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The role of the epidermis and cortex in gravitropic curvature of maize rootsIn order to determine the role of the epidermis and cortex in gravitropic curvature of seedling roots of maize (Zea mays L. cv. Merit), the cortex on the two opposite flanks was removed from the meristem through the growing zone; gravitropic curvature was measured with the roots oriented horizontally with the cut flanks either on the upper and lower side, or on the lateral sides as a wound control. Curvature was slower in both these treatments (53 degrees in 5 h) than in intact roots (82 degrees), but there was no difference between the two orientations in extent and rate of curvature, nor in the latent time, showing that epidermis and cortex were not the site of action of the growth-regulating signal. The amount of cortex removed made no difference in the extent of curvature. Curvature was eliminated when the endodermis was damaged, raising the possibility that the endodermis or the stele-cortex interface controls gravitropic curvature in roots. The elongation rate of roots from which just the epidermis had been peeled was reduced by 0.01 mM auxin (indole-3-acetic acid) from 0.42 to 0.27 mm h-1, contradicting the hypothesis that only the epidermis responds to changes in auxin activity during gravistimulation. These observations indicate that gravitropic curvature in maize roots is not driven by differential cortical cell enlargement, and that movement of growth regulator(s) from the tip to the elongating zone is unlikely to occur in the cortex.
Document ID
20040089878
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Bjorkman, T.
(University of Washington Seattle 98105, United States)
Cleland, R. E.
Date Acquired
August 21, 2013
Publication Date
December 1, 1988
Publication Information
Publication: Planta
Volume: 176
Issue: 4
ISSN: 0032-0935
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Space Biology
NASA Program Space Biology Research Associates
Non-NASA Center
NASA Discipline Plant Biology
NASA Discipline Number 40-10
NASA Discipline Number 40-99

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