Gravity-regulated formation of the peg in developing cucumber seedlings |
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Authors: | Hideyuki Takahashi Tom K Scott |
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Institution: | (1) Institute of Genetic Ecology, Tohoku University, Katahira, Aoba-ku, 980 Sendai, Japan;(2) Department of Biology, University of North Carolina at Chapel Hill, 27599 Chapel Hill, NC, USA |
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Abstract: | It has been proposed that peg formation in the vascular transition region (TR zone) between the hypocotyl and the root in
Cucurbitaceae seedlings is a gravimorphogenetic phenomenon. Initiation of the peg became visible 36 h after imbibition when
cucumber (Cucumis sativus L. cv. Burpee Hybrid II) seeds were germinated in a horizontal position at 24°C in the dark. Simultaneously, sedimented amyloplasts
(putative statoliths) were apparent in the sheath cells surrounding the vascular strands, and in the cortical cells immediately
adjacent to them, in the TR zone. In contrast, the other cortical cells, some of which were destined to develop into the peg,
contained amyloplasts which were not sedimented. These results suggest that the graviperception mechanism for peg formation
may be like that of statoliths in shoot gravitropism. By 48 h following imbibition, the cells of the TR zone still had sedimented
amyloplasts but had lost their sensitivity to gravity, possibly because of their maturation. |
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Keywords: | Amyloplast Cucumis (peg formation) Graviperception Peg formation (Cucurbitaceae) Root-shoot transition zone Statolith |
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