Tree Anatomy – Roots, Shoots & Leaves

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Tree Anatomy

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  • Throughout this lesson, I will be bouncing between the anatomy and physiology of trees. Anatomy is the study of the physical parts making up the tree, while physiology is the study of all of the chemical reactions going on inside of the tree.
  • organelle - a specialized part of a cell; analogous to an organ; "the first organelle to be identified was the nucleus“ photosynthesis - synthesis of compounds with the aid of radiant energy (especially in plants), the process by which a green plant uses sunlight to build up carbohydrate reserves
  • The apical Meristem is found at the tip of a shoot (and root), where it forms new leaves (or roots).
  • Plant growth hormones, known as auxins, influence a variety of plant processes and are produced in growth regions throughout the plant (red dots). Researchers have worked out the series of molecular events the hormone uses to make plants grow.
  • Any of a group of organic compounds that includes sugars, starches, celluloses, and gums and serves as a major energy source in the diet of animals. These compounds are produced by photosynthetic plants and contain only carbon, hydrogen, and oxygen, usually in the ratio 1:2:1.
  • Trees Survive Wounds and Infection Because They Are Highly Compartmented Plants That Compartmentalize the Injured and Infected Tissues.
  • Resistograph
  • Meristematic - slowly dividing cells
  • Epidermis (botany) , in plants, the outermost layer of cells covering the leaves and young parts of a plant
  • Cytokinins are compounds with Auxin.
  • Plants have about a dozen basic cell types that are required for everyday functioning and survival. Additional cell types are required for sexual reproduction.
  • The vascular system of diffuse-porous trees (such as a birch) is characterized by vessels spread evenly throughout the sapwood.  These vessels are produced regularly during the growing season.
  • Trees still continue to slowly grow roots, respire and take in water and nutrients.
  • Also known as a water sprout, they form on stems and branches, and suckers produced from the base of trees. In older wood, Epicormic shoots can result from severe defoliation or radical pruning.
  • Cypress, arborvitae
  • Heartwood is wood that has died and become resistant to decay as a result of genetically programmed processes.
  • The shoot Meristem, or growing point, of most plants contain three distinct layers of cells. These cells undergo division in order to produce many new cells.
  • This extra network takes up additional water and mineral nutrients and supplies them to the plant, in essence acting as an extension of the plant’s root system. In return, the plant gives some of its sugars as food to the fungus. It is a mutually beneficial relationship. 
  • Nodes also seal off the stem.
  • Water enters young roots or Mycorrhizae roots by a process called osmosis.
  • You might also recall parenchyma are the only cells that can engage in mitotic divisions. Subsequently, they are the only type of cell found in apical meristems. Some of these are shown in various stages of division in the mitosis unit.
  • Phloem transports photosynthate from sink to source in the same way as xylem transfers water from sources (soil) to sinks (leaves); and that arteries transfer oxygen from sources (lungs) to sinks (respiring cells); and that veins transfer sugars from sources (ileum) to sinks (liver). Xylem and phloem sometimes act like a circulatory system (water goes up; sugar comes down the trunk), but not always.
  • Like Carbon, oxygen
  • Photosynthesis is arguably the most important biological process on earth. By liberating oxygen and consuming carbon dioxide, it has transformed the world into the hospitable environment we know today
  • This response occurs because of the production and release of hormones, like auxins. The shoot system of a plant has another predictable response to the presence of light (phototropism) – you guessed it, stems will grow toward light. 
  • Examples are – elms, oaks, and ashes The picture is of an ash tree.
  • Phloem responsible for movement of sugars, produced in the leaves, to other plant parts. Sieve cells become crushed and are reabsorbed into the tree or incorporated into bark.
  • Plants with taproots are difficult to transplant . The presence of a taproot is why dandelions are hard to uproot — the top is pulled, but the long taproot stays in the ground, and re-sprouts.
  • Auxin is a growth regulator.
  • The new cells that are formed may then differentiate into epidermal, ground, or vascular tissue.
  • Companion cells retain their nucleus and control the adjacent sieve cells. Dissolved food, as sucrose, flows through the sieve cells.
  • The difference between water sprouts and suckers has to do with location. Water sprouts arise from adventitious/latent buds which occur above the ground 2.Suckers may arise from buds (probably adventitious) located below the soil level.
  • There are several layers of cells lined up in the upper portion of the leaf to receive the sunlight. Most of the photosynthesis which occurs in a leaf occurs in these cells. Carbon dioxide diffuses into the leaf through special openings (usually located on the underside of the leaf) called stomates . The opening and closing of a stomate is regulated by the two surrounding guard cells. Water and gas exchange doesn’t occur at any other place in the leaf except through the stomata because the epidermal cells making up the leaf surface are covered with a waxy covering called the cuticle .
  • The current explanation for how water can travel up hundreds of feet in trees is called the cohesion-tension theory . Water molecules do a great job of holding onto each other and certain electrically charged substances like the walls of xylem vessels (tension). A chain of water exists inside of the tree so that for every water molecule that exits through the stomate, another one enters the root. Transpiration creates a negative pressure in the xylem tissue (sapwood) which allows water to be pulled up the tree.
  • Tree roots tend to avoid each other when young, but as they grow they may be forced together and from a graft union. These grafts can conduct diseases from one tree to another.
  • root cap . Cells are rapidly pushed to the front to form the root cap for two functions: first, to protect the meristematic cells, located just to the rear, undergoing cell division. second, the outermost cells are sloughed off to help lubricate the movement of the rapidly growing root through the soil.   The root hairs are the primary source for absorption of water and minerals, yet often only live for a few weeks.
  • Ideally, growing trees should be fertilized throughout the year. The greatest amounts of nitrogen (N) based fertilizer should be applied during the early spring and summer months. Several light applications a year are preferred as the tree gets older. A soil test may be needed to determine the amounts of phosphorus (P), potassium (K). Read the label for proper ratios and application rates of N, P and K for trees
  • Most pruning should be limited to thinning cuts.
  • Tree Anatomy – Roots, Shoots & Leaves

    1. 1. Tree Biology – Roots, Shoots & Leaves Tree Stewards Training
    2. 2. Nick Bomber <ul><li>ISA Certified Arborist </li></ul><ul><li>ISA Certified Tree Climber Specialist & Evaluator </li></ul><ul><li>TCIA Certified Tree Care Professional </li></ul><ul><li>10 years experience in “Greens Industry” </li></ul><ul><li>Operations Manager for SavATree/SavALawn </li></ul>
    3. 3. Introduction <ul><li>Learn the structures and functions of the bud’s, leaves, wood and roots of a tree. </li></ul><ul><li>Understand the interaction of structure and function in tree biology. </li></ul><ul><li>Learn the basic composition of a tree’s vascular system and understand how water and carbohydrates are transported within this system. </li></ul>
    4. 4. First Half Agenda <ul><li>Key Terminology </li></ul>
    5. 5. Key Terms! <ul><li>Protoplasm </li></ul><ul><li>A complex colorless substance forming the living contents of a cell. </li></ul>
    6. 6. Chloroplast <ul><li>Specialized organelle found in some cells and is the site of photosynthesis. </li></ul>
    7. 7. Abscission Zone <ul><li>Area at the base of the petiole where cellular breakdown leads to leaf drop. </li></ul>
    8. 8. Absorbing Roots <ul><li>Fine, fibrous roots that take up water and minerals; most of them are within the top 12 inches of soil. </li></ul>
    9. 9. Adventitious buds <ul><li>Bud that arises from a place other than a leaf axil. </li></ul>
    10. 10. Anthocyanins <ul><li>Red, purple, or blue pigments; responsible for those colors in some parts of trees and other plants. </li></ul>
    11. 11. Antitranspirant <ul><li>Substance sprayed on plants to reduce water loss through the foliage. </li></ul>
    12. 12. Apical bud <ul><li>Terminal bud on a stem. </li></ul>
    13. 13. Apical dominance <ul><li>Condition in which the terminal bud inhibits the growth and development of lateral buds on the same stem. </li></ul>
    14. 14. Apical Meristem <ul><li>The growing points at the tips of shoots. </li></ul>
    15. 15. Auxin <ul><li>Plant hormone or substance that promotes or regulates the growth and development of plants; it is produced at sites where cells are dividing, primarily in the shoot tips. </li></ul>
    16. 16. Axial Transport <ul><li>Movement of water, minerals, or photosynthate longitudinally within a tree. </li></ul>
    17. 17. Axillary bud <ul><li>Bud in the axil of a leaf; lateral bud. </li></ul>
    18. 18. Branch Bark Ridge <ul><li>Top area of a tree’s crotch where the growth and development of the two adjoining limbs push the bark into a ridge. </li></ul>
    19. 19. Branch collar <ul><li>Area where a branch joins another branch or trunk created by the overlapping xylem tissues. </li></ul>
    20. 20. Buds <ul><li>Small lateral or terminal bulge on the stem of plant that may develop into a flower or shoot; undeveloped flower or shoot. </li></ul>
    21. 21. Cambium <ul><li>Layers of cells that give rise to the phloem and xylem and allow for the diameter to increase. </li></ul>
    22. 22. Carbohydrate <ul><li>Compound, combining carbon and water, produced by plants during photosynthesis. </li></ul>
    23. 23. Carotenoids <ul><li>A yellow, orange, or red pigment responsible for those colors in some parts of trees and other plants. </li></ul>
    24. 24. Chlorophyll <ul><li>Green pigment of plants, found in chloroplasts; it captures the energy of the sun and is essential in photosynthesis. </li></ul>
    25. 25. CODIT <ul><li>Compartmentalization Of Decay In Trees. </li></ul>
    26. 26. Companion cell <ul><li>Companion cells provide the energy for the tube cells. </li></ul>
    27. 27. Compartmentalization <ul><li>Natural process of defense in trees by which they wall off decay in the wood. </li></ul>
    28. 28. Cork cambium <ul><li>Meristematic tissue from which cork and bark develop to the outside. </li></ul>
    29. 29. Cuticle <ul><li>Waxy layer outside the epidermis of a leaf. </li></ul>
    30. 30. Cytokinin <ul><li>Plant hormone involved in cell division. </li></ul>
    31. 31. Bonus Question !!!!!!!!!!!!! <ul><li>Why do leaves change color? </li></ul><ul><li>In the fall, the concentration of chlorophyll decreases in concentration to reveal other pigments. These other pigments have been present throughout the year contributing to photosynthesis but their appearance was masked by the large concentration of chlorophyll pigments. </li></ul>
    32. 32. Deciduous <ul><li>Tree or other plant that loses its leaves sometime during the year and stays leafless generally during the cold season. </li></ul>
    33. 33. Decurrent <ul><li>Rounded or spreading growth habit of crown of tree. </li></ul>
    34. 34. Differentiation <ul><li>Process in the development of cells in which they become specialized for various functions. </li></ul>
    35. 35. Diffuse porous <ul><li>Pattern of wood development in which the vessels are distributed evenly throughout the annual ring. </li></ul>
    36. 36. Dormant <ul><li>State of reduced physiological activity in the organs of a plant. </li></ul>
    37. 37. Epicormic <ul><li>Arising from latent or adventitious buds. </li></ul>
    38. 38. Evergreen <ul><li>Tree or plant that keeps its needles or leaves year round; this means for more than one growing season. </li></ul>
    39. 39. Excurrent <ul><li>tree trunk continuous to top; many small lateral branches, slender silhouette. </li></ul>
    40. 40. Fiber <ul><li>Elongated, tapering, thick-walled cell that provides strength. </li></ul>
    41. 41. Geotropism <ul><li>Plant growth produced as a response to the force of gravity; it can be positive as in the roots, or negative as in the trunk. </li></ul>
    42. 42. Growth Rings <ul><li>Rings of annual xylem visible in a cross section of the trunk of some trees. </li></ul>
    43. 43. Guard cells <ul><li>Pair of cells that regulate the opening and closing of stomate due to a change in water content. </li></ul>
    44. 44. Gymnosperm <ul><li>Plant with seeds exposed. </li></ul>
    45. 45. Heartwood <ul><li>Inner, nonfunctional xylem tissues that provide structural resistance to the trunk. </li></ul>
    46. 46. Included bark <ul><li>Bark that becomes embedded in a crotch between branch and trunk or between codominant stems and causes a weak structure. </li></ul>
    47. 47. Internode <ul><li>The region of the stem between two successive nodes. </li></ul>
    48. 48. Lateral roots <ul><li>Side-branching root that grows horizontally. </li></ul>
    49. 49. Lenticel <ul><li>Opening in the bark the permits the exchange of gases. </li></ul>
    50. 50. Meristem <ul><li>Growing point in a stem. </li></ul>
    51. 51. Mycorrhizae <ul><li>A symbiotic association between a fungus and the roots of a plant. </li></ul>
    52. 52. Node <ul><li>Slightly enlarged portion of stem where leaves and buds arise. </li></ul>
    53. 53. Osmosis <ul><li>Diffusion of water through a semi-permeable membrane from a region of higher water potential to a region of lower water potential. </li></ul>
    54. 54. Parenchyma cells <ul><li>Thin-walled, living cells essential in photosynthesis and storage. </li></ul>
    55. 55. Petiole <ul><li>The stalk or support axis of a leaf. </li></ul>
    56. 56. Phloem <ul><li>Plant vascular tissue that conducts photosynthate; located to the inside of the bark. </li></ul>
    57. 57. Photosynthate <ul><li>General term for the products of photosynthesis. </li></ul>
    58. 58. Photosynthesis <ul><li>The process in green plants by which light energy is used to form organic compounds from water and carbon dioxide. </li></ul>
    59. 59. Phototropism <ul><li>Influence of light on the direction of plant growth. </li></ul>
    60. 60. Radial transport <ul><li>Movement of substances in a tree perpendicular to the longitudinal axis of the tree. </li></ul>
    61. 61. Ray <ul><li>Tissues that extend radially across the xylem and phloem of a tree. </li></ul>
    62. 62. Reaction zone <ul><li>A natural boundary formed by a tree to separate wood infected by disease organisms from healthy wood; important in the process of compartmentalization. </li></ul>
    63. 63. Respiration <ul><li>Process by which carbohydrates are converted into energy by using oxygen. </li></ul>
    64. 64. Ring porous <ul><li>Tree that form wide vessels early in the growing season and narrower vessels later in the season. </li></ul>
    65. 65. Sapwood <ul><li>Outer wood that actively transports water and minerals. </li></ul>
    66. 66. Sieve cells <ul><li>Long, slender phloem cells. </li></ul>
    67. 67. Sinker roots <ul><li>Downward-growing roots that take up water and minerals; most are in the top 12 inches of soil. </li></ul>
    68. 68. Source <ul><li>Plant part that produces carbohydrates; mature leaves are sources. </li></ul>
    69. 69. Stomata <ul><li>Small pores between two guard cells on leaves and other green plant parts through which gases are exchanged. </li></ul>
    70. 70. Bonus Question !!!!!!!!!!!!!!!!!! <ul><li>Why do leaves fall from the tree? </li></ul><ul><li>Hormones cause physical changes to cells located between the petiole and stem in an area called the abscission zone. There is controlled cell death in this region allowing the tree to shed the leaf and to protect the exposed stem tissue from desiccation and infection. </li></ul>
    71. 71. Symbiosis <ul><li>A mutually beneficial association of two different types of living organisms. </li></ul>
    72. 72. Tap root <ul><li>Central, vertical root that grows right below the trunk and is often choked off by development of other roots. </li></ul>
    73. 73. Terminal bud <ul><li>A bud at the end of a twig or shoot. </li></ul>
    74. 74. Tracheid <ul><li>Elongated, tapering xylem cell, adapted for support. </li></ul>
    75. 75. Transpiration <ul><li>Water vapor loss through the stomata of leaves. </li></ul>
    76. 76. Tropism <ul><li>Growth movement or variation of a plant as a response to an external stimulus such as light or gravity. </li></ul>
    77. 77. Vessels <ul><li>Stacked, tube like, water-conducting cells in the xylem. </li></ul>
    78. 78. 10 minute break!
    79. 79. Basic Structure: Cells and Tissues <ul><li>Similarities: Plant and Animal Cells </li></ul><ul><ul><li>Both cells have cytoplasm which is basically &quot;cell guts.&quot; </li></ul></ul><ul><ul><li>Both cells have an outer cell membrane which separates the external environment from the cell's cytoplasm. </li></ul></ul><ul><ul><li>Both cells have a nucleus containing DNA which controls the activities of the cell. </li></ul></ul><ul><ul><li>Both cells have numerous organelles called mitochondria to convert sugar into a more useful energy molecule. </li></ul></ul>
    80. 80. How does a tree grow? <ul><li>A tree grows two ways: branches and roots grow longer from buds and the trunk and branches grow wider thanks to an incredibly thin layer of cells located just under the bark called the vascular cambium. </li></ul><ul><li>Tissue that has the ability to divide and grow into new structures is called meristematic tissue. </li></ul><ul><li>Differentiation of cell basically means the cell gets a job. </li></ul>
    81. 81. Xylem and Phloem <ul><li>Xylem and phloem tissues are produced by meristematic cambium cells located in a layer just inside the bark of trees and shrubs. </li></ul><ul><li>These two tissues extend from the leaves to the roots, and are vital conduits for water and nutrient transport. In a sense, they are to plants what veins and arteries are to animals. </li></ul>
    82. 82. <ul><li>The Xylem has four primary functions: </li></ul><ul><ul><li>Conduction of water and dissolved minerals </li></ul></ul><ul><ul><li>Support of the weight of the tree </li></ul></ul><ul><ul><li>Storage of carbohydrates </li></ul></ul><ul><ul><li>Defense against the spread of disease and decay </li></ul></ul><ul><li>Tracheid are long and relatively narrow, and transport materials from the roots upward. </li></ul>Xylem
    83. 83. Phloem <ul><li>Responsible for the movement of sugars, produced in the leaves, to other plant parts. </li></ul><ul><li>Phloem transport requires energy. </li></ul><ul><li>The two most common cells in the phloem are the companion cells and sieve cells. </li></ul>
    84. 84. Stems <ul><li>Be familiar with the following structures, you should know not only where each is located, but you should also be familiar with the function of each structure. </li></ul>
    85. 86. Leaves <ul><li>FUNCTION OF LEAVES </li></ul><ul><ul><li>Leaves are the solar energy and CO 2 collectors of plants. </li></ul></ul><ul><li>Two words: photosynthesis & transpiration. </li></ul>
    86. 87. Photosynthesis <ul><li>Physiological process in which carbon dioxide and water are combined to produce sugar. </li></ul><ul><li>The process begins when sunlight strikes chlorophyll, a green pigment, inside of the chloroplasts. </li></ul><ul><li>A byproduct of this reaction, oxygen, will diffuse out of the leaf. </li></ul>
    87. 88. Transpiration <ul><li>A very small amount of the water absorb by the roots actually goes into photosynthesis. </li></ul><ul><li>95% of the water that enters the roots travels up through the xylem and out the stomates. </li></ul><ul><li>Transpiration can also be thought of as “tree sweating,” this will cool off the tree. </li></ul>
    88. 90. Roots <ul><li>Serve Four Primary Functions: </li></ul><ul><ul><li>Anchorage </li></ul></ul><ul><ul><li>Storage </li></ul></ul><ul><ul><li>Absorption </li></ul></ul><ul><ul><li>Conduction </li></ul></ul>
    89. 91. How do roots grow? <ul><li>The tip of very young roots are protected by a collection of cells called the root cap. </li></ul><ul><li>Behind the root cap is the root apical meristem which is rapidly dividing to produce cells which move forward to become the root cap. </li></ul><ul><li>After increasing in size, these cells now undergo differentiation (they get jobs) into xylem, phloem and root hairs. </li></ul>
    90. 93. Tree Physiology- Respiration <ul><li>Unlike photosynthesis, which is seasonal in most climates, at least some respiration occurs at all times (even during the dormant season). </li></ul><ul><li>Respiration is the oxidization of carbohydrates to provide energy to keep cells alive and to fuel growth. </li></ul><ul><li>Without a surplus of carbohydrates, tree vigor declines and eventually death occurs. </li></ul>
    91. 94. Excurrent and Decurrent Trees <ul><li>All tree have apical dominance. Trees that have strong apical control develop an excurrent form while trees with weak apical control develop a decurrent form. </li></ul><ul><li>In excurrent trees, the lateral branches remain inferior to the central leader. The central leader is able to maintain this condition because it maintains strong apical control and continually suppresses the development of lateral branches. </li></ul><ul><li>In decurrent trees, the central leader is unable to exert strong apical control and the lateral branches begin to grow just as fast as the central leader. </li></ul>
    92. 95. Excurrent or Decurrent
    93. 96. Plant Hormones <ul><li>Auxins produced in the terminal buds suppress the growth of side buds and stimulates root growth. They also affect cell elongation (tropism), apical dominance, and fruit drop or retention. </li></ul><ul><li>Gibberellins affect the rate of cell division, flowering, increase in size of leaves and fruits. </li></ul><ul><li>Cytokinins promote cell division, and influence cell differentiation and aging of leaves. </li></ul><ul><li>Abscisic acid is considered the “stress” hormone. It inhibits the effects of other hormones to reduce growth during times of plant stress. </li></ul>
    94. 97. Understanding hormones is key to proper pruning <ul><li>Reduction pruning releases the apical dominance caused by auxins from the terminal bud. </li></ul><ul><ul><li>This allows side shoots to develop and the branch becomes bushier. </li></ul></ul><ul><li>Thinning cuts remove a branch back to the branch crotch. </li></ul><ul><ul><li>This type of cut opens the plant to more light. </li></ul></ul>
    95. 98. A System of Defense <ul><li>Compartmentalization is a process by which trees limit the spread of discoloration and decay. </li></ul><ul><li>After a tree has been wounded, reactions are triggered that cause the tree to form boundaries around the wounded area. </li></ul>
    96. 99. CODIT – 4 walls <ul><li>Wall 1 is formed when the tree responds to wounding by “plugging” the upper and lower vascular system to limit vertical spread of decay. </li></ul><ul><li>Wall 2 is formed by the last cells of the growth ring, limiting inward spread. </li></ul><ul><li>Wall 3 is composed of ray cells that compartmentalize decay by limiting lateral spread. </li></ul><ul><li>Wall 4 Is the strongest wall and is the new growth ring that forms after injury. </li></ul>
    97. 101. Thank you!

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