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Plant Leaves: Expanded structures, usually green, of vascular plants, characteristically consisting of a bladelike expansion attached to a stem, and functioning as the principal organ of photosynthesis and transpiration. (American Heritage Dictionary, 2d ed)

Tree Identification: How To Use a Dichotomous Key

JoVE 10070

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University

A dichotomous key is a tool that identifies items in nature, such as leaves. This method is based on the idea of choosing between two characteristics. The word dichotomous comes from two Greek words that mean “to divide into two parts.” In a dichotomous key for leaf identification, each pair of phrases describes different features of the leaf. Only one of the phrases correctly applies to the leaf being keyed out. The correct phrase leads to the next pair of phrases, or states the name of the tree from which the leaf came. Using a field guide to trees and the iTree National Tree Benefits Calculator helps to identify trees in a field investigation, which shows the significance of trees in terms of their environmental benefits, such as storm water management, increasing property value, energy efficiency, air quality, and carbon sequestration.

 Environmental Science

Analysis of Earthworm Populations in Soil

JoVE 10002

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University

Using mustard, Lumbricus terrestris earthworm populations can be sampled directly from soil depths without landscape disturbance or toxicity. Earthworms can then be counted for data and statistical analysis using a bar graph and student’s t-test. Monitoring earthworm populations is a vital technique for environmental scientists, as multiple species of earthworms (most notably those from the suborder Lumbricina) have been invasively spreading throughout North America and South America. Exotic earthworms can be found on nearly every land mass and in nearly every ecosystem on the planet, and where and when these species become invasive has been a focus of international environmental research.1 Ecological invasion typically lowers biodiversity of an ecosystem by directly outcompeting, endangering, or otherwise contributing to the extirpation of native species. As ecosystem engineers, invasive earthworm species alter the cycling of nutrients through decomposition rates of organic matter on the upper horizons of soil, where plant roots mine for nutrients. Invasive Lumbricus species have both extirpated native earthworm species and have been shown to

 Environmental Science

Biofuels: Producing Ethanol from Cellulosic Material

JoVE 10014

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University

In this experiment, cellulosic material (such as corn stalks, leaves, grasses, etc.) will be used as a feedstock for the production of ethanol. The cellulosic material is first pretreated (ground and heated), digested with enzymes, and then fermented with yeast. Ethanol production is monitored using an ethanol probe. The experiment can be extended to optimize ethanol production by varying the feedstock used, pretreatment conditions, enzyme variation, yeast variation, etc. An alternative method of monitoring the reaction is to measure the carbon dioxide produced (using a gas sensor) instead of the ethanol. As a low-tech alternative, glucose meters (found in any drug store) can be used to monitor the glucose during the process, if an ethanol probe or carbon dioxide gas sensor is not available. With an increased emphasis on ‘inquiry-based learning”, scientific probes are becoming more popular. Handheld devices like the Vernier Lab Quest used in conjunction with a variety of probes (such as those for conductivity, dissolved oxygen, voltage, and more) allow for less focus on collecting data and/or making graphs and more on analyzing the data and making predictions. Anothe

 Environmental Science

Sonication Extraction of Lipid Biomarkers from Sediment

JoVE 10055

Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

The material comprising the living "organic" share of any ecosystem (leaves, fungi, bark, tissue; Figure 1) differs fundamentally from the material of the non-living "inorganic" share (rocks and their constituent minerals, oxygen, water, metals). Organic material contains carbon linked to a series of other carbon and hydrogen molecules (Figure 2), which distinguishes it from inorganic material. Carbon's wide valency range (-4 to +4) allows it to form up to four separate covalent bonds with neighboring atoms, usually C, H, O, N, S, and P. It can also share up to three covalent bonds with a single other atom, such as the triple bond in the often-poisonous cyanide, or nitrile, group. Over the past 4.6 billion years, this flexibility has led to an amazing array of chemical structures, which vary in size, complexity, polarity, shape, and function. The scientific field of organic geochemistry is concerned with the identification and characterization of the whole range of detectable organic compounds, called biomarkers, produced by life on this planet, as we

 Earth Science

A Rapid Laser Probing Method Facilitates the Non-invasive and Contact-free Determination of Leaf Thermal Properties

1Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V., 2Institute for Molecular Biotechnology, RWTH Aachen University, 3Fraunhofer Institute for Laser Technology ILT, Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.

JoVE 54835


Testing For Genetically Modified Foods

JoVE 10044

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University

Genetic modification of foods has been a controversial issue due to debated concerns over health and environmental safety. This experiment demonstrates technical understanding of how food DNA is genetically identified, allowing for educated decision making about the safety and potential dangers of using genetically modified organisms (GMOs) in food supplies. Polymerase Chain Reaction (PCR) is used to amplify food DNA to test for the presence of genetically modified DNA in food products. Presence of specific DNA bands is detected by using gel electrophoresis to pull extracted food DNA through a 3% agarose gel, a concentration dense enough to separate the bands of DNA containing the genetically modified DNA. Several controls are used in the electrophoresis procedure to ensure DNA is successfully extracted from test foods (plant primer), and to provide known examples of both genetically modified DNA (purchased genetically modified DNA) and non-genetically modified DNA (purchased certified non-GMO food control).

 Environmental Science

Tree Survey: Point-Centered Quarter Sampling Method

JoVE 10060

A number of methods are available for sampling forest communities. Point-centered quarter is one such method. It is used to gather information on the density, frequency, and coverage of tree species found in a forest. This information provides the ability to estimate the number of individual trees encountered, how often a certain tree occurs, how common the tree is compared to other trees, and the size of the tree. Compared to the standard plot analysis, the point-centered quarter method is more efficient, which is a major advantage. In a fixed-area plot sampling, a small portion of the total area of the forest is examined. In this small subsample, the density is determined directly by counting and identifying each tree. The ratio between size of the subplot and the overall forest size is used to determine the density for the entire forest.

 Environmental Science

Using High Resolution Computed Tomography to Visualize the Three Dimensional Structure and Function of Plant Vasculature

1U.S. Department of Agriculture, 2Department of Viticulture and Enology, University of California - Davis, 3Hawkesbury Institute for the Environment, University of Western Sydney, 4Advanced Light Source, Lawrence Berkeley National Lab, 5Citrus Research & Education Center, University of Florida

JoVE 50162


Carbon and Nitrogen Analysis of Environmental Samples

JoVE 10012

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University

Elemental Analysis is a method used to determine elemental composition of a material. In environmental samples such as soils, scientists are particularly interested in the amounts of two ecologically important elements, nitrogen and carbon. Elemental analysis by the flash combustion technique works by oxidizing the sample with a catalyst through combustion in a high-temperature chamber. The products of combustion are then reduced to N2 and CO2 and detected with a thermal conductivity detector. Unlike other methods for total nitrogen determination (Kjeldahl method) and total carbon determination (Walkley-Black, Heanes or Leco methods), the flash combustion technique does not use toxic chemicals and is therefore much safer to use. This video will demonstrate combustion-based elemental analysis using the Flash EA 1112 instrument from Thermo Fisher Scientific.

 Environmental Science

Dye-sensitized Solar Cells

JoVE 10328

Source: Tamara M. Powers, Department of Chemistry, Texas A&M University

Today's modern world requires the use of a large amount of energy. While we harness energy from fossil fuels such as coal and oil, these sources are nonrenewable and thus the supply is limited. To maintain our global lifestyle, we must extract energy from renewable sources. The most promising renewable source, in terms of abundance, is the sun, which provides us with more than enough solar energy to fully fuel our planet many times over. So how do we extract energy from the sun? Nature was the first to figure it out: photosynthesis is the process whereby plants convert water and carbon dioxide to carbohydrates and oxygen. This process occurs in the leaves of plants, and relies on the chlorophyll pigments that color the leaves green. It is these colored molecules that absorb the energy from sunlight, and this absorbed energy which drives the chemical reactions. In 1839, Edmond Becquerel, then a 19-year old French physicist experimenting in his father's lab, created the first photovoltaic cell. He illuminated an acidic solution of silver chloride that was connected to platinum electrodes which generated a voltage and current.1 Many discoveries and advances wer

 Inorganic Chemistry

Lead Analysis of Soil Using Atomic Absorption Spectroscopy

JoVE 10021

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University

Lead occurs naturally in soil, in levels ranging from 10-50 ppm. However, with the widespread use of lead in paint and gasoline in addition to contamination by industry, urban soils often have concentrations of lead significantly greater than background levels – up to 10,000 ppm in some places. Ongoing problems arise from the fact that lead does not biodegrade, and instead remains in the soil. Serious health risks are associated with lead poisoning, where children are particularly at risk. Millions of children in the U.S. are exposed to soil containing lead. This exposure can cause developmental and behavioral problems in children. These problems include learning disabilities, inattention, delayed growth, and brain damage. The Environmental Protection Agency has set a standard for lead in soil at 400 ppm for play areas and 1,200 ppm for non-play areas. Lead is also of concern in soil, when it’s used for gardening. Plants take up lead from the soil. Therefore, vegetables or herbs grown in contaminated soil can lead to lead poisoning. In addition, contaminated soil particles can be breathed in while gardening or brought into the house on clothing and footwear. It is recommended that s

 Environmental Science

Combining Analysis of DNA in a Crude Virion Extraction with the Analysis of RNA from Infected Leaves to Discover New Virus Genomes

1Texas A&M Agrilife Center at Dallas, 2Noble Research Center, Oklahoma State University, 3Department of Biology, College of Engineering and Natural Sciences, The University of Tulsa, 4Bioinformatics and Genomics Core Facility, Department of Biochemistry and Molecular Biology, Oklahoma State University

JoVE 57855

 Immunology and Infection

Conversion of Fatty Acid Methyl Esters by Saponification for Uk'37 Paleothermometry

JoVE 10158

Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

The product of an organic solvent extraction, a total lipid extract (TLE), is often a complex mixture of hundreds, if not thousands, of different compounds. The researcher is often only interested in a handful of compounds or, if interested in many, may need to remove unwanted constituents that are"in the way" or co-eluting. For example, the concentrations of individual compounds in a sample are often determined on a gas chromatograph coupled to a flame-ionizing detector (GC-FID), because the relationship between FID response (in pA) and the amount of compound in a sample (e.g., ng/µL) is both linear and sensitive. The GC portion of the instrument separates different compounds in a sample based on their boiling point, chemical structure, and affinity with a solid phase that can change according to application. The result is a chromatogram (Figure 1), showing the separation of different chemical constituents in time, as well as their relative concentration (calculated as the area under the curve). However, sometimes more than one compound elutes off the GC at a time (Figure 1). In this case, sample purification is required before compounds can be confidently quantified

 Earth Science

The Use of Induced Somatic Sector Analysis (ISSA) for Studying Genes and Promoters Involved in Wood Formation and Secondary Stem Development

1School of Ecosystem and Forest Sciences, Faculty of Science, The University of Melbourne, 2Victorian AgriBiosciences Centre, La Trobe University R&D Park, 3College of Biological Sciences, Department of Plant Biology, University of California, Davis, 4Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria

JoVE 54553


The Hawaii Protocol for Scientific Monitoring of Coffee Berry Borer: a Model for Coffee Agroecosystems Worldwide

1Oak Ridge Institute for Science and Education, 2Daniel K. Inouye US Pacific Basin Agricultural Research Center, United States Department of Agriculture-Agricultural Research Service, 3College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, 4Independent Consultant on CBB Management

JoVE 57204


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