Effects Of Root Exudates And Extracts On Growth Of Processing Tomato And Activities Of Soil Enzymes

Processing tomato is one of the important cash crops in Xin Jiang province China. Continuous cropping of processing tomato brought about many serious problems such as yield reduction, quality deterioration ect. Many studies show that continuous cropping obstacles are mainly caused by root exudates and residual roots in soils. Therefore, several experiments were carried out to study their effect on the growth of processing tomato seeding and the activities of enzymes in soils, which aims to reveal the mechanisms and probable causes of continue cropping obstacles, to provide scientific basis for solving the problems produced by continuous cropping as well as improve the yields and qualities of processing tomato in Xin Jiang Province. And offering technical support to the sustainable development of the processing tomato--the competitive industry in Xinjiang Province.Pot and simulation experiments as well as chemical analysis were adopted in our experiments. The root exudates of the processing tomatoes were collected and then fractionated into acid, alkaline and neutral solubles. They were added into culture mediums to investigatet the impact they exerted on the germinating rate, the growth of processing tomato seeding as well as the absorption of nourishment by the roots. Moreover, the extracts from processing tomato roots were also used to cultivate the soils to study their effects on the activities of soils. The main findings are as follows:1. The root exudates of the processing tomatoes may have an autotoxical effect on the germinating rates and seeding growth.. And the root exudates with different components and concentrations will cause an obvious decline in the germinating rates and index of the seeds. With the increasing concentration of the root exudates, the degree of suppression becomes more obvious. The acid-soluble root exudates has generated the greatest impact on the germinating rates, followed by neutral soluble, and the alkaline soluble exerted the smallest influence on the germinating rates, the average germination rates are reduced by 14.7%, 11.7% and 8.3% respectively. Compared with several concentrations, 50% solution of root exudates owns the most powerful suppression(the germination rates are down by 19.33%). The growth of processing tomato seedlings has been restrained under the function of the three components, which mainly weakens the root activities(reduced by 51.9～59.6%); and the root exudates may weaken the SOD activities in leaves of the processing tomatoes, increase the generation of the MDA, and improve the POD activity, which shows that the root exudates of the processing tomato may have an autotoxical effect.2. The root exudates has an adverse effects on the absorption of nourishment by the roots of the processing tomatoes. With the increase of concentration, the absorption of NO3―, H2PO4―, K+ will be restrained. It is observed that the most depressed NO3― and K+ uptake occurred with the addition of neutral acid fraction, respectively. As a consequence, it is inferred that several chemical inhibitors of growth and nutrient uptake of processing tomato seedlings should be contained in root exudates.3. The extracts of residual roots with different concentrations may have an obvious impact on the root activity and growth of the seedlings. With the increase of the concentration of extracts, the root activities of the seedlings will be weakened, and the numerical value of cytomembrane permeate MDA have been enhanced obviously, which shows that the cytomembrane have been damaged, while the SOD activity of the defensive system of the cell enzyme has shown a sign of declining, and the CAT activity increases before decreasing, the POD activity shows the trend of rising, which indicates that defensive systems are destroyed protecting cytomembrane from peroxidation of cytogrease and cytomembrane.4. The activities of catalase,invertase,phosphatases,urease and protease may be affected by the extracts of residual roots and the culture time. The activities of catalase and phosphataes in soils will be activated by the extracts from residual roots of the processing tomatoes. When the time for culturing the activities of catalase reaches 15 days, the activities will be most effective after adding 45% concentration of extracts. However, the activities of catalase and phosphatases in soils varied little, if any, compared to the treatment without extracts added as the culture period prolonged. As the culture time prolonged, the activities of urease increased in contrast to those invertase. The highter the concentrations of root extracts(the maximum reached 45﹪)were added, the stronger the activities of urease were detected. The activities of invertase were enhanced markedly by the addition of 45%and 30% concentration of root extract. As the culture time prolonged, the activities of protease increase at first and begin to decrease, and then increase again before declining. Similarly, the inhibition of protease got strong with the increment of extract concentration supplied. When the culture time reaches 35 days, the activities of protease processed with 45% concentration of residual root extracts will decrease to the lowest level.