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In a Special Paper in American Journal of Botany, vol. 85, pp. 897–909, Martin Canny explained his new theory of water transport via compensating pressure. In this issue two papers defend the standard theory of water transport via cohesion-adhesion-tension. First, Comstock's critique shows where Canny's theory is incompatible with basic biophysics and where tissue pressures cannot support the working of that theory. In the second paper, Stiller and Sperry refute predictions made by Canny in an experiment suggested by Canny to test the validity of his theory. They compare the xylem cavitation pressure among controls, mannitol-infused, and microwave-oven-killed stem segments of Betula nigra in a classic confrontation of experiment and theory. (see p. 1077)

The biophysics of plant patterns

The late Paul B. Green (1931–1998) will be remembered for a distinguished career in the area of plant morphogenesis. In this posthumous paper he has summarized some of his work on the role of physical factors in morphogenesis and included many new ideas for future research in the field. (see p. 1059)

Stigma biology

In 1877 Darwin described distylous and tristylous species, based mainly on style lengths. Features of stigma heteromorphism have since been noted. In their article Hermann et al. quantify stigma polymorphism very precisely in tristylous Lythrum salicaria (Lythraceae) by measuring the stigma diameters, structure of papillae, and density and distribution of papillae from flower samples of the three morphs. These fine-scale morphological differences may play a role in self-incompatibility mechanisms. (see p. 1121)

Stigma biology

In a series of straightforward and ingenious experiments, Fetscher and Kohn explore the behavior of the touch-sensitive stigma of Mimulus aurantiacus (Scrophulariaceae), whose bilobed stigma closes within 2 s of touch by a hummingbird pollinator. They demonstrate that closure of a pollinated stigma is usually permanent, but stigmata reopen rapidly if unpollinated and may reopen, though more slowly, if few ovules are fertilized. Stigma closure may be an adaptation that reduces intrafloral self-pollination or decreases interference between the two functions of hermaphroditic flowers, pollen receipt and pollen export. (see p. 1130)

CO₂ and tannin production in aspen clones

Mansfield et al. convincingly demonstrate that levels of foliar condensed tannins in trembling aspen (Populus tremuloides, Salicaceae) are affected by elevated CO₂ and that aspen clones respond differently to CO₂ enrichment. The implications of this research are important, given the role of genetic variability in evolutionary responses to global change and the role of plant chemistry in plant–herbivore and plant–pathogen interactions. (see p. 1154)

This Article Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Search for Related Content