PHYSIOLOGICAL ECOLOGY: Smart Seeds

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Science  04 Aug 2000:
Vol. 289, Issue 5480, pp. 699a
DOI: 10.1126/science.289.5480.699a

There are a variety of mechanisms that enable seeds to time the moment of germination so as to optimize the chances of survival, the detection of changes in the light, water, and temperature regimes being the most common. The ratio of red to far-red (R:FR) light is an important environmental factor, representing the amount of light available for photosynthesis beneath a canopy of competitors.

In some cases, these mechanisms are extremely subtle. Batlla et al. show that seeds may be able to anticipate the growth of a competitive canopy above them, thereby avoiding futile germination. The germination of seeds of Silene and Brassica placed under a developing wheat canopy was inhibited even at low leaf area indices (a measure of canopy cover) and very small reductions in ambient R:FR; seeds exposed to direct solar radiation slightly enriched with FR did not germinate either.

The ability to detect a canopy in the earliest stages of development, even if conditions are otherwise set fair, suggests that plants can glean more information from the light environment than hitherto thought, and reinforces the importance of the regeneration niche in permitting species coexistence. — AMS

Functional Ecology 14, 195 (2000).

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