| The test was conducted at the experiment station of Shenyang Agricultural University during2011to2012. PEG-6000was used to simulate drought stress environment in artificial climate chamber for studying the effects of different concentrations of PEG-6000on the response of31sorghum cultivars at the seed germination stage. And the purpose of this dissertation is to filter sorghum cultivars with better drought-resistance based on responses of sorghum cultivars at the seed germination stage with different drought stress, and the same time to explore suitable identifying methods for sorghum drought-resistance. Under outdoor potted conditions,4sorghum cultivars with different drought-resistance were used to study relationships among agricultural technology, physiologic and biochemical index and sorghum cultivars drought-resistance, and to reveal drought-resistant mechanism in many aspects. Drought-resistance identification and indicator selection were also studied to supply simple and allowable agricultural technology and physiologic and biochemical index, which could evaluate sorghum drought-resistant efficiently. Meanwhile, the study established sorghum drought-resistant identification indicator system to enrich research content of sorghum drought-resistant. And the study also supplied theory and method of breeding for drought-resistant in sorghum. And the main results were as followed:1. PEG-6000was used to simulate drought stress environment in artificial climate chamber for studying the effects of different concentrations of PEG-6000(80g/L,120g/L,150g/L,175g/L) on the response of31sorghum cultivars at the seed germination stage, with the objectives of screening drought-resistant cultivars and exploring suitable identifying methods for sorghum’s drought-resistance. Through principal component analysis (PCA) and Self-Organizing-Map (SOM) cluster analysis, the drought-resistance of31sorghum cultivars was evaluated. PCA showed that the payloads of relative bud length, relative root length and drought-resistance index during germination had the maximum values, and were used as the main evaluating indexes to identify drought-resistance capability of sorghum, and based on which the drought-resistant capabilities of31sorghum cultivars were ranked. Five groups of drought-resistance capabilities of31sorghum cultivars were divided based on SOM cluster analysis:4cultivars including Jiza305as highly drought-resistant,4cultivars including HL8as drought-resistant,8cultivars including LiaozalO as medium drought-resistant,7cultivars including Jinza103as drought-sensitive and8cultivars including Jinza93as highly drought-sensitive. It was concluded that parameters such as relative bud length, relative root length and germination drought-resistance index can be used as criteria for identifying sorghum’s drought-resistance, and that SOM cluster analysis is an important method for classifying drought-resistance.2. Results from this research indicated that drought tolerant cultivar was comparatively resistant to water stress owing to the greater increased in peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activities with lower malondialdehyde (MDA) content. Findings showed that the greater drought tolerant capacity was resulted from the superior ability to lower increase in free radicals along with higher increase in proline, water soluble sugar, and protein. Correlation analysis showed that leaf temperature serves an important role in influencing the sorghum water retention capacity, protective enzyme activity, as well as osmotic adjustment substance, resulting in the differential water stress responses between cultivars. This suggests that the leaf temperature might be useful as a critical criterion in selecting drought resistance sorghum. Additionally, there appears to be potential for using far infrared thermal imaging technology to appraise the capability of sorghum drought-resistant.3. The maximum photosynthetic efficiency (Fv/Fm), the apparent electron transport rate(ETR), actual photosynthetic efficiency (ΦPSⅡ) photochemical quenching coefficient (qL) and net photosynthetic rate (Pn) of sorghum leaves at different growth stages showed a downward trend, while the initial fluorescence (Fo) and non-photochemical quenching (NPQ) showed an upward trend, Photosystem Ⅱ (PS Ⅱ) reaction center of leaf was destroyed, resulting in a reduction of energy conversion efficiency of primary light. The Pn, ETR,(ΦPSⅡ and relative electron transfer rate (Pm) of drought-resistant cultivars (Jiza305and Jinza106) were higher than those of drought-sensitive cultivars (Jinza103and Jizal27), and their abilities of conversion of light energy were greater. The chlorophyll fluorescence parameters of ΦPSⅡ and relative electron transfer rate (Pm) in sorghum leaves of drought-resistant cultivars are important physiological characteristics for the drought-resistant sorghum cultivars.4. There had different trends of stomatal density, length, width and length/width on leaf ventral and back of4sorghum cultivars within drought stress at three different growth stages, but all that showed drought-resistant sorghum cultivars were less sensitive to drought stress, and drought sentitive sorghum cultivars were sensitive to drought stress. Correlation analysis indicated Pn was greatly positively correlated with stomatal conductance (Gs), transpiration rate (Tr), stomatal length and width on leaf ventral and back, and significantly positively correlated with length on the back. Meanwhile, leaf temperature different was greatly positively correlated with stomatal density on back and significantly positively correlated with width on ventral.With drought stress, the dry weights of above-ground and root of sorghum were decreased slightly, but the ratio of that was increased and which was significant in drought-resistant sorghum cultivars. Comparing with drought-sensitive cultivars, there was largely increased in total root length, total surface area, average diameter and root volume of drought-resistant sorghum cultivars and no obvious changes in yield of that with drought stress. The results of grey correlation analysis showed that the physiological characteristics of leaf, such as Pn、Tr and leaf dry weight, were closely related to sorghum drought resistance. |
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