Interactive effects of biostimulants and water stress on potted Pinot noir grapevines

Seaweeds extracts (SWE) are innovative and non-polluting tools that have become popular as biostimulants. Their effects on Pinot noir water potential, gas exchanges and fruit quality under drought stress and full irrigation were evaluated during the 2017 growing season. Differential irrigations were applied and Pinot Noir grapevines have been sprayed two times at label doses (3 g/L) during the vegetative growth, with the Ascophyllum nodosum exract, starting from veraison. During the season, measurements of single leaf gas exchange and stem water potential were made; moreover parameters of technological maturity (°Brix, acidity, pH) and phenological one were analyzed. The inhibition of gas exchange and increase of stomatal limitation induced by drought stress were not reduced by SWE where A.nodosum had positive effects on midday stem water potential. Under full irrigation SWE increased leaf gas exchange. No particular effect was observed on the technological parameters after the treatment. The application of the seaweed extract improved polyphenols accumulation in stressed theses, increasing wine grapes quality. A.nodosum can be useful to reduce negative effects of abiotic stress such lack of water and to improve polyphenols content in grapes, especially in genotypes with a limited phenolic profile like Pinot Noir variety.