Name: Assessing Transpiration Rates using Potometer - Concept
Uploaded: 2019-01-29T11:04:45.000Z
Duration: 3 min 58 s
Channel: JoVE

K12 Standards

new-york-state-science-learning-standards

New York State Science Learning Standards

High School

Life Science

Structure and Function

HS-LS1-2.

Transpiration

lab manual sub articles

Lab Manual Sub Articles

<p>Plants are found in almost every ecosystem in the world from deserts, to temperate forests, and down to the bottom of the sea. As a consequence of natural selection plants have evolved a stunning diversity of adaptations to deal with different environmental challenges. One of the key challenges plants face is maintaining proper hydration. Water is a critical resource that they depend upon for photosynthesis, structural support, and the transportation of nutrients and other important molecules. One way that plants can control their water balance is by regulating a process known as transpiration, which is essentially the evaporation of water from the aerial parts of a plant. This loss of water occurs primarily from pores on the leaves called stomata. But how does the water get here? </p>

<p>To answer this question let&#39;s look more closely underground. Here water enters the plants roots by osmosis then moves all the way up to the leaves through a vascular tissue called xylem. This channel of water is known as the transpiration stream. Because water molecules stick to each other and to the xylem walls, when it evaporates from stomata water from lower in the transpiration stream is pulled upwards to take its place&#8230;resulting in upward flow from the roots. Now let&#39;s take a closer look at a stoma. Each stomatal pore is bordered by two guard cells that can expand to open the pore and contract to close it. Plants open their stomata to take in carbon dioxide for photosynthesis and to release oxygen gas. Loss of water through transpiration is an unavoidable side effect of this process. </p>

<p>This trade off presents a particular challenge for plants living in arid environments and so they have evolved strategies to reduce their water loss as much as possible. One way they can do this is by growing leaves with small surface areas, presenting a small area over which transpiration can occur. This is why the leaves of desert plants such as creosote are relatively small. But going one step further plants from arid environments also have fewer stomata per unit area on their leaves allowing them to minimize water loss through transpiration. </p>

<p>In contrast plants that inhabit environments with plentiful water like rain forests can afford to lose a lot of water through transpiration. Such plants like this taro for example often develop leaves with large surface areas that increase their capacity to intercept light to fuel photosynthesis. These plants also have a high density of stomata compared to plants from arid habitats allowing them to maintain high rates of photosynthesis and to support large leaves and stems. </p>

<p>In this lab you&#39;ll measure transpiration rates and examine the frequency of leaf stomata in diverse plant species to reveal how plants from different habitats solve the problem of regulating transpiration.</p>


transpiration

<h4>Background</h4>

<p>All living organisms must carry out a set of basic functions in order to maintain themselves. One of these processes involves the transportation of materials throughout the organism. Therefore, organisms need to exchange materials with the environment, which can be seen on the small scale of cells transporting protein and other materials among one another or on a larger scale such as the water cycle, where water is continuously moving on, above, and below the surface of Earth. In both examples, the movement of materials from one area to another is a dynamic process regulated by both environmental and biological variables.</p>

<h4>Transpiration: A Driver for Water Transport</h4>

<p>Vascular plants, from the smallest ferns to the giant redwoods of California, transport water and the water-soluble materials throughout the plant by a system of bundles of vascular tissues that run from the roots to the tips of the plant. Specifically, water and nutrients are absorbed by the root hairs and transferred by osmosis into the plant&#39;s xylem, one of the two large vascular systems found in plants. Water is then transported to the tallest point of the plant and outwards into the leaves where photosynthesis takes place. Interestingly, only 1% of the water taken up by the plants is used for photosynthesis. The other 99% of the water is not directly used by the plant and is lost from the plant due to evaporation or guttation, also known as transpiration. Evaporation is the movement of water to the air, where guttation specifically refers to secretion of droplets of water from the pores of plants. Both processes combined make up transpiration in plants.</p>

<p>The leaves of plants play an important role in releasing the by-products of photosynthesis through their stomata, which are openings that allow the exchange of materials between the plant and the atmosphere. The stomata are bordered by guard cells, which regulate when the stomata open and close. This is the active site where the majority of water is lost due to evaporation, as well as the site where gases are exchanged with the atmosphere. Although it might at first seem like a bad strategy for a plant to lose water due to evaporation, it is inevitable in order to maintain the transportation of materials and water in the plant while maximizing gas input. Transpiration creates a lower concentration of water, thus a lower osmotic potential in the leaf. These differences in water concentration are responsible for driving the movement of water into the plant&#39;s leaves and also in releasing water into the atmosphere.</p>

<p>Water potential drives the uptake of water from the root hairs and also in transporting water to the tips of leaves. Water potential is the measure of the free energy of water, where water molecules move from areas of higher water potential to areas of lower water potential. When evaporation is high in leaves, this creates areas with lower water potential, or areas with less water, so water from the roots and stem is driven to the leaves. The cohesion and adhesion properties of water molecules enable this movement of water. Cohesion is the attraction of water molecules to each other and adhesion is the attraction of water molecules to other materials, such as the xylem walls. When water molecules exit through stomata, they pull water molecules underneath, causing water to move towards lower water potential.</p>

<h4>Environmental Factors</h4>

<p>Plant species differ widely in their physical characteristics as well as in their morphology and functions in the ecosystem. These differences among plant species and also similarities among distantly related plant species are shaped over time through evolution and more specifically by selection imposed by herbivores, pollinators, and other climatic and environmental factors. Therefore, differences in transpiration rates is influenced by both the environment and the plant species itself. The main environmental factors that drive the transpiration rate is temperature. Higher temperatures increase the rate of transpiration because water is lost via evaporation more quickly. Plants living in hot environments are prone to losing more water than plants located in cooler climates. Factors such as water availability, wind, sunlight, and others also help influence the transpiration rate in plants.</p>

<p>Plants living in hot and arid environments have specific adaptations that help them control water loss, such as the ability to store or conserve water. A group of plants in these environments, also known as Crassulacean acid metabolism or CAM plants, have evolved strategies, such as only opening their stomata for gas exchange at night in order to reduce water loss<sup>1</sup><strong>. </strong>Some other plant features specific to arid environments include reduced leaf surface area, fewer stomata, or having hairs on their leaves to conserve water. However, there is a tradeoff with limiting water loss and having an optimal rate of transpiration needed for photosynthesis. The rate of photosynthesis relates to a plant&#8217;s rate of growth and energy acquisition, which is related to rate of water intake and loss, so it is extremely important for plants to be able to balance this tradeoff. On the other hand, in environments where water is not a limiting resource, such as tropical rainforests, plants face different selective pressures that drive differences in transpiration rates. In these environments, natural selection may instead favor plant species that can transport water more quickly in order to outgrow their competing neighbors or grow tall enough to avoid being eaten by herbivores.</p>

<h4>Assessing Transpiration Rates</h4>

<p>The transpiration rates can be assessed indirectly by using a potometer, which is a device that measures the rate of water uptake of a leafy plant. The assumption of the potometer measurement is that transpiration will cause the water uptake, the amount of which can be quantified. In addition, scientists can determine relative transpiration rates of plants by observing the leaf structures, such as the sizes and numbers of stomata per unit area.</p>

<p>Examining plant transpiration rates can teach us not only how plants adapt to different environments, but can also provide information about how to best grow crops in different environmental conditions to increase food production and adjust our use of plants to adapt to global climate change and population growth. For example, transpiration rates are altered by global warming and other causes and can affect the global water cycle, which in turn can affect ecosystems as well as human populations<sup>2</sup>. Thus, understanding these changes would be necessary to develop strategies to remediate their negative effects. Moreover, studying transpiration rates of different crops can help identify crops with high water-use efficiency to increase the food production per unit of water and reduce the need for irrigation<sup>3</sup>.</p>

<h4>References</h4>

<ol class="references">
	<li><strong>IP, TIng.</strong> Crassulacean acid metabolism. <em>Ann REv Plant Physiol. </em>1985, Vol. 36, 595-622.</li>
	<li><strong>Schlesinger WH, Jasechko S.</strong> Transpiration in the global water cycle. <em>Agricultural and Forest Meteorology. </em>2014, Vols. 189-190, 115-7.</li>
	<li><strong>Coupel-Ledru A, Lebon E, Christophe A, Gallo A, Gago P, Pantin F, Doligez A, Simonneaua T.</strong> Reduced nighttime transpiration is a relevant breeding target for high water-use efficiency in grapevine. <em>PNAS. </em>2016, Vol. 113, 32: 8963-8.</li>
</ol>


Assessing Transpiration Rates using Potometer - Concept

Background

All living organisms must carry out a set of basic functions in order to maintain themselves. One of these processes involves the ...

Education

JoVE Lab Manual

Biology

Cellular Processes

photosynthesis

Photosynthesis

Autotrophs

Almost all living organisms on Earth depend on photosynthesis, which is the process that converts sunlight energy into a simple sugar called ...

cellular respiration

Cellular Respiration

Autotrophs and Heterotrophs

Living organisms require a continuous input of energy to maintain cellular and organismal functions such as growth, repair, ...

cell division

Cell Division

Cell division is fundamental to all living organisms and required for growth and development. As an essential means of reproduction for all living things, ...

enzyme activity

Enzyme Activity

Biological Catalysts

All living organisms continuously perform numerous biochemical reactions to sustain their presence. Most of these reactions require ...

cellular processes

Learn how transpiration moves water through plants, how stomata and guard cells control loss, and how temperature and plant traits affect the rate.

Water Movement in Plants | JoVE K12

Georgia Standards of Excellence

9-12

Botany

SBO1.

Transport

Prepare a high school transpiration lab with four plant species, 5 mL pipettes, tubing, water, clamps, and stomata slide materials.

Leaf Water Loss Lab Prep | JoVE K12

Compare transpiration rates in four leaf species using a potometer, leaf area measurements, and stomata counts to explore plant adaptation.

Measuring Leaf Water Loss in Plants | JoVE K12

<ul><li><a href="#" data-time="5">Comparing Transpiration Rates of Leaves
</a></li></ul>

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Comparing Transpiration Rates of Leaves
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">Before beginning the experiments, gather leaves from four plant species that represent different ecological strategies, so that you have enough for one set of leaves per student. NOTE: If leaf-bearing plants are not available locally, an alternative is to grow the plant species of interest in the laboratory, or to purchase plants from a gardening store.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">Next, cut lengths of rubber tubing to make roughly 50 cm sections and place one piece alongside a 5 mL pipette at each student workstation.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Then, set out a bucket or tray of water and ensure students have access to the appropriate clamps and stands.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Finally, set out bottles of clear nail polish, as well as clear tape and clean microscope slides for the stomata exercise.
</div></li></ul></li></ol>

<div class="section-question"><h4 class="question-sect">What is transpiration?</h4><p>Transpiration is the process of plants in which they absorb, distribute and subsequently release water. Evaporation is the movement of water to the air, while guttation specifically refers to secretion of droplets of water from the pores of plants. Both processes combined make up transpiration in plants.
</p></div><div class="section-question"><h4 class="question-sect">What is the mechanism of transpiration?</h4><p>Water potential drives the uptake of water from the root hairs and also in transporting water to the tips of leaves. When evaporation is high in leaves, this creates areas with lower water potential, or areas with less water, so water from the roots and stem is driven to the leaves. 
</p></div><div class="section-question"><h4 class="question-sect">Why do plants transpire?</h4><p>Transpiration allows carrying water and nutrients towards the photosynthesizing parts of the plant, and thus allows plant growth. 
</p></div><div class="section-question"><h4 class="question-sect">How do plants in different environments regulate transpiration?</h4><p>Some plants in hot and arid environments open their stomata for gas exchange at night in order to reduce water loss. Some others have reduced leaf surface area, fewer stomata, or hairs on their leaves. On the other hand, in humid environments such as rainforests, plants transpire quickly in order to outgrow their competing neighbors or grow tall enough to avoid being eaten by herbivores.
</p></div><div class="section-question"><h4 class="question-sect">Why study transpiration?</h4><p>We can learn how plants adapt to different environments. Moreover, we can study how current environmental changes affect plants and their ecosystem. Moreover, we can also use transpiration studies to identify crops that can grow in a specific climate.
</p></div>

Assessing Transpiration Rates using Potometer - Prep

Comparing Transpiration Rates of Leaves
ExpandBefore beginning the experiments, gather leaves from four plant species that represent different ecological ...

<p>Before beginning the experiments, gather leaves from four plant species that represent different ecological strategies, so that you have enough for one set of leaves per student. If leaf bearing plants are not available locally, an alternative is to grow the plant species of interest in the laboratory, or to purchase plants from a gardening store. Next, cut lengths of rubber tubing to make roughly 50 centimeter sections and place one piece alongside a five milliliter pipette at each student workstation.</p><p>Then set out a bucket or tray of water and ensure students have access to the appropriate clamps and stands. Finally, set out bottles of clear nail polish, as well as clear tape and clean microscope slides for the stomata exercise. Please take time to review the material list and the student protocol video to be fully prepped for the lab.</p>

<ul><li><a href="#" data-time="5">Comparing Transpiration Rates of Leaves
</a></li><li><a href="#" data-time="319">Results
</a></li></ul>

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Comparing Transpiration Rates of Leaves
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">To begin the experiment to measure the transpiration rates of leaves from different plant species, you will first create a tool called a potometer, using a piece of plastic tubing and 5 mL calibrated pipette.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">To assemble the device, simply attach the rubber tubing to the tip of the pipette.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Then, submerge the device into a bucket of water and move the pipette around under the water to fully fill the tube, taking care not to create bubbles.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Next, cap the open end of the tube with a pipette bulb to keep the water in.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Now, taking care not to spill water from the potometer, use a clamp and stand to hold the capped end of the pipette around 1 - 3 inches below the pipette bulb.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">Then, use a second clamp attached lower on the same stand to secure the open end of the rubber tubing.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Next, use a transfer pipette or dropper to remove water from the open end of the tubing until the water level in the pipette portion of the potometer rests at the zero line. HYPOTHESES: In this experiment, the experimental hypothesis might be that leaves from plant species more adapted to hotter or arid environments will have lower transpiration rates than those from humid or wet regions. The null hypothesis would be that leaves of the different plant species will not differ in their transpiration rates.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">To begin the experiment, carefully use scissors to cut the end of the petiole, or stalk, of the first leaf and then insert the leaf into the tubing.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Then, place a layer of lubricant around the area where the plant stem and rubber tubing meet to make a watertight seal.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Next, remove the pipette bulb and taking care not to disturb the setup, let the experiment run for the appropriate experimental period, typically 30 - 60 minutes.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">At the end of the allocated time, record the level of the water in the pipette, noting how much the level dropped in milliliters.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Then, refill and reset the potometer water level to zero, and then repeat the procedure for each of the remaining test leaves until the transpiration rates of all four leaves have been measured.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Next, to determine the surface area of the leaf samples, lay each leaf on a blank piece of paper and carefully trace the outlines.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Then, cut the outlines out and record the mass of each tracing.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Finally, cut out and weigh one four by four centimeter square of the same type of paper used to make the leaf tracings. This will act as a reference with known area and weight.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Next, you will need to quantify the number of stomata per unit area on each leaf. To do this, first prepare a slide mount by painting at least one square centimeter of the underside of each leaf with clear nail polish. IMPORTANT: Ensure you paint the bottom of the leaf, since the majority of the stomata are located there. 
</div></li><li data-sub-note-item="1-17"><div class="lab-step">When the nail polish is completely dry, carefully press a small piece of cellophane tape directly onto each patch and then gently peel off the tape to remove the painted on polish. NOTE: Use a piece of tape that is smaller than the microscope slide. 
</div></li><li data-sub-note-item="1-18"><div class="lab-step">Then, place each impression and tape onto a separate, clean microscope slide. HYPOTHESES: In this exercise, the alternative hypothesis could be that the leaves of the plants adapted to drier environments will have fewer stomata per unit area than the leaves of plants adapted to wetter environments. The null hypothesis might be that all plants species will have an equal number of stomata per unit area.
</div></li><li data-sub-note-item="1-19"><div class="lab-step">To observe each impression under the microscope, first use a low magnification to find areas of the leaf impression that contain stomata. These will appear as darker dots or impressions.
</div></li><li data-sub-note-item="1-20"><div class="lab-step">Then, switch to a higher magnification, keeping the sample viewing window centered on the stomata-containing area.
</div></li><li data-sub-note-item="1-21"><div class="lab-step">Draw and label your observations, making sure to label each sketch with the plant species.
</div></li><li data-sub-note-item="1-22"><div class="lab-step">Then, count and record the number of stomata in the field of view. You should perform this count a total of four times in four different areas of the leaf impression, and then determine the average number of stomata per counted area on the leaf.
</div></li><li data-sub-note-item="1-23"><div class="lab-step">To calculate the number of stomata per mm<sup>2</sup>, place a transparent plastic ruler on the microscope stage under the objective and measure the diameter of the field of view.
</div></li><li data-sub-note-item="1-24"><div class="lab-step">You can then use this number, the diameter or D, to calculate the area of the field of view in mm<sup>2</sup>.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">First, calculate the surface area of the 4x4 cm paper square to obtain the number of square centimeters.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Then, divide the weight of the paper square by the number of centimeters squared it covers to obtain the weight of 1 cm<sup>2</sup> of paper.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Finally, to calculate the surface area of each leaf, divide the weight of the leaf tracing by the weight of 1 cm<sup>2</sup> of paper. This will give you leaf area in centimeters squared.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">You should now convert this number to meters squared, the standard unit used for calculating transpiration rate.
</div></li><li data-sub-note-item="2-5"><div class="lab-step">To calculate the transpiration rate for each leaf, divide the total water loss you measured in the potometer in mL by the time the experiment was run for in minutes.
</div></li><li data-sub-note-item="2-6"><div class="lab-step">Then, divide this by the surface area of the leaf in m<sup>2</sup>.
</div></li><li data-sub-note-item="2-7"><div class="lab-step">Make a bar graph with the four different leaf species on the X axis, and their corresponding transpiration rates on the Y axis. Do these rates appear different?
</div></li><li data-sub-note-item="2-8"><div class="lab-step">Next, add a second Y axis to your chart and plot the average number of stomata per millimeter squared for each leaf that was observed under the microscope. Do you see a correlation between transpiration rate and number of stomata? If so, does this seem to have any relationship to the native environment the tree would typically inhabit?
</div></li></ul></li></ol>

Assessing Transpiration Rates using Potometer - Procedure

Comparing Transpiration Rates of Leaves
ExpandTo begin the experiment to measure the transpiration rates of leaves from different plant species, you will ...

<p>To begin the experiment to measure the transpiration rates of leaves from different plant species, you will first create a tool called a potometer, using a piece of plastic tubing and five milliliter calibrated pipette. To assemble the device, simply attach the rubber tubing to the tip of the pipette. Then, submerge the device into a bucket of water and move the pipette around under the water to fully fill the tube, taking care not to create bubbles.</p><p>Next, cap the open end of the tube with a pipette bulb to keep the water in. Now, taking care not to spill water from the potometer, use a clamp and stand to hold the capped end of the pipette around one to three inches below the pipette bulb. Then, use a second clamp attached lower on the same stand to secure the open end of the rubber tubing.</p><p>Next, use a transfer pipette or dropper to remove water from the open end of the tubing until the water level in the pipette portion of the potometer rests at the zero line. In this experiment, the experimental hypothesis might be that leaves from plant species more adapted to hotter or arid environments will have lower transpiration rates than those from humid or wet regions. The null hypothesis would be that leaves of the different plant species will not differ in their transpiration rates.</p><p>To begin the experiment, carefully use scissors to cut the end of the petiole, or stalk, of the first leaf and then insert the leaf into the tubing. Then, place a layer of lubricant around the area where the plant stem and rubber tubing meet to make a watertight seal. Next, remove the pipette bulb and taking care not to disturb the setup, let the experiment run for the appropriate experimental period, typically 30 to 60 minutes.</p><p>At the end of the allocated time, record the level of the water in the pipette, noting how much the level dropped in milliliters. Then, refill and reset the potometer water level to zero, and then repeat the procedure for each of the remaining test leaves until the transpiration rates of all four leaves have been measured. Next, to determine the surface area of the leaf samples, lay each leaf on a blank piece of paper and carefully trace the outlines.</p><p>Then cut the outlines out and record the mass of each tracing. Finally, cut out and weigh one four by four centimeter square of the same type of paper used to make the leaf tracings. This will act as a reference with known area and weight.</p><p>Next, you will need to quantify the number of stomata per unit area on each leaf. To do this, first prepare a slide mount by painting at least one square centimeter of the underside of each leaf with clear nail polish. When the nail polish is completely dry, carefully press a small piece of cellophane tape directly onto each patch and then gently peel off the tape to remove the painted on polish.</p><p>Then, place each impression and tape onto a separate, clean microscope slide. In this exercise, the alternative hypothesis could be that the leaves of the plants adapted to drier environments will have fewer stomata per unit area than the leaves of plants adapted to wetter environments. The null hypothesis might be that all plants species will have an equal number of stomata per unit area.</p><p>To observe each impression under the microscope, first use a low magnification to find areas of the leaf impression that contain stomata. These will appear as darker dots or impressions. Then, switch to a higher magnification, keeping the sample viewing window centered on the stomata-containing area.</p><p>Draw and label your observations, making sure to label each sketch with the plant species. Then, count and record the number of stomata in the field of view. You should perform this count a total of four times in four different areas of the leaf impression, and then determine the average number of stomata per counted area on the leaf.</p><p>To calculate the number of stomata per square millimeter, place a transparent plastic ruler on the microscope stage under the objective and measure the diameter of the field of view. You can then use this number, the diameter or D, and the formula shown to calculate the area of the field of view in millimeters squared. First, calculate the surface area of the four by four centimeter paper square to obtain the number of square centimeters.</p><p>Then, divide the weight of the paper square by the number of centimeters squared it covers to obtain the weight of one centimeter squared of paper. Finally, to calculate the surface area of each leaf, divide the weight of the leaf tracing by the weight of one centimeter squared of paper. This will give you leaf area in centimeters squared.</p><p>You should now convert this number to meters squared, the standard unit used for calculating transpiration rate. To calculate the transpiration rate for each leaf, divide the total water loss you measured in the potometer in milliliters by the time the experiment was run for in minutes. Then, divide this by the surface area of the leaf in meters squared.</p><p>Make a bar graph with the four different leaf species on the X axis, and their corresponding transpiration rates on the Y axis. Do these rates appear different? Next, add a second Y axis to your chart and plot the average number of stomata per millimeter squared for each leaf that was observed under the microscope.</p><p>Do you see a correlation between transpiration rate and number of stomata? If so, does this seem to have any relationship to the native environment the tree would typically inhabit?</p>

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10647.jpg

Cell Structure

Background
Cells represent the most basic biological units of all organisms, whether it be simple, single-celled organisms like bacteria, or large, ...

Visualizing Onion and Cheek Cells
ExpandImmediately before the experiment, wash and peel onion bulbs for the class.
Remove the entire brown outer skin and ...

Visualizing Onion and Human Cells
ExpandIn this experiment you will prepare different types of cells from a plant and animal, onion and human ...

What are Cells?

Cell Diversity

The concept of a cell started with microscopic observations of dead cork tissue by Robert Hooke in 1665. Hooke coined the term &#34;cell&#34; based on the ...

Cytoplasm

The cytoplasm consists of organelles and a framework of protein scaffolds called the cytoskeleton suspended in an aqueous solution, the cytosol. The ...

The Nucleus

The nucleus is a membrane-bound organelle that acts as a control center in a eukaryotic cell. It contains chromosomal DNA, which controls gene expression ...

The Central Dogma

The DNA Helix

Nucleic Acids

DNA as a Genetic Template

Structure of a Gene

A gene is the fundamental unit of heredity. Every individual has two copies of each gene, one inherited from each parent. Although most people contain the ...

Chromosome Structure

Base-pairing and DNA Repair

What is Gene Expression?

A gene is a stretch of DNA that serves as the blueprint for functional RNAs and proteins. Since DNA is comprised&#160; of nucleotides and proteins are ...

RNA Structure

The basic structure of RNA consists of a string of ribonucleotides attached by phosphodiester bonds. Although most RNA is single-stranded, it can form ...

Types of RNA

Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs perform diverse ...

Transcription

Transcription is the synthesis of RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. ...

Translation

Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes ...

Ribosomes

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that ...

Protein and Protein Structures

Proteins: From Genes to Degradation

From DNA to Protein

The flow of genetic information in cells from DNA to mRNA to protein is described by the central dogma, which states that genes specify the sequence of ...

Protein Folding

Proteins are chains of amino acids linked together by peptide bonds. Upon synthesis, a protein folds into a three-dimensional conformation, critical to ...

An Overview of Gene Expression

Gene expression is the complex process where a cell uses its genetic information to make functional products. This process is regulated at multiple ...

an-introduction-to-caenorhabditis-elegans

An Introduction to <em>Caenorhabditis elegans</em>

Caenorhabditis elegans is a microscopic, soil-dwelling roundworm that has been powerfully used as a model organism since the early 1970&rsquo;s.  It was ...

An Overview of Genetic Analysis

An organism&#8217;s physical traits, or phenotype, are a product of its genotype, which is the combination of alleles (gene variants) inherited from its ...

An Introduction to Cell Death

Necrosis, apoptosis, and autophagic cell death are all manners in which cells can die, and these mechanisms can be induced by different stimuli, such as ...

An Overview of Genetic Engineering

Genetic engineering &#8211; the process of purposefully altering an organism&#8217;s DNA &#8211; has been used to create powerful research tools and model ...

An Introduction to Cell Division

Cell division is the process by which a parent cell divides and gives rise to two or more daughter cells. It is a means of reproduction for single-cell ...

An Overview of Genetics and Disease

Many human diseases are associated with mutations or variations in genetic sequences. Some of these genetic variants are heritable, passed down from ...

an-introduction-to-cellular-and-molecular-neuroscience

An Introduction to Cellular and Molecular Neuroscience

Cellular and molecular neuroscience is one of the newest and fastest growing subdisciplines in neuroscience. By investigating the influences of genes, ...

Annexin V and Propidium Iodide Labeling

Staining with annexin V and propidium iodide (PI) provides researchers with a way to identify different types of cell death&#8212;either necrosis or ...

an-introduction-to-developmental-genetics

An Introduction to Developmental Genetics

Development is the complex process through which a single-celled embryo transforms into a multicellular organism. Developmental processes are guided by ...

Bacterial Transformation: Electroporation

The term &#x201C;transformation&#x201D; refers cellular ingestion of foreign DNA.  In nature, transformation can occur in certain types of bacteria.  In ...

an-introduction-to-molecular-developmental-biology

An Introduction to Molecular Developmental Biology

Molecular signals play a major role in the complex processes occurring during embryonic development. These signals regulate activities such as cell ...

bacterial-transformation-the-heat-shock-method

Bacterial Transformation: The Heat Shock Method

Transformation is the process that occurs when a cell ingests foreign DNA from its surroundings. Transformation can occur in nature in certain types of ...

an-introduction-to-saccharomyces-cerevisiae

An Introduction to <em>Saccharomyces cerevisiae</em>

Saccharomyces cerevisiae (commonly known as baker&rsquo;s yeast) is a single-celled eukaryote that is frequently used in scientific research.  S. ...

Cell Cycle Analysis

Cell cycle refers to the set of events through which a cell grows, replicates its genome, and ultimately divides into two daughter cells through the ...

An Introduction to Transfection

Transfection is the process of inserting genetic material, such as DNA and double stranded RNA, into mammalian cells. The insertion of DNA into a cell ...

Chromatin Immunoprecipitation

Histones are proteins that help organize DNA in eukaryotic nuclei by serving as &#8220;scaffolds&#8221; around which DNA can be wrapped, forming a complex ...

An Overview of Epigenetics

Since the early days of genetics research, scientists have noted certain heritable phenotypic differences that are not due to differences in the ...

community-dna-extraction-from-bacterial-colonies

Community DNA Extraction from Bacterial Colonies

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Luisa Ikner
Traditional methods of analysis ...

Cytogenetics

Cytogenetics is the field of study devoted to chromosomes, and involves the direct observation of a cell&#8217;s chromosomal number and structure, ...

embryonic-stem-cell-culture-and-differentiation

Embryonic Stem Cell Culture and Differentiation

Culturing embryonic stem (ES) cells requires conditions that maintain these cells in an undifferentiated state to preserve their capacity for self-renewal ...

DNA Gel Electrophoresis

DNA gel electrophoresis is a technique used for the detection and separation of DNA molecules. An electric field is applied to a gel matrix comprised of ...

Enzyme Assays and Kinetics

Enzyme kinetics describes the catalytic effects of enzymes, which are biomolecules that facilitate chemical reactions necessary for living organisms. ...

DNA Ligation Reactions

In molecular biology, ligation refers to the joining of two DNA fragments through the formation of a phosphodiester bond.  An enzyme known as a ligase ...

explant-culture-for-developmental-studies

Explant Culture for Developmental Studies

Explant culture is a technique in which living cells or tissues are removed from an embryo for continued development outside of the organism. This ex vivo ...

DNA Methylation Analysis

Methylation at CpG dinucleotides is a chemical modification of DNA hypothesized to play important roles in regulating gene expression. In particular, the ...

Expression Profiling with Microarrays

Microarrays are important tools for profiling gene expression, and are based on complementary binding between probes that are attached to glass chips and ...

Density Gradient Ultracentrifugation

Density gradient ultracentrifugation is a common technique used to isolate and purify biomolecules and cell structures. This technique exploits the fact ...

F&#246;rster Resonance Energy Transfer (FRET)

F&#246;rster resonance energy transfer (FRET) is a phenomenon used to investigate close-range biochemical interactions. In FRET, a donor photoluminescent ...

detecting-environmental-microorganisms-with-polymerase-chain-reaction

Detecting Environmental Microorganisms with the Polymerase Chain Reaction and Gel Electrophoresis

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - Arizona University
Demonstrating Author: Bradley Schmitz
Polymerase chain reaction (PCR) is ...

Gel Purification

Gel purification is used to recover DNA fragments after electrophoretic separation. DNA recovery from an agarose gel includes three basic steps: binding, ...

Detecting Reactive Oxygen Species

Reactive oxygen species are chemically active, oxygen-derived molecules capable of oxidizing other molecules. Because of their reactive nature, there are ...

Gene Silencing with Morpholinos

Morpholino-mediated gene silencing is a common technique used to study roles of specific genes during development. Morpholinos inhibit gene expression by ...

development-and-reproduction-of-the-laboratory-mouse

Development and Reproduction of the Laboratory Mouse

Successful breeding of the laboratory mouse (Mus musculus) is critical to the establishment and maintenance of a productive animal colony. Additionally, ...

Genetic Crosses

To dissect genetic processes or create organisms with novel suites of traits, scientists can perform genetic crosses, or the purposeful mating of two ...

drosophila-melanogaster-embryo-and-larva-harvesting-and-preparation

<em>Drosophila melanogaster</em> Embryo and Larva Harvesting and Preparation

Drosophila melanogaster embryos and larvae are easy to manipulate and develop rapidly by mechanisms that are analogous to other organisms, including ...

Genetic Engineering of Model Organisms

Transgenesis, or the use of genetic engineering to alter gene expression, is widely used in the field of developmental biology. Scientists use a number of ...

electrophoretic-mobility-shift-assay-emsa

Electrophoretic Mobility Shift Assay (EMSA)

The electrophoretic mobility shift assay (EMSA) is a biochemical procedure used to elucidate binding between proteins and nucleic acids. In this assay a ...

Genetic Screens

Genetic screens are critical tools for defining gene function and understanding gene interactions. Screens typically involve mutating genes and then ...

Genome Editing

A well-established technique for modifying specific sequences in the genome is gene targeting by homologous recombination, but this method can be ...

Protein Crystallization

Protein crystallization, obtaining a solid lattice of biomolecules, elucidates protein structure and enables the study of protein function. ...

in-ovo-electroporation-of-chicken-embryos

<em>In ovo</em> Electroporation of Chicken Embryos

Electroporation is a technique used in biomedical research that allows for the manipulation of gene expression via the delivery of foreign genetic ...

quantifying-environmental-microorganisms-and-viruses-using-qpcr

Quantifying Environmental Microorganisms and Viruses Using qPCR

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Bradley Schmitz
Quantitative polymerase ...

Induced Pluripotency

Induced pluripotent stem cells (iPSCs) are somatic cells that have been genetically reprogrammed to form undifferentiated stem cells. Like embryonic stem ...

rna-analysis-of-environmental-samples-using-rt-pcr

RNA Analysis of Environmental Samples Using RT-PCR

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Bradley Schmitz
Reverse ...

Isolating Nucleic Acids from Yeast

One of the many advantages to using yeast as a model system is that large quantities of biomacromolecules, including nucleic acids (DNA and RNA), can be ...

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

HS-LS1-1.

Transpiration

Description

Background

Transcript

Tags

More videos by Standards