Preliminary results on the evaluation of isohydric or anisohydric behaviour of vermentino and cannonau grapevines

Abstract

A lot of grapevine varieties have been distinguished in Isohydric or anisohydric according to their different behaviour in terms of water stress avoidance or tolerance. Several authors demonstrate this different behaviour within Vitis vinifera L., that is normally considered anisohydric, finding some varieties having the opposite behaviour (isohydric). Anisohydric varieties tend to “accept” important water restriction and consequently low stem water potential (SWP), limiting partially only the stomatal closure, while isohydric varieties limit stomatal closure at the beginning of stress, during the day, in correspondence of first stress signals and limiting as a consequence an excessive low SWP values. This difference in water stress behaviour make a change in the irrigation scheduling of isohydric or anisohydric variety. In fact an anisohydric verity should be irrigated with more attention and the water availability should be strictly calibrated while the irrigation of an isohydric variety could be more rough and reductive in terms of stress. This experience has been carried out to define the Cannonau (CNN) and Vermentino (VRM) behaviour to better define real water requirement and to improve their irrigation management. Two irrigation regimes were carried out on each variety to obtain water stress levels in two experiments characterized by a randomized blocks experimental design with 4 replications on each experiment. Physiological parameters were measured: SWP, stomatal conductance, net photosynthesis and productive parameters on grape. Preliminary results of the first year put in evidence on VRM a higher SWP level and higher stomatal conductance in both irrigation conditions, reducing the intrinsic WUE. On CNN the SWP resulted lower in well watered conditions in particular in July and August and gave a lower production and stomatal conductance in the two irrigation regimes. WUE was affected by irrigation more on CNN while VRM gave a Higher WUE (t/ha/mm). The meaning of physiological and productive results permits to give an anisohydric behaviour to VRM while CNN showed the isohydric behaviour.