Water availability dynamics have long-term effects on mature stem structure in Vitis vinifera

Vitis vinifera is a climbing vine with wide vessels and high hydraulic conductivity. There is a lack of data on the anatomical structure of the mature vine stem, and most current knowledge is based on first-year shoots. Moreover, the effect of drought stress on anatomical structure has been partly reported in shoots of Vitis vinifera but not in stems. In current study two irrigation approaches were applied on Vitis vinifera Merlot vines: constant (low, medium and high irrigation) and dynamic (early/late season water deficit). The following parameters were measured: trunk diameter, annual ring width and area, vessel diameter, specific hydraulic conductivity and stem water potential. High water availability early in the season (high irrigation and late deficit) resulted in vigorous vegetative growth (greater trunk diameter, ring width and area), wider vessels and increased specific hydraulic conductivity. The distribution of large xylem vessels was altered by drought stress, where high water availability early in the season caused a shift of the vessel population towards the wider frequency classes. Interestingly, the early deficit vines showed more negative water potential values late in the season compared to the low irrigation vines. This may imply an effect of anatomical structure on vine water status. Highlights Water availability early in the season determines vegetative growth and stem anatomical structure in mature Vitis vinifera vines.