Chapter 4 - Adaptive and Tolerance Mechanisms in Herbaceous Plants Exposed to Cadmium

Abstract

Herbaceous plants are plants that have no persistent woody stem above ground. They are classified following life-cycle classification as annuals, biennials or perennials. Native herbaceous species usually colonize on remediated soils with potential use in phytoremediation of heavy metals. In case of cadmium, many herbaceous species are suitable for phytoextraction and phytostabilization. Their mechanisms involving are immobilization, exclusion and compartimentalization. They can adapt and synthesize phytochelatins, metallothioneins, stress proteins and phenolic compounds to tolerate cadmium and other metals. In addition, endophytic microorganism also involves in the plants tolerant mechanism. Growing herbal plants to cover and remediate cadmium contaminated areas must be concerned. Especially shoot parts of hyperaccumulative plants, spreading of cadmium in top soil can be increased from falling leaves of their life cycles. The cadmium also enters the food chain via insects, birds, herbivores, etc. Moreover, application of herbal plants collected from contaminated area for folk medicines and raw materials of drug and food/feed should be prohibited or controlled base on reliable researches and knowledges. Finally, phytomanagement and harvesting processes for cadmium phytoremediation are depending on the tolerant mechanisms and life cycles of each herbal plant species.