1. Control Systems In Plants

2. Plant Hormones Five known classes of hormones control plant growth and development Auxin – promotes fruit growth Cytokinins – stimulate cell division Gibberellins – stimulate growth in leaves and stems Abscisic Acid – slows plant growth Ethylene – inhibits root growth

3. Tropisms Phototropism –bends shoot towards light; enhances photosynthesis Gravitropism – uses specialized plastids (statoliths). Roots display positive gravitropism (grows down towards the earth) and the shoot displays negative gravitropism (grows up out of the earth)

4. Tropisms Thigmotropism: Developmental response to mechanical stimulation Example: thicker stemmed plants are found in locations where the winds are strong

5. Turgor Movements Turgor movements are relatively rapid, reversible plant responses

6. Biological Clocks Biological clocks control circadian rhythms in plants and other eukaryotes

7. Photoperiodism Photoperiodism synchronizes many plant responses to changes of season

8. Phytochrome Phytochrome functions as a photoreceptor in many plant responses to light and photoperiod

9. Control Systems Control systems enable plants to cope with environmental stress

10. Plants The study of plants began when early humans began to distinguish edible plants from poisonous ones. Then began to make things from wood and other plant products.

11. Modern Science Today scientists aim for increasing crop productivity, but the fun of discovery is what motivates most plant scientists.

12. Plants Plant biology, one of the oldest branches of science, is driven by curiosity and need – curiosity about how plants work and a need to feed, clothe, and house an increasing human population. Plant biology is in the midst of a renaissance, in which new methods, coupled with clever choices of experimental organisms, have catalyzed a research explosion.