9.3 Growth in Plants

1. 9.3 Growth in Plants

2. Plant hormones: • Respond to changes in the environment • Regulate growth • Regulate reproduction and flowering • Regulate water loss • Regulate growth by controlling mitosis and cell division

3. Meristem Tissue • Undifferentiated tissues that become many different types of tissues • Located where plants exhibit major growth

4. 2 types of Meristems • Apical Meristems • Located at the top and the root of plants • Allows for growth of new leaves and flowers • Allows roots to grow down into the soil • Elongation of plant • Lateral Meristems • Responsible for secondary growth in woody plants • Allows them to increase stem and root thickness

5. Indeterminate Growth • Animal embryos have a fixed number of parts that will develop and are considered determinate growth • 2 legs, 2 arms, 10 fingers/toes etc. • The growth in plants is much different and is considered to be INDETERMINATE. • Meaning apical meristems can continue to increase the lengths of stem and root throughout the life of a plant and can produce any number of extra branches of the stem or root. They can also produce any number of extra leaves or flowers.

6. Mitosis and Cell Division • Occur in the shoot apex • Provide cells needed for extension of the stem at that location • Also important for development of leaves.

8. Tropisms • A directional movement in plants in response to a stimulus

10. Auxin (plant hormone) • Responsible for phototropism • Affects cells on the dark side of the plant • causes the cells away from light to elongate • When light shines directly down on a plant shoot auxin is equally distributed this causes the plant to grow straight • This hormone is released in abundance of blue light in the shoot tip.

12. Auxin • Auxin efflux pumps can set up concentration gradients of auxin in plant tissue. • Moves Auxin from cytoplasm to cell wall • Lower concentration on light side and higher concentration on dark side. • Auxin influences cell growth by changing the pattern of gene expression. • These genes cause secretion of H+ ions into cell walls that loosen connections in the cellulose fibers that allow cells to expand.

14. Micropropogation of plants • The practice of rapidly multiplying stock plant material to produce a large number of plants, using modern plant tissue culture methods. • Can create virus-free strains of existing plants • Can propagate rare species - Orchids • Uses tissue from shoot apex, nutrient agar gels and growth hormones • Used in plants to increase population faster than seeding time would allow • $$$$