The objectives of Dr. Meicenheimer's proposal are: 1. Develop an empirical model for flax stem growth and tissue differentiation in terms of spatial domains of relative elemental rates of cellular processes within the stem axis. 2. Compare this model with existing cellular models for root growth and tissue differentiation. 3. Test the hypothesis that two classes of substances (leaf dependent and leaf independent) regulate flax stem tissue patterns. Flax plants will be grown under uniform environmental conditions which give rise to steady state growth of stems. Computer aided analyses of high resolution scanning electron micrographs and serial transverse light microscopy sections of the stem will be used to construct empirical models of the cellular basis for growth and tissue differentiation of the stem axis. Chemical treatments which interfere with specific endogenous hormone levels within the stem will be used to alter the normal cellular processes within the stem axes. Models developed for chemically treated and untreated stems will be compared in tests of the working hypothesis. Patterns of external morphology and internal tisue anatomy of plant stem and root axes are created through the concerted processes of division and expansion of populations of cells initially comprising the apical meristems of these organs. The spatial domains of such cellular processes have been fairly well characterized for plant roots but we lack similar information for plant stems. This proposal addresses this lack.
