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What is a hormone? A hormone (from Greek ὁρμή, "impetus") is a chemical released by a cell, a gland, or an organ in one part of the body that affects cells in other parts of the organism. Generally, only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one cell to another. (Wikipedia, if you couldn’t tell) What hormones do you recall? In animals? In plants? What are they made of?
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Plant hormones
What is a hormone? How do they work?Where are they formed?What do they do?Other plant responses…
Refer to chapter 26 in text.
What is a hormone?
A hormone (from Greek ὁρμή, "impetus") is a chemical released by a cell, a gland, or an organ in one part of the body that affects cells in other parts of the organism. Generally, only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one cell to another. (Wikipedia, if you couldn’t tell)
What hormones do you recall?In animals?
In plants?
What are they made of?In animals?
In plants?
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How do they work? What do you recall about how (protein) hormones work?
signal transduction pathway - Hormone’s message is amplified
at each step.
← Simplified version.More realistic version. ↓
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&docid=fNevLSLeaBGYNM&tbnid=qZeiCiFQi7OgfM:&ved=0CAQQjB0&url=http%3A%2F%2Fmigration.wordpress.com%2F2007%2F08%2F25%2Fbasic-concepts-signal-transduction%2F&ei=x90ZUvjlGeLk2AWCpoHoCg&bvm=bv.51156542,d.b2I&psig=AFQjCNEL70hlKRfVRIp10HMRM4K-VkuW5A&ust=1377513283732384
Where are they formed?
In humans, formed in glands: In plants, formed in dividing tissues:
… so also in growing leaves and fruit.
Where do they go? Everywhere.
Auxins
Source: apical meristemsEffects: apical dominance, rooting, fruit growth
breaks cellulose for cell extension in phototropism halts abscission and fruit dropping
Application: e.g. seedless tomatoes, agent orange
What do you recall of these guys from “stems” and “roots”?(Phototropism? Gravitropism?)
http://edscitutors.co.uk/blog/2012/03/higher-biology-revision-phototropism-in-plants/
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Auxins cont.Auxin efflux pump:
In apoplasty (outside cells), auxins are non-polar, so can enter neighboring cells.←Inside cells, auxins are negatively charged, thus depending on permission, (opening of transport pumps) to exit the cell.←
This is how the auxin gradient across plant tissues is established.
What controls these passages? (under ongoing investigation)
http://home.earthlink.net/~dayvdanls/A
uxinTranspt.gif
Cytokinins What do you recall of these guys from the cell cycle?(Three stop points..?)
Same thing here.
Source: actively dividing roots; also seeds and fruitEffects: with auxins, or else callus forms
prevent senescence (sleep/death)Application: increase axillary growth
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Gibberellins What do you recall of these guys from germination?(After imbibition? Prompts amylase production?)
That’s not all...
Source: young leaves, roots, embryos, seeds and fruitEffects: stem elongation, increased growth
breaking dormancyApplication: increase size of flowers and plants
produce seedless grapes
http://botanyprofessor.blogspot.com/2013_01_01_archive.htm
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Abscisic Acid (ABA)
What do you recall of these from transportand … OK, ecology?(influences guard cells to close, and It turns out it doesn’t usually cause abscission)
Source: “green” tissue, monocot endosperm and rootsEffects: increases dormancy, encases buds, closes stomataApplication: slow grape maturation, reduce desiccation stress
http://ww
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Ethylene What do you recall of this… from anywhere?We haven’t hit it until now.
Source: especially fruit and apical meristemsEffects: reduces axillary buds, increases cellulase to
hasten ripening and abscission, reduces chlorophyll (hence intensifying fruit color)
Application: GMO fruit (tomatoes) to not generate ethylene,so they don’t ripen en-route, and then they’regassed at the store.
http://www.vce.bioninja.com.au/aos-2-detecting-and-respond/coordination--regulation/plant-hormones.html
This is a simplified recap of the preceding slides:The url at the bottom includes a BioNinja lesson on plant hormones.
Other Plant Responses
nastic movement: using turgor, e.g. to fold leaves ↓ epidermis: →
1st line of defense
2o metabolites (by products): →tannins, cyanogens, andalkaloids (morphine, nicotine, caffeine)for defense
iopscience.iop.org w
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(Why would a plant catch bugs?)
Other Plant Responses cont.
systematic acquired resistance or SAR:immunity against encountered pathogens,like acquired immunity.
(a bit of grazing helps plants)
hypersensitive response or HR:pathogen walled off,like innate immunity.
faculty.uca.edu www.udel.edu
hormonesignal transduction pathway auxinsauxin efflux pumpcytokininsgibberellinsabscisic acid ABAethylenenastic movementepidermis2o metabolites hypersensitive response HRsystematic acquired resistance SAR
