Ap Biology Lab Write Up: Transpiration in Plants

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Adriana Rempson
Mrs. Steeger
AP Biology-7
10 October 2012
Transpiration in Plants
Abstract: Our group wanted to see how transpiration would happen in plants when they were in different environments. The different environments we used were humidity and room environments. We measured transpiration using the whole plant method. Our results showed that the plants in a humid environment had greater transpiration rates than the plants in the room environment. Introduction: Pants absorb and transport water, nutrients, and ions from the surrounding soil via osmosis, diffusion, and active transport. once water and dissolved nutrients have entered the root xylem, they are transported upward to the stems and leaves as part of the process of transpiration, with a subsequent loss of water due to evaporation from the leaf surface. Too much water loss can be detrimental to plants; they can wilt and die (AP Bio Big Idea 4). The transport of water upward from roots to shoots in the xylem is governed by differences in water potential, with water molecules moving from an area of high water potential to an area of low water potential. The movement of water through a plant is facilitated by osmosis, root pressure, and the physical and chemical properties of water. Transpiration creates a lower osmotic potential in the leaf, and the TACT mechanism describes the forces that move water and dissolved nutrients up the xylem (AP Bio Big Idea 4). Our controlled group was our plant that we left in a room environment. Our experimental group was the plant that we put in humidity. The purpose was to find how transpiration works in plants in different circumstances. We also wanted to see if transpiration caused plants to lose mass. Our experimental hypothesis is: If plants are in a humid environment, they will transpire more than plants in a room environment. Materials and Procedures:

Our materials were:
Chinese Cabbage, a clear container, graph paper, a pencil, a scale, a calculator, clear cellophane tape, clear nail polish, scissors and a microscope. The procedure was:
1. Calculate leaf surface area.
2. Make a wet mount of nail polish stomata peel to view leaf epidermis. After we did this first procedure, we had to design and conduct an investigation. The procedure for that was: 1. Design an experiment to investigate one of the aforementioned questions or one of your own questions to determine the effect of an environmental variable(s) on the rate of transpiration in plants. 2. Make a hypothesis/prediction about which environmental factors will have the greatest effect on transpiration rates. Be sure to explain your hypothesis. 3. Conduct your experiments and record data and any answers to your questions in your lab notebooks or as instructed by your teacher. Write down any additional questions that arose during this study that might lead to other investigations that you can conduct. Our class did Option 2, which was the Whole Plant Method.

The materials for this experiment were:
Small potted plant, one-gallon size plastic food storage bag without zipper, and some string. The procedure for that was:
1. Saturate the plant with water the day/night before beginning your investigation. 2. Carefully remove a plant from the soil/pot, making sure to retain as much of the root system and keeping soil particles attached to the roots. Wrap the root ball of plants in a plastic bag and tie the bag around the base so that only the leaves are exposed. Do not water your plant any more until you finish your experiment! You can also keep the plant in the plastic pot and place it in the plastic bag. 3. Determine the mass of each plant and then its mass for several days under your environmental conditions. 4. Record your data in your lab notebook or as instructed by your teacher. We then had to make some calculations when our experiment was complete. The procedure for our calculations was: 1. Determine the total surface area of the leaves in...
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