Comparison of gibberellin-like substances from cotyledons and phloem exudate collected from cotyledons of Pharbitis nil in relation to photoperiodic flowering |
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Authors: | Kiyotoshi Takeno Charles F. Cleland |
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Affiliation: | (1) Smithsonian Environmental Research Center, 12441 Parklawn Drive, 20852 Rockville, MD, USA;(2) Tohoku University, Laboratory of Horticultural Science, Faculty of Agriculture, 981 Sendai, Japan;(3) USDA/CSRS/SBIR, 20250-2200 Washington, DC, USA |
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Abstract: | Gibberellin (GA)-like substances were analyzed in extracts from cotyledons and phloem exudate collected from cotyledons in photoinduced and vegetative seedlings of the short-day plant Pharbitis nil Chois. var. Violet, using high performance liquid chromatography (HPLC) and the dwarf rice bioassay, to see whether any specific GA-like substances were transported from the photoinduced cotyledons via phloem. Cotyledon extracts exhibited five peaks of free GA-like activity in HPLC, whereas only one or two active peaks were detected in phloem exudate extracts. The level of free GA-like activity was considerably lower in phloem exudate than in the cotyledons. In five out of six analyses of cotyledons and phloem exudate, there were substantially higher levels of free GA-like substances in photoinduced plants. Conjugated GA-like substances were present in much higher levels than free GA-like substances in the cotyledon extracts but the levels were not influenced by daylength. In phloem exudate extracts there was no conjugated GA-like substances. The free GA-like substances that are transported via phloem cochromatographed with GA5/20 and GA19 on HPLC. These were significantly higher in photoinduced plants and thus could have some influence on the photoperiodically-induced flowering in P. nil. |
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Keywords: | daylength flowering gibberellin Pharbitis nil phloem exudate |
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