7 - Stem Water Storage

Abstract

This chapter focuses on the ecological and physiological significance of stem water storage. The basic components necessary to examine the contribution of stem water storage are straightforward and include: determination of water uptake from the soil, water loss by the entire canopy, and changes in stem water content. The water storage capacity of plant tissues is defined as the amount of water that can be withdrawn for a given change in driving force (water potential) and the structural features that influence the same is discussed. Environments in which periods of high soil water availability are unpredictable, infrequent, and of short duration represent conditions well suited to within-plant water storage provided that net carbon gain can be sustained at very low total water loss rates. In most plants, stem water storage appears to be most important in enabling them to survive periods of drought. In addition, stem water storage may provide a strategic reserve during limited periods of adverse environmental conditions (e.g., giant rosette plants, dry-season flowering in tropical trees). Understanding the temporal dynamics of stem water utilization requires that it be examined in the context of stomatal behavior, roofing patterns, and stem hydraulic conductivity. Because of its close proximity to the transpiring surfaces, coordination between the hydraulics and patterns of water use are necessary to prevent the depletion of stem water stores prior to the onset of extreme conditions.