Water movement through plants How does water move through a plant? Which part of the plant does water enter? Which part of the plant does water leave? What do you know already? With the person next to you discuss for 1 minute what you already know about the movement of water through plants

Transpiration Transpiration is the movement of water molecules through the plant. Up from the roots, through Xylem vessels and evaporating out through the stomata in the leaves. Certain conditions affect the rate of transpiration. If it is warm, water is lost because of the increased movement of the molecules. The wind will blow away molecules near the stomata. Humidity will slow down water loss because the concentration gradient is small.

Transpiration in plants

Root hairs give plant roots a large surface area. Why do you think they have no chloroplasts?

Evaporation and transpiration Evaporation is the process of a liquid turning to gas. Transpiration is the release of water vapour from a plant through the leaves, causing water to move through the plant.

Xylem The xylem carries water and minerals from the roots to the leaves The cellulose cell walls contain extra layers of a chemical called lignin. Once xylem cells have formed the xylem they die making long thin vessels for water to move through

Phloem The phloem carries dissolved food such as sugars from the leaves to other areas of the plant Phloem cells are alive. If they are damages they cannot work properly.

Xylem & Phloem Xylem Tissue made of Tracheid cells transports water from root to leaves via - a. Capillary Action b. Transpiration Pull Phloem Tissue Made of sieve tubes and companion cells Transports food (organic molecules) from leaf to root or vice versa sugar transport

Position of xylem and phloem In the stem

Position of xylem and phloem In the root

Prepared Slide View – Leaf Cross Section

Guard Cells & Stomata Allow movement of CO2, H2O & O2 into or out of plant Transpiration – movement of water out of leaves (through stoma) Guard Cell Regulation

STOMATA

Potometer You can measure water loss by using a potometer

Affecting the rate of transpiration You can measure the rate of transpiration using a potometer

Affecting the rate of transpiration Light intensity Temperature increases Air movement Humidity falls

Transpiration When it is sunny the plant will photosynthesise more meaning stomata are open to allow more carbon dioxide in, more water can be lost.

Transpiration Wind will blow away molecules near the stomata causing evaporation to increase.

Transpiration As humidity increases the rate of transpiration decreases. The higher the humidity the more water there is in the air. How do you think this affects the rate of diffusion?

Wilting If a plant is losing more water than it can replace, it will begin to wilt. This will reduce the amount of water lost as the surface area is reduced.

What did you learn today? What is the scientific name for water moving through a plant? What is the name of the vein in plants that water moves through? Give 3 ways that affect the rate of transpiration and explain why. What is a potometer? How does wilting reduce water loss?

Test Yourself

What did you learn today? 1. What is the scientific name for water moving through a plant? Transpiration 2. What is the name of the vein in plants that water moves through? Xylem 3. Give 3 ways in which water is useful in plants Cools it down when it evaporates, used for photosynthesis, support, carries dissolved minerals

What did you learn today? 4. How do plants use osmosis to help them regulate water loss? Water osmoses into or out of the guard cells to open or close stomata. If guard cells are turgid, stomata is open. 5. Give 2 ways in which plants reduce water loss from them Few stomata, small leaves, stomata on the bottom of leaf, ability to close stomata (waxy cuticle), wilting

What did you learn today? 6. Why do water particles move out of the air spaces in leaves into the air? Because there is a higher concentration of water particles in the air space than outside the leaf so the water particles diffuse out of the leaf

To summarise