Abstract

Leaflet pairs from detached pinnae of Mimosa pudica opened after the pinnae had been irradiated with light (2 W·m−2) of 726 or 403 nm, whereas they remained almost closed with light of 585 or 656 nm. Light-induced leaflet opening was observed only in the daytime, from 6:00 to 16:00. Application of IAA at more than 30 μg/ml to the cut end of the pinna rachises made the leaflets open even in darkness with almost constant lag times of about 100 min which were independent of the concentration. NAA and 2,4-D also made the leaflet open at lower concentrations than IAA. Auxin-induced leaflet opening showed diurnal variation. Application of IAA for 2 to 6 min, depending on the concentration, was enough to open the leaflets. Autoradiography showed that IAA was transferred from the cut end of a rachis throughout a pinna within 4 min.

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