We could make probably a third or a half reduction in the amount of water used just by management alone. There's considerable wastage. Heij says work carried out in her Division and overseas shows how plants cope with water stress. Loveys and Dry started out trying to reduce vigour in cool-area grapevines.
Excess vigour produces too many leaves.
These shade the fruit, affecting its quality. They can also make disease control more difficult, and reduce yields in subsequent years. Their research focused on understanding the hormonal mechanisms that control vine growth, and hence, vigour. The role of this compound in controlling vigour therefore came under scrutiny. Increased concentrations of ABA in the leaves causes the stomata to close, preventing further leaf gas exchange.