Protective effects of arbuscular mycorrhizal fungi on wheat (Triticum aestivum L.) plants exposed to salinity

Little information is available concerning arbuscular mycorrhizal fungi (AMF) influence on carbon and nitrogen metabolisms in wheat under saline conditions. Thus, this study will shed light on some different mechanisms that play a role in the protection of wheat plants colonized by AMF against hyperosmotic salinity. Two wheat (Triticum aestivum L) cultivars, Sids 1 and Giza 168, were grown under non-saline or saline conditions (4.7 and 9.4 dS m(-1)) with and without AMF inoculation. Root colonization was adversely affected by increasing salinity level, particularly in Giza 168. Soil salinity decreased plant productivity, membrane stability index, photochemical reactions of photosynthesis, the concentrations of N, nitrate, chlorophyll, carbohydrates, and protein, the relative water content, and the activities of nitrate reductase and carbonic anhydrase. The reduction was more pronounced in Giza 168. Mycorrhizal symbiosis protected wheat against the detrimental effect of salinity and significantly improved the above parameters, especially in Sids 1. Under saline conditions, wheat plants colonized by AMF had higher gas exchange capacity (increased net CO2 assimilation rate and stomatal conductance, and decreased intercellular CO2 concentration), compared with non-mycorrhizal ones. Concentrations of soluble sugars, free amino acids, proline and glycinebetaine increased under saline conditions; these increases were more marked in salt-stressed plants colonized by AMF, especially in Sids 1. Soil salinization induced oxidative damage through increased lipid peroxidation and hydrogen peroxide levels, particularly in Giza 168. Mycorrhizal colonization altered plant physiology and significantly reduced the oxidative damage in plants exposed to salinity. Enhanced metabolism of carbon and nitrogen can be one of the most important mechanisms of plant adaptation to saline soils that are activated by AMF. This is the first report dealing with mycorrhization effect on the activity of carbonic anhydrase under saline conditions. (C) 2013 Elsevier B.V. All rights reserved.