Isolation and handedness of helical coiled cellulosic thickenings from plant petiole tracheary elements

Abstract

Leaf stalks (petioles) are critical components of the vascular system that conducts water from the roots to the photosynthetic apparatus of most green plants. Helical coiled cellulosic microfibrils that reinforce the tracheary elements in plant leaf petioles were isolated by a gentle treatment with alkali and acid chlorite from celery and from a number of tree species, including sugar maple, London plane, horse chestnut, tulip tree, paulownia and ginko. Analysis of the hydrolysate of celery coils gave glucose as the main product, but significant quantities of xylose and other sugars were also detected. Polarized light microscopy was used to determine the location, dimensions and handedness of the coils. The coils were made up of single or multiple parallel strands in contact, ranging up to 35 μm in diameter and several cm in length. The strand structure was chiral; significantly, only left-handed helices were observed. An attempt is made to rationalize the left-handed structure by comparison with the spontaneous handedness observed in vitro for cellulose nanocrystals suspensions. The ubiquitous presence of coiled thickenings in petiole vascular elements indicates their importance in plant functions. © 2014 The Author(s).