This lesson is a detailed explanation of the backcross breeding process. Variations based on whether backcrossing is performed with dominant, recessive, or multiple traits are discussed. Calculations associated with backcross breeding are explained.
View
Or 
Print
El uso repetido del mismo herbicida, puede provocar poblaciones de malezas que consisten de biotipos susceptibles (S) que son controlados y biotipos resistentes (R), que escapan al control para producir y retornar semilla con la característica de resistencia, al banco de semillas del suelo. Esta lección se enfocará en la dinámica poblacional de una población de malezas mezclada con biotipos S y R. Se comparará y contrastará la tasa a la que aparecen malezas resistentes en una población bajo diversas presiones de selección. ****** Esta lección se enfocará en la dinámica poblacional de una población mezclada (biotipos susceptibles y resistentes a un herbicida), y comparar y contrastar la tasa a la cual aparece resistencia al herbicida, en una población de malezas mezclada, bajo diversas presiones de selección.
View
Or Print
Through the repeated use of the same herbicide, weed populations can consist of susceptible (S)-biotypes that are controlled and herbicide resistant (R)-biotypes that are left behind to produce and return seed with the resistance characteristic back into the soil. This lesson will highlight the population dynamics of a mixed weed population, containing S- and R-biotypes, and compare and contrast the rate at which herbicide resistant weeds appear in a population under a diversity of selection pressures. ****** This lesson will highlight the population dynamics of a mixed (herbicide susceptible and resistant biotype) weed population, and compare and contrast the rate of appearance of herbicide resistance in a mixed population under a diversity of selection pressures.
View
Or Print
This lesson contains information about the Asteraceae family.
View
Or Print
This lesson reviews the basics of gene inheritance. It compares plants that are homozygous, heterozygous, and hemizgous for an allele and how gene expression is affected by the dominance of an allele. It also explains how to use a Punnett square to predict genotypic and phenotypic ratios of offspring.
View
Or Print
Esta lección se enfoca en entender el sistema de clasificación en el cual están organizados los herbicidas. Terminología como clasificación, jerarquía de clasificación, ejemplos de clasificación y un breve resumen de los ocho modos de acción, se discuten en esta lección. Una vez que esto se entiende, es mucho más fácil comprender herbicidas similares y saber por qué estos pueden exhibir ciertos síntomas en malezas y cultivos. Objetivos: 1. Entender la forma en que se clasifican los herbicidas y su importancia en el manejo de la resistencia herbicida 2.Entender la importancia de la clasificación de los herbicidas por modo de acción, en vez de familias 3.Ser capaz de entender la diferencia entre modo de acción y sitio de acción 4.Ser capaz de diferenciar entre familias de herbicidas, modos de acción, y sitios de acción 5.Entender nombre común, nombres comerciales y sitios de absorción
View
Or Print
This lesson will discuss erosion control practices in the agricultural and construction environments. The impact of erosion management practices will be demonstrated with exercises using a USLE calculator.
View
Or Print
En esta lección se examinarán los herbicidas que afectan los procesos celulares relacionados con la utilización de la luz, causando así daños a las plantas. Existen cuatro mecanismos básicos que serán estudiados: herbicidas que obstruyen la síntesis de protoporfirina IX; herbicidas que inhiben la síntesis de carotenoides; herbicidas que obstruyen la transferencia de electrones en el fotosistema II; y herbicidas que substraen electrones del fotosistema I. Todos ellos comparten la misma habilidad de causar daños celulares en presencia de luz.
View
Or Print
This lesson focuses on understanding the classification system into which herbicides are organized. Terms of classification, classification hierachy, examples of classification and a brief overview of the eight modes of action are all discussed in this lesson. Once this is understood it is much easier to grasp similar herbicides and know why they may exhibit certain symptoms to weeds and plants alike. Objectives: 1.Understand how herbicides are classified and why it is important for managing herbicide resistance 2.Understand the Importance of classification and herbicides by mode of action rather than chemical family 3.Be able to tell the difference between mode of action and site of action 4.Be able to differentiate between herbicide families, modes of action, and sites of action 5.Understand common name, trade names and sites of absorption
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
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 case study addresses where geographically soil addition of
municipal organic wastes occurs and how this addition affects soil
profile development and the use of soils as a sustainable resource.
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
Soil means different things to different people. To some, soil is something that must be swept away; to others it is just a material that sticks to your shoes. In both instances, soil is associated with unpleasantness. To the engineer, soil is something to be moved, manipulated or built upon. To the farmer and rancher, soil is the source of nutrients which crops use to produce the grain and with it the livestock needed to produce a profit on the farm and in agribusiness. For some of us, soils provide recreation through the development of landscapes or vegetable gardens. For all of us, soils are the medium that provides the food production that has been so successful in feeding our population.
[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 may look simple; however, it is an extremely complex system. It is most often described by its physical, chemical and biological properties and processes. Soil is organic or inorganic; inert or active; living or non-living. Soil contains many organisms: bacteria, nematodes, fungi, earthworms, and small animals. From a physical perspective the soil constitutes the building blocks upon which we walk, construct buildings, grow crops and filter natural and manmade compounds. Soil’s physical, chemical and biological properties and processes interact to enhance its value as a natural resource.
[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
To most gardeners, organic matter is like Husker football—everybody is a fan, but not everybody understands the details of the game. Anyone who uses a soil should have an interest in its organic matter content because so much about the soil is influenced by its organic matter content. In this lesson, we will increase our knowledge about soil organic matter to be able to understand its importance.
[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 pH is one of the most important chemical characteristics of the soil. For example, soil pH can affect availability of plant nutrients. In addition, the soil pH can affect the performance of preemergence herbicides, activity of microorganisms, the need for lime, soil bacteria activity, the best crop to be grown, and other characteristics.
[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 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 explains the procedure of introducing a new gene into a plant cell (transformation). It discusses the main goals of the transformation process and describes the four main methods of transformation.
View
Or Print
This lesson defines an 'event'. It explains the determining factors specific to an event, the qualities of a desirable event, and the identification and selection of desirable events.
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