Stomatal response of an anisohydric grapevine cultivar to evaporative demand, available soil moisture and abscisic acid.
by Rogiers S. Y., Greer D. H., Hatfield J. M., Hutton R. J., Clarke S. J, Hutchinson P. A., Somers A. (2012)
in Tree Physiol. 32(3): 249-261 – DOI: https://doi.org/10.1093/treephys/tpr131 –
Stomatal sensitivity to VPD and soil moisture was investigated in Semillon, an anisohydric Vitis vinifera L. variety whose leaf water potential (Ψl) is frequently lower than that of other grapevine varieties grown under similar conditions in the warm grape-growing regions of Australia.
A survey of Semillon vines across seven vineyards revealed that, regardless of irrigation treatment, midday Ψl was dependent on not only soil moisture but VPD at the time of measurement. Predawn Ψl was more closely correlated to not only soil moisture in dry vineyards but to night-time VPD in drip-irrigated vineyards, with incomplete rehydration during high night-time VPD.
Daytime stomatal conductance was low only under severe plant water deficits, induced by extremes in dry soil. Stomatal response to VPD was inconsistent across irrigation regime; however, in an unirrigated vineyard, stomatal sensitivity to VPD—the magnitude of stomatal response to VPD—was heightened under dry soils.
It was also found that stomatal sensitivity was proportional to the magnitude of stomatal conductance at a reference VPD of 1kPa. Exogenous abscisic acid (ABA) applied to roots of Semillon vines growing in a hydroponic system induced stomatal closure and, in field vines, petiole xylem sap ABA concentrations rose throughout the morning and were higher in vines with low Ψl.
These data indicate that despite high stomatal conductance of this anisohydric variety when grown in medium to high soil moisture, increased concentrations of ABA as a result of very limited soil moisture may augment stomatal responsiveness to low VPD.