Physiological Tolerance of Perennial Grasses to Heavy Metal Contaminated Soils

There are several environmental advantages in the use of perennial crops such as reduction of soil erosion, increased soil organic matter, low fertilizer and agrochemical demands and increased biodiversity. Bioproducts, biofuels and bioenergy appears as an alternative to replace petroleum based products and nowadays, using land to grow crops for bioenergy has become an increasingly important policy objective designed in the RED II (2018/2001/EU). In this context, marginal lands appear as an alternative for industrial crops production without threatening food production. Marginal lands can be understood as generally as unproductivity lands which are exposed to stress conditions such as limitations of nutrients or water, or contamination by hydrocarbons or heavy metals. Therefore, production of biomass in marginal soils is being recommended to lessen land use change ethical issues linked with competition with food crops. Contaminated soils hinder the cultivation of traditional food crops, while industrial crops can provide several ecosystem services. However, understanding the tolerance and the phytoremediation of each species to a single contaminant helps us to better clean up the polluted areas and it can be useful for organizing protocols aimed at the reclamation of these areas, reducing time and reducing management costs providing a renewable source for energy and bioproducts. The species suitable to heavy metals polluted soils can be divided in two group: exclusion and resistance. The mechanisms of exclusion prevent the accumulation of toxic concentrations in sensitive sites within the cell, and thus preventing negative effects. The mechanisms of resistance generally concern the development of proteins that allow the plant to resist to heavy metals, allowing the accumulation of the same contaminant in the aerial parts of plant. The aim of this work was to study the physiological response of plants tolerant to heavy metals, in particular, focused the attention on two non-food lignocellulosic perennial grasses: giant reed (Arundo donax L.) and African fodder cane (Saccharum spontaneum L. ssp. aegyptiacum), in soils contaminated by four heavy metals (Cd, Pb, Ni, Zn) with the purpose to observe the physiological response and the mechanisms of resistance in the increasing concentrations of the four soil heavy metals.