http://www. phschool. com/science/biology_place/labbench/lab9/xylem http://www.phschool.com/science/biology_place/labbench/lab9/xylem.html

Daily Warm-up Monday, April 21st What processes help move water up a tree? HW: -Read 42.4 Turn in: -Nothing

AP Lab 11: Transpiration What is transpiration? What do you know about transpiration?

Transpiration Evaporation of water from aerial parts of plants (not roots) Relies on hydrogen bonding of water molecules and the processes of cohesion and adhesion Water enters a plant through the root hairs, passes through the tissues of the root into the xylem, and travels up through the xylem vessels into the leaves Done by water potential (potential energy of water molecules). Water always moves from an area of high to low potential. Moevemnt is facilitated by osmosis, root pressure, and adhesion and cohesion of water molecules. Minerals are actively transported into the root. Accumulate and decrease the water potential. Water moves in by osmosis. Moves up xylem short ways due to root pressure. Upward pull due to transpiration. Due to cohesion and adhesion of water molecules. Transpiration begins with evaporation of water through the stomates. Moist air in these spaces have higher potential than those outside, causing evaporation. The moisture in the air spaces replaced by water from adjacent mesophyll cells by osmosis. Exerts a pull on the column of water molecules existing in the xylem all the way from the leaves to the roots.

What causes different rates of transpiration? Number of leaves Number of stomata Size of the leaf Presence of cuticle Light supply Temperature Relative humidity Wind Water supply

Adaptations for Reducing Water Loss Leaf structure Different photosynthesis: CAM plants Cuticle

Today’s Lab Working in groups Each group will receive one type of plant but must subject the plants to 4 conditions Wind (fan) Light (lamp) Room temperature (away from any drafts) Humidity (put within a bag that is misted with water) Will record each day’s mass in table at the beginning of class for remainder of week Demonstration

Steps Receive plant type, break into 4 separate plants Place plant’s roots in bag of water with 20-25 mL of water. Tie the bag tightly so that no air is able to escape. Weigh plant and record in table. Each person needs to make a table and record the group’s data. Set in proper conditions: fan, room temperature, humidity (bag placed over rest of plant), and light DEMO this

Daily Warm-up Monday, April 28th What type of graph might you use to display the change in % mass for each of the five days? HW: -Transpiration lab due 5/10 Turn in: -Nothing

Lab Notebook Title: Transpiration Lab Brief introduction Hypothesis- inquiry lab worksheet Methods (no materials required) Table Graph- line graph- one line for each treatment showing change in % mass each day Results- what did you find? Conclusion- why did you find what you did. Make sure to explain findings and say whether or not hypothesis is SUPPORTED. Include potential errors and future research. Questions from transpiration question sheet