Adaptive strategies to minimise iron limiting stress under climate change scenario: A study pertinent to iron stress response of two soybean (Glycine max (L.) Merr.) Genotypes

The response of soybean genotypes to iron deficiency stress under elevated CO2 and temperature condition could be guided by three critical rhizospheric processes viz. proton (H+) extrusion, root exudation and ferric chelate reductase (FCR) activity. In the present study, the iron efficient and responsive (FeER) genotype recorded an impressive performance over iron inefficient and responsive (FeIR) genotype in counteracting iron deficiency stress but experienced modest stress caused by the combined interaction between the genotype (G), environment (E) and HCO3- ion (B). The antagonistic interaction between Fe2+ with HCO3- ion resulted in greater iron stress. Plants grown in the absence of bicarbonate have significantly higher total chlorophyll content (1.79±0.04 mg g-1, mean ± SE) than plants grown in presence of bicarbonate (1.48 ± 0.06 mg g-1). To warfare the constraints in Fe availability, especially under more stressed e-[CO2+T] environmental condition in the presence of bicarbonate ion, the root system of iron efficient genotype of soybean (FeER) exuded out significantly higher amount of low molecular weight organic acids. Furthermore, the presence of bicarbonate ion in the nutrient solution exacerbated the iron deficiency stress and consequently resulted in higher proton extrusion (~1.2 fold increase), lower ferric chelate reductase activity (~1.3 fold decrease) and higher organic acid exudation (up to ~1.9 fold increase in malic acid). The intra-specific variability between contrasting genotypes and their response to elevated CO2 and temperature could be exploited to remediate emerging Fe deficiency of soybean plants under climate change scenario.