How pine cones open

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The scales of seed-bearing pine cones move in response to changes in relative humidity. The scales gape open when it is dry, releasing the cone's seeds1. When it is damp, the scales close up. The cells in a mature cone are dead, so the mechanism is passive: the structure of the scale and the walls of the cells composing the scale respond to changing relative humidity. Dissection of cones from the Monterey pine, Pinus radiata, revealed to us two types of scale growing from the main body of the cone — the ovuliferous scale and the bract scale. The larger ovuliferous scales respond to changes in relative humidity when removed from the body of the cone.

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Figure 1: Morphology and behaviour of pine cone scales.
Figure 2: Morphology and behaviour of pine cone scales.
Figure 3: Morphology and behaviour of pine cone scales.


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