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Culley et al. point out that there are at least two methods of calculating the genetic statistic G ST. Their paper shows that G ST values obtained from these methods can sometimes be substantially different, and a review of the literature reveals that both methods are often used indiscriminately. They strongly encourage authors of new studies to calculate G ST carefully, especially if comparisons will be made to other studies. (see p. 460)

Soil gases affect foxtail germination

Dekker and Hargrove present interesting data on the germination responses of giant foxtail (Setaria faberii), an invasive weed pest of U.S. agriculture, to naturally occurring soil gases. Several important new insights emerged: oxygen concentrations above that of the atmosphere (>20%) caused much greater seed germination and carbon monoxide had three different effects depending on its concentration. They conclude that germination/dormancy may be regulated by several interacting factors in the seed that control the amount of gases entering and leaving the seed. (see p. 410)

Thigmosense

Thigmo mechanisms are adaptations that permit plants to alter growth rates, change morphology, produce tropisms, avoid barriers, control germination, cling to supporting structures, infect a host plant, facilitate pollination, expedite the movement of pollen, spores, or seeds, and capture prey. Mechanical signalling in plants has been studied for over a century. Jaffe, Leopold, and Staples present a review summarizing what we have known, but in some cases forgotten, and raise important questions that need investigation now. They describe these subtle responses to touch in plants and fungi and propose possible transduction components. (see p. 375)

Aperture patterns

Ressayre et al. focus on cellular mechanisms involved in aperture number determination in Nicotiana (Solanaceae) species that produce pollen grains with different aperture numbers. Their observations of cleavage planes of microspore nuclei and differing microtubule distributions are beautifully presented. Complex cell divisions such as meiosis, even though completely symmetrical, could provide spatial cues for cell patterning. (see p. 393)

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