Effects of red light on the fluence–response relationship for pulse-induced phototropism of maize coleoptiles |
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Authors: | YJ LIU M LINO |
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Institution: | Botanical Gardens, Faculty of Science, Osaka City University. Kisaichi, Katano-shi, Osaka 576, Japan |
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Abstract: | Dark-adapted coleoptiles of maize (Zea mays L.) were treated with red light (3min at 10.5 μmol m?2S?1) and were Stimulated, after a dark interval, with a pulse of unilateral blue light to induce phototropism. Phototropic fluence-response curves were obtained in this way for different dark intervals. It was confirmed that the bell-shaped fluence-response curve for the first pulse-induced positive phototropism (FPIPP) shifts to higher fluences following the red-light treatment, the maximal shift being achieved at a dark interval of 2h. We found, however, that the two arms of the Fluence-response curve do not shift synchronously. The shift of the descending arm to higher fluences began at 15 min. The ascending arm showed a slight shift to lower fluences before a greater shift to higher flucnces. the change of the shift direction occurring at 30–40min. Accordingly, the fluence-response curve obtained for a 30 min dark interval was comparatively wide. Although dark-adapted coleoptiles showed only fPIPP, another bell-shaped fluence-response curve, representing the second pulse-induced positive phototropism (sPIPP), appeared gradually after the red-light treatment. These changes of the phototropic fluence– respnse curve following exposure to red light are likely to have adaptive values because they favour phototropism under brighter light. |
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Keywords: | Zea mays L adaptation blue light: coleoptiles maize phototropism phytochrome red light |
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