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Maybe it’s cold outside
Local intraspecific variation in the alpine plant Potentilla matsumurae is the theme of the paper by Shimono and Kudo, Hokkaido University, Sapporo (pp. 21-29). They have focused on plants growing in the fellfield and on plants growing in places where there are long-lasting snowbeds. In the Taisetsu Mountains in northern Japan the fellfield is a hostile habitat: the wind prevents accumulation of snow, the soil is frozen in winter, severe wind-chill occurs well into the spring (although there can also be very warm days) and plants are subject to drought stress in summer. By contrast, in the snowbeds of the Taisetsu Mountains, plants are protected from frost damage and, because of the water from the melting snow, from summer drought. However, although the snowbed is a less hostile habitat, the persistence of the snow cover shortens the potential growing season. Shimono and Kudo performed germination experiments in the two habitats. Seed lots from the fellfield plants exhibited sporadic germination, indicating variation in depth of dormancy, and consistent with adaptation to a habitat in which conditions in spring are very variable: early germinators, emerging when the soil temperature reaches about 5 degrees C, may later be damaged or even killed by a cold snap. Late germinators avoid this risk but their growing season is restricted, lessening the chances of survival in the subsequent winter. This is a strategy that spreads risk. In contrast, seed lots from snowbed plants require a higher temperature for germination (12-15 degrees C) and tend to germinate synchronously; the whole population thus takes advantage of the favourable conditions in the short growing season. The differences in germination requirements, operating in the wild on a local scale, are maintained in reciprocal transfer experiments. This suggests a genetic basis for the germination behaviour, leading to speculation about the molecular basis of these heritable variations.
Professor J. A. BryantUniversity of Exeter, UK
j.a.bryant{at}exeter.ac.uk
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