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Agriculture by Color
| Article
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19268 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
7 / 1991 |
2,012 Words |
| Author
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Joel Grossman
Joel Grossman is a former agricultural pest-control adviser
for the state of California. He is now a free-lance writer
living in Santa Monica, California. |
It's not easy being a vegetable. It's a harsh, competitive world out there, and plant life is more than just soaking up sunshine, water, and nutrients. Even surviving insects, disease, and extremes of heat, cold, wind, and assorted other environmental hazards is not enough when competitor plants are battling to gain the same space, light water, nutrients, and other resources.
Coming out on top against the competition requires defensive systems. Some plants, including a few of the most successful weed species, exude herbicidal compounds to stifle the competition. Most plants also rely upon an intelligence gathering system that senses changes in the environment (manifested as alterations in the color of light) and directs the plant to prepare for survival under conditions such as shade, where photosynthesis and plant growth would normally drop off.
This botanical intelligence gathering system uses phytochrome pigments--pale blue receptor proteins that act as environmental sensors--to detect and direct responses to changes in color of light. Seeds "know" when to germinate and flowers when to bloom because of changes in amounts of visible red and invisible far-red light detected by phytochrome within growing plants. Tomatoes grow taller and are more efficient when neighboring plants threaten to shade them out; their neighbors presence is sensed by phytochrome's detection of telltale reflected far-red light wavelengths and the resultant change in the ratio of far-red relative to red light.
The plant's competition-sensing system can be put to good use in agriculture. Plants can be fooled by growing them over colored mulches, thus changing the spectrum of reflected light they perceive. This deception permits control of vegetative growth, crop yield, protein content, and taste, and it can even be used to outwit pests. As these developments become commercialized, the color of agriculture may be transformed from its traditional dirty-soil look to something more like the wild creation of a fashion designer run amok with a rainbow palette.
Harvesting light
The components of white light can be separated by a prism into a rainbow mixture of red, orange, yellow, green, blue, indigo, and violet. The green chlorophyll pigments in leaves absorb much of the red and blue from white light. Some green light is absorbed by chlorophyll, but enough is reflected or transmitted to make leaves appear green. Green leaves also reflect or transmit nearly all
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