9.3 Water/Sugar Transport in Plants p. 331 – 340 Water transport in xylem vessels Sugar transport in phloem vessels Uptake of water in roots

NO PUMP!!!! So what happens? Root pressure (osmosis) Cohesion/adhesion of water Transpiration Water enters the root due to osmosis Water moves up the xylem by cohesion/adhesion of water Water leaves the leaves through transpiration

Plant Vascular System Interconnected tubes Extend throughout plant Made of Xylem and Phloem = specialized TISSUES that transport water, minerals and sugars throughout the plant

Xylem Transports water and dissolved minerals from soil to leaves Start out as living cells then DIE Only the cell walls remain Cells linked end to end to make long tubes called XYLEM VESSELS

Xylem Vessels

Xylem Vessels

Several cell types: tracheids and vessel elements

Phloem Transport sugar (sap) from leaves to rest of plant

Phloem Vessels Live cells Arranged end to end in long connecting tubes

SPECIALIZED PHLOEM CELLS Sieve tubes and companion cells are specialized to carry sap (sugar water)

How does water move through the plant without a pump????

H20 absorption in roots Root hairs increase surface area for osmosis

1. Root Pressure Soil outside root is hypotonic to root cell so water enters cell by osmosis

2. Cohesion of Water Molecules Water sticks to other water molecules and forms a long chain of water molecules and pull each other along

3. Adhesion of Water Molecules Water sticks to inside walls of xylem

4. Transpiration of water out of leaves The water concentration is higher inside the leaf cells than outside (in air) Therefore, water moves from an area of high concentration (HYPOTONIC inside the cells) to an area of lower concentration (HYPERTONIC outside the cells) As water molecules move out, they “pull” the string of water molecules up through the xylem

Transpiration - animation http://techalive.mtu.edu/meec/module01/Transpiration.htm

VIDEO CLIPS: WATER TRANSPORT VIDEO 1 – Water transport in plants http://www.youtube.com/watch?gl=CA&hl=en&v=J1PqU B7Tu3Y VIDEO 2 – Vascular System http://www.youtube.com/watch?gl=CA&hl=en&v=w6f2BiFi XiM VIDEO 3 - Transpiration

PHLOEM TRANSPORT – SUGAR 1. Glucose is produced in the leaves (palisade cells and spongy mesophyll cells)

PHLOEM TRANSPORT 2. Sugars are actively transported from the LEAVES to the PHLOEM tissue What does “active transport” mean? a) b)

PHLOEM TRANSPORT 3. Once the sugars are “pumped” into the phloem tissue, the water follows due to osmosis After the sugars have left the phloem tissue, what is the tonicity of the palisade cells in relation to the phloem tissue? Which way does the water flow?

PHLOEM TRANSPORT 4. After the water flows INTO the phloem tissue, pressure is very high (ie – many particles in a confined space) Pressure gradients always try to reach equilibrium – therefore, the sap/water moves from high pressure to low pressure (ie – DOWN the phloem tubes to the roots) The pressure in the root cells is relatively low compared to the phloem tubes

PHLOEM TRANSPORT http://www.pearsoned.ca/school/science1 1/biology11/sugartransport.html

Malpighi’s Experiment – Tree Girdling In 1686, Italian scientist Marcello Malpighi wanted to find out what would happen if he removed a ring of phloem tissue from a tree.

He learned that a swelling developed above the ring and a sweet-tasting fluid oozed out of this swelling.

He also discovered that his trees became weakened and died soon after the ring was removed. Why did the trees die?

ASSIGNMENT: Check Your Understanding Page 340 #1 - 6