How is Cd Incorporated in Biominerals Eliminated by Tobacco Trichomes?

Abstract

In tobacco plants, elimination of Zn and Cd via the production of Ca-containing grains at the top of leaf hairs, called trichomes, is a potent detoxification mechanism. When tobacco plants were grown in a nutrient solution containing an amount of Cd and low Ca supplement, most of the grains were oblong-shaped and low-Cd-substituted calcite. When exposed to the same amount of Cd and high Ca supplement, grains were more abundant and diverse in compositions, and in total more Cd was eliminated. Most grains in the high Ca/Cd experiment were round-shaped and composed predominantly of Cd-substituted vaterite, a usually metastable calcium carbonate polymorph, and subordinate calcite.