Search

Unexpected bioaccumulation and biomagnification of heavy metal(loid)s (HMs) in the environment have become a predicament for all living organisms, including plants. The presence of these HMs in the plant system raised the level of reactive oxygen species (ROS) and remodeled several vital cellular biomolecules. These lead to several morphological, physiological, metabolic, and molecular aberrations in plants ranging from chlorosis of leaves to the lipid peroxidation of membranes, and degradation of proteins and nucleic acid including the modulation of the enzymatic system, which ultimately affects the plant growth and productivity. Plants are equipped with several mechanisms to counteract the HMs toxicity. Among them, seed priming (SP) technology has been widely tested with the use of several inorganic chemicals, plant growth regulators (PGRs), gasotransmitters, nanoparticles, living organisms, and plant leaf extracts. The use of these compounds has the potential to alleviate the HMs toxicity through the strengthening of the antioxidant defense system, generation of low molecular weight metallothionein's (MTs), and phytochelatins (PCs), and improving seedling vigor during early growth stages. This review presents an account of the sources, uptake and transport, and phytotoxic effects of HMs with special attention to different mechanism/s, occurring to mitigate the HMs toxicity in plants employing SP technology. Novelty statement: To the best of our knowledge, this review has delineated the consequences of HMs on the crucial plant processes, which ultimately affect plant growth and development. This review also compiled the up to dated information on phytotoxicity of HMs through the use of SP technology, this review discussed how different types of SP approaches help in diminishing the concentration HMs in plant systems. Also, we depicted mechanisms, represent how HMs transport and their actions on cellular levels, and emphasized, how diverse SP technology effectiveness in the mitigation of plants' phytotoxicity in unique ways. [ABSTRACT FROM AUTHOR]

• Heat stress in plants causes several morphological, physiological and molecular changes affecting growth and yield attributes. • Seed priming is an eco-friendly technology to induce uniform and rapid emergence of seed that leads to better stand establishment and improvement in yield, under both optimal and adverse environments. • Nitrate priming of seeds improves seed germination, crop growth, nitrogen metabolism and increases nitrate reductase activity, enabling reversal of heat stress induced responses in plants, maintaining the yield potential of the plants. Exhaustion of natural sources due to expanding usage leads to an increase in global temperature. Heat stress and rising CO 2 severely impact crop growth and catastrophic loss of agriculture ecosystem, productivity and quality. The physiological and metabolic processes of plants are affected by heat stress due to denatured proteins, lipid structure, alteration in membrane integrity and inactivation of enzymes incurred at various growth stages. To diminish heat stress losses in plants, many techniques such as conventional breeding, genetic engineering, molecular breeding were used by the agriculturists, which helped develop tolerant varieties of crops with increased quality and production. Recent advancement in seed priming has many fold impacts such as mitigation of stress via improving tolerance mechanisms in plants, reduction in soil and water pollution, improved production and food quality of important agriculture crops. It is one of the low-cost, reliable and profitable crop improvement techniques. Nitrates have several roles in modulating the plant processes. Priming with nitrate salts improves nitrate reductase and amylase activity, nitrogen, amino acid and chlorophyll content in leaves, causes increase in proline, sugar content, antioxidant metabolism, grain yield, protein and nutrient content in various crops. Despite positive responses of nitrate seed priming, this technology has been less applied in the area of crop production in the field condition. Considering these facts, this review depicts responses of the plants under heat stress and their management through nitrate seed priming. [ABSTRACT FROM AUTHOR]

An experiment was conducted in both laboratory (germinative attributes) and field conditions (growth attributes) with completely randomized design (CRD) and randomized block design, respectively, to view the responses of different priming treatments in two wheat varieties: HUW-234 (V1) and BHU-3(V2). In the present study, seeds were primed with water (hydro; T2), Mg (NO3)2 (T3), ZnSO4 (T4), and a combination of both salts (T5). Their carry over effects were observed on the germinative and vegetative phases of growth. All treatments were compared with the performance of nonprimed control seeds (T1). Maximum germination percentage (98.33, 100%) was noted with T3, whereas length of shoot (8.83, 10.23 cm) and root (9.47, 10.73 cm) and their fresh (0.34, 0.45 g) and dry weights (0.05, 0.07 g) were recorded maximum in T5 for both varieties; however, the vigor index I and II showed varietal difference, but primed sets were found always superior with respect to nonprimed control. Study of plant height, leaf number and area, fresh and dry weights of total leaves and stem showed the best performance under combined use of both salts, i.e., Mg (NO3)2 and ZnSO4 as priming agents, followed by ZnSO4, Mg (NO3)2, hydro, and the nonprimed one. The study of biochemical parameters such as protein content and nitrate reductase activity of leaves showed the highest increment in combined priming treatment and increased 63.77, 90.37, 37.44% and 12.81, 5.61, 7.75%, respectively, after 35, 45, and 60 days after sowing. It is likely that chlorophyll, nitrogen, iron, and zinc content also followed a similar pattern and were enhanced in combined priming treatments as compared to nonpriming treatment. Therefore, the result suggests that priming seeds with Mg (NO3)2 and ZnSO4 worked synergistically at varietal level and improved growth attributes at field conditions. [ABSTRACT FROM AUTHOR]