The primary effects of potentially toxic concentrations of metal ions on root physiology will be studied using plant genotypes that exhibit considerable difeferences in stress resistance or tolerance, in order to distinguish between those alterations thar are specifically related to higher stress resistance or tolerance from those that only indce multiple secondary strains which lead to inespecific defense mechanisms thar are unable to protect plants from ion toxicity. Three different ion stresses with a high economical and environmental interest are considrered, using in each case experimental designs thar are relevant from the environmental point of view: Al toxicity, excess Na\super +\nosuper and heavy metal contamination (Zn and Ni). Our investigation on Al toxicity will address the site of primary toxicity effects either in the apoplast or the plasmamembrane of root tip cells using cell pressure probe techniques in relationto both Al exclusion mechanisms based on toot tip exudates ang regulation of root elongation growth in tropical maize varieties differing in al resistance. Studies on ion stress by excess Na\super +\nosuper will be focused on the effects of alterations inthe ion and water balance on plasmalemma H\super +\nosuper -ATPase activity and hormonal regulation of root growth in subspecies of \i Medicago arborea\i0 differeing in salt tolerance. Plant species thar are able to hiperaccumulate and tolerate extremely high metal concentrations in their tissues such as \i Thlaspi caerulescens\i0 and \i Alyssum pintodalivae\i0 will be used for heavy metal tolerance studies.
|Effective start/end date||1/10/98 → 1/10/01|