How does a plant know the time to flower?  A new study describes a process involving genes, sunlight sensors, switches, clocks, feedback loops and messages.

The research, published in Science, focused on a protein that is sensitive to day length.  The longer the day, the more the protein is produced.  Its activity is controlled by the circadian clock, a set of genes and proteins that keep time in all plants and animals.  In the lab plant Arabidopsis, this protein, named FKF1, is allowed (when the days become long enough) to activate another protein that activates flowering.  This second protein, though, has to travel from the leaves where it is made to the tips of the stem.  There, it turns on the flowering system.

The paper described the complexity of the system:

The FKF1 photoperiod sensor uses multiple, partially redundant switches to allow strong activation in long days. As the Sun rises higher in the sky each day when spring approaches, plants can sense the increased intensity in the blue-light range of the spectrum each afternoon through multiple photoreceptors, including FKF1. The complexity of this mechanism even in a temperate species such as Arabidopsis suggests that it has the flexibility to regulate successful reproduction in a wide range of environments.

In other words, their lab plant has probably one of the simpler systems.  Seasonal response is probably even more complex in some plants and animals, but even bacteria are known to have circadian clocks of Paley-like complexity.  Neither the paper nor the summary on PhysOrg mentioned evolution….

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