Modulation of Cadmium Toxicity in Wheat by Foliar Application of Sodium Nitroprusside

Abstract

Cadmium (Cd) is harmful to plants as well as animals and causes serious threats to human health. Thus, it is imperative to understand the mechanisms of Cd effects through Cd-induced physio-biochemial determinations as well as its accumulation, transportation and the relationships with growth, antioxidant systems and the mineral nutrients. Furthermore, the contribution of exogenous sodium nitroprusside (SNP) in alleviating the Cd toxicity in wheat is largely unknown and needs to be dissected. The experiments were conducted using different Cd (control, 0.3, 0.6, 0.9 and 1.2 mM) regimes without or with an exogenous nitric oxide (NO) donor, SNP (0.15 and 0.30 mM) on four cultivars of wheat (Punjab-2011, AARI-2011, Millat-2011 and Sehar-2006). The exogenous application of SNP was efficient in recovering growth of Cd-stressed wheat plants. Cd reduced the growth attributes, chlorophyll contents, gas exchange attributes, total flavonoids, anthocyanin contents, leaf relative water contents (LRWC), essential nutrients, total phenolics, soluble proteins, and grain yield components while increased leaf relative membrane permeability, total free amino acids, proline, glycinebetain (GB), reducing and non-reducing sugars, ascorbic acid, malondialdehyde (MDA), hydrogen peroxide (H2O2) and the activity of ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) irrespective of wheat cultivars. More effective level of SNP was 0.30 mM which under Cd stress improved growth and physiological attributes of wheat plants. Punjab-2011 and AARI-2011 showed better performance than Millat-2011 and Sehar-2006 in Cd-stress environment. NO exogenous application was useful to improve shoots and roots fresh and dry biomasses, chlorophyll contents, photosynthetic rate, total flavonoids, anthocyanin contents, LRWC, uptake of essential nutrients, total phenolics, soluble proteins, and grain yield components under Cd stress. Moreover, NO inverted the toxic effects of Cd on leaf relative membrane permeability, total free amino acids, proline, glucose and sucrose, MDA, H2O2 and the activities of APX, CAT, POD irrespective of wheat cultivars. Overall, the results elaborated that exogenous NO recuced the Cd toxicity in wheat.