Excretion in plants

a project on science ;

1. EXCRETION IN PLANTS

2. 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: give examples of waste substances and how they are excreted by plants. state the importance of excretion to plants. 3

4. Salt crystals on the leaf surface of the Black Mangrove 4

5. Salt glands on Button mangrove leaf petioles 5 salt gland

6. What is Excretion? Excretion in Plants 6 Why carry out excretion? It helps to maintain homeostasis of the internal environment. It is a characteristic of all living organisms It involves the removal from the body of waste substances that are formed during cellular metabolic activities, such as respiration, and which if left in the body could be toxic.

7. O 2 is excreted from photosynthesis 7

8. What ‘waste’ from respiration is excreted? Glucose + Oxygen  Carbon Dioxide + Water + Energy released and made available C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + 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.  Excretion in Plants 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. Excretion in Plants 9

10. Ornamental plants form Calcium Oxalate crystals in (leaf) cells for excretion Excretion in Plants 10 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

11. Calcium Oxalate crystals from Pomegranate leaf (left) and Tilia sp . Excretion in Plants 11 Development of the calcium oxalate crystal in pomegranate  Calcium oxalate crystal in Tilia sp. 

12. Water, brought to leaves via veins, is excreted during transpiration Excretion in Plants 12

13. Functions of stomata 1. Gas Exchanges and 2. Transpiration Excretion in Plants 13 Oxygen, Carbon dioxide can diffuse in/out Water vapour diffuses out. Guard cell ,

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 . Excretion in Plants 14

15. Various wastes are removed during leaf fall Waste compounds are often stored in dead heartwood, bark and leaves which die/fall off. Excretion in Plants 15 When chlorophyll breaks down, other compounds in leaves give the characteristic autumn colors seen just before leaf fall.

16. Latex (white) can be excreted from plants Excretion in Plants 16

17. Gum oozes out of a branch Gum Excretion in Plants 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. O 2 , CO 2 ). Because salts are so removed, excretion also serves the important function of osmo -regulation which maintains homeostasis . Excretion in Plants 18

19. Excretion in Plants 19