Plants wait for the lights to change to red

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If we want to grow vegetables in a garden, we pick a nice sunny spot and clear a space free from other plants that might shade them. Sunlight provides the energy for photosynthesis: the more light, the bigger they grow. But plants are not so simple; they never are. Growth is an investment. More leaves mean more photosynthesis and greater returns, but all good investors will tell you to keep a little back for a rainy day. In PNAS, Yang et al. (1) show that plants manage this balance between saving and investment depending on the quality of light, not just the quantity. In plants, the phytochrome photoreceptors detect red and far-red (near infrared) light. Yang et al. (1) show that loss of phytochrome results in a general risk-averse strategy to growth. Instead of allocation toward growth, more resources are allocated toward resilience, and at the heart of this change in strategy there is a change in metabolism at a quite fundamental level.

The phytochrome photoreceptors are proteins that bind a tetrapyrrole chromophore, allowing them to absorb light. These phytochromes exist in two photo-interconvertible forms: an inactive, red-absorbing “Pr” form and an active, far-red–absorbing “Pfr” form. Absorption of light by the chromophore causes it to change conformation and this, in turn, causes a change in conformation of the phytochrome protein from the Pr form to the Pfr form or vice versa (2). The active Pfr form is translocated from the cytoplasm to the nucleus, where it interacts with a number of transcription factors to mediate changes in plant physiology (3). One of the earliest demonstrations of phytochrome action was in the germination of lettuce seeds, where pulses of red light were found to trigger germination, while pulses of far-red light inhibited germination (4). Along with a suite of other plant …
Original languageEnglish
Pages (from-to)7301-7303
Number of pages3
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number27
Early online date24 Jun 2016
Publication statusPublished - 5 Jul 2016

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