The Effects Of Selenium On Tomato And Lettuces And The Characteristics Of Selenium Accumulation

Selenium is one of essential trace elements which play important roles in normal physiology of human body. Foods, which absorb selenium from the soil directly or indirectly, are main sources for human beings to get selenium. However, the distribution of selenium in the soil is extremely limited on the earth's surface. Selenium lack is especially serious in some areas (For example, about 30% of the national territory of China are selenium shortage seriously). So to develop the selenium-enriched fruits and vegetables is very important for meeting the demand of selenium of the human body. The effects of selenium on two common vegetables---tomato and lettuces have been studied and the characteristics of selenium accumulation of the two experimental plants have been analyzed under the conditions of different selenium-supplied means, selenium concentration and treatment time for exploiting selenium-enriched fruits and vegetables.The results showed that the vegetative growth, chlorophyll content, Vc content and weight of fruit in single tomato and the spatial distribution of selenium on the tomato plants were related closely not only to selenium concentrations, but also the varieties of tomatoes when they were treated under different selenium concentration. For example, 2mg/L selenium might inhibit the vegetative growth of the tomato variety"Gaogao", but benefit to another variety"Taotailang"and could increase the weight of fruits of single plant of"Taotailang"; 1~2mg/L selenium could help tomato to synthesis soluble sugar, especially for"Taotailang"; 1~2mg/L selenium could reduce the chlorophyll content of"Gaogao", but had a reverse effect on that of"Taotailang". Under 1~2mg/L selenium, the selenium accumulation effects of tomato were related positively to the quantity of selenium in the environment. The leaf's selenium content of"Gaogao"was the highest, but the fruit selenium content of"Taotailang"was the highest, both stem's selenium content were the lowest."Taotailang"could be taken as a potential variety of tomato for exploiting selenium-enriched fruits and vegetables.Some physiological indices of lettuces also changed after treated by different selenium contents. Under 0~12mg/L of selenium, Less than 4mg/L selenium was beneficial to the chlorophyll synthesis of lettuces; under 2~8mg/L of selenium, 2mg/L could decrease the SOD activity, but would increase the SOD activity when selenium contents were above 2mg/L. There was a significant relationship between selenium contents and sulfur contents of the varieties of lettuces (South Korea"Xiajihong", US"Ziyeshenhe"and"Dasu"). The selenium contents of"Xiajihong"was the biggest, it should be the appropriate selenium-enriched variety of lettuce to be cultivated.