| Many corresponding identification methods and indexes on wheat drought-resistance have beenpresented by worldwide scholars in recent years. However, there are no clear drought-resistance measuringstandards on most morphological and physiological indexes now. In this experiment, several factors,including physiological and biochemical changes such as relative water content (RWC) in leave,water-holding capacity, protective enzymes activities and proline content in flag leave together with theircorrelation with drought resistance under stress, also the shape of the different wheat cultivars ingerminating, seedling and later development stages, are studied respectively by means of droughtstimulation indoor and water control in rain shelter. Thus, morphological, physiological and chemicalindexes related to early stage identification are established. Three grades, stronger, intermediate and weakerdrought-resistance, are established after the cultivars identification of drought resistance index andcoefficient. Furthermore, according to these identification, measurable criterion of drought resistanceidentification by morphological, physiological and biochemical indexes in early drought resistanceidentification stage are raised:1 Morphological indexes: during the germinating stage, the anti-stress indexes (stresscondition/control) of the length of coleoptile and radicle together with the number of the side-radicle can beused to identify drought resistance. Under the stress of OEG6000 (-0.975Mpa), if the anti-stress index ofthe length of the coleoptile, radicle and the number of the side-radicle are greater than 0.7,1,0.6 respectively,those cultivars are the stronger drought-resistance ones while those under 0.5,0.8,0.5 are the opposite. Inthe seedling stage, the ratio of root/shoot under osmosis stress can be regarded as drought resistanceidentification index. It is a stronger drought resistance cultivar if that ratio is greater than 0.6 while aweaker one under 0.5.2 Physiological and biochemical indexes: under the condition of osmotic stress, droughtresistance of wheat cultivars can be identified by relative proline, CAT and SOD content (stress/control) ofleave and coleoptile in germinating and seedling stage together with RWC and water-holding capacity ofleave in seedling stage. Those are the stronger drought-resistance cultivars if the relative water holdingcapacity of leave is greater than 60% while weaker ones less than 50%.Moreover, it can be concluded that the cultivars are stronger drought resistance ones if the prolinerelative content (treatment/control) of leave in coleoptile and seedling stage more than 2.2 and 3.5respectively while weaker ones no more than 1.5 and 2.5 respectively. Furthermore, it can be regarded asstronger ones when their relative root activity is greater than 0.5 while weaker ones less than 0.4.After the systematic comparison of the drought stress in germinating, seedling and later stages withdifferent wheat cultivars, two points are concluded as follows:First, drought resistance of different cultivars can be reflected by the anti-stress index with thenumber of side-roots in germinating stage. Next, the confirmed morphological, physiological and chemicalindexes related to early identification of wheat drought resistance at present have been quantified in thisexperiment.We have studied early drought-resistance identification indexes of different wheat cultivars in thisproject and have bound those with the study of later development and the drought-resistance. Then we havea comparative study on consistence of drought-resistance identification of morphological, physiologicaland chemical indexes under osmotic stress in different stages. Thus more theoretical bases, which areoffered to early stage drought resistance identification of dry-land wheat, help to build one systematicbreeding procedure of wheat drought resistance based on their morphological, physiological and chemicalindexes on early stage binding with conventional breeding methods. |
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