- 2018年05月08日17:13 来源：小站整理
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Red and Far-red
Light isan important environmental factor in most ecosystems. Photosynthetic organismsin particular must sense and respond to light cues to optimize their growth andmetabolism. The quantity, direction and spectral make-up (the color or'quality') of the light sensed by an organism conveys information regarding theabiotic and biotic environment and can be used to control adaptive responses.One superfamily of photosensory receptors comprises the phytochromes ('plantcolor'), which absorb in the red/far-red part of the spectrum. These receptorswere first discovered in plants in the 1950s, but have more recently beenidentified in a broad spectrum of eukaryotic and prokaryotic phyla.
Far-redlight is light at the extreme red end of the visible spectrum, between red andinfra- red light. Usually regarded as the region between 710 and 850 nmwavelength, it is dimly visible to some eyes. It is largely reflected ortransmitted byplantsbecause of the absorbance spectrum of chlorophyll, and itis perceived by the plant photoreceptor phytochrome. However, some organismscan use it as a source of energy in photosynthesis. Far-red light also is usedfor vision by certain organisms such as some species of deep-sea fishes.
Test Point – TPO28L3
Plants are also able to distinguish betweenspecific wavelengths of light that the human eye cannot even see! Specificallythere’s a wavelength called far-red. Although why they call it far- red ... Imean, it is not red at all. It lies in the infrared range of the spectrum. Wecan’t see it, but plants can sense it as a different wavelength.
OK. Now I need to mention another thingabout photosynthesis. I didn’t explain how different wavelengths of light affectphotosynthesis. When a plant absorbs light for performing photosynthesis, itonly absorbs some wavelengths of light and reflects others.
Plants absorb most of the red light thathits them, but plants only absorb some of the far-red light that hits them.They reflect the rest. Remember this, because it’s going to be relevant in anexperiment I want to discuss.
This fascinating experiment showed thatplants not only detect and react to specific wavelengths of light, plants canalso detect and react to changes in the ratio of one wavelength to another.This experiment was called the Pampas experiment.