Physiological Ecology Of Arbuscular Mycorrhiza Under Stress Conditions

Owing to human destroy and natural disaster, modern agriculture are facing increasingly serious questions of resource, environment and ecology, soil degeneration among them has become the first harm factor to develop agriculture. Soil degeneration includes corrosion, barren, saline and alkali soil, arenaceous soil, asidic soil and so on. Recently, with irrigated fields and multiple crop indexes increasing, the areas of K fertilizer deficiency and saline were gradually expanded. They have seriously retarded rapidly development of our agriculture, and become the key factors to improve high and steady yield of plants. Arbuscular mycorrhizal (AM) fungi are a kind of soil microorganism distributes in the soil system entensively. Symbiosis can be formed between AM fungi and host plant above 90 percent, and exists in all kinds of lands. It has been reported that AM fungi can improve plant stress tolerance. This is because the symbiosis can promote host plant to absorb soil mineral elements, modulate water status, and sustain normal physiological and chemical metabolism. So, the study on physiological ecology of AM has important practiced value. It can provide agriculture with theoretical basis.With pot culture two plant species (tobacco and cotton) and three AM fungal isolates were used to investigate the effect on the growth of tobacco and its mechanism under K fertilizer deficiency, on the growth of cotton and its mechanism with salt stress in this study. The main conclusions obtained are as follows:1. The result showed that tobacco and cotton highly depended on AM fungi for growth and development, being significantly raised the infection rate when they had been inoculated. Under K fertilizer deficiency the infection rate of equal mixture of Glomus mosseae and Glomus caledonium on tobacco are the highest. Salt stress can retard the infection rate of AM fungi, but AM fungal inoculation could change the infective curve of AM fungi of cotton,and improve infection rate in early and middle pierod.2. AM fungi can improve growth of plants by bettering status of K fertilizer deficiency and salt stress. The growth of tobacco inoculated equal mixture of Glomus mosseae and Glomus caledonium was higher than the plant with K fertilizer. Under salt stress AM fungi could increase growth and biomass of the inoculated plants, and the effects on cotton was better under low salt stress.3. AM fungi can increase biomass of the inoculated tobacco and decrease quantityof K fertilizer application. There is certain selectivity between cotton and AM fungi species, the effects of equal mixture of Glomus mosseae and Glomus caledonium on cotton named NC89 was the best among fungi used in this study.4. AM fungi can increase chlorophyll and soluble protein content, change balance of ions and low relative component of sodium and chlorine of ions so as to relieve metabolic disorder and promote metabolism normal performance.5. AM fungi can raise activity of protective enzymes and modulate isozymes of SOD and POD to express in salt tolerance. Fungi inducting isozymes to produce were influence of adjustment to environment; salt stress inducting to produce was exhibition of AM fungi to modulate internal metabolize activity.6. The reasions of arbuscular mycorrhizal fungi enhancing stress tolance and retarding senescene were the positive effects of AM fungi on improving nutrient status and physiological metabolism to progress growth of plants and the indirect effects of AM fungi on raising activity of protective enzymes.