Marine Bioactive Substances (IPA Extract) Improve Foliar Ion Uptake and Water Stress Tolerance in Potted "Vitis vinifera" Plants.

The effect of marine bioactive substances (IPA extract) on K+ and Ca2+ fluxes and water stress tole- rance was evaluated on potted Vitis vinifera plantlets. Different foliar treatments were compared during the experiment: a control treatment (distilled water), a pure fertilizer treatment (9-5-4 at 2%), and a marine bioac- tive substances (IPA extract, supplied by BiotechMarine, Roullier Group, Pontrieux, France) treatment added to a fertilizer (0.1% solution of IP A extract with distilled water and 9-5-4 at 2%). Ion fluxes, measured by selec- tive non-invasive microelectrodes, were monitored in leaves. IPA extract significantly enhanced both potassium and calcium fluxes compared to the other treatments. Total dry weight and macro- and micro-nutrient content were subsequently measured: results showed an improved growth in IPA extract plants, together with a better capacity in accumulating macronutrients in plant organs, but not micronutrients, especially in leaves. Marine bioactive substances were finally tested for their effectiveness in promoting water stress tolerance: IP A extract was very effective in inducing waterstress tolerance, maintaining a higherleaf water potential and stomatal con- ductance during the stress period, and inducing a quick recovery in rehydrated plants.