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MECHANICAL PROPERTIES WITHIN THE GROWTH ZONE OF CORN ROOTS INVESTIGATED BY BENDING EXPERIMENTS I. PRELIMINARY OBSERVATIONS
Author(s) -
Silk Wendy Kuhn,
Beusmans Jack M. H.
Publication year - 1988
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1988.tb08805.x
Subject(s) - curvature , bent molecular geometry , bending moment , bending , materials science , stress (linguistics) , deformation (meteorology) , moment of inertia , bending stiffness , logarithm , composite material , geometry , physics , mathematics , mathematical analysis , classical mechanics , thermodynamics , linguistics , philosophy
Bending experiments were performed to analyze mechanical properties within the apical 15 mm of the primary root of corn, Zea mays. Force required to maintain a root in a bent shape declined with the logarithm of time, indicating significant stress relaxation. Spatial distributions of local curvature, strain due to bending, and geometrical moment of inertia were calculated from digitized photographs of mechanically bent roots during and after imposition of a bending moment. When roots were bent to nonuniform curvature (maximum K = 3 cm –1 at the location 8 mm from the root tip), “irreversible” curvature (residual curvature 4 hr after release of the bending moment) was approximately 44% of initial curvature. This percentage of irreversible curvature (and associated bending strain) was uniform throughout the growth zone. When roots were bent to uniform curvature of either 1 cm –1 or 1.67 cm –1 , “springback” curvature (residual curvature after two minutes of bending) varied from 60% of initial curvature in the apical regions (at 4 mm) to 85% of initial curvature at the base of the growth zone. The results are consistent with a model in which total strain is proportional to stress, and irreversible strain at a particular location is proportional to total strain at the same location.