PJB-2013-384
EFFECT OF NICKEL AND CADMIUM ON GLUCOSINOLATE PRODUCTION IN THLASPI CAERULESCENS
SAEED AHMAD ASAD1, 2*, SCOTT YOUNG2 AND HELEN WEST2
Abstract
Hyperaccumulator plant species are studied because of their potential for cleaning up land contaminated with heavy metals, but another aspect of study relates to the reason for hyperaccumulation. The most accepted hypothesis over the last decades is elemental defence hypothesis stating that accumulated heavy metals defend the plants against herbivores and pathogens. Glucosinolates in hyperaccumulators are also known to defend the plants against these environmental stresses. Current study was designed to test any trade-off between these 2 types of defences in Thlaspi caerulescens. Thlaspi plants were grown in glass house at different Ni and Cd concentrations where clipping damage with scissors was applied to substitute herbivory. The maximum foliar Ni was observed as 233.20 mg kg-1 whilst, maximum Cd uptake was reported to be 119.63 mg kg-1 of dry mass of Thlaspi shoots. The maximum uptake of Ni was 2-4 times higher while that of Cd was 4-10 times higher as compared to that applied in substrate. The Ni uptake by Thlaspi was far below than the threshold value, the concentrations commonly used to define hyperaccumulation. There was a positive correlation between soil metal addition and concentration of shoot metals. Generally, lower concentrations of glucosinolates were observed in plants with higher foliar Cd concentrations, while in case of Ni treated plants, glucosinolates were induced at elevated metal application. Trade-offs between 2 types of chemical defences was only observed at highest Cd concentrations while Ni application increased the level of glucosinolates. The overall conclusion partially supported the ‘trade- off hypothesis’.
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