Changes in leaf water status in grapevine graftlings treated with growth regulators

The effect of foliar application of plant growth regulators, paclobutrazol (1000 mg/L), chlorcholine chloride (200 mg/L) and gibberellic acid (100 mg/L) on leaf water status in grapevine graftlings of cv Cardinal was investigated. After stratification and waxing, young vines were planted into vegetation pots and grown in a glasshouse. Foliar treatments were applied once, twice or three times during the vegetative period, starting on 25 July and every 15 days thereafter. Values of total water potential (Tl) and of relative water content (RWC) were measured over the same period. Results indicate a tendency of increased TL values in leaves of plants repeatedly treated with a growth inhibitor paclobutrazol (-1.18 Mpa) compared with untreated (-1.36 Mpa) as well as plants treated twice with gibberellic acid (-1.37 Mpa). RWC in leaves was significantly increased in the second half of the vegetative period when paclobutrazol was applied twice (78%) in comparison with control (75%). Values of both investigated indices point to a more favorable water status of plants treated during the vegetative period with growth inhibitors compared with untreated and plants treated with gibberellic acid.