HORNER, HARRY T.*, ALBERT P. KAUSCH, AND BRUCE L. WAGNER. Department of Botany & Bessey Microscopy Facility, Iowa State University, Ames, IA 50011-1020, AgriBioTech, Inc., 530 Liberty Lane, West Kingston, RI 02892, and W.L. Gore & Associates, 3250 W. Kiltie Lane, PO Box 300, Flagstaff, AZ 86002-0300. - Ascorbic acid serves as precursor for oxalate synthesis in calcium oxalate idioblasts of Yucca torreyi in liquid root culture.
Liquid-cultured primary roots of Yucca torreyi L. (Agavaceae),
similar to its intact roots, develop uninterrupted files of calcium
oxalate crystal idioblasts in their cortex, beginning just back of the
terminal meristem. Each single file of idioblasts displays an
'ontogenetic' sequence acropetally. 14C-labeled glycolic
acid, glyoxylic acid and ascorbic acid, potential precursors of
oxalate were each added to different flasks, containing a sterile
liquid root-growth medium and the isolated roots, and allowed to
interact with the roots for 45 min. After thorough washing, the roots
continued to grow for periods from 1.6-h to 24-h post incorporation.
Autoradiography of root sections with the labeled ascorbic acid at the
earlier incorporation times showed concentrations of silver grains
over the idioblasts, and primarily over the vacuole crystal bundles
and cytoplasmic plastids. The glyoxalic acid- and glycolic
acid-labeled root sections showed a lesser amount of silver grains
distributed over the entire sections, but not concentrated over the
crystal idioblasts. These results strongly suggest that ascorbic acid
is the primary precursor of oxalate in the crystal idioblasts of
Yucca torreyi primary roots, and supports other recent
biochemical data regarding oxalate synthesis in higher plants. The
use of roots in liquid culture containing uninterrupted files of
developing crystal idioblasts could serve as a model system for
additional biochemical, physiological and molecular studies dealing
with understanding the formation and functional significance of
crystal idioblasts in higher plant organs.
Key words: ascorbic acid, autoradiography, crystals, culture, idioblasts, oxalate, roots, Yucca