Red Light and Auxin Effects on 86Rubidium Uptake by Oat Coleoptile and Pea Epicotyl Segments

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Abstract
Apical segments of etiolated oat (Avena sativa L. cv. Victory) coleoptiles showed enhanced uptake of [86Rb+] when tested 30 minutes after a 5-minute red irradiation. The response was partly reversible by far red light. Uptake was sensitive to carbonyl cyanide m-chlorophenyl hydrazone, but not to isotonic mannitol. Indoleacetic acid (10−7 molar) caused a very pronounced and rapid stimulation of uptake. Basal coleoptile segments also exhibited a red light-enhanced uptake, but not an effect of red light on changes in the pH of the medium. The [86Rb+] uptake of third internode segments from etiolated peas (Pisum sativum L. cv. Alaska) was not affected by either red light or auxin. This tissue also showed no red light effect on acidification of the medium. It is concluded that alteration of [86Rb+] flux is not a general feature of phytochrome action.