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Unformatted text preview: B I O L O G Y 12 2 3 2-Feb-10 Gardiner 1 Gas Exchange in Plants No Trachea, no gills, no lungs How Do They Do It? 3 B I O L O G Y 12 2 3 2-Feb-10 Gardiner 2 Remember • In plants all gas exchange is done locally • Each living cell exchanges gas directly with environment • No special system for gas exchange as in animals • Vascular tissues do not transport gases to tissues B I O L O G Y 12 2 3 2-Feb-10 Gardiner 4 B I O L O G Y 12 2 3 2-Feb-10 Gardiner 5 Gas Exchange • Occurs by diffusion across a cell membrane • Gas must first dissolve in a film of water • No serious problem for aquatic plants and protists – Each in direct contact with water or only a few cells away B I O L O G Y 12 2 3 2-Feb-10 Gardiner 6 Kelp • Large only in one or two dimensions • Kelps 60 to 70 metres in length – Blades very thin – No cell very far from surface – Total gas exchange area is large in relation to volume of algae B I O L O G Y 12 2 3 2-Feb-10 Gardiner 9 Land Plants • In land plants the requirements of water conservation conflict with those of gas exchange 1. Respiratory surface area of adequate dimensions 1. Roots - branching, root hairs, mycorrhizae 2. Leaf – intercellullar spaces B I O L O G Y 12 2 3 2-Feb-10 Gardiner 10 Land Plants 2. Protecting fragile gas-exchange surface 1. Outer body coverings 1. Waxy cuticle 2. Bark-however these make maintenance of an adequate exchange surface difficult B I O L O G Y 12 2 3 2-Feb-10 Gardiner 11 Land Plants 3. Keeping the tissues moist 1. Xylem delivers water to cells to keep them moist 2. Bark, epidermis and cuticle help retard water loss 2-Feb-10 Gardiner 12 SYSTEM LARGE SURFACE AREA SMALL DISTANCE CONCENTRATION GRADIENT Human lungs 600 mil ion alveoli with a total area of 100m² each alveolus = 1 cel thick constant ventilation replaces the air Fish gil s feathery filaments with secondary lamel ae lamel ae = 2 cel s thick...
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This note was uploaded on 04/18/2010 for the course BIOLOGY 1223 taught by Professor Gardiner/lajoie during the Fall '09 term at UWO.
- Fall '09