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ROOT CONTRACTION IN FREESIA (IRIDACEAE)
Author(s) -
Ruzin Steven E.
Publication year - 1979
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.1537-2197.1979.tb06254.x
Subject(s) - biology , parenchyma , iridaceae , anatomy , contraction (grammar) , botany , biophysics , endocrinology
The contractile roots of the horticultural variety Freesia hybrida Bailey (Iridaceae) were determined to contract via a growth/collapse mechanism. Contraction is initiated by a radial growth of middle and outer cortical parenchyma cells which is morphologically evident by an expanded diameter of the root. No concomitant decrease in length of the actively growing cells was observed. Shortening of the root is caused by axial tension produced by the radial growth of cells contiguous with nonexpanded cells distally. Centripetal collapse of expanded cells, coupled with passive shortening of inner cortical parenchyma and stelar tissues, releases axial tension slowly, returning the shortened root to equilibrium. Inner cortical parenchyma cells shorten in an accordion‐like manner facilitated by partial dissolution of middle lamellar material.