| This study investigated the possible involvement of antioxidative enzymes, photosynthetic ability, growth response to salt stress and the effect of Si to induce tolerance against salt stress in tomato (Lycopersicon esculentum M.cv.) plants. This study was carried out in Institute of Vegetable Science, Deprtament of Horticulture, Huajiachi campus, Zhejiang University, Hangzhou, China during 2000 - 2003. Results obtained were statistically analysed for examining their significance influence and they were discussed below.Tomato plants were grown in nutrient solution, NaCl, Si or Mn was added to induce the stress at different concentrations. Silicon the mineral substrate is the most abundant element in the soils for most of the world's plants. The ability of Si to ameliorate the negative effect of NaCl on growth rate was well documented. Improvement of plant growth by addition of Si is beneficial for increased tissue tolerance to high Manganese concentrations, to alleviate both biotic and a biotic stress in plants.In our study added silicon significantly increased the SOD, CAT, DR, GR activity and decreased GPOD, APX activity, MDA concentrations and H2O2 levels in tomato leaves under different salt stress concentrations. Addition of Si to the nutrient solution decreases the proline content and ascorbic acid under 150, 200 mM NaCl as compared to salt treated plants without Si. Si enhanced enzymes activity protecting the plant tissues from membrane oxidative damage induced by salt, thus mitigating salt toxicity and improving the growth of tomato plants. Our results showed that the scavenging system form the primary defense line in protecting the chloroplasts against superoxide radicals in tomato plants. This indicates that Si may act to alleviate salt stress in tomato by decreasing the permeability of plasma membrane, maintaince of cell form and structure.The dry matter production was increases due to better photosynthesis under salt stress upon addition of Si overall growth of salinised tomato plants could be improved by addition of Si. Addition of Si not significantly influenced on photosynthesis, stomatol conductance, and enzymes activities when plants were grown under salt stress induced with low salt concentration 50 mM NaCl. Under higher salt concentration induced salinity 100, 150, 200 mM NaCl, the alleviation effect of Si was noticed interns of improvement in photosynthetic ability, growth, and enzyme activity in tomato plants.In another experiment, influence of Si on tomato plants grown under with or without higher Mn concentration. In these experiment treatments except dry matter of root, different treatments influence significantly the dry matter accumulation in different parts of plants. Silicon supply only during preculture resulted in significantly higher dry matter accumulation of leaves at normal Mn concentration. Si supplies during preculture recorded significantly higher dry weight, SOD, CAT, DR activities in tomato plants at higher Mn treatment. This indicates that Si supply during the preculture alleviated the effect of Mn toxicity due to ameliorating effect of Si. Si supplies at higher Mn treatment resulted in reduction of GPOD, APX activity. The nutrient solution containing Mn and Si incorporated into the cell walls during pretreatment has a similar or even stronger beneficial effect than Si supplied at higher Mn treatment.Addition of Si to the nutrient solution had improved the tomato plants by raising photosynthesis activity (Pn), stomotal conductance (gs), intercellular CO2 (Ci), chlorophyll content and chlorophyll fluorescence parameters (Fv/Fm, PSII, ETR, Fv'/Fm') had exchanged by addition of Si in the presence of 150, 200 mM NaCl after 7th day of treatments. Salt treated plant depresses the photosynthetic capacity, chlorophyll content and chlorophyll fluorescence of tomato in the absence of Si. Addition of Si to the nutrient solution resulted on increases plasma membrane H+ -ATPase, tonoplast H+ PPase in both leaf, root of tomato plants and decreases the tonoplast H+ -ATPa... |
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