title: A tracheid-differentiation factor from pine needles.
abstract: Exogenous indol-3yl-acetic acid (IAA), alone and together with several cytokinins, was ineffective in promoting the complete differentiation into tracheids of cambial derivatives of Pinus contorta Dougl.; IAA alone promoted cambial cell division and primary-wall growth in cambial derivatives throughout the stem's length. In contrast, a single pair of needles on a stem cutting in light promoted neither cambial cell division nor primary-wall growth in cambial derivatives but did promote complete differentiation of cambial cells into tracheids; tracheids differentiated only near the junction of the foliated short shoot with the stem. Clear inter-and intracellular differences in the extent of tracheid differentiation occurred in response to a single needle pair and have suggested the hypothesis that a specific tracheid-differentiation factor regulates the differentiation of cells into proto-, meta-, or secondary-xylem tracheary elements through an interaction with IAA.
authors.affiliation: Department of Botany and Microbiology, University College of Wales, SY23 3DA, Aberystwyth, Dyfed, U.K..
authors.forename: R A
authors.initials: RA
authors.lastname: Savidge
authors.forename: P F
authors.initials: PF
authors.lastname: Wareing