ABSTRACT
Heavy metal (HM) stress is threatening agricultural crops, ecological systems, and human health worldwide. HM toxicity adversely affects plant growth, physiological processes, and crop productivity by disturbing cellular ionic balance, metabolic balance, cell membrane integrity, and protein and enzyme activities. Plants under HM stress intrinsically develop mechanisms to counter the adversities of HM but not prevent them. However, the exogenous application of abscisic acid (ABA) is a strategy for boosting the tolerance capacity of plants against HM toxicity by improving osmolyte accumulation and antioxidant machinery. ABA is an essential plant growth regulator that modulates various plant growth and metabolic processes, including seed development and germination, vegetative growth, stomatal regulation, flowering, and leaf senescence under diverse environmental conditions. This review summarizes ABA biosynthesis, signaling, transport, and catabolism in plant tissues and the adverse effects of HM stress on crop plants. Moreover, we describe the role of ABA in mitigating HM stress and elucidating the interplay of ABA with other plant growth regulators.
ABSTRACT
Artificial polyploidy that brings about increase in cell size confers changes in histo-morphology leading to altered phenotype, causing changes in physiological attributes and enhanced concentration of secondary metabolites. The altered phenotype is generally a manifestation of tissue hardiness reflected as robust plant type. Based on a case study undertaken on an industrially important grass, Cymbopogon khasianus (2n = 60) valued for its citral rich essential oil, here we report that the artificial polyploidy not only brings about enhancement in concentration of essential oil but also facilitates lodging tolerance. The latter is contributed by ploidy mediated changes that occur to the cells and tissues in various plant organs by way of increased wall thickening, tissue enhancement and epidermal depositions that enable robust features. An exhaustive illustrated account covering various micro-/macro-morphological, skeletal and histochemical features constituting growth and development vis-a-vis ploidy mediated changes is presented highlighting the novelties realized on account of induced polyploidy.
