DOCSLIB.ORG

Physiology of Pruning Fruit Trees Richard P

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Physiology of Pruning Fruit Trees Richard P PUBLICATION 422-025 Physiology of Pruning Fruit Trees Richard P. Marini, Extension Specialist, Horticulture; Virginia Tech Introduction ways plants can grow. Woody plants are pruned to maintain a desired size and shape and to promote a certain type of growth. Primary growth is the increase in length of shoots Ornamental plants are pruned to improve the aes- and roots, and is responsible for increases in can- thetic quality of the plant, but fruit trees are pruned opy height and width. to improve fruit quality by encouraging an appro- Secondary growth is the increase in thickness of priate balance between vegetative (wood) and stems and roots. reproductive (fruiting) growth. Annual pruning of Both types of growth require cell division followed fruit trees always reduces yield, but enhances fruit by cell enlargement and differentiation. quality. Pruning increases fruit size because excess flower buds are removed and pruning encourages Plant Growth the growth of new shoots with high-quality flower Meristems are regions of cell division and there buds. Pruning improves light penetration into the are two types of plant meristems. An apical mer- canopy, and light is required for flower-bud devel- istem is located at the tip of every shoot and root opment, fruit set and growth, and red color devel- (Figure 1). As cells divide in these apical mer- opment. Pruning also makes the canopy more open istems, the shoots and roots elongate as cells are and improves pest control by allowing better spray piled one on another. Behind the region of cell penetration into the tree; air movement throughout division is a region of cell differentiation, where the canopy is increased, which improves drying cells enlarge and differentiate into various tissues. conditions and reduces severity of many diseases. In the axil of each leaf is a small apical meristem This publication describes why plants respond to called an axillary meristem that forms an axillary pruning and other forms of plant manipulation used bud, which usually remains dormant until well to train trees. This information applies to all plants, after the subtending leaf is fully developed. An but application to fruit trees is emphasized. axillary bud may remain dormant or develop into Pruning fruit trees is somewhat of an art based on a lateral branch or a flower. an understanding of plant physiology and develop- There are two distinct layers of meristematic tissue ment. In other words, if we understand how plants within the stem or root responsible for secondary grow and how they will respond to different types growth, the vascular cambium and the cork cam- of plant manipulations, we can alter vegetative bium (Figure 2). The vascular cambium is a cyl- growth and fruiting to obtain trees and fruit with inder of specialized cells, usually five to ten cells desirable characteristics. thick, running the length of the plant, including the A basic understanding of certain aspects of plant roots, and is responsible for the radial growth of physiology is a prerequisite to understanding prun- plant parts. Phloem cells are produced to the out- ing. Unlike animals, plants continue to increase side of the cambium and xylem cells are produced in size throughout their lives. There are only two to the inside of the cambium. www.ext.vt.edu Produced by Communications and Marketing, College of Agriculture and Life Sciences, Virginia Polytechnic Institute and State University, 2009 Virginia Cooperative Extension programs and employment are open to all, regardless of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. An equal opportunity/affirmative action employer. Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. RIck D. Rudd, Interim Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Alma C. Hobbs, Administrator, 1890 Extension Program, Virginia State, Petersburg. vascular phellogen Leaf cambium primordia Apical meristem bumps phloem xylem periderm (bark) axillary Figure 2. Longitudinal cross-section of a tree trunk shows buds the vascular and cork cambiums. Figure 1. Longitudinal section of shoot tip shows an apical a vegetative bud is sliced longitudinally during meristem, successively older leaf primordia, and axillary the winter and viewed under magnification, the bud primordia. apical meristem at the tip, leaf primordial (devel- oping leaves), axillary meristems, developing axil- Downward transport of sugars, nutrients, and hor- lary buds, and procambial tissue (tissue that will mones from the top of the tree to the roots occurs develop into the cambium) are all visible. in the phloem tissue. Xylem cells are tube shaped, become hollow and die to form a pipe-like sys- Buds on fruit trees usually have about seven tem through which water, hormones and mineral leaves and initial shoot elongation in the spring nutrients move from the roots to the top of the tree. results from cell expansion. During late June and Most of the radial growth of woody plants is due July some of the shoot apices will flatten out and to activity of the vascular cambium, but a small develop into flower buds. Flower buds are actu- amount results from activity in another lateral ally modified shoots and the various flower tissues meristem, the cork cambium, located outside the (petals, stigmas, anthers, etc.) are actually modi- vascular cambium. The cork cambium (phellogen) fied leaves. Although the process of switching together with the cork cells, constitute the perid- from vegetative to reproductive buds is not fully erm: a protective layer of suberized dead cork cells understood, hormones that can be influenced by forming the bark. Suberization is the impregnation environmental factors, stresses, and plant nutrition of cell walls of cork tissue with a fatty substance control the process. called suberin. Each season new layers of cells are There are several things we can do to influence produced and appear as growth rings when viewed whether or not a bud becomes a flower bud or in cross-section. Over time, the xylem cells at the remains vegetative. In general, factors that favor center of the trunk or limb are crushed and become rapid growth, such as high nitrogen levels in the nonfunctional as transport pipes, but they do pro- shoot tissues, inhibit the development of flower vide structural support to hold the plant upright. buds. Applying growth-promoting plant growth While grafting it is important to line up the cam- regulators such as gibberellins usually inhibits biums of the scion and the rootstock to ensure a flower-bud induction, whereas ethylene may pro- successful graft union. mote flower-bud development. Mild stresses such as shoot bending and water stress may also pro- Buds mote flower-bud development. Buds are important to the vegetative and reproduc- Producing annual crops of high-quality fruit tive growth of trees. Fruit tree training and, to a lesser requires a balance between reproductive and veg- extent, pruning primarily involves bud manipula- etative growth. Fruit producers use various tech- tion. Buds are actually undeveloped shoots. When niques, including pruning, branch bending, and 2 plant growth-regulator sprays, to manipulate tree Classification by arrangement on the stem growth and flowering. Often these techniques The bud arrangement influences the arrangement affect bud dormancy, so knowledge of buds and of a fruit tree’s branches and thus the tree’s shape bud dormancy is essential if we are to understand and how easy it is to manage. A node is the joint on how pruning influences tree growth. It is also a stem where a leaf is or was attached (Figure 3). important to be able to identify the different types Axillary buds are located in the axis above where a of buds on a tree, especially to distinguish between leaf is attached to the stem. In apples there is usu- flower and vegetative buds. ally only one leaf per node, whereas three leaves Buds may be classified as to location, contents, or often arise from a node on peach shoots. When a activity. leaf falls in the autumn, a leaf scar remains just below the axillary bud (Figure 3). Buds are oppo- Classification by content Several types of buds site when there are two at the same node but on commonly develop on fruit trees. Vegetative opposite sides of the stem. Forsythia is an example buds only develop into leafy vegetative shoots. of a plant with opposite buds. Buds are alternate Flower buds produce only flowers. Stone fruit when there is only one from each node and no one trees (peach, nectarine, apricot, plum, and cherry) bud is on the same side of the stem as the one next produce vegetative buds and flower buds. Apple above or below it. Deciduous fruit trees have buds and pear trees produce vegetative and mixed that spiral along a shoot (Figure 4). The spiraling buds. Both leafy shoots and flowers emerge from three-dimensional arrangement of leaves around a mixed buds. stem is known as Phyllotaxy and is expressed as a fraction, where the numerator is the number of Classification by location turns to get to a leaf directly above another and the Terminal buds are located at the tip of a shoot. denominator is the number of buds passed. On stone fruit trees terminal buds are vegetative buds. Terminal buds on apple and pear trees are usually vegetative; however, some varieties such Terminal bud as ‘Rome Beauty’ produce mixed buds terminally Node and are referred to as “tip bearers” or “terminal Internode bearers.” Most mixed buds on apple and pear Node Lateral bud trees are formed terminally on short, less than six- inch, shoots that terminate with a rosette of leaves. Leaf scar These short shoots are called “spurs.” Lateral buds form in the axils of leaves and are often referred Flower bud scar to as “lateral buds” or “axillary buds.” On stone- Lenticel fruit trees, lateral buds may be either vegetative Terminal bud scar or flower.
Load more

Recommended publications
  • The Control of Shoot Branching: an Example of Plant Information Processing
    Plant, Cell and Environment (2009) 32, 694–703 doi: 10.1111/j.1365-3040.2009.01930.x The control of shoot branching: an example of plant information processing OTTOLINE LEYSER Department of Biology, Area 11, University of York, York YO10 5YW, UK ABSTRACT the apical–basal axis defined by the establishment of the shoot apical meristem at one end, and the root apical mer- Throughout their life cycle, plants adjust their body plan istem at the other. Post-embryonically, the meristems give to suit the environmental conditions in which they are rise to the entire shoot and root systems, respectively. Fur- growing. A good example of this is in the regulation of thermore, the tissues they establish can produce secondary shoot branching. Axillary meristems laid down in each leaf meristems, which if activated can produce entirely new formed from the primary shoot apical meristem can remain axes of growth with the same developmental potential as dormant, or activate to produce a branch. The decision the primary root or shoot from which they were derived. whether to activate an axillary meristem involves the assess- Thus, the body plan of a plant is determined continuously ment of a wide range of external environmental, internal throughout its life cycle, allowing it to be exquisitely envi- physiological and developmental factors. Much of this infor- ronmentally responsive. Plants can alter their body plan to mation is conveyed to the axillary meristem via a network suit their environment, and thus the environmentally regu- of interacting hormonal signals that can integrate inputs lated development of new growth axes is functionally from diverse sources, combining multiple local signals to equivalent to environmentally regulated animal behav- generate a rich source of systemically transmitted informa- iours.
    [Show full text]
  • Signals Regulating Dormancy in Vegetative Buds
    International Journal of Plant Developmental Biology ©2007 Global Science Books Signals Regulating Dormancy in Vegetative Buds Wun S. Chao* • Michael E. Foley • David P. Horvath • James V. Anderson Biosciences Research Laboratory, Plant Science Research, 1605 Albrecht Blvd., Fargo, ND 58105-5674, USA Corresponding author: * [email protected] ABSTRACT Dormancy in plants involves a temporary suspension of meristem growth, thus insuring bud survival and maintenance of proper shoot system architecture. Dormancy regulation is a complex process involving interactions of various signals through specific and/or overlapping signal transduction pathways. In this review, environmental, physiological, and developmental signals affecting dormancy are discussed. Environmental signals such as temperature and light play crucial roles in regulating development and release of bud dormancy. Physiological signals including phytochrome, phytohormones, and sugar are associated with changes in dormancy status that occur when plants perceive environmental signals. Developmental signals such as flowering and senescence also have an effect on bud dormancy. Currently, many genes and/or gene products are known to be responsive directly or indirectly to these signals. The potential roles for these genes in dormancy progression are discussed. _____________________________________________________________________________________________________________ Keywords: flowering, hormones, phytochrome, senescence, signaling, sugar, temperature Abbreviations: ABA, abscisic
    [Show full text]
  • Pruning Concepts; Apple
    Winter Pruning for Best Results Dr. Ron Perry Department of Horticulture Michigan State University • Pruning: removal of a branch by mechanical means. • WHY: – Facilitate ease of cultural practices – Increase light penetration • Better fruit bud differentiation • Better fruit color & quality • Faster wound healing with UV light • Better flower bud development of flowering trees – Decrease mechanical injury to fruit & limbs • Limb rub • Fruit abrasion WHY: – Decrease fruit-bearing surface: better ratio of foliage/fruit • Better fruit size • Decrease fruit numbers • Decrease alternate bearing – Renew growth • Renews spur growth and vegetative growth – Maintain training system / structural framework – Remove broken, dying, & diseased branches – Better canopy air circulation= less disease, fruit cracking, better wound healing What happens to un-pruned trees? – Trees are Larger – Many branches; bush form (multi trunk) – Yield small fruits – Dense canopy – Bark inclusion – Poor structure / framework – More broken and diseased branches Plant Responses to Pruning • Pruning is a dwarfing process, that stimulates growth at localized sites ? From: Myers, S.C. and A. T. Savelle. 1996. Coordination of Vegetative and Reproductive Growth: Root restriction, branch manipulation and pruning. In, Tree Physiology Growth and Development, pub. by Good Fruit Grower, pp 69-80. Pruning……. • Removes usable reserves, both nitrogenous and carbohydrates. • Reduces next years’ growth potential • Loss of cambial /meristematic surface = net loss in wood growth • Growth near cuts is stimulated; overall, tree is reduced or dwarfed. • Therefore: pruning increases shoot growth but reduces total shoot and root growth. From: Forshey, C., D. Elfving and R. Stebbins. 1992. Training and Pruning Apple and Pear Trees. Pub. By Amer. Soc. Hort. Sci., 166 pages Plant Responses to Pruning Young Trees – Delays onset of fruit production in young trees – Reduces yields in early years – Strengthens framework scaffolding in young trees • Mature Trees – Reduces stored carbohydrates in wood.
    [Show full text]
  • Prospects for Disrupting Rhizome Apical Dominance Prior to Chemical Treatment of Phalaris Arundinacea Craig A
    RESEARCH REPORT Prospects for Disrupting Rhizome Apical Dominance Prior to Chemical Treatment of Phalaris arundinacea Craig A. Annen ABSTRACT Reed canarygrass (Phalaris arundinacea) is a widely distributed invasive species that dominates many natural areas and restoration sites. Cost-effective suppression and restoration strategies need to be developed for plant communities affected by this species. Pretreatments designed to disrupt rhizome apical dominance may augment herbicide performance by making reed canarygrass rhizomes more susceptible to herbicide applications. I tested whether coupling pretreatment disking or kinetin application to herbicide application would enhance chemical control relative to only solitary herbicide application. I also evaluated the relative performance of two grass-selective herbicides, sethoxydim and fluazifop. All treatments suppressed reed canarygrass and indirectly led to improvements in existing native species abundance com- pared to the untreated control. In terms of reed canarygrass suppression, non–reed canarygrass aboveground biomass, and species diversity (Shannon’s diversity), fluazifop performed as well as sethoxydim. Reed canarygrass biomass was consistently lower in plots where either disking or kinetin pretreatments were coupled with herbicide application than in plots receiving only herbicide treatment, though the degree of additional suppression varied with choice of herbicide. When sethoxydim was used for follow-up herbicide applications, disking reduced reed canarygrass biomass more than
    [Show full text]
  • Light Regulation of Axillary Bud Outgrowth Along Plant Axes: an Overview of the Roles of Sugars and Hormones
    REVIEW published: 18 October 2019 doi: 10.3389/fpls.2019.01296 Light Regulation of Axillary Bud Outgrowth Along Plant Axes: An Overview of the Roles of Sugars and Hormones Anne Schneider 1, Christophe Godin 2, Frédéric Boudon 3, Sabine Demotes-Mainard 1, Soulaiman Sakr 1 and Jessica Bertheloot 1* 1 IRHS, INRA, Agrocampus-Ouest, Université d’Angers, SFR 4207 QuaSaV, Beaucouzé, France, 2 Laboratoire Reproduction et Développement des Plantes, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, INRIA, Lyon, France, 3 CIRAD, UMR AGAP & Univ. Montpellier, Montpellier, France Apical dominance, the process by which the growing apical zone of the shoot inhibits bud outgrowth, involves an intricate network of several signals in the shoot. Auxin originating from plant apical region inhibits bud outgrowth indirectly. This inhibition is in particular Edited by: Benoit Schoefs, mediated by cytokinins and strigolactones, which move from the stem to the bud and that Le Mans Université, France respectively stimulate and repress bud outgrowth. The action of this hormonal network is Reviewed by: itself modulated by sugar levels as competition for sugars, caused by the growing apical Kosuke Fukui, sugar sink, may deprive buds from sugars and prevents bud outgrowth partly by their Okayama University of Science, Japan signaling role. In this review, we analyze recent findings on the interaction between light, Tibor Janda, in terms of quantity and quality, and apical dominance regulation. Depending on growth Centre for Agricultural Research (MTA), Hungary conditions, light may trigger different pathways of the apical dominance regulatory network. Libo Xing, Studies pinpoint to the key role of shoot-located cytokinin synthesis for light intensity and Northwest A&F University, China abscisic acid synthesis in the bud for R:FR in the regulation of bud outgrowth by light.
    [Show full text]
  • Basic Principles of Pruning Woody Plants
    Basic Principles of Pruning Woody Plants Cooperative Extension Service The University of Georgia College of Agricultural and Environmental Sciences/Athens Basic Principles of Pruning Woody Plants By S. C. Myers and G. L. Wade, Extension Horticulturists tuning is one of the most important cultural practices for maintaining >dy plants, including ornamental trees and shrubs, fruits and nuts. It lives both art and science; art in making the pruning cuts properly, and nee in knowing how and when to prune for maximum benefits, here are numerous reasons for pruning. Sometimes you want to train irect the growth of plants into a particular form or within a specified :e, like a formal hedge. Or you may want to prune mature plants to :rol or limit their size and shape, as in the case of fruit trees which are ted low to the ground to aid picking or hedge plants pruned at a partic- height. For fruiting plants, pruning plays an important role in improv- overall fruit quality, primarily by increasing light penetration into the nfortunately, many people approach pruning with a great deal of ap- lension. Others view pruning as a chore and give little forethought to nique as they hastily get the job done. Proper pruning requires a basic ;rstanding of how plants respond to various pruning cuts. The prin- :s and guidelines in this publication will help you master common ling techniques. Shoot Growth and Apical Dominance ru can partly determine the characteristic shape and size of a woody t and its response to pruning by the plant’s natural pattern of shoot ^th.
    [Show full text]
  • Plant Hormones
    Plant Hormones - AUXIN - CYTOKININ - ETHYLENE - ABSCISIC ACID - GIBBERELLIC ACID Coordination of Development via Hormone action • The major plant hormones: - Auxins Hormones that promote/control - Cytokinins growth (direction) - Gibberellins - Abscisic acid Survival hormones (tend to inhibit - Ethylene growth) Auxin - promotes cell elongation - inhibits lateral meristem activity - promotes root formation Auxin and differential growth: Gravitropic growth responses of Arabidopsis seedlings Cotyledons (embryonic leaves) Turn seedling 90o Hypocotyl (embryonic stem) Root Hypocotyl shows a negative gravitropic response Root shows a positive gravitropic response Areas of differential growth (one side grows faster than the other) Auxin and shoot apical dominance • Decapitation of the apical bud releases the lateral buds. In the absence of auxin coming from the shoot apex, lateral buds become active leading to branching (and a more bushy shoot development) Cytokinin - promotes cell division/shoot formation - promotes lateral meristem activity - controls sink/source identity of plant organs - delays senescence auxin cytokinin Cytokinin and shoot apical dominance • By increasing the cytokinin concentration in the shoot, lateral buds become active resulting in increased branching (and a more bushy shoot development) Cytokinin Gibberellin - promotes stem elongation growth - promotes seed germination Ethylene - inhibits cell expansion - accelerates senescence - accelerates fruit ripening Ethylene effects on etiolated seedlings Arabidopsis seedlings grown in the dark display an etiolated growth pattern: 1) unexpanded cotyledons Exposure to ethylene during 2) Apical hook growth in the dark results in: 3) long thin hypocotyl 1) Exagerated apical hook curvature 2) Much shorter and thicker hypocotyl Abscisic acid - promotes stomatal closure - inhibits seed germination Abscisic Acid and drought stress Abscisic acid is a signal of this emergency situation.
    [Show full text]
  • Regulation of Shoot Apical Meristem and Axillary Meristem Development in Plants
    International Journal of Molecular Sciences Review Regulation of Shoot Apical Meristem and Axillary Meristem Development in Plants Zhihui Xue 1, Liya Liu 1 and Cui Zhang 1,2,* 1 Key Laboratory of Plant Molecular Physiology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; [email protected] (Z.X.); [email protected] (L.L.) 2 College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China * Correspondence: [email protected] Received: 30 March 2020; Accepted: 19 April 2020; Published: 21 April 2020 Abstract: Plants retain the ability to produce new organs throughout their life cycles. Continuous aboveground organogenesis is achieved by meristems, which are mainly organized, established, and maintained in the shoot apex and leaf axils. This paper will focus on reviewing the recent progress in understanding the regulation of shoot apical meristem and axillary meristem development. We discuss the genetics of plant meristems, the role of plant hormones and environmental factors in meristem development, and the impact of epigenetic factors on meristem organization and function. Keywords: shoot apical meristem; axillary meristem; transcription; plant hormones; epigenetics 1. Introduction Plants are unique in their ability to continuously produce new organs throughout their life cycles. The process of continuous organogenesis depends on the activity of pluripotent cells. Some of these stem cells are located at the tips of shoot and root known as apical meristems. During embryogenesis, the shoot apical meristem (SAM) and root apical meristem (RAM) are established in the shoot apex and root apex, respectively. In monocots, such as rice and maize, the SAM is formed laterally, at the base of a single cotyledon [1].
    [Show full text]
  • Csbrc1 Inhibits Axillary Bud Outgrowth by Directly Repressing the Auxin Efflux Carrier Cspin3 in Cucumber
    CsBRC1 inhibits axillary bud outgrowth by directly repressing the auxin efflux carrier CsPIN3 in cucumber Junjun Shena,1, Yaqi Zhanga,1, Danfeng Geb,c, Zhongyi Wanga, Weiyuan Songa, Ran Gua, Gen Chea, Zhihua Chenga, Renyi Liud,e, and Xiaolan Zhanga,2 aBeijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Ministry of Education Joint International Research Laboratory of Crop Molecular Breeding, China Agricultural University, 100193 Beijing, China; bShanghai Center for Plant Stress Biology, Chinese Academy of Sciences, 201602 Shanghai, China; cShanghai Center for Plant Stress Biology, University of Chinese Academy of Sciences, 100049 Beijing, China; dCenter for Agroforestry Mega Data Science, Fujian Agriculture and Forestry University, 350002 Fuzhou, China; and eFujian Agriculture and Forestry University-University of California, Riverside (FAFU-UCR) Joint Center for Horticultural Biology and Metabolomics, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, 350002 Fuzhou, China Edited by Elliot M. Meyerowitz, HHMI and California Institute of Technology, Pasadena, CA, and approved July 15, 2019 (received for review May 10, 2019) Shoot branching is an important agronomic trait that directly de- factors (5). Auxin is synthesized in the shoot apex and acts as a termines plant architecture and affects crop productivity. To pro- repressor for branching and serves as the primary signal impos- mote crop yield and quality, axillary branches need to be manually ing for apical dominance (6). The main shoot tip produces a removed during cucumber production for fresh market and thus massive amount of auxin, which moves downward within the are undesirable. Auxin is well known as the primary signal impos- stem and represses axillary bud outgrowth.
    [Show full text]
  • The Shapes of Trees: a Matter of Compromise
    The Shapes of Trees: A Matter of Compromise Peter Thomas he whole point of a tree’s woody is to ensure that the skeletonleaves get as much light as pos- sible. At the same time, the tree must attend to its needs for pollination and seed dispersal and cope with environmen- tal challenges like high winds and poor soil-all the while investing as efficiently as possible in its woody structure. The enormous range of tree shapes that we see-from the unbranched stems of palms and tree ferns to the tall spires of conifers, the oaks’ broad, spreading crowns, and the multiple stems of old yews-all represent compromises among these often conflict- ing goals. The nature of the compromise can be hard to pinpoint, but some gross generali- zations are possible. Tree shapes can be divided simplistically into two categories: the conical outline of comfers and the rounded dome of hardwoods. Comfers of high latitude and altitude are typically steeply pyramidal with short branches that slope downwards to help shed snow and to intercept the maximum amount of light from a sun that is low on the horizon. The very similar shape found on conifers in dry regions, by contrast, appears to be an adaptation for intercept- the least amount of (and there- ing light Sitka spruce (Picea sitchensis) mth the typical spire of comfers with fore the least heat) when the sun is at its whorls of short branches. Perthshme, Scotland noonday hottest, thereby reducing the amount of water loss needed for cooling. where the light is diffused and in effect comes Pines farther south in savanna-type climates, from over the whole sky-the environment of such as the Mediterranean stone pine (Pinus most of Great Britain and the Pacific coast of pmea), develop a flat-topped, umbrella shape North America, where most trees take on the that helps resist drying winds by allowing leaves same roughly spherical shape.
    [Show full text]
  • Hormones 101
    PLANT HORMONES 101 Greene, D. [email protected] University of Massachusetts, Stockbridge School of Agriculture, Amherst, MA KEYWORDS Plant growth regulators, Plant hormones, auxins, gibberellins, cytokinins, abscisic acid, ethylene, directors of plant growth and development, naturally occurring compounds. ABSTRACT The growth and development of a plant is directed and guided by hormones produced by the plant. Plant hormones generally do not participate directly in the growth of a plant but they do send the signals that lead to gene expression and gene activation, enzyme activation and/or synthesis that ultimately results in developmental changes. There are five universally recognized major classes of hormones: auxins, gibberellins, cytokinins, abscisic acid and ethylene. There are two hormones that have a less dominant role in the regulation of plant growth and development: brassinosteroids and the jasmonates. Major Hormones Auxins: This group of hormones was the first to be discovered in the 1930s. Indole-3- acetic acid is the primary endogenous auxin found in most plants. While it is limited in the number of field uses it is probably has the greatest influence on how trees are grown and managed. Auxins do promote cell elongation. Apical dominance. Auxins are produced in the apical buds of shoots and diffuse downward inhibiting the growth and development of bud below. If the apical bud is removed or pruned off then inhibition of growth is lifted and lateral buds start to develop. These buds develop until they become dominate and reestablish the apical dominance. Growth of lateral buds are allowed due to the buildup of sugars and the presence of cytokinins.
    [Show full text]
  • Why Pruning Basil Makes the Plant Bushy
    Walking Water Experiment Why Pruning Basil Makes the Plant Bushy Grades: Time: 6 weeks Lesson summary: The Little Green Thumbs teacher’s manual contains lots of reminders for you to prune basil plants. The natural growth of basil is tall and if not pruned, the plant will grow tall and leggy. Pruning causes the side shoots to grow and you end up with a fuller, bushier plant. In a LGT indoor garden this is important because a pruned basil plant fits better under the lighting, giving it more light for photosynthesis. Besides, a bushy plant looks good and produces more basil for your students to taste and sample! Students will learn about this phenomenon by comparing two basil plants, one that is pruned and one that is left to grow naturally. What’s the big idea? Outcomes or purpose: • Students will learn that they can Why is it that those tiny side shoots on a basil influence how a plant grows. stay small unless the plant is pruned? And why is it that a pruned basil plant grows side shoots and becomes bushy? Teacher background: This is an adaptation of some plants where the main shoot is dominant. Botanists call this apical dominance. Apical simply means tip – like the top of a mountain or the top shoot of a plant. We can think of the word dominant as meaning the boss. The boss gives orders and controls what others do. So, let’s call the main shoot at the top of the plant “the boss”. In plants with apical dominance, the side shoots stay small.
    [Show full text]