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Some plants replenish nectar dynamically, in ways that can only be detected by more complex observations. As part of a larger research program on pollination relationships in Penstemon, Castellanos et al. show that flowers of P. speciosus regulate both nectar volume and sugar content. They used clever and painstaking techniques to obtain data from Penstemon flowers: replenishment was measured hourly on three different days of a flower's lifespan and proper controls were used. They also added artificial nectar to flowers and measured changes in volume and concentration. They discuss why homeostasis in nectar production is likely imprecise. (see p. 111)

Mating-system evolution in sister genera

Armbruster et al. combine an analysis of probable selfing and outcrossing mechanisms among related taxa with an analysis of their phylogeny. Using sister genera Collinsia and Tonella (Scrophulariaceae), together comprising 22 specieas, they show for the first time that large- and small-flowered taxa are often most closely related and that at least six evolutionary shifts have occurred between the two flower sizes. Small-flowered taxa are early to self pollinate and probably inbreeding, while large-flowered taxa are late to self pollinate and largely outcrossing. (see p.37)

Acorn production in clonal oaks

In two papers in this issue Abrahamson and Layne present long-term data on acorn production in clonal oaks of Florida. One examines 27 years of annual variation in acorn production for five clonal oak species in upland habitats of south-central peninsular Florida. The other compares acorn crops in burned and unburned grids for four species of clonal oaks in sandhill vegetation in the same part of Florida. The authors document rapid post-fire recovery of acorn production in fire-prone habitats. (see pp. 119 and 124)

From splash-cup and springboard to squirt-corner

Rain-operated seed dispersal is unusual in flowering plants. Two mechanisms have been described so far: splash-cup and springboard. Here Pizo and Morellato describe a new seed dispersal mechanism in the Neotropical rainforest herb Bertolonia mosenii (Melastomataceae), which they term 'squirt-corner.' When a raindrop strikes the mature fruit, the droplet forces the seeds outward to the corners of the triangular capsule and the seeds are released. The authors verify this dispersal mechanism experimentally. (see p. 169)

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