The Effect Of Inoculation Of AM Fungi On The Fe Absorption Of Citrus

The soil salinization endangers agricultural production seriously. Iron chlorosis of food crop plants and fruit trees grown on alkaline, or calcareous soils is a widespread agricultural problem in the world. Although abundant in these soils, iron is often insoluble and therefore is unavailable for the plants roots. Statistics show that potential iron-deficiency exists in plants growing in 25%-30% soils of the globe. Fruit trees are very important economic crops in people's life, the iron deficiency of fruit trees is a main production problem that affects amount of fruit increase and the benefit of fruit growers. Unfortunately, the widespread problem of iron chlorosis of fruit trees remains poorly understood and the results of the methods for its correction are not satisfactory, and they sometimes cause serious environmental problems as well. While in recent years, the bioengineering measures have demonstrated the great superiority of comprehensive treatment.Arbuscular mycorrhizas are mutualistic symbioses that form between arbuscular mycorrhizal (AM) fungi and the roots of host plants. The symbioses are characterized by bi-movement of nutrients where carbon flows to the symbiosis and inorganic nutrients or water move to the plants, thereby becoming a transported carrier between the roots of host plant and soil. Thus, AM symbioses are important for growth and development of host plants. Citrus is one of important fruit species in southern China, most of citrus trees are cultivated in highland, Citrus has rare and short root hairs in field and is fairly dependent on AM fungi that are most Glomus species. Citrus is very susceptible to iron chlorosis that is the most frequent nutritional problem in this type of fruit due to high calcium or high pH in soil, which cause decreased yield and neglectly affected of fruit quality.This experiment aimed at the application and popularization of citrus. Aimed at the phenomenon that citrus has the difficult to absorb iron nutrition, this test made use of Carrizo citrange (P. trifoliata (L.) Raf.×C. sinensis (L.)Osbeck) and Satsuma mandarin(Citrus unshiu Marc.)as materials to study the effects of inoculation treatment, different pH value of soil in cropland, on citrus growth and physiological and biological indexes. And then the data obtained were used to have correlation statistical analysis, to offer the reasonable grounds for the popularization and salt-resistance breeding of citrus.In this study, Carrizo citrange(P. trifoliata (L.) Raf. X C.sinensis (L.)Osbeck) and Satsuma mandarin(Citrus unshiu Marc.) were used as the test materials, and three arbuscular mycorrhizal fungi of Glomus in order to evaluate the effect and mechanism of AM fungi on iron uptake in citrus, so as to provide basic theory for improvement of mineral elements. The main contents and results in the present study are as follows:(1)Study on effects of AM fungi on citrusExperiment was carried out in pot culture and effects of three Glomus species(Glomus mosseae, G.etunicatum and G. eburneun) on mycorrhizal infect percentage, plant growth in Carrizo citrange(P. trifoliata (L.) Raf. X C.sinensis(L.) Osbeck)were studied. Different AM fungi showed the difference of inter-species in citrus. The results showed that inoculation with G. mosseae had the greatest effects compared with G. etunicatum and G. eburneun in citrus, it had highest AM colonization, plant height, stem diameter, root volume. It suggested that G. mosseae was the best in the three AM fungus in citrus. It showed that G. mosseae was the most suitable for citrus in the three AMF. In the test, we studied the effects of absorption of minerals'nutrition under the condition inoculated AMF:The results showed that inoculating AMF is conducive to absorption of mineral nutrition, especially the absorption of microelements Fe, macroelements N and P was notable.(2)Effects of AM fungus on iron uptake in citrus under different pH conditionsUnder the field condition, annual citrus plants with the same management level were chose to plant in three kinds of soils with different pH value, then each of treatments has a difference between inoculated and noninoculated AM fungi(AMF). The effect of the AM fungi(Glomus mosseae) on iron contents in citrus rootstock Carrizo citrange (P. trifoliata (L.) Raf. X C. sinensis(L.) Osbeck) and Satsuma mandarin (Citrus unshiu Marc.) was studied in sand pot culture under different pH ranges. The test was carried out at three different pH levels by applying nutrient solution at pH 5.5～6.4,6.5～7.4,and7.5～8.5. The main test results could be generalized as follows:1. Through the contrastive analysis on leaves in different pH levels, we find that the high pH and low soil Fe can affect citrus chlorosis, leading to the effective iron content was decreased.2. It was confirmed that inoculating could effectively promote the synthesis and accumulation of soluble protein, enhance the content of oxygen free radical scavengers and praline, increase their accumulation in leaf, improve it's resistance saline and alkaline. The results show that inoculation of arbuscular mycorrhizal fungi could reduce or significantly reduce the concentrations of superoxide anion radical and hydrogen peroxide in leaves of the citrus rootstocks. AM infection also increased the activities of antioxidant enzymes including peroxidase, catalase and ascorbic oxldase, helping to alleviate oxidative damage and enhancing hign pH resistance of host plants.3. We studied the effects of AMF inoculation in different soil pH value in this experiment. The results showed that AMF inoculation could significantly promote the absorption of the microelement Fe when the soil pH value was higher. It was important for exploitation of mineral soils.4. It was showed that at high pH stress, AM fungi can increase iron absorption of citrus and improve the iron chlorosis phenomenon caused by the iron deficiency.