Lesson 7– Plant organ systems, water movement

Plant organ systems Root system - Ususally underground 2. Shoot system -usually above ground

Shoot and Root systems working together To move nutrients, water and hormones throughout plants via vascular bundles (xylem + phloem)

Marcello Malpighi’s experiment (1686) Question raised: what happen if the flow of materials in the vascular bundles was interrupted? Describe what happen in the picture Removing phloem led to swelling of tree bark above the cut. Sweet fluid dripped out of the swelling Tree died a few weeks after the experiment What do you think happened?

Movement of materials in vascular bundles Phloem moves sugars from where to where? From leaves to other organs Xylem moves water and minerals from where to where? From roots to other organs What would the results have been if the xylem is removed? Water from root can’t reach leaves, no photosynthesis take place. Plant will also die out

What happen to plant when no or too much water? No water: Nutrients in soils can’t be dissolved and taken up No water for photosynthesis Plants will die Too much water: Root cells die as not enough O2 in soil to get energy from cellular respiration

How is water moved through xylem? Water transported up the plant against gravity Water first absorbed by the root hairs Water and nutrients then enter the root by osmosis (= the movement of water from a place of higher WATER concentration to a place of lower WATER concentration) until it they reach the xylem Before entering xylem, water and nutrients are filtered through the waxy cell membranes of the endodermis.

How is water moved through xylem? (cont.) A combination of root pressure, loss of water through stomata (leaf openings) and adhesion and cohesion properties of water helps move water up the plants. Adhesion: ability of water molecules to stick to certain surface (e.g. xylem’s wall) Cohesion: ability of water molecules to stick to one another

How is sugar moved through plant? Glucose from leaves must first converted into sucrose Sucrose is soluble in water and is transported through plants via phloem When reaching root, sucrose is converted into starch If plants needs starch from root, starch must be converted back to sucrose because starch is water insoluble Starch is then transported upward as sap Collecting maple sap

How do shoot and root systems depend on one another? What is produced in the leaves that needed by the rest of the plants? Explain how without the shoot systems the products produced by leaves will be of limited use for plant survival? Explain how photosynthesis is not possible without the shoot system?

Hands-on exploration Purpose: locate the structure that helps move water through celery stalk In a group of 2 design and set up an experiment in class using provided materials: Celery stalk Food coloring Beakers What is that structure? Draw a cross section of the celery stalk with the structure labelled

Review questions Do question 10, 11, 13, 14, 16, 17, 18, 20, 26, 27, 28, 29, 30 Page 80-81