Ehleringer, J.R., and J.D. Marshall. 1995. Water relations of parasitic plants, p. 125-140. In M.C. Press and J.D. Graves (eds.), Parasitic Plants. Chapman and Hall, London.

In this chapter, we focus on the water relations of hemi-parasitic plants in relation to their physiology, growth, and life-history characteristics. Holo-parasitic plants are discussed in the context of how their water relations differ from those of hemi parasites. The water relations of hemi-parasitic plants differ substantially among species. The available data indicate that a combination of diversity in parasite-host connections and life-history differences have lead to varying degrees of either convergence or divergence with that of their hosts. We can broadly categorize hemi-parasites as being annual versus perennial and obligate versus facultative. As elaborated below, these differences in life-history behavior explain much of the variation in water relations among hemi-parasites. The water relations of a plant are often difficult to interpret outside the context of how factors such as transpiration influence photosynthetic activity, carbon import, mineral nutrition, and energy balance, and this is particularly true of parasitic plants. Thus, an emphasis of this chapter is on linking these interacting factors. Recent reviews by Fisher (1983), Raven (1983), Stewart and Press (1990) and Press and Whittaker (1993) have also focused on parasitic water relations, and the reader is referred to those contributions for a more comprehensive water-relations review.