Biology 2601A/B Lecture Notes - Lecture 21: Vascular Tissue, Indole-3-Acetic Acid, Flattening
20 Dec 2017
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Involve the accumulation of new cells, material, cellulose, etc. Cells that gain and loose turgor, inflate and deflate: reversible movements. Terminology of movement: nutation - rotational movements, tropism - directed movement, phototropism, gravitropism, nastic movement - undirected response. Just movement in response to a stimulus: no direction. Nutation aka circumnutation: circular or elliptical movement of the apex of stem, root, tendril, etc, clockwise or counter-clockwise, usually is species-specific, ex. Climbing vines and tulips: passion flower, growth in a circular movement, this movement is irreversible, growth effects are reversible. How does this happen: controlled shift in the region of most active cell division, movement of fast dividing tissue in a circular motion. Figure: cross section of stem, dots are fast growing cells, arrow is path of movement, directionality of growth is partly driven by allocation of hormones, plants have hormones that regulate growth and transitions, ex. Auxin - key regulator of cell division and growth: drives irregular cell division.
