Salinity is a major abiotic stress that limits plant growth and productivity. Role of silicon (Si) nutrition and arbuscular mycorrhiza (AM) in mitigating salt stress has gained importance in recent years. Legumes are sensitive to salinity and are considered low Si-accumulators. AM have been reported to increase Si uptake in mycorrhizal plants. However, little is known about the alleviative role of Si and/ or AM in mitigating salt stress in Cicer arietinum L. (chickpea). Therefore, the present study was aimed to evaluate the individual and cumulative effect of Si and AM (Funneliformis mosseae) on nutrient status, growth and productivity of salt tolerant HC 3 and salt sensitive CSG 9505 genotypes of chickpea under salinity stress conditions. The genotypes were subjected to 0, 60, 80,100 mM NaCl and 0, 4 mM potassium silicate-K 2 SiO 3 treatments in the presence and absence of AM fungi. The results indicated that the Si and AM treatments improve the endogenous nutrients profile, growth characteristics and yield attributes under salinity stress. AM was found to be more efficient in improving growth and productivity while Si was more beneficial in improving K ? /Na ? ratio. Mycorrhization mediated significant improvement in Si uptake and as a result, Si supplementation along with mycorrhization reduced Na ? content significantly, improved growth, yield and nutrient uptake, arrested chlorophyll pigment damage and increased RUBISCO activity. HC 3 was more responsive to mycorrhization and Si nutrition than CSG 9505. The study will contribute to our understanding of Si and/or AM mediated salinity tolerance mechanism for developing chickpea genotypes resistance to salt stress.

Salinity is the major environmental constraint that affects legume productivity by inducing oxidative stress. Individually, both silicon (Si) nutrition and mycorrhization have been reported to alleviate salt stress. However, the mechanisms adopted by both in mediating stress responses are poorly understood. Thus, pot trials were undertaken to evaluate comparative as well as interactive effects of Si and/or arbuscular mycorrhiza (AM) in alleviating NaCl toxicity in modulating oxidative stress and antioxidant defence mechanisms in two Cicer arietinum L. (chickpea) genotypes-HC 3 (salt-tolerant) and CSG 9505 (salt-sensitive). Plants subjected to different NaCl concentrations (0-100 mM) recorded a substantial increase in the rate of superoxide radical (O2 (·-)), H2O2, lipoxygenase (LOX) activity and malondialdehyde (MDA) content, which induced leakage of ions and disturbed Ca(2+)/Na(+) ratio in roots and leaves. Individually, Si and AM reduced oxidative burst by strengthening antioxidant enzymatic activities (superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GPOX)). Si was relatively more efficient in reducing accumulation of stress metabolites, while mycorrhization significantly up-regulated antioxidant machinery and modulated ascorbate-glutathione (ASA-GSH) cycle. Combined applications of Si and AM complemented each other in reducing reactive oxygen species (ROS) build-up by further enhancing the antioxidant defence responses. Magnitude of ROS-mediated oxidative burden was lower in HC 3 which correlated strongly with more effective AM symbiosis, better capacity to accumulate Si and stronger defence response when compared with CSG 9505. Study indicated that Si and/or AM fungal amendments upgraded salt tolerance through a dynamic shift from oxidative destruction towards favourable antioxidant defence system in stressed chickpea plants.

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Bolan et al., 2014). The Comprehensive Environmental Response, Compensation, and Liability Act permanently listed As as no. 1 and Cd as no. 7 out of 275 in its priority list of hazardous materials (ATSDR, 2007).Arsenic and Cd toxicity cause oxidative stress by changing the composition and fluidity of membrane lipids, displacing essential metals in plant pigments or enzymes and thereby inactivating photosynthesis and respiration, and obstructing uptake and transport of water and nutrients, further reducing protein synthesis and carbohydrate metabolism along with diminished growth and yield (

Cadmium (Cd) causes oxidative damage and affects nodulation and nitrogen fixation process of legumes. Arbuscular mycorrhizal (AM) fungi have been demonstrated to alleviate heavy metal stress of plants. The present study was conducted to assess role of AM in alleviating negative effects of Cd on nodule senescence in Cajanus cajan genotypes differing in their metal tolerance. Fifteen day-old plants were subjected to Cd treatments--25 mg and 50 mg Cd per kg dry soil and were grown with and without Glomus mosseae. Cd treatments led to a decline in mycorrhizal infection (MI), nodule number and dry weights which was accompanied by reductions in leghemoglobin content, nitrogenase activity, organic acid contents. Cd supply caused a marked decrease in nitrogen (N), phosphorus (P), and iron (Fe) contents. Conversely, Cd increased membrane permeability, thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H2O2), and Cd contents in nodules. AM inoculations were beneficial in reducing the above mentioned harmful effects of Cd and significantly improved nodule functioning. Activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) increased markedly in nodules of mycorrhizal-stressed plants. The negative effects of Cd were genotype and concentration dependent.