Plant hormones Essay

This essay has a total of 1657 words and 11 pages.

Plant hormones

Plant hormones are specialized chemical substances produced by plants. They are the main
internal factors controlling growth and development. Hormones are produced in one part of
a plant and transported to others, where they are effective in very small amounts.
Depending on the target tissue, a given hormone may have different effects.

Plant hormones play an integral role in controlling the growth and development of plants.
A plant hormone is generally described as an organic compound synthesized in one part of
the plant and translocated to another part, where in low concentrations elicits a
physiological response.

There are five generally recognized classes of plant hormones; some of the classes are
represented by only one compound, others by several different compounds. They are all
organic compounds, they may resemble molecules which turn up elsewhere in plant structure
or function, but they are not directly involved as nutrients or metabolites.

















Hormone Source Action
Auxins apical meristem (only moves down),
embryo of seed,
young leaves • Control of cell elongation
• apical dominance (prevents lateral buds)
• prevents abscission
• continued growth of fruit
• cell division in vascular and cork cambium
--formation of lateral roots from pericycle
--formation of adventitious roots from cuttings
Gibberellins Roots and young leaves • Cell (stem) elongation (works in stems and leaves, but not roots)
• breaking seed/bud dormancy
• stimulating fruit set
Cytokinins roots, embryos, fruits
actively growing • Promote cell division
--signal axillary/lateral bud growth
--prevent leaf abscission
• chloroplast development
• breaking dormancy in some seeds
• enhance flowering
• promote fruit development
Abscissic Acid leaves, stems, green fruit • Reduces cell division (helps
maintain dormancy of seeds and buds)

• prepare plants for winter
1. decreasing cell division
2. developing protective scales
3. deposition of waterproofing substances
• closes stomata
Ethylene tissues of ripening fruit,
nodes of stems,
senescent leaves, flowers Growth inhibitor
• fruit ripening
• leaf abscission
• initiation of flowering
• apical hook of some dicots



AUXINS: Nature of Auxins
Compounds are generally considered auxins if they can be characterized by their ability to
induce cell elongation in stems and otherwise resemble indoleacetic acid (the first auxin
isolated) in physiological activity. Auxins usually affect other processes in addition to
cell elongation of stem cells but this characteristic is considered critical of all auxins
and therefore defines the hormone.

Functions:
1. Stimulates cell elongation
2. Stimulates cell division in the cambium and, in combination with cytokinins in tissue culture
3. Stimulates differentiation of phloem and xylem
4. Stimulates root initiation on stem cuttings and lateral root development in tissue culture
5. Mediates the tropistic response of bending in response to gravity and light
6. The auxin supply from the apical bud suppresses growth of lateral buds
7. Delays leaf senescence
8. Can inhibit or promote (via ethylene stimulation) leaf and fruit abscission
9. Can induce fruit setting and growth in some plants
10. Involved in assimilate movement toward auxin possibly by an effect on phloem transport
11. Delays fruit ripening
12. Promotes flowering in Bromeliads
13. Stimulates growth of flower parts
14. Promotes (via ethylene production) femaleness in dioecious flowers
15. Stimulates the production of ethylene at high concentrations
Gibberellins: The Nature of Gibberellins
Unlike the classification of auxins which are classified on the basis of function,
gibberellins are classified on the basis of structure as well as function. All
gibberellins are derived from the ent-gibberellane skeleton. All gibberellins are acidic
compounds and are therefore also called gibberellic acids (GA) with a different subscript
to distinguish between them. GA's are widespread and so far present in both flowering
(angiosperms) and non-flowering (gymnosperms) plants as well as ferns. They have also been
isolated from lower plants such as mosses and algae, at least two fungal species and most
recently from two bacterial species. There have been over 90 GA's isolated, all of which
are most likely not essential to the plant. Instead, these forms are probably inactive
precursors or breakdown products of active gibberellins.





Continues for 6 more pages >>




  • None Provided4
    None Provided4 CHAPTER 32 The tallest tree is the Redwood (Sequoia sempervirens) approx 110 m The tallest Angiosperm is the Australian Eucalyptus regnans Water Uptake and transport (Fig. 32.1) = water is essential because: transport solute, cool the body, photosynthesis and Turgor pressure Osmosis- movement of H2) through a semi-impermeable membrane Osmotic potential ( o)-depend on dissolve solute: Hi concentration means more negative o. Isoosmotic-two solution with same o; Hypoosmotic- solution
  • Theory of Evolution
    Theory of Evolution CHARLES DARWIN AND THE THEORY OF EVOLUTION It is commonly thought today that the theory of evolution originated from Darwin in the nineteenth century. However, the idea that species mutate over time has been around for a long time in one form or another. Therefore, by Darwin\'s time the idea that species change from one type into another was by no means new, but was rejected by most because the proponents of evolution could not come up with a satisfactory mechanism that would
  • Genetic Engineering
    Genetic Engineering Genetic Engineering: A leap in to the future or a leap towards destruction? Introduction Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree-shrew, to ape, to human far exceeds the time from an analytical engine, to a calculator, to a computer. However, science, in the past, has always remained distant. It has allowed for advances in production, transportation, and even entertainment, but n
  • Animal testing
    Animal testing This theme song to a popular cartoon is a farce dealing with experiments carried out on animals. In the cartoon one mouse is made very smart and wants to take over the world while the other is clearly not as smart. While the cartoon makes jokes, the reality is that mice and other animals re being used for medical tests every day. For some people this testing brings up ethical questions. One of the biggest questions: is it really necessary to take the lives of animals in the name o
  • Ethics of Animal testing
    Ethics of Animal testing This theme song to a popular cartoon is a farce dealing with experiments carried out on animals. In the cartoon one mouse is made very smart and wants to take over the world while the other is clearly not as smart. While the cartoon makes jokes, the reality is that mice and other animals re being used for medical tests every day. For some people this testing brings up ethical questions. One of the biggest questions: is it really necessary to take the lives of animals in
  • Aromatherapy
    Aromatherapy Aromatherapy Speech Can you remember the smell of chocolate chip cookies baking in your mother\'s oven? When you smell that scent again, do childhood memories flood your mind? Ever wonder why? Aromatherapy will explain how your sense of smell triggers thoughts and how it affects your emotions and your mood. Learn how you can use this information to improve your health, your feelings, and your life. Aromatherapy is the art, and science, of using oils extracted from aromatic plants to
  • Charles Darwin2
    Charles Darwin2 Charles Darwin and the Development and impact of the Theory of Evolution by Natural and Sexual Selection Introduction It is commonly thought today that the theory of evolution originated from Darwin in the nineteenth century. However, the idea that species mutate over time has been around for a long time in one form or another. Therefore, by Darwins time the idea that species change from one type into another was by no means new, but was rejected by most because the proponents o
  • Evolution2
    evolution2 INTRODUCTION Theories explaining biological evolution have been bandied about since the ancient Greeks, but it was not until the Enlightment of the 18th century that widespread acceptance and development of this theory emerged. In the mid 19th century english naturalist Charles Darwin - who has been called the "father of evolution" - conceived of the most comprehensive findings about organic evolution ever1. Today many of his principles still entail modern interpretation of evolution.
  • Galoleo
    Galoleo The seventeenth century marked the beginning of spectacular changes in science that to this day flourish. However, during these times, science and faith would clash, and in their terrible conflict, the two were severed, to continue in divergent directions and to lose their common ground that continues at the present. The Aristotelian point of view that the Earth was the center of the universe was a universal, Biblical belief that no one dared to question. However, one mans discoveries w
  • Abstract
    Mr1 Abstract Dietary and activity habits were self evaluated over three days (one week day and a weekend). Analysis of 3-day diet records showed mean daily energy and carbohydrate intake to be insufficient to support estimated requirements. Mean intakes of vitamins and most minerals exceeded the Recommended Dietary Allowances (RDAs) except Retinol Eq. which was *66% of RDA,Vitamin B12, Vitamin B6, Vitamin C, Folate, Iron, and Phosphorous were *300% of the RDA.Introduction There is a natural link
  • Abstract
    Mr1 Abstract Dietary and activity habits were self evaluated over three days (one week day and a weekend). Analysis of 3-day diet records showed mean daily energy and carbohydrate intake to be insufficient to support estimated requirements. Mean intakes of vitamins and most minerals exceeded the Recommended Dietary Allowances (RDAs) except Retinol Eq. which was *66% of RDA,Vitamin B12, Vitamin B6, Vitamin C, Folate, Iron, and Phosphorous were *300% of the RDA.Introduction There is a natural link
  • Smog
    Smog Smog has been around for a pretty long time, people just knew it as something else. Smog comes from the word smoke and fog, and that\'s practically what it is. It was a serious problem before, before nature and humans went unharmed in the presence of smog but now it\'s serious. What does all of this polluted air do to the body? The answer depends on the situation. How long a person is exposed to pollution, the type and concentration, the place, time and day, temperature, weather and more. B
  • Animal rights
    animal rights Animal Rights Every year an estimated 25-35 million animals are subjected to painful and cruel testing in laboratory experiments. These experiments are performed to better the health of human beings by means of research. Many of these non-human animals are put through tests that you would not wish on your worst enemy. Many wonder if the means justify the ends in these particular experiments. Controversy occurs when there is a perception that the animals being used in the experiment
  • Aromatherapy
    Aromatherapy There are literally hundreds of types of unconventional medicines. An unconventional medicine is any type of therapy that is different from traditional medicine in the way that it focuses on a patients mind, body, and inner energy, to aid in healing. Some, use magic charms, colour therapy, sound therapy, and juice therapy, in which natural juices are used as tonic therapies. Flower remedy is a system of natural medicine that uses remedies distilled from blooming plants and trees, a
  • Chernobyl1
    Chernobyl1 La era nuclear empieza a partir de la Segunda Guerra Mundial, a 50 aos de este suceso histrico, dos ciudades nuevas se han levantado de las cenizas atmicas de esta catastrfica guerra. En una de estas ciudades, Chernobyl, a diez aos de la explosin nuclear, poblaciones enteras han sido abandonadas alrededor del reactor destruido, para escapar del agua y del alimento contaminados producidos en el suelo que una vez fuera rico. En el mismo perodo desde la Segunda Guerra Mundial, la
  • Food
    food Athletic Enhancers / In this research paper I will be discussing the ever-popular athletic supplements: Creatine, Androstenedione, and HMB. It has been proven that these supplements when taken in the proper doses will produce phenomenal results in athletic performance. They are taken by athletes of all fields of play in order too give them that extra edge over competition. Creatine monohydrate, which is the number one supplement preferred by athletes, is not a mineral, herb, or steroid. Cre
  • Genetic Engineering1
    Genetic Engineering1 Genetic Engineering, history and future Altering the Face of Science Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree-shrew, to ape, to human far exceeds the time from analytical engine, to calculator, to computer. But science, in the past, has always remained distant. It has allowed for advances in production, transportation, and even entertainment, but never in history will science be
  • Genetic Engineering1
    Genetic Engineering1 Genetic Engineering, history and future Altering the Face of Science Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree-shrew, to ape, to human far exceeds the time from analytical engine, to calculator, to computer. But science, in the past, has always remained distant. It has allowed for advances in production, transportation, and even entertainment, but never in history will science be
  • History of Chemistry
    History of Chemistry History of Chemistry Introduction: Humans have always been very curios creatures. The have always wondered about what they are and why they are here. Our limited knowledge of the environment has always urged for new things to be discovered. The desire to understand the world better has made people search for rational answers, for principles and laws. For centuries people have tried to unlock the mysterious world that surrounds them. History: Because myths did not explain thi
  • Music Therapy
    Music Therapy Music Therapy Music therapy is the prescribed use of music and musical interventions in order to restore, maintain, and improve emotional, physical, physiological, and spiritual health and well-being (Lindberg). So one finds the selections under the New Age/Relaxation section of the record store about as relaxing as water torture? Just because one\'s taste runs more to Sousa than to soothing doesn\'t mean one can\'t reap all these relaxation benefits music is supposed to have. Musi
  • Career Review Pharmacist
    Career Review Pharmacist Introduction On the surface, daily routines of Pharmacists may appear to be rather simplified and involves little work hazard and responsibilities. As pharmacists dispense prescribed drug and medicine by doctors or dentists, they may provide assistance to those who seeks help with non-prescribed products. This is a correct yet very generalized view of pharmacist, this career interacts with many different industries. As an example, technology plays key role for pharmacist
  • PROSPECTUS OF HONOURS COURSES
    Mr PROSPECTUS OF HONOURS COURSES 2000/2001 This document contains information on all Honours courses on offer next year together with important information about admission to Honours and assessment in Honours courses. Please retain it for reference throughout the session. Douglas Brodie, Associate Dean. ADMISSION AND APPLICATION PROCEDURE 2 LIST OF COURSES ON OFFER AND NOT ON OFFER IN 2000/2001 4 COURSE ENTRIES A) COURSES ON OFFER 2000/2001 5 - 23 B) COURSES NOT ON OFFER 2000/2001 25 - 28 HONOUR
  • Darwin
    darwin Introduction It is commonly thought today that the theory of evolution originated from Charles Darwin in the nineteenth century. However, the idea that species mutate over time has been around for a long time in one form or another. Therefore, by Darwins time the idea that species change from one type into another was by no means new, but was rejected by most because the proponents of evolution could not come up with a satisfactory mechanism that would explain this change. But how did D
  • Genetic Engineering history and future
    Genetic Engineering history and future Genetic Engineering, history and future Altering the Face of Science Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree-shrew, to ape, to human far exceeds the time from analytical engine, to calculator, to computer. But science, in the past, has always remained distant. It has allowed for advances in production, transportation, and even entertainment, but never in hist
  • None Provided1
    None Provided1 GENENTIC ENGINEERING Ray Fonseca Professor Matthews Anthropology 1 Genetic Engineering: A leap in to the future or a leap towards destruction? Introduction Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree-shrew, to ape, to human far exceeds the time from an analytical engine, to a calculator, to a computer. However, science, in the past, has always remained distant. It has allowed for advanc
  • What are We Breathing
    What are We Breathing Poor air quality is the culprit for the consequences that are being suffered by many human and plant communities. Air pollution, smog, or acid rain; it may be called whatever you like, it is the effects that it is causing that are important. Although many people associate smog with Los Angeles, it is not the only area that has been effected by poor air quality. Many national parks, aquatic systems, and other populated areas are showing major signs of air pollution. "A larg
  • Genetics
    Genetics Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree-shrew, to ape, to human far exceeds the time from an analytical engine, to a calculator, to a computer. However, science, in the past, has always remained distant. It has allowed for advances in production, transportation, and even entertainment, but never in history has science be able to as deeply affect our lives as genetic engineering will undou
  • Endangered Species of New York
    Endangered Species of New York Endangered Species of New York FACTS & HISTORY What exactly does the term endangered species denote? There can be numerous definitions that correctly describe the term. It is any plant or animal whose survival is in jeopardy of becoming extinct. Extinction, of course, is when the species no longer exists, and there is no way it can be brought back to this earth. In most cases, the cause of this displeasing calamity is generally human-related. As more time goes on,
  • None8
    none8 The Evolution of Animals Eukaryotes come in two grades of organization: single-celled (protists) and multicellular (plants, animals, and fungi). The world today is full of complex multicellular plants and animals: how, why, and when did they evolve from protists? Proterozoic Protists A single-celled eukaryote or protist can carry chlorophyll (it can be an autotrophic, photosynthetic, "alga"), it can eat other organisms (it can be an organotrophic, "protozoan" "animal"), or it may do both.
  • Shroud of Turin
    Shroud of Turin Shroud of Turin Introduction: Millions of words have been written about the remarkable cloth preserved at Turin. More recently, most of these writings dealt with one basic question, was it the actual winding sheet of the crucified Christ, bearing an imprint of His body? Or was the whole thing a gigantic hoax? A fantastic forgery of the Middle Ages? Erudite men have lined up on both sides of that compelling query. Some of the facts about the Holy Shroud have something to do with
  • None Provided16
    None Provided16 This theme song to a popular cartoon is a farce dealing with experiments carried out on animals. In the cartoon one mouse is made very smart and wants to take over the world while the other is clearly not as smart. While the cartoon makes jokes, the reality is that mice and other animals re being used for medical tests every day. For some people this testing brings up ethical questions. One of the biggest questions: is it really necessary to take the lives of animals in the name
  • Philosophy of Science
    Philosophy of Science Philosophy of Science Final Paper on Darwin It is commonly thought today that the theory of evolution originated from Darwin in the nineteenth century. However, the idea that species mutate over time has been around for a long time in one form or another. Therefore, by Darwin\'s time the idea that species change from one type into another was by no means new, but was rejected by most because the proponents of evolution could not come up with a satisfactory mechanism that w
  • Altering the Face of Science
    Altering the Face of Science Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree shrew, to ape, to human far exceeds the time from analytical engine, to calculator, to computer. But science, in the past, has always remained distant. It has allowed for advances in production, transportation, and even entertainment, but never in history will science be able to so deeply affect our lives, as genetic engineering
  • Alternative medicines
    alternative medicines Modern medicine is in a period of profound change. Everyday, more and more ideas from other cultures are being transferred and integrated into our society. Many treatments that people are now familiar with have come from other traditions. Aspirin and quinine are two familiar examples of treatments that have been westernized by science. Alternative medical traditions will not replace western medicine, but instead are adding a new dimension of treatment that will only stre
  • Cloning A misunderstood and Underestimated Science
    Cloning A misunderstood and Underestimated Science On February 23rd of 1997, an announcement was made that would shake the world and, inevitably, change it forever. Ian Wilmut, an embryologist with a genetic research facility named the Roslin Institute in Scotland, claimed that he and a group of scientists had successfully cloned a sheep. The sheep, named Dolly, was revolutionary in the Bioengineering world because it was the first mammal to be cloned directly from the genetic material of anoth
  • Evolution3
    Evolution3 Major Themes in Evolution The world around us changes. This simple fact is obvious everywhere we look. Streams wash dirt and stones from higher places to lower places. Untended gardens fill with weeds. Other changes are more gradual but much more dramatic when viewed over long time scales. Powerful telescopes reveal new stars coalescing from galactic dust, just as our sun did more than 4.5 billion years ago. The earth itself formed shortly thereafter, when rock, dust, and gas circlin
  • Genetic engineer
    genetic engineer Anti-technologists and political extremists misinform, and over exaggerate statements that genetic engineering is not part of the natural order of things. The moral question of genetic engineering can be answered by studying human evolution and the idea of survival of the fittest. The question of safety can be answered by looking at the current precautions of the industry. The concept that society needs to understand is that with the right amount of time and money genetic engin
  • Genetic Engineering history and future Altering th
    Genetic Engineering history and future Altering the Face of Science Genetic Engineering, history and future Altering the Face of Science Paper By: Phillip O. Alvarez Z. Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree-shrew, to ape, to human far exceeds the time from analytical engine, to calculator, to computer. But science, in the past, has always remained distant. It has allowed for advances in producti
  • Genetic Engineering4
    Genetic Engineering4 Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree shrew, to ape, to human far exceeds the time from an analytical engine, to a calculator, to a computer. However, science, in the past, has always remained distant. It has allowed for advances in production, transportation, and even entertainment, but never in history has science be able to so deeply affect our lives, as genetic engineeri
  • Photosynthesis
    Photosynthesis Plants are one of the many wonders of the world. They are considered autotrophs; they do not rely on outside sources for their food. They create their own food by the process of photosynthesis. Photosynthesis is when green plants and certain other organisms use light energy to change carbon dioxide and water into the glucose. In so doing, photosynthesis provides the basic energy source for almost all organisms. An extremely important byproduct of photosynthesis is oxygen, on whic
  • The Gaia Hypothesis
    The Gaia Hypothesis The Gaia Hypothesis The Gaia Hypothesis is a hypothesis that was developed by James Lovelock and Lynn Margulis in the late 1970\'s. James Lovelock is a British scientist, an atmospheric chemist, and also an inventor with an education in human physiology. Lynn Margulis was a microbiologist during the 1970\'s at Boston University. She also originated the theory of the eukaryotic cell arising as a result of endosymbiotic cell capture. This theory is the one that gave her the cr
  • The theory of Evolution
    The theory of Evolution The theory of evolution, as set forth by Charles Darwin in 1859, stated that all plant and animal life evolved over long periods of time from simple to more complicated forms through mutation and adaptation. He also taught that only the fittest of each species would survive. He further postulated that the first living cell evolved in a "warm warm little pond" and that it took billions of years for the present diversity of living things to evolve. At the time, it was thou
  • The Future Of Human Evolution
    The Future Of Human Evolution The Future of Human Evolution Darwinism and Evolution Evolution, the science of how populations of living organisms change over time in response to their environment, is the central unifying theme in biology today. Evolution was first explored in its semi-modern form in Charles Darwin \'s 1859 book, Origin of Species by means of Natural Selection. In this book, Darwin laid out a strong argument for evolution. He postulated that all species have a common ancestor fro
  • Coevolution, With Particular Reference To Herbivor
    Coevolution, With Particular Reference To Herbivory COEVOLUTION with particular reference to herbivory BIOL 0106 ASSESED COURSEWORK RORY AULD JANUARY 2000 COEVOLUTION WITH PARTICULAR REFERENCE TO HERBIVORY Of all the extant organisms in the world, it is believed that terrestrial plants and their natural ‘enemies\' constitute more than forty percent. Moreover, plants exhibit a remarkable diversity of supposedly defensive characteristics including trichomes, spines, silica, secondary chemical co
  • The Dog
    The Dog The Dog Domestic dog, carnivorous mammal, generally considered the first domesticated animal. The domesticated dog has coexisted with human beings as a working partner and household pet in all eras and cultures since the days of the cave dwellers. It is generally believed that the direct ancestor of the domestic dog is the wolf, originally found throughout Europe, Asia, and North America. Remains of a dog, estimated to be 10,500 years old, have been found in Idaho. TAXONOMY Kingdom: Anim
  • Chinese Medicine
    Chinese Medicine Chinese Medicine Traditional medicine of China has a long historical and cultural background dating back about 2500 years. The ancient Chinese people were able to reach a level of social stability that included the ability to treat disease of emotional, physical, and spiritual origins. Although a belief in spirits as the cause of disease has remained in China even to the present day, the view that the body obeyed a natural order struck a chord in the intellectual elite of ancien
  • Genetic Engineering: A Leap In To The Future Or A
    Genetic Engineering: A Leap In To The Future Or A Leap Towards Destruc IntroductionScience is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree-shrew, to ape, to human far exceeds the time from an analytical engine, to a calculator, to a computer. However, science, in the past, has always remained distant. It has allowed for advances in production, transportation, and even entertainment, but never in history has scienc
  • Cloning
    Cloning Research Paper on Cloning We have seen comic material in the movies and on television. The entertainment industry usually shows it in a humorous situation such as Danny Devito and Arnold Schwannager as genetically engineered twins while Michael Keaton was duplicated to make his life easier. Cloning is only achieved after intensive research and experimentation where as in the movies; it is made out to be as easy as 1, 2, 3. Even though animal and human cloning has only been announced rece
  • Genetic Engineering, History And Future
    Genetic Engineering, History And Future Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree-shrew, to ape, to human far exceeds the time from analytical engine, to calculator, to computer. But science, in the past, has always remained distant. It has allowed for advances in production, transportation, and even entertainment, but never in history will science be able to so deeply affect our lives as genetic eng
  • Genetics
    genetics Introduction Science is a creature that continues to evolve at a much higher rate than the beings that gave it birth. The transformation time from tree-shrew, to ape, to human far exceeds the time from an analytical engine, to a calculator, to a computer. However, science, in the past, has always remained distant. It has allowed for advances in production, transportation, and even entertainment, but never in history has science be able to so deeply affect our lives as genetic engineerin