Nitric oxide (NO) has been shown to be an important signaling molecule in mammalian and plant physiology. The notion that exogenous application of NO in the form of a solution-based NO donor, for example, sodium nitroprusside (SNP), can counteract the toxicity of heavy metals in plants has been supported experimentally in many studies in the past decade. However, some recent studies also appeared to have casted doubts about this. Moreover, there does not appear to have been any assessment of the practical or agricultural significance of applying NO exogenously for ameliorating heavy metal toxicity in plants, particularly during postgerminative seedling growth. The main features of the relevant studies were examined critically. The issues discussed in relation to the studies of applying NO and heavy metal treatment of seedlings during postgerminative growth might also be relevant to studies at other plant growth and developmental stages. It is concluded that the agricultural significance of exogenous application of NO to alleviate heavy metal toxicity in plants remains to be established.
Keywords: Abiotic stress, alleviation of metal toxicity, antioxidants, Arabidopsis thaliana, catalase, cPITO, crop protection, environmental pollution, morphological alterations, nitric oxide, oxidative stress, peroxidase, postgerminative seedling growth, pretreatment, reactive oxygen species (ROS), root elongation, root growth inhibition, sodium nitroprusside (SNP), yellow lupin.