Effect of the fungus Piriformospora indica on physiological characteristics and root morphology of wheat under combined drought and mechanical stresses

摘要

Abstract This study was done to evaluate the effects of the root-colonizing endophytic fungus Piriformospora indica on wheat growth under combined drought and mechanical stresses. Inoculated (colonized) and non-inoculated (uncolonized) wheat (Triticum aestivum L. cv. Chamran) seedlings were planted in growth chambers filled with moist sand (at a matric suction of 20?hPa). Slight, moderate and severe mechanical stresses (i.e., penetration resistance, Q p, of 1.17, 4.17 and 5.96?MPa, respectively) were produced by a dead-load technique (i.e., placing a weight on the sand surface) in the root medium. Slight, moderate and severe drought stresses were induced using PEG 6000 solutions with osmotic potentials of 0, –0.3 and??0.5?MPa, respectively. After 30 days, plant physiological characteristics and root morphology were measured. An increase in Q p from 1.17 to 5.96?MPa led to greater leaf proline concentration and root diameter, and lower relative water content (RWC), leaf water potential (LWP), chlorophyll contents and root volume. Moreover, severe drought stress decreased root and shoot fresh weights, root volume, leaf area, RWC, LWP and chlorophyll content compared to control. Catalase (CAT) and ascorbate peroxidase (APX) activities under severe drought stress were about 1.5 and 2.9 times greater than control. Interaction of the stresses showed that mechanical stress primarily controls plant water status and physiological responses. However, endophyte presence