Foliage application and seed priming with nitric oxide causes mitigation of salinity-induced metabolic adversaries in broccoli (Brassica oleracea L.) plants

Abstract

Nitric oxide (NO) has a diverse role in plant metabolism under stressful cues. This study was carried out to evaluate the effectivity of exogenously applied (pre-sowing and foliar) NO to minimize the adversaries of salinity stress on broccoli plants. Experimental design was completely randomized along with four replicates. Two levels of nitric oxide, control (0 mM) and 0.02 mM were applied on broccoli plants subjected to salt stress (120 mM) and non-stress conditions. Data showed that salinity stress significantly reduced fresh or/and dry weights of roots and shoots, root length, chlorophyll (a and b) contents, while it significantly increased total phenolics, hydrogen peroxide (H2O2), malondialdehyde (MDA), glycine betaine, proline, ascorbic acid, activities of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) enzymes. The external application of NO via both pre-treatment as well as foliar application improved chlorophyll a, total phenolics, glycine betaine, and activities of SOD, CAT and POD enzymes while it was more helpful in lowering levels of H2O2 and MDA, however, it remained ineffective for shoot length. Overall, both modes of NO were effective in improving plant growth, chlorophyll a, proline and glycine betaine contents under stress conditions. The results indicated that external use of NO is beneficial for minimizing the salinity adversaries in broccoli plants.