Role of Arbuscular Mycorrhizae in the Alleviation of Ionic, Osmotic and Oxidative Stresses Induced by Salinity in Cajanus cajan (L.) Millsp. (pigeonpea)

Abstract

Salinity stress causes ion toxicity and osmotic imbalances, leading to oxidative stress in plants. Arbuscular mycorrhizae (AM) are considered bio‐ameliorators of saline soils and could develop salinity tolerance in crop plants. Pigeonpea exhibits strong mycorrhizal development and has a high mycorrhizal dependency. The role of AM in enhancing salt tolerance of pigeonpea in terms of shoot and root dry weights, phosphorus and nitrogen contents, K+ : Na+, Ca2+ : Na+ ratios, lipid peroxidation, compatible solutes (proline and glycine betaine) and antioxidant enzyme activities was examined. Plants were grown and maintained at three levels of salt (4, 6 and 8 dSm−1). Stress impeded the growth of plants, led to weight gain reductions in shoots as well as roots and hindered phosphorus and nitrogen uptake. However, salt‐stressed mycorrhizal plants produced greater root and shoot biomass, had higher phosphorus and nitrogen content than the corresponding uninoculated stressed plants. Salt stress resulted in higher lipid peroxidation and membrane stability was reduced in non‐AM plants. The presence of fungal endophyte significantly reduced lipid peroxidation and membrane damage caused by salt stress. AM plants maintained higher K+ : Na+ and Ca2+ : Na+ ratios than non‐AM plants under stressed and unstressed conditions. Salinity induced the accumulation of both proline and glycine betaine in AM and non‐AM plants. The quantum of increase in synthesis and accumulation of osmolytes was higher in mycorrhizal plants. Antioxidant enzyme activities increased significantly with salinity in both mycorrhizal and non‐mycorrhizal plants. In conclusion, pigeonpea plants responded to an increased ion influx in their cells by increasing the osmolyte synthesis and accumulation under salt stress, which further increased with AM inoculation and helped in maintaining the osmotic balance. Increase in the antioxidant enzyme activities in AM plants under salt stress could be involved in the beneficial effects of mycorrhizal colonization.

Induction of salt stress tolerance in cowpea [<italic>Vigna unguiculata</italic> (L.) Walp.] by arbuscular mycorrhizal fungi

“…Sodium ion has antagonistic relationship with several other ions like potassium. In present study higher concentration of sodium and lowered concentrations of other ions like potassium, phosphorus, magnesium under salt stress is in concurrence with the findings of Hashem et al, (2015) for tomato and Garg and Manchanda (2009) for Cajanus cajan. AMF not only reduced the deleterious effect of excess sodium by reducing its uptake but also caused a significant increase in uptake of other important mineral elements like potassium, phosphorous, calcium and magnesium.…”

Plant growth-promoting rhizobacteria reduce adverse effects of salinity and osmotic stress by regulating phytohormones and antioxidants in Cucumis sativus

“…The findings of the present study have shown that plants with PGPR association have lower electrolytic concentrations than control plants under salinity and drought stress. This indicates a lower permeability of the plasma membrane mainly attributed to the integrity and stability of cellular tissues by the PGPR interactions compared with non-PGPR interactions (Garg & Manchanda 2009).…”

“…Environmental stresses can establish higher electrolytes discharge (like K ions) through displacement of membrane-associated Ca from plasma lemma. Resultantly, membrane permeability is damaged and aggregate higher efflux of electrolytes inside plant cell/tissues (Garg & Manchanda 2009). The findings of the present study have shown that plants with PGPR association have lower electrolytic concentrations than control plants under salinity and drought stress.…”

Effects of arbuscular mycorrhiza inoculation on plant growth, biological and physiological parameters and mineral nutrition in pepper grown under different salinity and p levels

“…Prevention of lipid peroxidation and maintenance of membrane integrity has been considered as one of the key processes in salinity tolerance (Garg and Manchanda 2009). The measurement of electrolyte leakage from plant tissues is a classical method to estimate membrane integrity in response to environmental stresses, senescence, fruit ripening, etc.…”