Biology M3 Excretion in Plants
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Plants excrete waste through various methods without a dedicated excretory system. They excrete gases like oxygen and carbon dioxide through diffusion, water and excess salts through structures like stomata and salt glands, and solid crystals and compounds through storage in leaves, bark, and wood that are later shed. Excretion maintains plant homeostasis by regulating salts and removes byproducts of metabolic processes like respiration.
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Biology M3 Excretion in Plants
- 1. Module 3 Unit 8 Lesson 6 EXCRETION IN PLANTS
- 2. Credits: http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookplantanat.html http://en.wikipedia.org/wiki/Autumn_leaf_color and http://life.bio.sunysb.edu/marinebio/mg_06.jpg Introduction Animals are known to excrete wastes and usually have a special set of organs or a system that carries out that function. Do you think flowering plants like these also carry out excretion?
- 3. Objectives You should be able to: 1. give examples of waste substances and how they are excreted by plants. 2. state the importance of excretion to plants. 3
- 4. Salt crystals on the leaf surface of the Black Mangrove http://commons.wikimedia.org/wiki/File:Avicennia_germinans-salt_excretion.jpg 4
- 5. Salt glands on Button mangrove leaf petioles salt gland Photo: http://hdl.handle.net/123456789/271 or http://dspace.mona.uwi.edu/handle/123456789/271 5
- 6. What is Excretion? Why carry out excretion? 6
- 7. O2 is excreted from photosynthesis Photo: http://www.1ststeps.org/Science/Photosynthesis/photosynthesis.htm 7
- 8. What ‘waste’ from respiration is excreted? Glucose + Oxygen Carbon Dioxide + Water + Energy released and made available C6H12O6 + 6O2 6CO2 + 6H2O + Energy This means that oxygen combines with sugars present in cells to break molecular bonds, thus releasing the energy contained in those bonds. The other products of the respiratory reactions are carbon dioxide and water, which can be excreted if not needed then by the plant. 8
- 9. Guttation - The loss of excess water as liquid drops from the margins of leaves of herbaceous plants, occurring when root pressure is high and transpiration is low. The water usually contains sugars and/or salts. http://www.rosenfreundehannover.de/botanik.php http://en.wikipedia.org/wiki/Guttation9
- 10. Ornamental plants form Calcium Oxalate crystals in (leaf) cells for excretion www.library.okstate.edu/.../red_emerald.jpg The cells of these plants contain Calcium oxalate crystals which are eliminated when the leaves die and fall off. www.flowersgrowing.com/.../12/diefenbachia.jpg www.dkimages.com/.../previews/917/70024692.JPG 10
- 11. Calcium Oxalate crystals from Pomegranate leaf (left) and Tilia sp. Pomegranate Leaf: http://www.botany.org/plantimages/ImageData.asp?IDN=abot92-12 Tilia sp.: http://waynesword.palomar.edu/ww0601c.htm Development of the calcium oxalate crystal in pomegranate Calcium oxalate crystal in Tilia sp. 11
- 12. Water, brought to leaves via veins, is excreted during transpiration Source: http://iusd.k12.ca.us/uhs/cs2/images/Leaf%20Cross-section.jpg 12
- 13. Functions of stomata 1. Gas Exchanges and 2. Transpiration Oxygen, Carbon dioxide can diffuse in/out Water vapour diffuses out. Guard cell Source: http://www.worldofteaching.com/powerpoints/biology/plantsgeneral.ppt#262,13, 13
- 14. Excretion of gases by diffusion On woody stems - openings or pores in the layer of bark which is impervious to gases or water. Oxygen and Carbon Dioxide can diffuse through lenticels that develop in the bark. http://www.tutorvista.com/content/biology/biology-ii/respiration/plants-gaseous-exchange.php 14
- 15. Various wastes are removed during leaf fall • Waste compounds are often stored in dead heartwood, bark and leaves which die/fall off. http://www.na.fs.fed.us/spfo/pubs/misc/leaves/leaves.htm • When chlorophyll breaks down, other compounds in leaves give the characteristic autumn colours seen just before leaf fall. 15
- 16. Latex (white) can be excreted from plants Source: http://www.desert-tropicals.com/Articles/Stem_cuttings/Euphorbias.html 16
- 17. Gum oozes out of a branch Gum Source: http://waynesword.palomar.edu/ecoph13.htm 17
- 18. Summary • Excretion is the removal from the organism’s body of waste substances produced during cellular metabolism. • Plants do not have any set excretory system, so, getting rid of wastes often involves storing the substance (e.g. Calcium Oxalate, tannins) in some plant tissue, passing it out onto leaf surfaces (e.g. salts) or diffusion (e.g. O2, CO2). • Because salts are so removed, excretion also serves the important function of osmo- regulation which maintains homeostasis. 18