Plant Hormones and the Endocrine System Chapters 39 and 45 (in brief) Campbell Reece.
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Transcript of Plant Hormones and the Endocrine System Chapters 39 and 45 (in brief) Campbell Reece.
Plant Hormones and the Endocrine SystemChapters 39 and 45 (in brief)Campbell • Reece
Cell Communication in Plants
Response2 main types of responses:
Increased or decreased transcription of mRNA to make enzymes
Activation of existing enzymes
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
Plant TropismsGrowth response toward or
away from stimuliPhototropism – response to
lightGravitropism – response to
gravityThigmotropism – response
to touch
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
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 Autocrine signaling – target cell is itself
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
Chemical Classes of Hormones
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
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
Negative Feedback
Positive Feedback