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Kim et al. make important contributions to our understanding of the phylogeny of the Magnoliaceae, a group that constitutes one of the key lineages of living basal angiosperms. Using ndhF data, they demonstrate that many of the major lineages within the family are not monophyletic and they establish some intriguing and previously unrecognized relationships. The separated clades in the molecular tree are considerably different from traditional taxonomic dispositions in the family. (see p. 717)

Chilling effects: enhanced frost sensitivity

Beerling et al.'s study of effects of simulated global change on leaf ice nucleation temperatures adds to the global climate change literature and is especially relevant for predicting future vegetation shifts in temperate and subarctic regions. The authors show that both increased UV-B radiation (due to the thinning of the ozone layer) and CO₂ enrichment increase the frost sensitivity of leaves of natural stands of dwarf woody shrubs in northern Sweden by raising the temperatures of ice crystal formation. The mechanism is undetermined, but the progressively higher flux of UV-B radiation for terrestrial vegetation at high latitudes in the Northern hemisphere is well documented. (see p. 628)

Internal pressurization in Pragmites culms

Arkebauer et al. made careful field measurements of the internal pressurization of gases in culms of Phragmites australis over two seasons and were able to correlate convective transport with environmental conditions, including wind speed, relative humidity, incident radiation, and air temperature. Phragmites is an increasingly important wetland species capable of contributing significant quantities of methane to the atmosphere via convective throughflow. Novel findings were that large pressure changes can occur over short time periods and that there is low pressure at high wind speeds. (see p. 653)

The "modern" Archaeopteris

Fairon-Demaret and Leponce address the fascinating issue of photosynthetic display in the progymnosperm Archaeopteris roemeriana, a plant that has become a crucial taxon for interpretations of lignophyte biology. Their detailed study of compression fossils from Belgium shows clearly that the leaves are dimorphic (suggested from previous anatomical work) and demonstrates the presence of a new leaf type in Archaeopteris. The combination of anisophylly and shoot dorsiventrality to optimize light interception may be the earliest such evidence in the fossil record. Archaeopteris is progressively being revealed to be astonishingly "modern" in organization. (see p. 729)

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