain weight and the yield per plant were the same in flowering stage as in pod-setting stage.The100-grain weight was changed dynamically in s-shape curve under drought stress, the more serious the drought stress and the longer the stress duration, the greater the decline. Changes of dry substance accumulation can be described by logistic model which could give objective demonstration, the fitted effect was better. Rewater produced equivalent compensation effects in seedling stage, but partial compensation effect in flowering and pod-setting stage, and didn’t change significantly in other stages.8. After drought stress, seeds were waterless-dressed with uniconazole that is within certain concentration ranges. All of the canopy morphological and physiological parameters, protective enzyme activities, osmoregulation substance, canopy and root dry weight, ratio of root to canopy increased with increasing uniconazole concentration, except the plant height and the content of MDA which decreased significantly. The final yield and composition factors, pod number per plant and grain number per pod didn’t change significantly, while the100-grain weight and the yield per plant were increased. However, when the seeds were treated with high concentrations uniconazole, all the parameters except plant height had the opposite tendency comparing to those under lower uniconazole concentration. |
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