10 Transpiration

# 10 Transpiration - Experiment Transpiration 10 Water is...

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Biology with Calculators 10 - 1 Experiment 10 Transpiration Water is transported in plants, from the roots to the leaves, following a decreasing water potential gradient. Transpiration , or loss of water from the leaves, helps to create a lower osmotic potential in the leaf. The resulting transpirational pull is responsible for the movement of water from the xylem to the mesophyll cells into the air spaces in the leaves. The rate of evaporation of water from the air spaces of the leaf to the outside air depends on the water potential gradient between the leaf and the outside air. Various environmental factors, including those conditions which directly influence the opening and closing of the stomata, will affect a plant’s transpiration rate. This experiment will measure transpiration rates under different conditions of light, humidity, temperature, and air movement. The data will be collected by measuring pressure changes as the plant takes up water into the stem. 1. Figure 1 MATERIALS LabPro or CBL 2 interface metric ruler TI Graphing Calculator masking tape DataMate program 100-watt light source Vernier Gas Pressure Sensor plastic gallon size bag with twist tie utility clamps heater, small electric ring stand fan with slow speed plant cuttings aerosol spray container or plant mister plastic tubing clamps graph paper or Graphical Analysis dropper or Beral pipette razor blade or scalpel program

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10 - 2 Biology with Calculators Experiment 10 PROCEDURE 1. Position the ring stand, utility clamps, and Gas Pressure Sensor as shown in Figure 1. 2. Slip a plastic tubing clamp onto a 36-42 cm piece of plastic tubing as shown in Figure 2. Bend the tubing into a U shape and have another student use the 1.0-mL pipet to fill the tube with water. Add water to the tube until it is nearly full. Tap the tubing to expel any air bubbles that form inside the tube. 3. Select a plant which has a stem roughly the same diameter as the opening of the plastic tubing. Using a scalpel or razor blade, carefully cut the plant one inch above the soil. Place the plant under water against a hard surface and make a new cut at a 45° angle near the base of the stem.
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10 Transpiration - Experiment Transpiration 10 Water is...

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