Transpiration Lesson objectives• All will be able to describe transpiration• Most will be able to explain differences in transpiration speed• Some will suggest reasons why plants compromise between gas exchange and water loss
How do tall trees get enough water?Redwoods are the tallest species of tree inthe world - the tallest was 120 metres.How does a plant this size get waterfrom its roots to the branches at thetop?What experiment could show that watertravels up stems?
TranspirationTranspiration can be measured using a potometer. A cut plant stem is sealed into the potometer using a rubber bung. An air bubble is introduced to the capillary tube. The distance the bubble travels shows how much water the stem has taken up.
1. Record a definition of transpiration2. Where do plants lose water?3. Transpiration will often lead to water loss by the plant so what is its purpose and what is the major advantage?
Transpiration• Sort the statements out into the correct order to show how water moves to the top of the plant
TranspirationExperiment Distance bubble moved after each minute in mmTime in 1 2 3 4 5 6 7 8 9 10minA 2 3 5 7 10 11 13 15 18 20B 13 24 38 49 73 75 89 114 118 152C 5 12 18 24 30 35 41 47 53 58
Is the rate of transpiration constant?Transpiration is a bit like a straw, pulling water upthe plant. Sometimes the pulling force will bestronger and the plant will lose more water.The speed at which a plant loses water is calledthe rate of transpiration.What environmental factors will affectthe rate of transpiration? humidity (amount of moisture in the air) light intensity temperature air movement (wind).
How does a plant control water loss?1. Waxy waterproof layer (cuticle)2. Stomata on the underside of the leaf (not expose to sun)3. Wilting. Leaves collapse reducing surface area4. Stomata close