Effect Of Drought Stress And Rewatering On Physiological Characteristics In Different Proso Millet Varieties

Soil water is the main biological factor limiting crop productionin dry area. It is essential to reveal crop's response to water stressand rewater effect for breeding and setting up high yield andwater-saving technology system. With three differentdrought-resistant proso millet varieties (drought-tolerant 'Longmi4'and '5283huang' and drought-sensitive 'Jinshu7'), the physiologicalcharacteristics effect were studied under the condition ofmoderate and severe drought stress at early stage and rewateringat jointing stage and booting stage in pot culture. The main resultsare as follows:(1) Drought stress affected on a series of process from growth,physiology to yield formation, and the greater the stress level thegreater negative effects on them. Under drought stress at earlyperiod, the plant height, leaf area, dry weight of shoot, total rootlength and dry weight of root decreased, but ratio of root and shoot increased; At the same time,the root activity and soluble proteincontents showed a downward trend, but root's SOD and PODactivity, proline and MDA and soluble suger contents showed ariseward trend; the relative water contents, chlorophyll contents,leaf net photosynthetic rate (Pn), transpiration rate (Tr), stomatalconductance (Gs), CO2concentration (Ci) and leave's Fv/Fo andFv/Fm also showed a downward trend. The effects were strongerunder severe drought stress than under moderate drought stress.(2)After rewatering in different period, the growth and thetested various physiological indexes of different proso milletvarieties had different degrees of decovery. Plant height, dry matteraccumulation quantity of root and shoot,and various physiologicalindexes exceeded its corresponding drought contrast afterrewatering, presented compensatory or ultra compensatory effect,and the compensatory degree enhanced with the stress timeextended and its degree intensified. The conmensation effect ofdrought were strong under moderate drought stress, but weakunder severe stress, this suggested more severe stress thestronger effect on the tested various physiological indexes; Theconmensation effect of drought were stronger after rewatering atjointing stage than at booting stage, this suggested it was notobvious during longer time. (3)The tested various physiological indexes of three differentproso millet varieties had different amplitude under drought stressand rewatering condition. The drought-tolerant 'Longmi4' had aclear advantage. Under drought stress, plant height, dry matteraccumulation quantity of root and shoot of drought-tolerant'Longmi4' had the smallest decreased, after rewatering had thelagerest increased, presented ultra compensatory effect.Meanwhile, The root activity,root's soluble protein contents, therelative water contents, chlorophyll contents,leaf netphotosynthetic rate (Pn), transpiration rate (Tr), stomatalconductance (Gs), CO2concentration (Ci) and chlorophyllfluorescence parameters of drought-tolerant 'Longmi4' also had thesmallest declined, after rewatering had the lagerest increased. Itsuggested that the compensation of 'Longmi4' was significantlystronger than another varieties. But the ratio of root and shoot,root's SOD and POD activity, proline and MDA and soluble sugercontents showed the lagerest riseward trend, after rewateringshowed the lagerest downward trend. It was considered that underdrought stress and rewatering,'Longmi4' had more strongercompensation ability. The drought-sensitive 'Jinshu7' haddisadvantage under drought stress and rewatering.(4) Grain yields were significantly decreased under drought stress. The effects were stronger under severe drought stress thanunder moderate drought stress. Sensitivity to drought judged byyield in different varieties ranked in the order of 'Jinshu7','5283huang','Longmi4'. Compared with drought stress, rewateringincreased yields. The conmensation effect of drought were strongerunder moderate drought stress than under severe stress, and werestronger after rewatering at jointing stage than at booting.Compared with CK, the yield of 'Longmi4' presented ultracompensatory effect during drought stress at seedling stage andrewatering at jointing stage. Therefore, it was considered thatunder drought stress and after rewatering, drought-tolerant'Longmi4' kept high yields, which had stronger adopt ability.