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Effects of Drought Stress on Physioecological Characteristics of Typical Plants in the Ecotone between Dry Valley and Mountain Forest

Author: CaiHaiXia
Tutor: YangWanQin;WuFuZhong
School: Sichuan Agricultural University
Course: Forest cultivation
Keywords: Arid valley Ecotone Typical plant Drought Stress Growth and adaptation Photosynthesis Antioxidant enzyme activity Nutrient use
CLC: Q948
Type: Master's thesis
Year: 2010
Downloads: 53
Quote: 0
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Abstract


Global warming and human disturbance arid areas become more and more serious water shortage. Arid soil nutrient content is also getting lower and lower with the expansion of the arid region. Arid region with semi-arid growing lack of water and nutrients will severely limit the growth and regeneration of plants, how to improve the arid zone vegetation status, it will be a very serious problem. The arid valley of the Minjiang River - Mountain Forest Ecotone is to stop the arid region areal extent, alleviate the dry valley of Minjiang River on the extension of the most important areas, but also the \conditions ecotone vegetation system plasticity. Learn interleaved with native plants in the arid environment of the adaptation mechanism is of great significance to improve the arid zone vegetation coverage. Arid valley in the upper reaches of the Minjiang River - Mountain forest ecotone typical plant green foxtail (Setaria viridis), chengiana (Cupressus chengiana), sea buckthorn (Hippophae rhamnoides) and Salix (Salix paraqplesia), as the research object, the control experiment sheds moisture through the year, from plant growth - the photosynthetic physiology - nutrient accumulation and distribution start, systematic study of the characteristics of the four plant growth and adaptation to drought stress and drought tolerance attempts to explore the four plants. The preliminary conclusions are as follows: drought stress had significant effects on four typical plant growth. 4 species of plant height, basal diameter, number of leaves, leaf area, biomass production decreased with the increase in the degree of drought stress, but the proportion of underground biomass and R / S increases with increasing drought stress. The four plant species in total biomass production: sea buckthorn gt; Minjiang River Park gt; alpine willow gt; Setaria. Drought stress also significantly reduced the weed, sea buckthorn and Salix specific leaf area (SLA), leaf area ratio (LAR). Drought stress significantly reduced the four plant photosynthetic pigment content and chlorophyll a / b ratio of carotenoids and chlorophyll and leaf gas exchange parameters change, but the photosynthetic pigment content did not differ significantly between the two drought stress . Severe drought stress significantly reduced the alpine willow chlorophyll a / b (Chl a / b) value, but the increase of sea buckthorn CHL a / b the value, and the value of of Cupressus and Setaria Chl a / b had no significant impact. Drought stress reduced plant daytime net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), an increase of the coefficient of stomatal limitation (Ls) and water use efficiency (WUEi). In better conditions relative water plant net photosynthetic rate decline may be because the stomatal limitation, non-stomatal limitation may be the main reason for the decline in photosynthetic rate in severe drought stress conditions. Drought stress increased by 4 species of proline (Pro) and malondialdehyde (MDA) content, enhanced cell membrane permeability, peroxidase (POD), superoxide dismutase (SOD) and hydrogen peroxide enzyme (CAT) activity. 4 plant species relative electrical conductivity in the same water conditions there is no significant difference, Setaria MDA content in the same drought stress were lower than the other three species, Salix MDA content in the same drought stress are higher than other 3 species, Salix leaves Pro content in the same drought stress were lower than the other three plants. The same water conditions, Setaria and sea buckthorn leaf POD activity were significantly higher than Salix and chengiana, sea buckthorn leaf SOD activity were greater than the other three species. The same drought stress the Setaria and sea buckthorn leaf CAT activity were significantly higher than chengiana and Salix. 4 species C, N and P accumulation with increasing drought stress significantly reduce the distribution pattern of C, N and P also changed, N, P utilization efficiency increases with increasing drought stress. Under the same drought stress, sea buckthorn C, N, P total accumulated volume is greater than alpine willow and chengiana. Under drought conditions, sea buckthorn mainly by P limit, while the other three species by N limit. Comprehensive analysis showed that drought stress seriously affect the arid valley of the upper reaches of the Minjiang River - Mountain forest ecotone typical plant growth, changing the distribution pattern of biological production, reducing the plant photosynthetic rate, and enhance the activities of antioxidant enzymes, reducing plant nutrients content accumulation, changing the nutrient use efficiency, drought tolerance of different woody plants: sea buckthorn gt; Minjiang River Park gt; Salix. These results suggest that the continued proliferation of the arid region will seriously affect the ecotone plant growth, but also for vegetation restoration species selection and species in the practice of configuration to provide a certain theoretical basis.

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