PHYSIOLOGICAL RESPONSES OF GRAPEVINES TO WATER STRESS
This review covers the physiological responses of grapevines to water stress. Stress reduces both water and turgor potential in grapevines but stressed plants try to maintain turgor potential by osmotic adjustment. The reduction in leaf water potential induces stomatal closure and increases abscisic acid levels in the leaves. Stomatal closure leads to reduced photosynthesis and transpiration, while severe stress can also affect the photochemical and enzymic reactions of photosynthesis. Shoot growth is more sensitive to water stress than crop yield. In stressed plants yield losses can be caused by reductions in inflorescence initiation, fruit set and fruit size as well as by increased fruit abscission. Yield losses are greater when stress occurs prior to the ripening stage of fruit development than during ripening. Mild stress during the ripening stage hastens the maturation processes in fruits and this leads to increases in the concentration of sugars and anthocyanin pigments and decreases in acid and pH levels in the fruit. Some major gaps in our knowledge of the subject of water stress are what effects stress has on respiration, translocation, hormones, mineral nutrition, physiological activity of roots, root growth and fruit quality.
Nagarajah, S. (1989). PHYSIOLOGICAL RESPONSES OF GRAPEVINES TO WATER STRESS. Acta Hortic. 240, 249-256