Vol. 28, No. 5(May 2023)

Stimulated to the leaves, the sensitive plant (Mimosa pudica) folds its leaves one after another. To elucidate the mechanism, a transgenic M. pudica was produced so that the cytosolic Ca²⁺ concentration can be observed as fluorescence by GCaMP6f (Hagihara et al. (2022) Nat. Commun. 13: 6412, DOI: 10.1038/s41467-022-34106-x). When a leaflet was wounded, the fluorescent signal caused by Ca²⁺ propagated through the veins to the tertiary pulvinus at the base of the leaflet, immediately followed by a movement of the pair of leaflets to fold inwards. And, Ca²⁺ signals were propagated to the adjacent tertiary pulvini sequentially, and the leaflets were also folded successively. At this time, electrical signals were transmitted simultaneously with the fluorescent signals. The authors also observed that the immotile M. pudica was more susceptible to feeding damage by insects, suggesting that the movement above protects the plant from feeding damage.

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