Water transport and aquaporins in grapevines

Abstract

Water use and yield in plants are positively linked, and grapevines are no exception. Increased demand for water resources has focused interest on vine physiological factors that may determine how water use affects yield and quality. Yield (Y) depends on transpiration efficiency (W), total amount of water incident on vines (I), transpiration rate (T), and harvest index (HI, proportion of total dry matter removed as harvested product): Y = I x T/I x W x HI (Gibberd et al. 2001). Crop water use efficiency (WUE = Y/I) can be improved by an increase in one or other of three factors; T/I, W or HI. Yield may not be the primary goal for the production of quality wine grapes, but in circumstances where grape quality seems to be linked to yield and thus the relationship between quality and water use is likely to have the same terms as above but with additional non-linear components. We introduce the topic of this chapter through this discussion of WUE, because each of the parameters apart from I that determine WUE are dependent on the regulation of water flow across cellular membranes. Embedded in these membranes exist protein-channels permeable to water called aquaporins. As such, aquaporins control the rate of water transport through grapevines and therefore warrant special attention in the molecular biology andbiotechnology of grapevines.