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Role of Hydropriming and Magneto-Priming in Developing Stress Tolerance

germination and hypocotyl length (Zeid & Shedeed, 2006), plant growth, and

development in rice (Manickavelu et al., 2006). Drought stress reduced the

spikes per plant, number of grains and number of tillers in barley (Hordeum

vulgare) (Samarah, 2005), reduced the yield in pigeon pea by 40–55% (Nam

et al., 2001) resulting in poor seed material. Seed priming induces drought

resistance through changes in molecular mechanisms such as stress proteins

and AQP, hormone signaling, cell membrane stability, osmotic adjustments,

antioxidant defense, and morphological mechanisms by phenotypic plasticity.

Thus, the use of different seed priming agents is encouraged (Farooq et al.,

2009). Hydropriming was used for seed invigoration for effective germina­

tion of seeds in maize (Janmohammadi et al., 2008), seed growth in chickpea

(Kaur et al., 2002), and cotton (Casenave & Toselli, 2007) under salinity and

drought. Nadali et al. (2020) evaluated quinoa cultivars for drought stress

response. Hydro priming significantly enhanced growth and seed yield along

with a comparatively lower lipid peroxidation and electrolyte leakage in all

the three quinoa cultivars. Hydropriming increased germination and seedling

growth under salt and drought stresses in sunflower (Kaya et al., 2006).

4.3.3 HEAVY METAL STRESS

Plants exhibit varied response to heavy metal phytotoxicity, that may occur

due to volcanic eruptions, forest fires, surface mineralization, and spon­

taneous combustion or by human actions such as mining and agriculture

(Nagajyoti et al., 2010). Human-produced contamination occurs through

automobiles, use of pesticides, fertilizers, generator stations, metal smelters,

mills, refineries, and municipal incinerators (El-Ramady et al., 2015). Heavy

metals that require the growth and development of plants can be catego­

rized as essential and nonessential nutrients. The essential nutrients are also

known as micronutrients such as Cu, Ni, Zn, Mo, Fe, Co, and Mn, involved

in different metabolic processes such as redox reaction and electron transfer,

etc. The nonessential nutrients are toxic for plants such as Cd, Cr, As, Pb,

and Hg (Rai et al., 2004; Sebastiani et al., 2004). Metals can further be clas­

sified based on physiochemical functions as redox and nonredox metals. The

redox metals, i.e., Fe, Cu, Cr, and Mn (Jozefczak et al., 2012; Valko et al.,

2005) cause oxidative injury that produces ROS resulting in DNA breakage,

damaged photosynthesis mechanism, defragmented proteins, disruption in

the cell and cell death (Flora, 2009; Schutzendubel, 2002). Non-redox metals

include Hg, Al, Ni, cadmium, and Zn (Jozefczak et al., 2012; Valko et al.,

2005) are involved in binding of sulfhydryl group, glutathione depletion