Experimental volumetric determination of transpiration intensity

Summary

When a branch with leaves is inserted in a burette filled with water, the leaves are still constantly undergoing transpiration. The strength of transpiration varies with the type of plant and is influenced by external factors (temperature, humidity, light, etc.). The amount by which the volume of water in the buret decreases reflects the strength of transpiration.

Operation method

Experimental volumetric determination of transpiration intensity

Principle

When a branch with leaves is inserted in a burette filled with water, the leaves are still constantly undergoing transpiration. The strength of transpiration varies with the type of plant and is influenced by external factors (temperature, humidity, light, etc.). The amount by which the volume of water in the buret decreases reflects the strength of transpiration.

Materials and Instruments

Burette Rubber stopper Iron stand Small rubber tube Tube thermometer

Move

II. Instruments

1. titration tube (25 ml); 2. rubber stopper; 3. iron stand with iron clamp; 4. small rubber tube with clamp; 5. tube thermometer.

III. Experimental Procedure

1. Select a rubber stopper suitable for the mouth of the burette and make a small hole (the branch will not leak if inserted into the hole).

2. Select the appropriate rubber tube cut 3-4cm, tightly set on the tip of the burette with a clamp to tighten the rubber tube so that it does not leak.

3. Fill the burette with cold boiled water. Select a leafy branch of cotton or tobacco to be immersed in water and cut it so that air does not enter into the catheter. Insert this branch into the rubber stopper hole on the burette and extend it about 5 cm into the tube. Invert the burette so that it does not drip and adjust the water level in the tube to reach the highest scale.

4. First inverted buret fixed on the iron frame. Then put the iron frame in the environment of the measurement (such as different light intensity and wind speed), and then remove the rubber tube with the clamp, and note down the water level scale and the time when the water level starts to move.

5. Observe and record the water level scale at regular intervals. Determine the leaf surface temperature with a semiconductor spot thermometer and record it.

6. after 24 hours make a final observation and record, then cut off all the leaves from the branches and calculate the total leaf area on each branch using the weight method.

Common Problems

Transpiration intensity was calculated by the following formula:



Determination of leaf area is calculated as follows:

The total leaf area on the branch was determined by weighing a 100 cm weighing paper as W1, tracing each leaf cut from the branch on the weighing paper with a pencil according to its actual size, and then weighing it as W2:

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