Roots and water - Transport of water to plant roots in soil

Publisher Website
Google Scholar
Abstract
The theory of water uptake by a single root is reviewed, including infinite and finite systems, and constant and variable diffusivity. This theory predicts the water potential and content at the root surface will depend upon soil and root parameters, most of which are readily determinable, but the uptake rate of water per unit length of root is uncertain. Uptake rates averaged over whole root systems will usually be small, suggesting only very small gradients of water content around roots, but it is likely that local rates may, on occasion, be much larger than the averages, and the possibility of large gradients cannot then be dismissed. Certain special effects may alter these conclusions, particularly salt accumulation around roots and no contact or partial contact of roots with soil. Both demand a fast uptake rate of water before they become important, and salt accumulation is unlikely to be important except in saline soils. Methods of dealing with whole root systems are briefly considered. Differing root density can be dealt with by subdividing the root volume into compartments, or by regarding the problem as one of dispersion pattern. Further advance requires better information about local boundary conditions imposed by roots on the surrounding soil.