The Study Of Allelopathy On The Grafted Watermelon

Watermelon is a annual watermelon in the Cucurbitaceae, which was economic crops of edible, medicinal and other uses for long history of cultivation in China. Watermelon is a strictly vegetable needing to avoid re-cropping, prone to the phenomenon of continuous cropping obstacles. To overcome the problem of watermelon cropping obstacles, breeding disease-resistant varieties and grafting were mainly taken in the production. The effect of the study on the watermelon allelopathic have been reported, but there were very rarely reports about allelopathic effects of watermelon roots, stems and leaves after grafting. Therefore, the test by studying the grafted watermelon root, stem and leaf aqueous extracts on watermelon seedling growth and development of its physiological characteristics of the liquid, and the watermelon rhizosphere microbial population shows the following conclusions:1. After aqueous extracts of watermelon residue treated watermelon seedlings, its height, root length and stem diameter were affected at some degrees. Grafted watermelon residue treated with aqueous extracts, when its concentration is less than5g/L, the watermelon plant height, root length and stem diameter growth were promoted as the concentration decreasing. When the concentration is higher than5g/L, the watermelon plant height, root length and stem diameter growth were inhibited and the inhibition was strengthen with increasing concentrations. The use of grafted watermelon debris treated with aqueous extracts of watermelon seedlings, and its promoting role was strong and the inhibition was weak.2. The chlorophyll content of watermelon seedlings was affected by aqueous extracts of different parts of the watermelon residue treated. As follows:when the concentration of aqueous extracts of the root of the grafted watermelon was less than lOg/L, the chlorophyll content increased with decreasing concentration. When the concentration was higher than1Og/L, the chlorophyll content decrease with increasing concentration; In other treatments, the chlorophyll content increased with decreasing concentration when the concentration was less than5g/L, and the chlorophyll content decrease with increasing concentration when the concentration was higher than5g/L,3. When the watermelon seedlings were treated by the aqueous extracts of different parts of the watermelon residue, the net photosynthesis rate, stomatal conductance, intercellular CO2concentration showed the phenomenon to be promoted at lower concentration and inhibited at higher concentration. The performance were following:the net photosynthesis and rate, stomatal conductance and intercellular CO2concentration increased with decreasing concentration when the concentration of aqueous extracts of the root of the grafted watermelon was less than5g/L, and the net photosynthetic rate, stomatal conductance and intercellular CO2concentration decreases with the concentration increased when the concentration was higher than5g/L. The other treatments showed that the net photosynthesis and the rate stomatal conductance and intercellular CO2concentration increased with decreasing concentration when the concentration of aqueous extracts of the root of the grafted watermelon was less than2.5g/L, and the net photosynthetic rate, stomatal conductance and intercellular CO2concentration decreases with the concentration increased when the concentration was higher than2.5g/L. 4. POD activity decreased first and then increased when watermelon seedlings were treated by aqueous extracts of s. SOD activity increased at first and then decreased. POD activity was the strongest in the watermelon residue concentration20g/L, while the activity of SOD was the strongest in the watermelon residue concentration2.5g/L. The reason for the occurrence of this situation may be SOD is very sensitive to free radicals. MDA is reduced at first and then increased, which indicated that high concentrations of aqueous extracts damage the structural integrity of cells.5. The number and types of microorganisms in the soil were affected by the aqueous extracts of watermelon debris. When its concentration is less than5g/L, the number of bacteria and actinomycetes gradually increase, but the number of fungi decreased with the concentration reducing. When the concentration was higher than5g/L, the number of bacteria and actinomycetes gradually decrease, the number of fungi gradual increase with the concentration increasing.6. The grafted watermelon within a certain range can reduce watermelon continuous croping obstacles...