Growth Factors in Plants

10 Key excerpts on "Growth Factors in Plants"

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  eBook - PDF

  Physiology of Woody Plants

  • Paul Kramer(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  Growth Regulators Introduction 531 General Controls 532 Scope of the Problem 532 Two Kinds of Coordinating Systems 533 Naturally Occurring Hormones 533 Auxins 534 Gibberellins 537 Cytokinins 539 Ethylene 541 Abscisic Acid 542 Other Growth Inhibitors 543 Interactions of Hormones 544 Growth Regulators and Disease 544 General References 545 INTRODUCTION The structure of trees and other woody plants was described in Chapter 2 and their growth in Chapters 3 and 4. This chapter deals with hormones, specific substances that regulate or control growth and development in plants. Growth in simple terms refers to increase in size by cell division and enlargement, and development refers to the differentiation of cells into the various tissues and organs that finally produce a mature plant. These processes are relatively easy to observe in growing plants, beginning with germinating seeds. The first step in growth is the imbibition of water and the swelling of seeds, followed by the release of existing enzymes and synthesis of new ones, the hydrolysis of stored food, its translocation to growing points, and the synthesis of new metabolites and tissue (see Chapter 14). Cell division, enlargement, and differentiation into the various structures of the seedling produce a plant that eventually grows to maturity with a characteristic form and produces flowers, fruits, and seeds. All of this is easy to observe, but difficult to understand. The problem is to explain how the numerous physical and biochemical processes included in the growth and development of a plant are controlled and programmed so they occur in the proper sequences and quantities to produce a well-proportioned, efficiently functioning organism. The origin 531 532 15. Growth Regulators GENERAL CONTROLS Scope of the Problem It has been mentioned previously that growth and development are controlled by both external and internal factors.

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  Cell Growth

  • Biba Vikas, Michael Fasullo, Biba Vikas, Michael Fasullo(Authors)
  • 2020(Publication Date)
  • IntechOpen

    (Publisher)

  1 Chapter 1 Plant Growth Hormones Amira Shawky Soliman Abstract Many factors can cause and affect cell growth in the plant such as external (environmental) and internal factors; one of the most important internal factors is plant growth hormones. Many hormones required for cell growth, such as auxins, gibberellins, brassinosteroids, ethylene, jasmonates, salicylic acid, strigolactones and cytokinins which able to accelerate or promote growth, but, some hormone-like abscisic acid has an adverse effect on growth which increases seed dormancy by inhibiting cell growth. Also, plant hormones are able to breakdowns dormancy for many plants and can alleviate abiotic stress (salinity, extreme temperatures and, drought,…) which led to enhance germination and improve growth for many plants, whether naturally occurring in the plant or by adding it to the plant in its artificially formed or in the form of bio- or nano-fertilization in order to increase the produc-tivity and improve its efficiency under extreme conditions. Therefore, this chapter will highlight and will provide data for the positive or/and negative effect of these hormones on many plants to achieve a rapid germination method. It will also shed light on the relationship of these hormones to some enzymes to accelerate growth. Keywords: plant hormones, seed germination, dormancy, cell growth, inhibition 1. Introduction Plant hormones (phytohormones) are not nutrients, but chemicals and not all plant cells respond to hormones, but those cells that do are programmed to respond at specific points in their growth cycle. The greatest effects occur at specific stages during the cell’s life, with diminished effects occurring before or after this period [1]. Plants need hormones at very specific times during plant growth and at specific locations. They also need to disengage the effects that hormones have when they are no longer needed.

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  Synthetic Plant Growth Regulators

  • Hota, Dharamvir(Authors)
  • 2021(Publication Date)
  • Genetech

    (Publisher)

  1 Synthetic Plant Growth Regulators Growth and development of plants is regulated by a combination of genetic factors and environment influences. Hormones can function as signal molecules that trigger signal transduction pathways in cells. Such pathways often result in the synthesis of transcription factors that in turn promote synthesis of enzymes that facilitate chemical reactions within the cell. Signal transduction pathways are equally important for chemical messaging in plants as in animals and both environmental cues and hormones serve as signal stimuli. Plant hormones, or plant growth regulators, are chemicals produced by plants that alter growth patterns and/or maintenance of the plant. They can be found in many cells and tissues, although plant hormones seem to be concentrated in meristems and buds (which are dormant shoot meristems). Growth regulators control cell activities by sending chemical signals or messages to cells to do something or to not do something, including activating the genes that code for specific enzymes. Plant hormones inhibit as well as promote cellular activities. In contrast to animal hormones, which generally have very specific effects, the hormones identified in plants most often regulate division, elongation and differentiation of cells. This ebook is exclusively for this university only. Cannot be resold/distributed. Most hormones have multiple effects in plants. Plant hormones work in very small concentrations. In most cases, the effect plant hormones have on the plant depends on the location of and concentration of the hormone relative to other hormones in the specific tissues. Plant hormones often work in conjunction with each other, and have overlapping effects. They also work with environmental stimuli. There are several classes of plant hormones, including a number of recently “discovered” ones.

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  Plant Propagation Concepts and Laboratory Exercises

  • Caula A. Beyl, Robert N. Trigiano, Caula A. Beyl, Robert N. Trigiano(Authors)
  • 2016(Publication Date)
  • CRC Press

    (Publisher)

  47 4 Plant Growth Substances Used in Propagation Caula A. Beyl, David W. Burger, and Zong-Ming Cheng Plant growth regulators (PGRs) are a group of organic substances that are capable of exerting large effects in plants in terms of gene expression, growth, and devel-opment, although they occur in relatively low concen-trations, usually in nano- (10 –9 ) to micro- (10 –6 ) molar amounts. Endogenous PGRs, those that the plant biosyn-thesizes for itself and are naturally occurring, are called “hormones.” The word “hormone” is derived from the Greek word hormone , which means “that which sets in motion.” These plant hormones or phytohormones con-trol processes such as cell division and enlargement, root and bud initiation, dormancy, flowering, and ripen-ing. Horticulturists make use of the unique features of synthetic growth regulators and apply them exogenously (originating outside of the plant) to generate desired responses in the plant. When a plant is developing from a germinating seed, endogenous growth regulators or hormones are responsible for directing the development of shoots and roots via cell division and enlargement. In traditional plant propagation with cuttings, PGRs have enhanced adventitious rooting for even many hard-to-root species. PGRs have been used to stimulate germi-nation, enhance flowering, and enlarge fruit. In tissue culture, we make use of the ability to direct growth using growth regulators to stimulate the development of non-zygotic embryos, the growth and development of callus, the proliferation of axillary shoots, and the development of adventitious roots.

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  Introduction to Horticultural Science

  • Richard N. Arteca(Author)
  • 2014(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  As you learned earlier, auxins were the first class of plant hor-mones discovered more than 80 years ago. Since this time, five additional classes of plant hormones have been recognized: gibberellins, cytokinins, abscisic acid (ABA), ethylene, and, the newest, brassinosteroids. Numerous advances have been made in the use of plant growth regulating substances on a practical scale, along with basic research at the biochemical, physiological, and molecular levels. Today, the use of plant growth regulating compounds in agriculture is on the rise and will continue to increase as more scientific information becomes available. Plant growth regulators are used in agriculture for a variety of purposes, which will be discussed in more detail later in this chapter: ■ delaying or promoting ripening (ethylene). ■ inducting rooting (auxins). ■ promoting or delaying abscission (ethylene). ■ controlling fruit development (auxins, gibberellins, and cytokinins). ■ controlling weeds (auxins). ■ controlling size (growth retardants that block gibberellin biosynthesis). Key definitions in this area are as follows: Plant hormone or phytohormone is a naturally occurring organic compound that is: ■ chemically characterized. ■ biosynthesized within the plant. ■ broadly distributed in the plant kingdom. ■ a specific biological activity at extremely low concentrations. ■ fundamental to regulating physiological phenomena in vivo in a dose-dependent manner and/or due to changes in sensitivity of the tissue during development. A plant growth regulator is an organic compound other than a nutrient (mate-rial that supplies either energy or essential mineral elements) that in small amounts promotes, inhibits, or otherwise modifies any physiological process in plants. A plant growth regulator includes both synthetic and naturally occurring regulators. All plant hormones are plant growth regulators, but not all plant growth regula-tors are plant hormones.

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  Plants, Chemicals and Growth

  • F.C. Steward(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  This is obvious for reasons which are implicit in the very different organization and manner of growth and development of higher animals and plants, and in the very different nutritional organization of their con-stituent cells. Plant growth regulatory substances, natural or synthetic, have tradition-ally been identified by certain operational terms; namely, as auxins (which by derivation cause an increase in size) (Thimann, 1969); as cytokinins which characteristically cause an increase in the number of cells (Skoog and Armstrong, 1970); as gibberellins, which were first prominent in effecting an increase in elongation growth of otherwise dwarfed plants (Lang, 1970); as the still hypothetical florigens which are supposed to mediate flowering (Chailakhyan, 1968b; Lang, 1965), as the so-called abscisins (Addicott and Lyon, 1969; Wareing and Ryback, 1970); and more 38 3. History and Modern Concepts of Growth-Regulating Substances recently, as the newly erected group known as morphactins (Schneider, 1970; Ziegler, 1970). A dormin should cause previously growing cells or organs to enter a period of quiescence, rest, or dormancy; an abscisin, should activate cells in the region known as the abscission layer (see page 59) which is involved in leaf fall, fruit drop, etc.; a morphactin should be a morpho-logically active substance. These various terms for classes of growth regula-tors do not describe chemical substances per se, for each term may apply collectively to substances with a baffling array of structures. Similar ends may often be achieved by very different chemical means, so that a given substance may, under different circumstances, cause responses which might place it in different operational classes. A given substance may behave in ways that classify it as an auxin in one situation, or as a cytokinin in another.

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  eBook - ePub

  Plant Abiotic Stress Physiology

  Volume 2: Molecular Advancements

  • Tariq Aftab, Khalid Rehman Hakeem(Authors)
  • 2022(Publication Date)
  • Apple Academic Press

    (Publisher)

  In order to reduce the negative impacts on crop production worldwide, plants adapted various hormonal response pathways to resolve the environmental stressful conditions. Endogenous plant hormones play an important role in stressful environmental conditions by facilitating development, allocation of nutrients, and transitions from source to sink. Additionally, due to hormonal interactions, plant design and canopy shade can fine-tune the adaptive mechanism against diverse stress conditions. Abscisic acid (ABA), ethylene, salicylic acid, brassinosteroids, and jasmonic acid play a vital role in plant reaction to abiotic stresses among plants growth regulators. In addition, plants can detect favorable environmental conditions through other hormones including auxins, gibberellins, cytokinins, and strigolactones. The ABA is the main biomolecule created by drought and salinity in response to stress. Ethylene helps the plants in cold, drought with salinity, and overwatering. Jasmonic acid helps plants to recover from mechanical injuries and drought stress. The content of salicylic acid increases in response to different abiotic stresses such as drought salinity freezing and heavy metal toxicity. Brassinosteroids control the antioxidant activity of carbohydrate metabolism chlorophyll content to enhance plants growth under stress. In this chapter, an overview of plant hormones, their signaling, and perception is discussed in detail. In addition, a detailed account on phytohormones and their crucial role in tolerating environmental constraints is also deliberated.

  5.1 Introduction

  Plant growth regulators are identified in small concentrations as compounds of organic nature other than nutrients, which affect plant physiological processes. These compounds are either natural or synthetic, which plays a major role in their yield, quality, and harvesting processes when applied directly to plants [1 ]. Herbicides that are applied to plants are also called regulators of plant growth [2 –4 ]. Such plant growth regulators are called “plant hormone” when generated inside plants. Hormones derived from the Greek word meaning “growing or stimulating activity” [5 , 6 ]. According to the Environmental Protection Agency, plant growth regulators are described as “any component or mixture of components that accelerates or reduces the growth rate of the plant, changes in plant behavior, and plant maturation after application in small amounts by physiological action.” When applied in large quantities, the same plant growth regulator is considered as herbicide [7 ].

  Plant hormones regulate or alter processes of plant growth, such as leaves or flower formation, stem elongation, fruit maturation, and development. The practice of using regulators for plant growth in agriculture first began in the United States in 1930. Today, the use of plant growth regulators also has been extended in modern agricultural practices, because of their advantages in meeting the needs of the growing population. The first natural plant growth regulator to be discovered and successfully used in pineapple to improve flower production [8 ]. There are five classes of compounds in the principal division of endogenous plant growth regulators. These include auxins, gibberellins (GAs), ethylene, cytokinins, brassinosteroids (BRs), strigolactones, salicylates, jasmonates, polyamines, and some peptides, all represent new phytohormone families [9 , 10

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  Survey of Biological Progress

  Volume 1

  • George S. Avery, E. C. Auchter, G. W. Beadle, George S. Avery, E. C. Auchter, G. W. Beadle(Authors)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  Growth Hormones and Tissue Growth in Plants BY PHILIP R. WHITE The Lankenau Hospital Research Institute and the Institute for Cancer Research, Philadelphia, Pennsylvania SYNOPSIS Growth hormones (auxins) are known to control a wide variety of phenomena in plants. The spread of these phenomena is so great that the least common denominator appears to be the physiology of the cell itself rather than at any higher level of organization. One of the most versatile and precise methods of studying the physiology of cells of complex organisms is the technique known as tissue culture. This technique as regards plants has been applied in the United States almost exclusively to the study of tumor tissues, which grow satisfactorily without external sources of hormones and hence tell us nothing about hormone physiology. In France, however, tissue cultures of nontumor tissues, which require external sources of growth hormones, have been extensively studied. Although these studies clearly demonstrate the important role which such substances play in all growth, they have also resulted in the accumulation of evidence that under certain circumstances the capacity of a tissue to produce these substances may become greatly enhanced over the level normal to that tissue. This altered capacity for hormone production appears to be responsible for the develop-ment of certain malignant types of tumors in plants. The mechanisms involved in this enhancement are not yet fully understood. They present several possibilities, each of which has its counterpart in the theories of the mechanisms of cancer production in animals and in man. Further elucidation of this problem should prove to be of considerable importance. INTRODUCTION Theophrastus divided plants first into root, stem and leaf, these into bark, wood and pith, and these in turn into sap, fiber, veins and flesh. The first are organs, the second tissues, and the third materials.

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  Biostimulants in Plant Science

  • Seyed Mahyar Mirmajlessi, Ramalingam Radhakrishnan, Seyed Mahyar Mirmajlessi, Ramalingam Radhakrishnan(Authors)
  • 2020(Publication Date)
  • IntechOpen

    (Publisher)

  The plant hormone auxin is the key regulator of many aspects of plant growth and development, including cell division and stretching, differentiation, tropisms, apical dominance, senescence, abscission, and flowering. The cytokinins are mainly responsible for cell division, besides affecting many other processes, such as vascular development, apical dominance, and nutrient mobilization, especially when interacting with auxins [11]. Gibberellic acid has a marked effect on the seed germination process, activat-ing hydrolytic enzymes, such as α -amylase and protease, which actively act in the unfolding of the reserve substances, facilitating the mobilization of the endosperm. In addition, they promote the breakdown of dormancy, stem elongation and growth, cell division, and, consequently, leaf expansion [12]. According to Ref. [13], the biostimulant is composed of cytokinin, indole-butyric acid, and gibberellic acid, applied in seed, increased the seedling emergence percentage of Gossypium hirsutum L., as well as leaf area, height, and growth of seedlings. The algal extract applied via leaf yielded higher seed yield of Glycine max (L.) Merr [14]. An increase in the quantity and quality of Allium cepa L. bulbs with foliar application of putrescine and amino acid glutamine was observed [15]. L-glutamic acid is an important amino acid that acts as a central molecule in the metabolism of higher plants [16], being the precursor of the synthesis of chlorophyll in leaves [5], and the carbon regulatory function and nitrogen metabolism [17]. Glutamate is also a precursor of arginine and ornithine, which in turn act on the synthesis of poly-amines, which can act on plants, minimizing stress conditions [18, 19]. In addition to these amino acids, others are important in cell metabolism with the expressive diversity of biological functions. The application of extracts from algae or other plants have beneficial effects on growth and stress adaptation.

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  Plant Physiology 10

  A Treatise: Growth and Development

  • F.C. Steward(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  C H A P T E R FIVE Growth Regulators: An Account of Hormones and Growth Regulation T H O M A S G . B R O C K A N D P E T E R B . K A U F M A N I. Introduction 277 II. Abscisic Acid 278 A . Molecular Structure 278 B. Roles in Growth and Development 279 C. Mechanism of Action of Abscisic Acid 279 I I I . Auxins 288 A . Molecular Structure 288 B. Roles in Growth and Development 290 C. Mechanism of Action of Auxin 290 IV. Cytokinins 300 A . Molecular Structure 300 B. Roles in Growth and Development 301 C. Mechanism of Action of Cytokinins 301 V. Ethylene 308 A . Molecular Structure 308 B. Roles in Growth and Development 309 C. Mechanism of Action of Ethylene 309 V I . Gibberellins 315 A . Molecular Structure 315 B. Roles in Growth and Development 317 C. Mechanism of Action of Gibberellins 317 V I I . Summary 325 References 326 It has been almost 20 years since the natural plant hormones were reviewed in this series, by Κ. V. Thimann in 1972. It is thus an appro-priate time to approach these topics again in light of the immense amount of information that has accrued. Our task, then, will be to ex-tend the information covered in earlier works and bring them up to I. Introduction Plant Physiology A Treatise Vol. X: Growth and Development 277 Copyright © 1991 by Academic Press, Inc. All rights of reproduction in any form reserved. 278 T H O M A S G. B R O C K A N D P E T E R B . K A U F M A N date. Emphasis will be placed on the structure of the basic molecules, their roles in the regulation of plant growth and development, and their mechanism of action. We shall discuss only the major endogenous plant growth regulators: auxins, gibberellins, cytokinins, abscisic acid, and eth-ylene. A number of relatively new, native growth regulators are also of great interest, including the brassinosteroids [reviewed by Mandava (162)] and polyamines [reviewed by Evans and Malmberg ( 8 7 ) ] . How-ever, because of space limitations, these cannot be covered here.

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