Transpiration Lab Write Up Purpose/Question: How do environmental factors affect the transpiration process in plants? Research: Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. Transpiration is essentially evaporation of water from plant leaves. It occurs chiefly at the leaves while their stomata are open for the passage of CO2 and O2 during photosynthesis. Transpiration is not simply a hazard of plant life.

It is the "engine" that pulls water up from the roots to supply photosynthesis (1%-2% of the total), bring minerals from the roots for biosynthesis within the leaf, and cool the leaf. There are four different conditions that affect transpiration. They are wind, humidity, heat, and light. These four conditions may change rate of water loss through transpiration by either losing more water, or less. Plants have adapted to create the C4, and CAM pathway. In the both pathway the plant takes CO2 and stored.

Since CO2 can be taken up and stored for later use in photosynthesis, the plant reduces water loss by having less stomata open during the day since most of its needed CO2 has already been taken up at night. With the abundance of CO2 stored, the plant can then use the stored CO2 for photosynthesis and reducing photorespiration by reducing or completely eliminating accidental O2 uptake. Materials: 1) 5 small plants 2) Fish tank 3) Water spray bottle 4) Water 5) Heat lamp 6) Fan 7) Regular lamp 8) Mass weighter ) Place to record weight Procedure: Place Lamp, Heat lamp, fan, and fish tank in different areas where they won’t affect the other. Spray the fish tank with water and to make a humid environment and keep spraying everyday to ensure the tank is wet. Water all of your plants. Weigh all the plants on the original day, Monday, and record the weight. Place a plant in every condition. With the extra plant, place it in an area without a specific condition to use as a control plant. Do not water the plants the rest of the week.

Every day, weigh the plants and record its water loss for every plant. At the end of the week, create a chart for the amount of water loss and compare with the control plant. Data Table: Days | Monday| Tuesday| Wednesday| Thursday| Friday| Windy| 108. 2mg| 101. 1mg| 94. 1mg| 89. 7mg| 81. 7mg| Humidity| 103. 8mg| 103. 4mg| 103. 4mg| 103. 4mg| 103. 1mg| Light| 118. 8mg| 112. 1mg| 105. 0mg| 98. 4mg| 92. 9mg| Heat| 104. 3mg| 95. 8mg| 86. 8mg| 78. 7mg| 70. 1mg| Control| 115. 3mg| 115. 3mg| 115. 3mg| 115. 3mg| 115. 3mg| Analysis: Conclusion:

Environmental factors, such as heat, humidity, light and wind, affect the rate of transpiration by making the plant loose either more or less water. In conditions such as wind, when there is no breeze, the air surrounding a leaf becomes increasingly humid thus reducing the rate of transpiration. When a breeze is present, the humid air is carried away and replaced by drier air. The opposite of that is the humidity where the plant lost very little water. It lost very little water because its environment was wet, so the plant did not need to diffuse much water.

In heat, the air was hot and dry, so the plant lost water because it’s surrounding needed water to cool it down. Plants transpire more rapidly at higher temperatures because water evaporates more rapidly as the temperature rises. At 30°C, a leaf may transpire three times as fast as it does at 20°C. Finally, light lost a steady amount of water because plants transpire more rapidly in the light than in the dark. This is largely because light stimulates the opening of the stomata (mechanism). Light also speeds up transpiration by warming the leaf.

I expected these results because it makes sense and I researched before completing the experiment. Some avoidable errors that could have happened would be accidentally splashing water on a plant or putting the conditions too close together. Some unavoidable errors could be the weather outside. Even if the experiment is conducted inside, the hot summer air or cold winter air could drift in the room, affecting the plants transpiration rate. Some further investigations I would make are things such as whether the type of plant affects the rate, or if the type of heat lamp or fan will change the results as well.