WATER-STRESS AND ROOTSTOCK INFLUENCE ON LEAF GAS-EXCHANGE OF GRAFTED AND UNGRAFTED GRAPEVINES

In order to investigate the effects of rootstocks on plants of the gen us Vitis subjected to gradually increased levels of water stress we st udied the links between abscisic acid in leaves and the major leaf phy siological parameters. Cuttings of Vitis vinifera cv. Muller Thurgau w ere grafted onto three hybrid rootstocks (H1, H8, H26) and grown in po ts. Own-rooted plants of V. vinifera and own-rooted hybrids were also cultivated in an identical manner. Vines were tested during 7 and 14 d ays of water stress (i.e. daily water supply reduced to 66% of well-wa tered plants). Water stress reduced net photosynthesis and stomatal co nductance with large differences between grafted and ungrafted vines. Significant differences were observed after only 14 days of water stre ss. In particular two grafting combinations, V. vinifera grafted on H1 (V/H1) and H8 (V/H8), did not show net photosynthesis reduction after 14 days of water stress. Water use efficiency increased with water st ress whereas carboxylation efficiency was reduced. Net photosynthesis, stomatal conductance and carboxylation efficiency were affected by th e rootstock genotype combination, so that under water stress only some rootstock genotypes transferred drought tolerance to the scion. Absci sic acid in leaves increased significantly from Control to 7 and 14 da ys of water stress but the relations with CO2 assimilation rate, stoma tal conductance and carboxylation efficiency appeared to be affected b y the genotype of the vegetative apparatus. Our data show that the int eraction between scion and rootstock with regard to production perform ance under water deficits may be an important consideration in vineyar d planting strategies. (C) 1998 Elsevier Science B.V.