Ascorbic acid: A precursor of oxalate in crystal idioblasts of Yucca torreyi in liquid root culture

Liquid-cultured primary roots of Yucca torreyi L. (Agavaceae), which are si milar to its intact roots, develop uninterrupted files of calcium oxalate c rystal idioblasts with raphide bundles in their cortex, beginning just prox imal to the terminal meristem. Each single file of idioblasts displays a ba sipetal ontogenetic sequence. [1-C-14]glycolic acid, [1-C-14]glyoxylic acid , and L-[1-C-14]ascorbic acid, all of which are potential precursors of oxa late, were each added to different flasks that contained a sterile liquid m edium and isolated roots and were allowed to interact with the roots for 45 min. After thorough washing, the roots grew for periods that extended from 1.6 h to 24 h postincorporation before being fixed for light microscope au toradiography. Autoradiography of root sections with the L-[1-C-14]ascorbic acid at the 1.6-6.0-h incorporation times showed concentrations of silver grains over the idioblasts, primarily over the vacuole crystal bundles and cytoplasmic plastids. The [1-C-14]glyoxalic acid- and [1-C-14]glycolic acid -labeled root sections showed a smaller amount of silver grains distributed over the entire sections, but these grains were not concentrated over the crystal idioblasts. These results strongly indicate that the L-[1-C-14]asco rbic acid is the immediate precursor of oxalate in the crystal idioblasts o f Y. torreyi primary roots and support more recent biochemical data regardi ng oxalate synthesis in higher plants. The use of roots in liquid culture c ontaining uninterrupted files of developing crystal idioblasts could serve as a model system for additional biochemical, physiological, and molecular studies that seek to understand the formation and functional significance o f crystal idioblasts in higher plant organs.