Responses of wheat plants associated with arbuscular mycorrhizal fungi to Short-term water stress followed by recovery at three growth stages

Abstract

Mycorrhizal and non-mycorrhizal wheat plants (Triticum aestivum L. cv. Sakha 93) were subjected to water stress by increasing irrigation period from one week to two weeks at different stages of plant growth (i.e., tillering, heading or grain-filling stages) and then reirrigated till harvest (recovery periods). Water stress reduced all growth parameters of wheat plants (plant height, fresh and dry matter and leaf area) as well as the plant productivity. The reduction was more pronounced when the plants subjected to water stress at heading stage. The presence of mycorrhizal fungi, however, stimulated all these parameters at all growth stages of wheat plants and their effect was pronounced in the aerial biomass than in root biomass. Mycorrhizal application increased also the shoot water content of plants under well-watered and water stress conditions. In addition, higher uptake of nutrients (N, P, K, Mg and Ca) in the shoots and grains of wheat plants was obtained as a result of mycorrhizal inoculation regardless of the plant growth stage at which the drought stress was applied. The photosynthetic pigments were also stimulated either at well-watered or at water-stressed conditions by mycorrhizal fungi. The total pigments by mycorrhizal plants under well-watered conditions were higher than non-mycorrhizal ones by 60% and by 57, 67 and 65% when the water stress treatment was applied at tillering, heading and grain-filling stages respectively. Mycorrhizal spore population and the percentage of mycorrhizal colonization were reduced by the water stress treatments. However, high levels of colonization and sporulation occurred at all stress periods. Wheat plants showed 118% dependency on the mycorrhizal fungi for its biomass production under well-watered conditions. However, the mycorrhizal dependency was 134, 133 and 124% when the stress treatment was applied at tillering, heading and grain-filling stages, respectively. The recorded improved growth, nutrient uptake and productivity of wheat plants demonstrate the potential of mycorrhizal inoculation in reducing the adverse effects of drought stress on wheat plants grown in semiarid areas of the world.