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Physical basis for altered stem elongation rates in internode length mutants of PisumBiophysical parameters related to gibberellin (GA)-dependent stem elongation were examined in dark-grown stem-length genotypes of Pisum sativum L. The rate of internode expansion in these genotypes is altered due to recessive mutations which affect either the endogenous levels of, or response to, GA. The GA deficient dwarf L181 (ls), two GA insensitive semierectoides dwarfs NGB5865 and NGB5862 (lka and lkb, respectively) and the slender' line L197 (la crys), which is tall regardless of GA content, were compared to the wild-type tall cultivar, Torsdag. Osmotic pressure, estimated by vapor pressure osmometry, and turgor pressure, measured directly with a pressure probe, did not correlate with the differences in growth rate among the genotypes. Mechanical wall properties of frozen-thawed tissue were measured using a constant force assay. GA deficiency resulted in increased wall stiffness judged both on the basis of plastic compliance and plastic extensibility normalized for equal stem circumference. Plastic compliance was not reduced in the GA insensitive dwarfs, though lka reduced circumference-normalized plasticity. In contrast, in vivo wall relaxation, determined by the pressure-block technique, differed among genotypes in a manner which did correlate with extension rates. The wall yield threshold was 1 bar or less in the tall lines, but ranged from 3 to 6 bars in the dwarf genotypes. The results with the ls mutant indicate that GA enhances stem elongation by both decreasing the wall yield threshold and increasing the wall yield coefficient. In the GA-insensitive mutants, lka and lkb, the wall yield threshold is substantially elevated. Plants possessing lka may also possess a reduced wall yield coefficient.
Document ID
Document Type
Reprint (Version printed in journal)
Behringer, F. J.
(Cornell University Ithaca, New York 14853)
Cosgrove, D. J.
Reid, J. B.
Davies, P. J.
Date Acquired
August 21, 2013
Publication Date
January 1, 1990
Publication Information
Publication: Plant physiology
Volume: 94
ISSN: 0032-0889
Subject Category
Life Sciences (General)
Funding Number(s)
Distribution Limits
NASA Discipline Number 29-20
NASA Program Space Biology
Non-NASA Center
NASA Discipline Plant Biology

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