Grape berry transpiration influences ripening and must composition in cv. Tempranillo (Vitis vinifera L.)

The implications of grape berry transpiration for the ripening process and final grape composition were studied. An experiment was conducted, under controlled conditions, with fruit-bearing cuttings of Vitis vinifera L. cv. Tempranillo. Three doses of the antitranspirant di-1-p-menthene were applied directly to the bunch at the onset of veraison: 1%, 5%, and 10% (v/v) (D1, D5, and D10, respectively). A treatment with bunches sprayed with water (D0) was also included as a control. Grape and bunch transpiration, and total soluble solids (TSS) accumulation rate decreased as the dose of antitranspirant increased, thus resulting in the lengthening of the ripening period. Bunch transpiration rates were linearly correlated with the elapsed time between veraison and maturity, and with the TSS accumulation rate. The evolution of pH, malic acid and total skin anthocyanins during ripening did not show remarkable changes as a consequence of the artificially reduced bunch transpiration. However, a decoupling between TSS and anthocyanins was observed. At maturity, the bunches treated with D10 had significantly lower must acidity and higher pH and extractable anthocyanin levels, these differences being likely associated with the lengthening of the ripening period. The results show a clear implication of grape transpiration for the ripening process and final grape composition, and give new hints on the direct application of antitranspirants to the bunch as a way to regulate sugar accumulation while avoiding the concurrent delay of color development.