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Germination response of Phragmites australis and Typha latifolia to diurnal fluctuations in temperature
Published online by Cambridge University Press: 22 February 2007
Abstract
Germination responses to 45 combinations of diurnal mean temperature and amplitude were examined in freshly collected seeds of two wetland perennials: Typha latifolia L. and Phragmites australis (Cav.) Trin. ex Steudel. Nearly all seeds (>95%) germinated in favourable temperature regimes. Mean temperature (range 10–30°C) and amplitude (range 0–20°C) affected final germination of both species. P. australis required a high amplitude (> 10°C) for germination over the entire range of mean temperatures. Final germination of T. latifolia was more sensitive to mean temperature than P. australis. The germinated proportion of T. latifolia had a maximum around 20°C, above which it decreased, and amplitudes were more stimulating at low than at high levels of mean temperature. The germination rate was rapid and increased with mean temperature for both species. More than 50% germination was achieved within 1–3 d at favourable temperatures. It is proposed that the thermal requirements provide the non-dormant seeds with a season-sensing mechanism which postpones germination of seeds dispersed during autumn, winter or early spring, until the soil surface is heated by the sun in the spring and sufficiently large diurnal fluctuations of temperature occur. Furthermore, the amplitude requirement implies a strong avoidance mechanism for germination of P. australis in sites with small temperature fluctuations (e.g. below water tables), whereas seeds of T. latifolia appear to be less exacting in the requirements when the soil or water becomes warmer.
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- Copyright © Cambridge University Press 1999
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