Silicon Uptake, Distribution And Its Subsequent Function In Several Plants

Several plants including cucumber (Cucumis salivas L.) , rice(Oryza saliva L.), maize(Zoy vugare), soghum(Soglmm vulgre), zoysiagrass(Zoysia japonica Steud) and tall kscue(Festuca arundinaces Schreb), were used to study: (a)silicon absorption from nutrient solution added in different forms of ethylsilicate, silicic acid or silicate sodium; (b)silicon distribution in different parts of plants. (c)The effects of silicon on the resistance of salt stress in tall fescue and zoysiagrass.(d) silicon distribution on the surface of zoysiagrass seeds and the possible effect on seeds germination. Results obtained are as follows: 1 .Ethylsilicate could not be absorbed by plants when growth medium pH value maintained manually between 5.5 to 6.0. It would be hydrolyzed at any other pH value if the pH value of nutrient solution was not controlled. Zoysiagrass, maize and soghum were able to absorb either from ethylsilicate, silicic acid or silicate sodium. The similar amount of silicon was absorbed by plants when silicic acid or silicate sodium were supplied as silicon source.This showed that both silicic acid or silicate sodium could be effectivly taken up by plants.2.Results of long term silicon absorbtion experiment showed that different plants had different ability to absorb silicon. For maize plants, shoots silicon content was significantly higher than roots. Silicon content decreased according to the following order: Older leaves>3rd-6th leaves>new leaves>stem. The distribution of silicon in cucumber plants shown the same rule.But silicon content in roots of tomato was much higher than shoots, and silicon content decreased in the following sequence: old leaves> middle position leaves>new leaves >stem.3.By comparing the change of silicon uptake and distribution in plants of silicon of two kinds of turfgrass when suffered salt stress. The results showed that salt stress could enhance silicon uptake and accumulation in tall fescue and zoysiagrass. Silicon didn't improve plant growth in nutrient solution without or with low salt supply. Under this condition, silicon application could increase sodium content in roots, but decrease sodium content in shoots. Silicon could also increase potassium content of plants under salt stress, as a result increased K/Na selectiviy. Silicon could also improve zoysiagrass sodium secreation of salt gland. 4.Resuts obtained by using scanning electrol microscopy showed that glume struture was relative intense. Results of x-ray microanalysis showed that silicon was mainly deposited in glumes and glume cap, rather than in embryo!. The Si ditribution greatly hindered the permeating ability of glume pore, which resulted in low germination of zoysiagrass seeds in nature condition. This proved that silicon deposition could be one of the main factors of dormancy of zoysiagrass seeds. Eliminating silicon could break the dormancy of seeds and increase the germination percentage and germination energy. On the other hands, silicon deposition could also protect seeds from damage of environmental stress s. In a word, silicon distribution in zoysiagrass seeds was very important that it safeguarded seeds in unfavorable environment, but handicaped seeds germination under adaptable condition.