Brassicas: Responses and tolerance to heavy metal stress
Authors: Ahmad, P., Qadir, S., Hameed, A., Nisa, N., Azooz, M.M., Wani, M.R., Hasannuzaman, M. and Kazi, A.G.
Pages: 1-36
DOI: 10.1007/978-1-4614-8824-8_1
Abstract:Brassica is considered as an important crop all over the world owing to its economically important products. B.juncea and B.napus are cultivated as oilseed crops globally. Heavy metal (HM) stress is one of the abiotic stresses that limit plant growth and development. Root and shoot lengths and fresh and dry weights have been observed to act as accumulators as well as indicators of metal toxicity in crops. Brassica has a potential to combat the metal-induced stress, thereby reducing the damage by undergoing various types of adaptations. However, cost-effective techniques are available in order to minimize the toxicity and to protect the surroundings from HM stress. Decrease in chlorophyll content confers to weak uptake of mineral ions due to the interference of HMs in plants. Nevertheless, low concentrations of some HMs demonstrate an efficient yield in some species. HMs disturb the composition of fatty acids and as a result lead to tremendous changes in lipid membrane that may ultimately cause lipid peroxidation. Proline accumulation enhances the tolerance level under osmotic stress and is known to regulate the water balance in crop plants. Increased glutathione (GSH) in B. napusand B. juncea, on exposure to HMs, has shown its active involvement in detoxification of free radicals either directly or through certain enzymes. Phytochelations are one of the important methods to reduce the phytotoxicity by binding complexes with high-affinity ligands in the vacuole, thereby keeping the released toxins away from the metalsensitive metabolic centers in the cytoplasm. Ascorbate–GSH cycle plays an efficient role in reactive oxygen species (ROS) detoxification released through abiotic stress. Besides, ROS shows release of new isozymes of peroxidases. Genetic engineering has been established to enhance the plant’s ability to endure and mitigate the environmental stress. This involves the insertion of foreign DNA into nuclear genome and genomic chloroplast. However, gene expression can be regulated by various promoters. Several transgenic approaches have been carried out successfully with enhanced accumulation of HMs in B. juncea cultivars. There is lot of scope to understand the mechanism of HM uptake as well as the capacity of plants to withstand the environmental stresses.
Source: Scopus