Plant Hormones and the Endocrine System

1. Plant Hormones and the Endocrine System Chapters 39 and 45 (in brief) Campbell • Reece

2. Cell Communication in Plants

3. Response • 2 main types of responses: • Increased or decreased transcription of mRNA to make enzymes • Activation of existing enzymes

4. Plant Hormones • AKA Plant Growth Regulator • Almost all aspects of plant growth and development are under hormonal control to some degree • A single hormone may regulate many different processes • Multiple hormones may influence a single process • Response depends mostly on the amount of a hormone compared with other hormones

5. Plant Tropisms • Growth response toward or away from stimuli • Phototropism – response to light • Gravitropism – response to gravity • Thigmotropism – response to touch

6. Hormones in Animals • A molecule that is secreted into the extracellular fluid, circulates in the blood or hemolymph, and communicates regulatory messages throughout the body • Hormones elicit a specific response from its target cells, but cells lacking the receptor for that hormone are unaffected • Endocrine system – regulates reproduction, development, energy metabolism, growth, and behavior

7. Types of Signaling Molecules • Hormones – secreted by endocrine cells or glands • Travel via blood or hemolymph throughout body • Local regulators – reach target cells solely by diffusion • Paracrine signaling – target cells lie near secreting cell • Autocrinesignaling – target cell is itself

8. Types of Signaling Molecules • Neurotransmitters – cross synapses • Neurohormones – specialized neurons secrete molecules into the bloodstream to reach target cells • Pheromones – chemicals that are released into the external environment

10. Chemical Classes of Hormones

11. Cellular Response Pathways • Water-soluble hormones travel freely through the bloodstream, bind to cell-surface signal receptors • Change molecules in the cytoplasm OR regulate gene transcription • Lipid-soluble hormones travel in the bloodstream bound to transport proteins, diffuse across the membrane, bind to an intracellular signal receptor • Regulates gene transcription

13. Multiple Effects of Hormones • Many hormones create more than one type of response in the body • The type of response depends on the molecules that receive or produce the response

14. Negative Feedback

15. Positive Feedback