Cytokinin content and water relations of `Cabernet Sauvignon grapevine exposed to drought stress

The effect of root inoculation by mycorrhizal fungi (Glomus mosseae) on zeatin/zeatin riboside (Z/ZR),isopentenyladenine/isopentenyladenosine (iAde/iAdo) and water relations in grapevine (Vitis vinifera L. `Cabernet Sauvignonʹ) was studied. Two soil moisture treatments (well-watered or stressed) and mycorrhizal colonization (present or absent) were applied to plants in pots grafted onto eight grapevine rootstocks (110 Richter, 41BMgt, 1103 Paulsen, 5BB Kober, 44-53 Malegue, 140 Ruggeri and 101-14Mgt). Cytokinin production of mycorrhizal (M) plants was greater than that of non-mycorrhizal (NM) ones. In both well-watered and stressed plants, concentrations of Z/ZR in shoot tips ranged from 2.75 to 87.7 ng g-1 dry wt., being higher than those of iAde/iAdo in most cases, ranging from 4.01 to 25.2 ng g-1 dry wt. Significantly lower concentrations for both types of cytokinins were found in stressed plants. M stressed vines had higher predawn leaf water potential, stomatal conductance and CO2 assimilation rates than NM stressed ones. Between M and NM plants, no significant differences were found in pruning weight or leaf P concentrations. Rootstock had a considerable effect on shoot growth, leaf P content, and cytokinin production. In stressed M plants, the rootstocks 110R, 1103P, and 140 Rug. had higher cytokinin concentrations and improved water relations.