Effects Of Different Factors On Assimilation Of Different Forms Of Nitrogen And Production Of Arginine By Arbuscular Mycorrhizal Fungus

Arbuscular mycorrhizal(AM) fungus are the the most common Endomycorrhizal Fungus. The main structures of AM fungus include mycelium,spore, arbuscule and vesicles. When the spores germinate and mycelium grows to the root, AM fungus establishes a mutualistic symbiosis with the host plants, supplying nutrition and water to host plants by extraradical mycelium (ERM). AM fungus cannot carry on the photosynthesis and symbiosis carbohydrate, so carbohydrate must be delivered from plants to AM fungus for the growth and development of AM fungus. ERM of AM fungi are able to take up and assimilate different formats of nitrogen, such as ammonium, nitrate and amino acids and then assimilate into arginine to translocation to the intraradical mycelium. In the intraradical mycelium arginine released N to the host plant or formed other amino acids with C skeleton.In this study, AM fungus (Glomus intraradices) was associated with the host plant (Sorghum bicolor L. Moench) and grown in three-part pot culture system. We studied the effects of light, organic acid, and salt stress on AM fungus assimilated exogenous nitrogen and produced Arg by determination of some index.(1) The aim of this part of research is to study the different illumination intensity on the growth and development of AM fungus. The results showed that growth and development of AM fungus were affected by different illumination intensities. The mount of spores and the rate of root infectiong were the highest in17600lx light condition, while the host plant grew the best under13200lx light condition. We can summarize that the growth of AM fungus were best in the highest illumination intensity of the three levels. However the growth of AM fungus and the growth of host plant were not positive correlation.(2) The aim of this part of research is to study the effects of different illumination intensity on the assimilation of different kinds of nitrogen and production of arginine generated by arbuscular mycorrhizal fungus. They were examined by measuring arginine contents of the extraradical mycelium (ERM) and mycorrhizal roots. The results showed that the effects of different nitrogen uptake and incorporation into arginine were different in three levels of illumination intensity. When Gin was the exogenous nitrogen in4800lx and NH4NO3was the exogenous nitrogen in17600lx, the arginine concentration in the extraradical mycelium and mycorrhizal roots was higher than other exogenous nitrogen. In13200lx the capability of arginine formation in ERM was ranked in order of Arg>Gln>Urea>NH4NO3and it in mycorrhizal roots was Gln>Arg>Urea>NH4NO3. Hence dry weight of ERM, spores amount and root infection were improved by high light intensity, viz.176001x>13200lx>4800lx.(3) The aim of this part of research is to study the assimilation of different nitrogen and production of arginine generated by arbuscular mycorrhizal fungus in salt stress. The result showed that the growth and development of AM fungus were restrained specifically manifested in the low rate of root infection from24%-53%. ERM absorbing exogenous nitrogen and then producing Arg were affected by salt stress. Arg content was different due to different nitrogen treatments. AM fungus absorbed NO3-easier than the other nitrogen in salt stress. The data of SOD, POD, CAT, MDA and Pro showed that there were toxic action of salt stress in the host plant.We also found that exogenous can release the toxicity of the salt stress in the plant connected with AM fungus.(4) The aim of this part of research is to study the effect of organic acid on the assimilation of different nitrogen and production of arginine generated by arbuscular mycorrhizal fungus. The result showed that organic acid could enhance the growth of ERM, viz. tartaric acid> citric acid> salicylic acid> malic acid> acetic acid, but there was no effect on spores amount. Although ERM was increased, the average Arg content in ERM was decreased. Arg content in ERM was lower than mycorrhiza. In different formats of nitrogen,organic acid can affect the amount of Arg in mycorrhiza. There were no significant effects on total nitrogen content of shoots in different organic acid, and total nitrogen content of shoots was decrease by salicylic acid.