Effects of drought stress and mycorrhizal fungi on some morphophysiological characteristics of lettuce (Lactuca sativa L.)

Arbuscular mycorrhizal fungi benefit from a symbiotic relationship with the plant، which is currently one of the strategies used to reduce stress. The experiment was factorial in a randomizing complete block with three replications. The first factor was three levels of drought stress including: D1 (%100)، D2 (%80)، D3 (%60) field capacity of soil moisture and the second factor included six level mycorrhizal: G1 (Glomus mosseae)، G2 (Glomus intraradices)، G3 (Glomus fasiculatum)، G4 (mixture of three fungal species G1، G2، G3) in sterile soil، C1 (Control 1 without fungus in sterile soil)، C2 (Contorl2، without fungus in non-sterile soil). The measured traits were fresh and dry weight of shoot، root colonization (%)، electrolyte leakage (%)، total chlorophyll content and proline accumulation. Results showed that the effect of drought stress on all traits was significant except for fresh weight and colonization of root lettuce (P<0. 01). The lowest and highest fresh and dry weights of shoot were observed in D1 and D3 treatments، respectively. Application of mycorrhizal fungal inoculum on all traits was significant except for root fresh weight (P<0. 01) and (P<0. 05). Using G. mosseae was the most important effect in most of the growth characteristics. Interactions between mycorrhizal fungi and drought stress on contents of total chlorophyll and proline accumulation (P<0. 01) were significant. The highest and lowest total chlorophyll contents obtained were at 60% moisture، respectively، in plants inoculated with mycorrhizal fungi (G. mosseae) and control plants (control 1). To increase the resistance of plants to drought stress a G. mosseae is recommended to be used.