The Light Quanta Modulated Physiological Response of Brassica Juncea Seedlings Subjected to Ni(II) Stress

TL;DR

This study investigates how light and Ni(II) stress influence Brassica juncea seedlings' metal uptake and biomass, revealing that moderate growth and metal accumulation optimize phytoremediation efficiency.

Contribution

It introduces a detailed analysis of the interplay between light, metal concentration, and plant response, highlighting the importance of balanced growth for effective Ni removal.

Findings

Light enhances Ni toxicity at root and plant levels.

Moderate biomass growth correlates with maximum metal removal.

Cp varies logarithmically with Cs and M follows a power-law with Cp.

Abstract

This work is a study of the inter-relationship between parameters that principally affect metal up-take in the plant. The relationships between the concentration of metal in the growth medium, Cs, the concentration of metal absorbed by the plant, Cp, and the total biomass achieved, M, all of which are factors relevant to the efficiency of phytoremediation of the plant, have been investigated via the macro-physiological response of Brassica juncea seedlings to Ni(II) stress. The factorial growth experiments treated the Ni(II) concentration in the agar gel and the diurnal light quanta (DLQ) as independently variable parameters. Observations included the evidence of light enhancement of Ni toxicity at the root as well as at the whole plant level, the shoot mass index as a possible indicator of shoot metal sequestration in B. juncea, the logarithmic variation of Cp with Cs and the power-law dependence of M on Cp. The sum total of these observations indicate that for the metal accumulator B. juncea with regard to its capacity to accumulate Ni, the overall metabolic nature of the plant is important; neither rapid biomass increase nor a high metal concentration capability favor the removal of high metal mass from the medium, but rather the plant with the moderate photosynthetically driven biomass growth and moderate metal concentrations demonstrated the ability to remove the maximum mass of metal from the medium. The implications of these observations in the context of the perceived need in phytoremediation engineering to maximize Cp and M simultaneously in the same plant, are discussed.