| The Syzygium hancei community is the most saved intact native vegetation types in Guangxi coastal transition zone, but now its habitat was severely damaged by individualized disturbance and industrial development and other reasons, that leads to the difficulties of natural regeneration of S. hancei, community degradation and other serious problems. This paper through artificial control three gradient shading, three aridity gradient interaction stress test to pots of S. hancei seedlings, contrast set with full sunlight, adequate water interactive processing. By measuring the growth index, physiological and biochemical indexes and photosynthetic indexes to explore and discover seedling growth rhythm, stress resistance and relationship with environmental conditions, clarify the S. hancei seedlings growth and development characteristics and environment influence mechanism, to provide a scientific basis for the S. hancei community protection and restoration. Test results show that:(1) Height growth, ground diameter growth, biomass of each site and ground/underground dry weight ratio of seedlings under shading and drought stress were significantly decreased with the increase of stress, and the size of influence is shade> drought. Under light shading seedlings grow well, moderate and severe shade stress had significant effects on seedling growth, and the growth indexes were significantly inhibited; The effect of drought on seedling growth index was secondary in the interaction of the two factors, and it also showed the inhibition effect.(2) Through the analysis of the changes of soluble sugar, soluble protein and free proline content with shade-drought stress, think of S. hancei seedlings under CK and light shading treatment had higher cell activity, active physiological metabolism, so the content of soluble protein and proline is quite high. When the seedlings in moderate shade stress, they decreased, because test seedlings subjected to adversity persecution, cells in the physiological metabolism is abate, and when the seedlings in the heavy shading and drought stress, the cell will make a resistance response to adversity, namely osmotic adjustment in order to make the soluble protein and free proline content increased.(3) The three enzyme activities of seedling protective enzyme system increased with the increasing of shading and drought stress, and the size of influence to S. hancei POD, CAT activity is shade> drought in the interaction of shade-drought stress, the size of influence to SOD activity is drought> shade. And the effects of shading stress on POD, CAT and SOD activity were all activated, the effects of drought on POD, CAT and SOD activities were all inhibited. The MDA content was remarkable affected by shade-drought stress, which was significantly affected by drought stress, negatively correlated with the effect of shading stress.(4) The CK contents of chlorophyll a and chlorophyll b are the lowest, and increased with the increase of shading and drought stress, but the CK chlorophyll a/b is the highest, the chlorophyll a/b of light shading slightly less than that of the CK, and decreasing with the deepening of the degree of the interaction stress. Test seedlings under the same shading treatment, chlorophyll a/b changes little with the increasing drought stress.(5) The photosynthetic parameters LCP, Pn, Tr, WUE and Rd all showed a decreasing trend with the increase of interaction stress, and the WUE of CK was the smallest, indicating that the water use efficiency of plants under stress was higher than that under normal conditions.Through the above conclusions, shade and drought interaction stress effects of S. hancei seedlings is remarkable and the size of effect is shade> drought, seedling under light shading can still be normal growth. |
PDF Full Text Request