Different impacts of exogenous gibberellic acid (GA3) onwater relation and CO2 gas exchange in grape
leaves were studied on four varieties belong to various ecogeographical groups. GA3 treatment resu
in increasing cell wall rigidity in some cultivars and affected the linear correlation between ela
ity modulus (‘ε’) and relative water content at the turgor loss point (RWCTLC). The response of cul
‘Riesling’ agreed with the hypothesis; GA treatment resulted in increasing ‘ε’ values (‘ε’ > 12MPa),
cating decreased cell wall elasticity. According to pressure–volume analysis, osmotic potential a
turgor (˘100) in treated ‘Sauvignon Blanc’ vines was higher compared to the controls. Results of an
sis demonstrated that the four varieties showed a negative linear correlation between apoplastic w
content (AWSD%) and leaf water potential at the turgor loss point (TLP) and a positive linear correla
between AWSD% and RWCTLP. Values of Ci and PN showed a positive exponential correlation; Ci va
increased parallel with increasing net CO2 assimilation in a range between 10 and 24 Pa of Ci bo
control and treated vines. In each cultivar, intrinsic water use efficiency (WUEi ) increased at red
stomatal conductance. GA3 treatment resulted in favourable values of WUEi as expected for cul
‘Kadarka’ (group of convarietas pontica).WUEi was significantly (P < 0.05) lower in the GA3 treated v
compared to the controls in most of the varieties irrespective of different ecogeographical groups.