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Seeing red
Natural History, Nov, 2004 by Daniel Smith, Marcelo J. Yanovsky, Jorge J. Casal, Earle W. Cummings
In their article "How Plants 'See'" (9/04), Marcelo J. Yanovskv and Jorge J. Casal report that grass plants can sense and respond to varying ratios of red to and red light. To a plant, higher ratios signal that tow other plants grow in the vicinity: the plant responds by producing more shoots than it would in a more populous neighborhood. But have the investigators expanded their experiments by shining supplemental red lights on only one side oft plant, to see if it would send out shoots on that side only?
Also, it is known that plants respond to information ill pheromones. Has anyone tried to determine whether plants respond to sound, as well?
Daniel Smith
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Cedar Rapids, Iowa
MARCELO J. YANOVSKY AND JORGE J. CASAI REPLY: To our experiments, we found no obvious indication that grasses produce fewer shoots in the direction of light with a relatively low red-to-far-red ratio (which is indicative of neighbors). Nevertheless, Ariel Novoplansky of Ben-Gurion University of the Negev in Israel re ported several years ago that the purslane plant (Portulaca oleracea) avoids sprouting shoots towards plastic objects that reflect light with a low red-to-far-red ratio.
Whether plants interact with their neighbors via senses other than sight is still controversial There is good evidence in the laboratory that plants can "smell" volatile signals from neighbors under attack by insects. It is still being debated whether this capability" plays an important role in plant-to-plant communication under natural conditions, where the concentration of volatile signals could be much lower than the ones in the laboratory.
The evidence in favor of biologically meaningful responses by plants to sound is weak.
One of the illustrations in Messrs. Yanovsky and Casal's fine article is good art but bad science. On page 37 the root system of a tree is shown as the mirror image of its canopy; extending only as Far and wide into the earth as the canopy does into the sky. In reality, tree roots extend far wider than the canopy does and lie mostly near the surface, where nutrients and favorable conditions are more readily available.
Earle W. Cummings
Geyserville, California
COPYRIGHT 2004 Natural History Magazine, Inc.
COPYRIGHT 2008 Gale, Cengage Learning
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