McDonald and Davis consider how shoot systems respond to drying and N-deficient soil, in terms of their stomatal behaviour and growth, via the transmission of root-derived chemical signals. Malone considers the major hypotheses that have been proposed with particular attention being given to hydraulic pressure signals and the hydraulic dispersal of chemical signals. At a different, intracellular level of communication, a wide variety of second messengers couple extracellular stimuli to a characteristic physiological response. Webb et al. Consider progress made in establishing similar roles for calcium in plant signalling in the context of the mammalian paradigms.
The effects of UV-B radiation on plants have been extensively investigated in recent years. Jordan considers progress in understanding the chain of events from perception of UV-B to signal transduction and consequent changes in gene expression and regulation.
Smith and Smith assess the various hypotheses erected over the years to explain structure and function of the host-parasite interface formed by vesticular-arbuscular (VA) mycorrhizas, an important and widespread mutualistic symbioses of a wide range of higher and some lower plants.