Physiological indicators to assess water status in potted grapevine (Vitis vinifera L.)

Many physiological parameters were compared to identify the most sensitive and reliable indicator of grapevine water status. One-year-old potted grapevines (Vitis vinifera L., cvs. ‘Sangiovese’ and ‘Cabernet Sauvignon’) were studied under two irrigation treatments: 100% and 0% of daily water consumption. Measurements of pre-dawn (PD) and midday (MD) leaf water potential (Ψw), MD stem water potential (ΨS), leaf temperature (T°L) and stomatal conductance (gS) were taken throughout twenty days and analyzed in conjunction with climatic data, relative cumulative sap flow (RCSF) and the maximum daily shrinkage (MDS) of the vine stock. Physiological indicators showed substantial differences in sensitivity. The first indication of changes in vine water status was the increase of MDS and the decrease of gS. MDS and RCSF revealed significant differences between the two irrigation treatments even when PDΨw, up to now widely accepted as the benchmark of water status indicators, did not show any significant variation. Measurements of water potential showed ΨS to be a better indicator of vine water status than Ψw and T°L. In conclusion, we classified the tested indicators according to a descending order of their early detection capability: gS = MDS > RCSF > PDΨw = MDΨS > T°L > MDΨw.