The selective control of broadleaf weeds in cereal grain crops by auxinic herbicides has made this group one of the most widespread and important herbicide families in use. These herbicides were the first organic herbicides developed that were selective or able to kill one group of plants, but not another (i.e. kill broadleaf, but not grass plants). This lesson will introduce the major features of these herbicides, discuss their major uses and describe the symptoms of the injury they cause as well as introduce how they kill sensitive plants.
View
Or 
Print
The selective control of broadleaf weeds in cereal grain crops by auxinic herbicides has made this group one of the most widespread and important herbicide families in use. These herbicides are thought to act as hormone mimics. This lesson will detail how these herbicides are related structurally and physiologically to the natural plant hormone, auxin (indole-3-acetic acid; IAA) and explain the biochemical mechanisms which may be involved in their action. The mechanism of cell to cell transport and cellular uptake of auxins will be reviewed as well as how they cause cell elongation and induce ethylene biosynthesis. Receptors, signal transduction pathways and changes in gene expression for the natural hormone, IAA, will be described and related their role in auxinic herbicide activity.
View
Or Print
This scenario accompanies the online lesson, "Transpiration - Water Movement Through Plants", and is designed to allow you to apply the concepts learned in that lesson to a real-life problem.
View
Or Print
This lesson will discuss the corn rootworm complex, which consists of
the northern, western, and southern corn rootworm, focusing on the
northern and western species. The information in this lesson will focus
on the biology of corn rootworms in the north central Corn Belt,
including Iowa and Nebraska. Crop producers, crop scouts, students, and
the general public may find the information in this lesson helpful for
identifying corn rootworm, other corn pests, and the feeding damage
caused by each insect.
View
Or Print
Herbicides must be absorbed into plants in order to be effective. Herbicide absorption can occur through leaves, roots or both. The process by which herbicides kill weeds, called mode of action, requires herbicide absorption and may also require herbicide movement or translocation within the plant. Translocation means that the herbicide moves from the site of absorption to some other plant part. Foliar applied herbicides that have the necessary characteristics to move in the phloem will translocate to areas of the plant that are actively growing; however, not all foliar-applied herbicides move from the leaves that intercepted the spray solution. Herbicides that are absorbed but not translocated are called contact herbicides, while herbicides that translocate to shoot or root meristems are called systemic herbicides. Absorption and translocation of xylem mobile herbicides will be discussed in another lesson.
View
Or Print
This lesson will examine herbicides that adversely affect light-related processes, thereby causing damage to plants. There are four basic mechanisms that will be studied in this class of agents: herbicides that inhibit or block synthesis of Protoporphyrin IX; herbicides that inhibit synthesis of carotenoids; herbicides that block Photosystem II electron transfer; and herbicides that divert electrons from Photosystem I. All share the ability to cause cellular damage in the presence of light.
View
Or Print
En esta lección se detallarán los procesos bioquímicos que son afectados por los herbicidas que inhiben la síntesis de aminoácidos en las plantas. Se describirá también la importancia de los aminoácidos y las proteínas. De igual manera, se presentará un estudio detallado del herbicida glifosato [N-(fosfonometil)-glicina], incluyendo los avances hechos por la biotecnología.
View
Or Print
This lesson will detail the biochemical mechanisms that are affected by herbicides which inhibit a plant’s ability to synthesize amino acids. The significance of amino acids and proteins will also be described. The herbicide glyphosate, will be studied at length, including the advances made by biotechnology.
View
Or Print
Herbicides that inhibit the production of the branched chain amino acids valine, leucine and isoleucine are used for total vegetation management and selective weed control in a wide variety of crops. There are currently four different chemical families that share this MOA. Before the development of glyphosate-tolerance crop technology, branched chain amino acid inhibitors were the mainstay for several major row crops. While this is still a very important herbicide MOA, the major increase in herbicide resistance weeds since 1980 has been the direct result selection pressure from these herbicides. There are currently more weed species resistant to branched chain amino acid inhibitors than any other herbicide MOA.
View
Or Print
En esta lección se describe la naturaleza de la luz, la energía de los fotones y como dicha energía puede ser transferida a las biomoléculas. Se describen también tanto los procesos benéficos como los procesos dañinos por medio de los cuales las biomoléculas disipan la energía recibida.
View
Or Print
La transpiración es la pérdida de agua en forma de vapor por las plantas. El agua es absorbida del suelo por las raíces y transportada en forma líquida por el xilema hacia las hojas. En las hojas, unos pequeños poros permiten que el agua (H2O) escape a la atmósfera en forma de vapor, al tiempo que se permite la entrada de bióxido de carbono (CO2) para la fotosíntesis. De toda el agua absorbida por las plantas, menos del 5% es retenida y utilizada para crecimiento y almacenamiento. En esta lección se explicará porque las plantas pierden tanta agua, la ruta que ésta sigue dentro de la planta, como pudieran las plantas controlar la pérdida excesiva de agua y como las condiciones ambientales influyen en la pérdida de agua por las plantas.
View
Or Print
En esta lección se examinarán las dos principales clases de pigmentos fotosintéticos: las clorofilas y los carotenoides. Se analizarán sus estructuras bioquímicas y su biosíntesis, y se explicará además la organización de estos pigmentos en los sistemas fotosintéticos, que son complejos proteicos que colectan y convierten la energía luminosa en energía química.
View
Or Print
This lesson focuses on the process of eutrophication; the relationship between land application of manure and soil phosphorus (P) dynamics on P delivery to surface waters; and on the P dynamics in water bodies that result in increased P available to aquatic vegetation.
View
Or Print
Descripción: El control selectivo de malezas de hoja ancha en cultivos de cereales utilizando herbicidas auxínicos ha hecho de éstos una de las familias de herbicidas actualmente en uso más ampliamente distribuidas e importantes. Estos herbicidas fueron los primeros herbicidas orgánicos desarrollados que presentaron selectividad; es decir, capaces de matar un cierto grupo de plantas sin afectar a otros grupos (por ejemplo: matar plantas de hoja ancha pero no las de hoja angosta; en este documento se utilizará el término "gramíneas" para referirse a las plantas de hoja angosta o cereales). En esta lección se presentarán las principales características de los herbicidas auxínicos, se discutirán sus principales usos y se describirán los síntomas de daño que causan. De igual forma, se indicará la forma en que estos herbicidas matan a las plantas sensibles.
View
Or Print
Descripción: El control selectivo de malezas de hoja ancha en cultivos de cereales por los herbicidas auxínicos ha hecho de éstos una de las familias de herbicidas actualmente en uso mas ampliamente distribuidas e importantes. Se cree que estos herbicidas actúan como simuladores hormonales. En esta lección se detallará la relación estructural y fisiológica entre los herbicidas auxínicos y la fitohormona natural auxina (ácido indol-3-acético; IAA por sus siglas en inglés) y se explicarán los mecanismos bioquímicos que pueden estar involucrados en su modo de acción. Se revisará el mecanismo de transporte de célula a célula y la absorción de las auxinas por las células, así como también la forma en que estas moléculas causan elongación celular e inducen la síntesis de etileno. De igual forma, se describirán los receptores, las rutas de transferencia de señales y los cambios en expresión genética inducidos por la fitohormona natural IAA y su relación con la actividad de los herbicidas auxínicos.
View
Or Print
This lesson will take an indepth view of how plants handle foreign chemicals (xenobiotics) such as herbicides. It will discuss the three main phases that plants use to handle toxic chemicals, which enzymes are involved in these biochemical conversions, how these processes help protect crops again phytotoxic chemicals and consider the importance of these processes to successful weed management.
View
Or Print
Lesson one is a general description of the overall process of genetic engineering. A basic explanation of the five steps for genetically engineering a crop is provided. Details for each step are given in later lessons of this course. The five steps are:
- Locating an organism with a specific trait and extracting its DNA
- Cloning a gene that controls the trait
- Designing a gene to express in a specific way
- Transformation, inserting the gene into the cells of a crop plant
- Plant breeding to get the transgene into an elite background
View
Or Print
This lesson will examine the two major classes of phototsynthetic pigments, chlorophylls and carotenoids, their biochemical structures and their biosynthesis. The organization of these pigments into photosynthetic pigment, which are protein complexes that harvest light and convert its energy into biochemical energy will be explained.
View
Or Print
-Creating unique individuals or perfect little clones -Genetics of it all--Peas in Darwin's pods
View
Or Print
This lesson will focus on molecular principles involved in the detection of biotechnology derived proteins in crops, using the lateral flow ELISA.
View
Or Print
Overview: Herbicides must be absorbed into plants in
order to be effective. Plant roots and below ground shoots have few
barriers to herbicide absorption; however, interactions with soil
particles and soil organic matter have significant impacts on the
amount of herbicide available for plant absorption. Plant roots and
below ground shoots (hypocotyls or coleoptiles) are lipophilic by
nature and do not have thick, waxy cuticles like leaves. Lipophilic and
hydrophilic herbicides reach the root surface by bulk transport in soil
water; however, there are a few examples of herbicides that reach the
root as a vapor or gas. Soil-applied herbicides can translocate to the
shoot or remain in the root system. Soil-applied herbicides translocate
to the shoot in the xylem and tend to accumulate in mature leaves that
transpire the most water. The lipophilic/hydrophilic nature of the
herbicide will determine if the herbicide translocates to the shoot.
Absorption and translocation of phloem-mobile herbicides will be
discussed in another lesson.
View
Or Print
Soils - Part 9 addressed how soil testing works and the proper method of taking soil samples. The purpose of soil testing is to provide a rational basis for making fertilizer recommendations. The impact of not having the optimum crop nutrition can be yield loss, economic expense and environmental contamination. For many years, it has been widely known that fertilizer recommendations for a given crop often vary widely, depending on who is making the recommendation. With the development of site- specific nutrient management, more emphasis is being placed on soil sampling as a basis for predicting response to applied fertilizer. This lesson will explain several approaches to making fertilizer recommendations and will discuss why recommendations may vary widely when different approaches are used to interpret soil tests.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
View
Or Print
Nitrogen (N) is one of the most abundant elements on earth, and after carbon (C), hydrogen (H), and oxygen (O), it’s the element living creatures need most. The atmosphere over each square foot of the earth’s surface — which is 78 percent dinitrogen (N2) gas — contains approximately 6,000 pounds of nitrogen. However, most of the earth’s nitrogen (98 percent) is in rock, sediment, and soils. The amount of nitrogen in rocks is about 50 times more than that in the atmosphere, and the amount in the atmosphere is approximately 5,000 times more than in soils (Stevenson, 1982).
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
View
Or Print
Phosphorus fertilizers are second only to nitrogen in importance for growing crops in Nebraska; however, the principles affecting efficient phosphorus use are totally different. Nitrogen is a mobile nutrient, both in the plant and in the soil, while phosphorus moves very little in the soil. Additionally, total plant requirements are much lower for phosphorus than for nitrogen. For example, leaves commonly contain 10 times more nitrogen than phosphorus. However, phosphorus is concentrated in the grain so that only about 2.5 times more nitrogen is removed in harvested grain compared to phosphorus.
Potassium (K) is an essential plant nutrient. Next to nitrogen, crops absorb potassium in greater amounts than any other nutrient. It is a vital component of numerous plant functions including nutrient absorption, respiration, transpiration, and enzyme activity. Potassium is unique because it does not become part of plant compounds, but remains in ionic form in the plant. Potassium remaining in plant residues after harvest and in manure are quickly returned to the soil when water leaches through the plant residue.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
View
Or Print
Sixteen elements are known to be essential for plant growth. These are divided into two groups: macronutrients — those elements used in relatively large quantities and micronutrients — those needed in very small amounts.
Macronutrients | ||
Carbon (C) | Nitrogen (N) | Calcium (Ca) |
Hydrogen (H) | Phosphorus (P) | Magnesium (Mg) |
Sulfur (S) | Potassium (K) | Oxygen (O) |
Micronutrients | ||
Zinc (Zn) | Copper (Cu) | Boron (B) |
Iron (Fe) | Manganese (Mn) | Molybdenum (Mo) |
Chlorine (Cl) |
|
|
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
View
Or Print
During the first seven lessons, we have discussed a variety of topics related to soils, ranging from their formation to how nitrogen reacts in the soil. In Soils - Part 8, we are going to shift gears and discuss some common fertilizers and their characteristics. These will include the common nitrogen and phosphorus fertilizers, as well as many fertilizers that provide micronutrients to the soil. In this chapter, no attempt is made to judge the value of each type of fertilizer.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
View
Or Print
Soil tests are part of a four-step process of determining and providing nutrients to agronomic crops. The four steps are:
1) soil sampling,
2) soil analysis,
3) result interpretation and decision making, and
4) fertilizer application.
This chapter will focus on Steps 1 and 3 — soil sampling and result interpretation and decision making. It will not examine specific laboratory procedures or address fertilizer application issues. Until very recently, soil testing was conducted on a field basis. Site-specific management and the associated technologies of fertilizer application and yield monitoring are enabling agriculture management to reduce the area associated with each soil test to the subfield level. The article, "Soil Testing and Nutrient Recommendations," from Nutrient Management for Agronomic Crops in Nebraska, includes further information on soil testing.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
View
Or Print
This lesson describes the nature of light, the energy within photons and how this energy may be transferred to biological molecules. In addition, the beneficial and harmful methods for de-exciting molecules will be described.
View
Or Print
This lesson explains the technique of tissue culture as used in plant transformation. It discusses important issues, such as the use of selectable markers, genotype specificity, and tissue culture alternatives.
View
Or Print
This lesson and its animation follows the journey of water through a plant from its uptake by roots to its evaporation from the leaf surface. How this journey is altered by plant characteristics such as stomata and cuticles as well as by changes in the environment will be described.
View
Or Print