Metal resistance mechanisms use to be ion specific. Nonetheless, these different mechanisms are based on a common pattern of strategies: 1. Exclusion from roots or shoots, 2. Accumulation in non toxic form and in compartments with low metabolic activity and 3. changes in growth patterns that allow either reorientation of root growth into less toxic soil zones or enhancement of the root or shoot capacity to exclude or to store the excess metal in a non-toxic way. The project's purpose is to contribute to the fundamental knowledge of these resistance mechanisms and their integration into the processes of plant growth and development using different, representative models of accumulator and non-accumulator plants and considering metal cations with different toxicity mechanisms: Na+ which causes both ionic and osmotic stress; Al3+ and Cu2+ which strongly affect root developmental patterns; Pb and Ni both exhibiting big differences in their in planta mobility according to their binding to organic ligands. The role of organic ligands in Al and heavy metal exclusion by root exudates and in metal compartmentation and transport, as well as the relevance of the endodermal barrier in metal transport to shoots, will be investigated by means of root pressure probe techniques and by the anlysis of root exudates, transpiratory fluxes and growth. The mechanisms of metal-induced changes in tissular patterns of roots will be addressed by investigations on cell cycle and auxin transport inhibition. The role of Na+ transporters and ABA in salt stress resistance and growth regulation under salinity stress will be studied in bean and Medicago (models for non accumulator and accumulator, respectively) and in transgenic tomato overexpressing a Na+ antiporter. This project will provide new, relevant information on the role of plant growth regulators, especially auxin, ABA and polyamines in the adaptative growth responses of plants under ion toxicity stress.
|Effective start/end date||13/12/04 → 13/12/07|