METAL STRESS ON SEED GERMINATION AND GROWTH

Heavy metals are non-biodegradable which form the major group of environmental pollutants and can harm humans and other living organisms via food chains, often leading to toxicosis, thus are bringing attention towards themselves for studies and research. The heavy metals which can cause toxic effects to plants; leading to less productivity and effecting the agro-ecosystem; include lead, cadmium, copper, cobalt, nickel etc. The metal toxicity in plants manifest through an array of physiological and metabolic alterations which may include alteration in key enzyme activities, protein mobilization, photosynthesis and synthesis of metal detoxifying compounds due to induction of oxidative stress. There is an increase in the generation of reactive oxygen species on accumulation of metal ions in plant tissues which can be decreased with the help of antioxidants due to its ability to trap free radicals. Also in some plants metals as trace elements are essential for normal metabolic function but are toxic in higher concentrations thereby are hampering the physiological and metabolic functions of plants. Further, it has been observed that due to metal stress some plants produce heat shock proteins and which can affect the photosynthesis by destabilizing enzymes. This review is summarized to understand the effect of metal stress on seed germination and growth.