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Analysis of peg formation in cucumber seedlings grown on clinostats and in a microgravity (space) environmentIn young cucumber seedlings, the peg is a polar out-growth of tissue that functions by snagging the seed coat, thereby freeing the cotyledons. Previous studies have indicated that peg formation is gravity dependent. In this study we analyzed peg formation in cucumber seedlings (Cucumis sativus L. cv Burpee Hybrid II) grown under conditions of normal gravity, microgravity, and simulated microgravity (clinostat rotation). Seeds were germinated on the ground, in clinostats and on board the space shuttle (STS 95) for 1-2 days, frozen and subsequently examined for their stage of development, degree of hook formation, number of pegs formed, and peg morphology. The frequency of peg formation in space grown seedlings was found to be nearly identical to that of clinostat grown seedlings and to differ from that of seedlings germinated under normal gravity only in a minority of cases; approximately 6% of the seedlings formed two pegs and nearly 2% of the seedlings lacked pegs, whereas such abnormalities did not occur in ground controls. The degree of hook formation was found to be less pronounced for space grown seedlings, compared to clinostat grown seedlings, indicating a greater degree of decoupling between peg formation and hook formation in space. Nonetheless, in all seedlings having single pegs and a hook, the peg was found to be positioned correctly on the inside of the hook, showing that there is coordinate development even in microgravity environments. Peg morphologies were altered in space grown samples, with the pegs having a blunt appearance and many pegs showing alterations in expansion, with the peg extending out over the edges of the seed coat and downwards. These phenotypes were not observed in clinostat or ground grown seedlings.
Document ID
20040088911
Acquisition Source
Kennedy Space Center
Document Type
Reprint (Version printed in journal)
Authors
Link, B. M.
(University Park 16802 United States)
Cosgrove, D. J.
Date Acquired
August 21, 2013
Publication Date
December 1, 1999
Publication Information
Publication: Journal of plant research
Volume: 112
Issue: 1108
ISSN: 0918-9440
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAG10-0205
Distribution Limits
Public
Copyright
Other
Keywords
STS-95 Shuttle Project
manned
Non-NASA Center
NASA Discipline Plant Biology
Flight Experiment
short duration

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