• Potometer experiment results

    Potometer experiment results

    It is instead lost through transpiration, the evaporation of water through the leaf surface and stomata, and through guttation, which is the loss of water from the vascular tissues in the margins of leaves. There are three levels of transport in plants: uptake and release of water and solutes by individual cells, short distance cell to cell transport at tissue and organ levels, and long distance transport of sap by xylem and phloem at the whole plant level.

    The transport of water is controlled by water potential. Water will always move from an area of high water potential to an area with low water potential. This water potential is affected by pressure, gravity, and solute concentration. Water moves into the plant through osmosis and creates a hydrostatic root pressure that forces the water upward for a short distance, however, the main force in moving water is the upward pull due to transpiration.

    Transpiration decreases the water potential in the stele causing water to move in and pull upward into the leaves and other areas of low water potential. Pressure begins to build in the leaves, so to prevent downward movement, guttation occurs.

    Guttation occurs through leaf openings on the leaf margins called hydrathodes. Loss of water through transpiration can be facilitated by the opening and closing of the stomata depending on environmental conditions.

    potometer experiment results

    There are three types of cells in plants: parenchyma, sclerenchyma, and collenchyma. Parenchyma cells are the most abundant and are not specialized. They are found in the mesophyll of leaves, the flesh of fruits, the pith of stems, and the root and stem cortex. Sclerenchyma are elongated cells that make up fibers. They have thick secondary walls and the protoplasts often die as they grow older.

    They are used for support and are found in vascular tissue. Collenchyma cells are living at maturity and have a thickened secondary wall. In Lab 9A, all of the plants in this experiment will lose water through transpiration, but those affected by the heat sink and the fan will lose a larger amount of water due to the environmental conditions. This transpiration will pull water from the potometer into the plant.

    The structure and cell types of a stem cross-section can be observed under a microscope. The materials needed for this exercise were a pan of water, timer, a beaker containing water heat sinkscissors, 1-mL pipette, a plant cutting, ring stand, clamps, clear plastic tubing, petroleum jelly, a fan, lamp, spray bottle, a scale, calculator, and a plastic bag.

    The tip of the pipette was placed in the plastic tubing and they were submerged in a tray of water. Water was drawn into the pipette and tubing until no bubbles were left. The plant stem was cut underwater and inserted into the plastic tubing. Petroleum jelly was immediately placed around the tube edging to form an airtight seal around the stem. The potometer was allowed to equilibrate for ten minutes.

    The plant was exposed to a fan, which was placed one meter away and set on low speed. The time zero reading was recorded and then it was continually recorded every three minutes for 30 minutes. After the experiment, all the leaves were cut off the plant and massed by cutting a one cm2 box and massing it. A nut-and-bolt microtome was obtained and a small cup was formed by unscrewing the bolt.

    Lab 9 Transpiration Example 2 ap

    The stem was placed in the microtome and melted paraffin was poured around the stem. The paraffin was allowed to dry and the excess stem was cut off. The bolt was twisted just a little and then cut with the blade.Your browser seems to have Javascript disabled. We're sorry, but in order to log in and use all the features of this website, you will need to enable JavaScript in your browser. To measure the rate of transpiration we use a piece of equipment called a potometer.

    A potometer measures how factors such as light, temperature, humidity, light intensity and wind will affect the rate of transpiration. The potometer measures the amount of water lost from a leafy shoot by monitoring the rate at which an air bubble moves along the narrow tube as the leafy shoot sucks up water to replace the water lost by the transpiration of the plant. A potometer provides an indirect measurement of the transpiration rate — it measures how fast water is absorbed, which is related to how fast water vapour is being lost.

    It cannot measure how fast water vapour is being given off directly. As the leafy twig transpires, the air bubble moves to towards the plant. The quicker the air bubble moves, the faster the leafy twig is transpiring. To determine the effect of environmental conditions on transpiration rate using a simple potometer. A potometer measures the rate of transpiration by measuring the movement of water into a plant.

    The following experiment uses a simple hand made potometer. Learners will be divided into four groups as each group will investigate a different factor and then all the results can be shared at the end of the investigation. Each of the four groups that investigated different environmental conditions should contribute their results for the final analysis. Write down anything you observed about the plants, the plastic bags and the rate of water loss from the plant.

    What can you conclude regarding the rate of transpiration at different light intensities? Was there higher or lower water loss when you left the plant overnight compared to when you monitored it throughout the day?

    How can you improve this experiment to determine the effects of different light intensities on transpiration? In this experiment what are the key variables we are controlling for? Have we properly controlled for these? This is a lesson from the tutorial, Plant Systems and you are encouraged to log in or registerso that you can track your progress. Log In.

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    potometer experiment results

    Search Log In. Measuring Rate of Transpiration. To do 6 min read. Fact: A potometer provides an indirect measurement of the transpiration rate — it measures how fast water is absorbed, which is related to how fast water vapour is being lost. Potometer measures the rate of transpiration.A potometer is a piece of apparatus designed to measure water uptake in a leafy shoot.

    There are 2 types of potometer — the bubble potometer and the weight potometer. As water is transpired from the leaves, the shoot absorbs water from the potometer. The distance the air bubble moves in a certain period of time can be used to calculate the rate of water uptake.

    The apparatus is set up under water to prevent the entry of any unwanted air bubbles. The junction between the shoot and potometer is sealed usually with petroleum jelly to prevent any air leaks. The apparatus is reset using the reservoir or syringe so that water uptake in the same leafy shoot can be measured — making the investigation more reliable.

    It can also be reset in order to investigate the effect of a different environmental factor e. When investigating the effect of an environmental factor it is important that all others factors are kept constant to ensure the experiment is valid.

    The apparatus and plant is weighed and then left for a period of time. When reweighed the amount of water lost by the plant can be calculated. A top pan balance that measures to two decimal points provides great accuracy. A potometer can measure the amount of water taken up by a leafy shoot but cannot provide an accurate value for the amount of water transpired, because some water will be used in photosynthesis and to provide turgor.

    Potometer A potometer is a piece of apparatus designed to measure water uptake in a leafy shoot. Bubble potometer As water is transpired from the leaves, the shoot absorbs water from the potometer. Weight potometer The apparatus and plant is weighed and then left for a period of time. Uses of water A potometer can measure the amount of water taken up by a leafy shoot but cannot provide an accurate value for the amount of water transpired, because some water will be used in photosynthesis and to provide turgor.The potometric results shown in Fig.

    Since the plant draws up water as it loses it by transpiration, you are able to measure the rate of transpiration. Wilting and Guttation This section explains to the learners how excessive loss of water can cause plants to wilt and lose some of their structural support. The potometer responds to a change in water use as little as 1-mL. Potometer is an instrument used to find the rate of transpiration.

    This pushes the air bubble to the left providing a precise measure of the volume of water used. Using a potometer to measure transpiration in biology. Why and how will you measure the area of leaves used? In my case, the enviornmental factor was wind, which is the factor that will mosts increase the rate.

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    Transpiration - Potometer Practical no rating 0 customer reviews. Suggest and explain the ways in which sieve cells are adapted for mass transport. However, the universality of the original calibration has been questioned and, in many cases, proved to be inaccurate. If more plants were used or the experiment was repeated even more, the investigation's reliability would have increased. Despite efforts to reduce runoff, recent studies have predicted a drastic increase in pollution due to runoff which introduces the danger of manmade salts entering water tables.

    The student took several measurements during each experiment and calculated the mean rate of movement of the gas bubble. To design and conduct an experiment to explore other factors, including different environmental variables, on the rate of transpiration. The base of the stem is covered with cellophane to ensure that moisture from the soil does not affect the results of the experiment. Each group should compare their results with the rest of the class.

    This may be achieved by fitting a flexible material to the neck of the potometer that holds the shoot to act as a seal e. This information will be used to estimate your plants leaf surface area in step 13 below.

    Investigating Transpiration in Plants Hypothesis I predict that the plant will loose more water through transpiration when the fan is closer to the plant. The type of potometer you will use consists of a ringstand with a burette clamp which supports a leaf connected to a pipet by a piece of rubber tubing.

    For my experiment I chose 3 minutes; To reset the bubble open the reservoir slowly pushing the bubble back to the start of the potometer; When your investigation is complete, work out the leaf area of you shoot by drawing around each leaf on graph paper and counting up the squares; ResultsFor a cut shoot in a flask, place plastic film over the flask opening to prevent evaporation from the water surface.

    I think that the distance of the fan from the plant and the water loss are inversely proportional, that is the greater the distance between fan and plant, the smaller the percentage loss of mass. The instrument was tested by monitoring the water uptake rates of 3-week-old tobacco seedlings and detached tobacco plant organs, following exposure to changes in light intensity and addition of NaCl, HgCl2 or abscisic acid to the root medium.

    The user has full control of various experimental parameters so that he or she can carry out the experiment on their PC just as if they were remotely controlling the real experiment.This section explains how various environmental factors can change the rate of transpiration, and also examines how the structure of the leaves has adapted to minimise this water loss.

    Learners will need to understand the factors that affect the transpiration rate such as temperature, light intensity, wind and humidity. Simple experiments can be conducted to demonstrate these factors.

    Crockett Science AS Biology Activity 15 Using a Potometer to measure Water Uptake

    Transpiration is a process that involves loss of water vapour through the stomata of plants. Transpiration is thought to be a 'necessary cost or evil' to allow the plant to absorb water from the soil. It is an inevitable process. Turgidityor turgor pressure, refers to the water content of cells and how this lends structural support to the plant.

    When cells absorb water, the vacuoles fill up and the cytoplasm increases, pushing against the cell membranes, which in turn push against the rigid cell walls. This makes the cells rigid, or turgid. Transpirational pull : results from the evaporation of water from the surfaces of the mesophyll layer in the leaf to the atmosphere, through the stomata. Evaporation of water from the leaves surface causes a negative pressure suction force in the xylem that pulls water from the roots and soil.

    This results in water being drawn up the xylem vessel. Transpirational pull draws water from the roots to the leaves because of the effects of capillary action. The primary forces that create the capillary action are adhesion and cohesion. Adhesion is the attraction that occurs between water and the surface of the xylem, and cohesion is the attraction between water molecules. We will revisit transpirational pull and capillarity later in the chapter when we examine how water is transported in the plant.

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    Capillary action occurs when the adhesion of water molecules to the walls of the vessel is stronger than the cohesive forces between the water molecules. Have you ever seen fluid in a drinking straw move higher than the level of the fluid in the glass? This happens due to capillary action. The narrower the straw, the greater the capillary action, and therefore, the higher the fluid will rise in the straw.

    Cohesion refers to the intermolecular, attractive forces that hold molecules in solids and liquids together. Imagine a drop of water on a waxy surface like wax paper.The causes of water uptake are photosynthesis and transpiration.

    It is assumed that this is due to the cutting taking in water which in turn is necessary to replace an equal volume of water lost by transpiration. Here it is assumed that any loss in mass is due to transpiration. There are two main types of potometers: the bubble potometer as detailed belowand the mass potometer.

    The mass potometer consists of a plant with its root submerged in a beaker. This beaker is then placed on a digital balance; readings can be made to determine the amount of water lost by the plant. The Limitations in using the potometer: Introducing the air bubbles is not very easy. The twig may not remain for a long time. Any change in the outside air temperature may affect the position of the air bubble on the capillary tube. Potometer do not measure the lost water during the transpiration but measures the water uptaken by the cut shoot.

    Set up the conditions of the experiment, such as alterations to lighting placing the plant in bright light or shadowwind directing a fan at the plantand humidity.

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    When a twig is cut from a plant, it should be immediately put under water only the cut portion. Then, a small part is cut under water. This prevents entry of air into the xylem vessels. The conditions of the potometer, other than the alteration that is being tested, should not be changed during a test, as outside conditions such as temperature determine water uptake. The potometer does not measure the rate of transpiration accurately because not all of the water that is taken by the plant is used for transpiration water taken might be used for photosynthesis or by the cells to maintain turgidity.

    The potometer measures the rate of uptake of water. To measure transpiration rate directly, rather than the rate of water uptake, utilize a scientific instrument which quantifies water transfer at the leaves.

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    From Wikipedia, the free encyclopedia. This article needs additional citations for verification.Transpiration cannot be measured directly so instead it is measured indirectly, either by measuring the decrease in mass of a plant due to water loss, or by measuring the volume of water absorbed.

    The decrease in mass of a plant due to transpiration can be investigated using the following method:. The results are shown here.

    Measuring Rate of Transpiration

    What conclusions can you make from the results above? Give two pieces of evidence to support your conclusion. You can conclude that most transpiration happens from the lower surface of the leaf:. Transpiration cannot be measured directly as some of the water will be used in photosynthesis. The rate of transpiration can be calculated by measuring the distance travelled by an air bubble in a capillary tube over a given time. The faster the bubble moves, the greater the rate of water uptake — and so the greater the assumed rate of transpiration.

    The potometer is set up underwater to avoid unwanted air bubbles in the xylem of the plant which may disrupt the transpiration stream. All joints are sealed with petroleum jelly to make it as airtight as possible.

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    The faster the bubble moves, the greater the rate of water uptake — and so the greater the rate of transpiration. The rate of transpiration is affected by several factors, including:.

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    This table shows the effects of different factors on the rate of transportation. Investigating transpiration Transpiration cannot be measured directly so instead it is measured indirectly, either by measuring the decrease in mass of a plant due to water loss, or by measuring the volume of water absorbed.

    Decrease in mass The decrease in mass of a plant due to transpiration can be investigated using the following method: Select four leaves of similar size. Cover the surfaces of the leaves with petroleum jelly as shown in the diagram. Record the initial mass of the leaves. After 24 hours record the mass of the leaves and calculate the percentage decrease in mass. Reveal answer up. Upper only. Lower only. Evaporation and diffusion are faster at higher temperatures.

    Humidity decreases the concentration gradient between the inside and outside of the leaf — this reduces transpiration.

    potometer experiment results

    Wind speed. Moving air removes water vapour, increasing the rate of diffusion of water vapour from the leaf. Light intensity. The stomata open wider to allow more carbon dioxide into the leaf for photosynthesis.


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