Control Systems In Plants

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.