Medicinal Plants Lecture 6
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Questions and Answers

What term is used to describe wood that forms later in the season, typically in summer or early autumn?

  • Winter wood
  • Spring wood
  • Early wood
  • Late wood (correct)

    • What characterizes the transition between early wood and late wood in a growth ring?

  • A visible color change
  • A gradual blending
  • A distinct sharp line (correct)
  • A soft transition

    • Which statement is true regarding the structure of growth rings in trees?

  • Growth rings are perfectly circular.
  • Each ring consists of distinct early and late wood without lines between them. (correct)
  • Every tree has more late wood than early wood.
  • There are multiple lines between early and late wood.

    • When does late wood typically form in a tree's growth cycle?

    <p>In the summer or early autumn (D)</p> Signup and view all the answers

    What type of wood forms first in the growing season?

    <p>Early wood (A)</p> Signup and view all the answers

    What is the primary reason for the composition of vascular bundles in plants?

    <p>They facilitate the transport of nutrients and water. (B)</p> Signup and view all the answers

    In a vascular bundle, which additional component is present in dicots but not in monocots?

    <p>Cambium (D)</p> Signup and view all the answers

    Which of the following accurately describes the composition of vascular bundles in monocots?

    <p>Phloem and xylem only (D)</p> Signup and view all the answers

    What is a distinguishing feature of dicot leaves related to their vascular bundles?

    <p>Vascular bundles are organized in a ring. (C)</p> Signup and view all the answers

    Why is it important to understand the composition of vascular bundles in plant classification?

    <p>It helps identify plant species. (D)</p> Signup and view all the answers

    What happens to the vessels in most woody plants after their formation?

    <p>They become functional for a few years. (C)</p> Signup and view all the answers

    How long do the vessels in woody plants frequently remain functional?

    <p>For one year. (A)</p> Signup and view all the answers

    In regards to sapwood and heartwood, which statement is true?

    <p>Sapwood vessels function only for a limited time. (D)</p> Signup and view all the answers

    What is a characteristic of the vessels in woody plants?

    <p>They function for a limited duration and then become non-functional. (D)</p> Signup and view all the answers

    Which of the following statements best describes the lifespan of vessels in woody plants?

    <p>Vessels are functional only for a few years after being formed. (A)</p> Signup and view all the answers

    What characterizes the water conducting elements formed in spring wood?

    <p>They are wider than those formed in the following season. (B)</p> Signup and view all the answers

    Which season is associated with the formation of early or spring wood?

    <p>Spring (C)</p> Signup and view all the answers

    How do water conducting elements compare between spring wood and wood formed in the following season?

    <p>Spring wood elements are more developed and wider. (D)</p> Signup and view all the answers

    What is primarily developed in trees during spring?

    <p>Leaves and branches (A)</p> Signup and view all the answers

    What happens to the structure of water conducting elements after spring wood formation?

    <p>They transition to narrower sizes. (A)</p> Signup and view all the answers

    What are tyloses?

    <p>Enlarged protrusions of pit membranes (A)</p> Signup and view all the answers

    Which type of plant cell gives rise to tyloses?

    <p>Parenchyma cells (B)</p> Signup and view all the answers

    In which structure can tyloses protrude into?

    <p>Vessel or tracheid lumen (A)</p> Signup and view all the answers

    The half-bordered pits from which tyloses arise are found in which part of a plant's anatomy?

    <p>Xylem (A)</p> Signup and view all the answers

    Which of the following statements regarding tyloses is false?

    <p>They originate from dead cells. (D)</p> Signup and view all the answers

    What tissue type do xylem and phloem belong to?

    <p>Conducting tissues (D)</p> Signup and view all the answers

    Which process are chloroplasts primarily responsible for?

    <p>Photosynthesis (B)</p> Signup and view all the answers

    What is the term for the arrangement of xylem in roots?

    <p>Exarch xylem (A)</p> Signup and view all the answers

    Lenticels are structures that serve as replacements for which plant structures?

    <p>Stomata (C)</p> Signup and view all the answers

    Annual rings in old stems can be counted due to the formation of which tissue?

    <p>Spring and summer wood (B)</p> Signup and view all the answers

    Flashcards

    Vascular bundles in plants

    Vascular bundles are structures in plants that contain phloem and xylem tissues, responsible for transport of water, nutrients, and sugars.

    Dicot vs. Monocot vascular bundles

    Dicot stems have vascular bundles arranged in a ring with cambium in between xylem and phloem, while monocots have scattered vascular bundles without cambium.

    Dicot leaf vascular bundles

    Dicot leaf vascular bundles typically have a network of veins.

    Monocot leaf vascular bundles

    Monocot leaf vascular bundles usually have parallel veins.

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    Cambium in vascular bundles

    Cambium is a layer of meristematic cells that produces new xylem and phloem cells, allowing for secondary growth in dicots.

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    Annual rings

    Growth rings in trees, formed by differing thicknesses of wood during seasons.

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    Spring wood

    Wider wood cells formed in the spring when new growth occurs.

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    Early wood

    The wider wood formed in the spring due to new growth.

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    Water conducting elements

    Structures in trees which transport water.

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    New branches and leaves

    Parts of a plant that grow during the spring.

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    Late wood

    The denser wood formed during the later part of the growing season (summer or early autumn), typically characterized by smaller, thicker-walled cells.

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    Tree rings

    The visible concentric circles on the cross-section of a tree trunk, representing one year of growth.

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    Distinguishing late and early wood

    While there's no distinct line within a single ring, the late wood of one year and the early wood of the next year are separated by a sharp line.

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    How does wood density vary within a ring?

    Within a single annual ring, the late wood is denser due to smaller, thicker-walled cells compared to the early wood.

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    Sapwood

    The outer layer of wood in a tree that transports water and nutrients. This active layer is composed of living cells.

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    Heartwood

    The inner, non-functional core of a tree. It is composed of dead cells and provides structural support.

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    Vascular vessel lifespan

    In most trees, the cells responsible for water transport within the vascular system live for only a short time, often just one year.

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    How does sapwood become heartwood?

    As sapwood ages, the cells die and become filled with resins and other compounds, turning into heartwood. This process strengthens the wood.

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    Why is heartwood darker?

    Heartwood is darker because it contains resins and other compounds that accumulate over time as the cells die.

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    Tyloses

    Protrusions of pit membranes from living parenchyma cells that block the lumen of vessels or tracheids.

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    Pit membrane

    The thin wall separating two adjacent cells, allowing communication through pits.

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    Half-bordered pit

    A type of pit with a thickened border on one side.

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    Parenchyma cell

    Living cells in plant tissue that perform various functions, including storage and photosynthesis.

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    Lumen

    The hollow interior space of vessels or tracheids.

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    What are xylem and phloem?

    Xylem and phloem are conducting tissues responsible for transporting water, nutrients, and sugars throughout the plant.

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    What are chloroplasts responsible for?

    Chloroplasts are responsible for photosynthesis, the process by which plants convert light energy into chemical energy.

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    Endarch xylem

    Endarch xylem is the arrangement of xylem in roots where the protoxylem (older xylem) is located towards the center of the root, while the metaxylem (younger xylem) is located towards the outer part.

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    What do lenticels replace?

    Lenticels are structures that replace the function of stomata in woody stems, allowing for gas exchange.

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    How are annual rings formed?

    Annual rings are formed due to the different thicknesses of wood produced during spring and summer, creating visible rings in the stem.

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    Study Notes

    Medicinal Plants Lecture 6

    • The lecture covered medicinal plants, specifically focusing on 2024/2025, Lecture 6.
    • The lecturers were Dr. Amal F. Soliman (Associate Professor of Pharmacognosy) and Dr. Walaa Safwat (Lecturer of Pharmacognosy).
    • The lecture included a detailed discussion of secondary thickening/growth.

    Dicot and Monocot Stems

    • Dicot stems have vascular bundles composed of phloem and xylem only.
    • Monocot stems have vascular bundles composed of phloem, cambium, and xylem.
    • The difference in vascular bundle structure helps distinguish dicot and monocot stems.

    Dicot Leaf

    • The leaf presented is a dicot leaf.
    • This is determined by its structure, specifically its vascular bundle arrangement.

    Secondary Thickening/Growth

    • Occurs in most dicot roots and stems.
    • Increases the diameter of organs through vascular cambium and cork cambium activity.
    • Lateral meristems (vascular cambium and cork cambium) play a critical role.

    Secondary Growth in the Stem

    • Interfascicular cambium formation creates a continuous ring.
    • The cambium produces secondary xylem inwards and secondary phloem outwards.
    • Secondary xylem and phloem form rings traversed by medullary rays.

    Formation of Cork

    • Periderm arises in the subepidermal cortex.
    • Parenchyma cells become meristematic, forming cork cambium.
    • Cork cambium produces cork cells (phellem) and phelloderm (secondary cortex).
    • Suberin is secreted to the cork cells walls, making them waterproof and pathogen-resistant.

    Lenticels

    • Lenticels form beneath stomata when the epidermis is lost due to periderm formation.
    • They allow gas exchange in woody stems that have lost their epidermis.
    • Lenticels are a group of loosely organized bark cells for gas exchange.

    Short Summary of Secondary Growth

    • Tissues grow outside the vascular cambium forming the bark.
    • Tissues grow inside the vascular cambium forming the wood.

    Sapwood and Heartwood

    • Sapwood conducts water and nutrients; it's light-colored and remains functional for a few years.
    • Heartwood stops conducting water, becomes darker; it contains substances that protect from decay and microbial attack.

    Tyloses

    • Tyloses are balloon-like structures that block vessel cavities in heartwood.
    • They form from living parenchyma cells and obstruct water transport.

    Anatomy, Taxonomy, Physiology

    • The lecture also likely covered additional information related to Introduction to Pharmacognosy and additional lectures on Medicinal Plant anatomy, taxonomy and physiology.

    Quizzes

    • A variety of quizzes related to the plant structure concepts were covered.

    Additional Concepts

    • Casparian strips in Monocot roots and their location
    • Leaf characteristics determining a dicot or monocot leaf
    • The main function of sapwood

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    Related Documents

    Lecture 6- Medicinal Plants 2024/2025 (Mansoura National University) PDF

    Description

    Explore the insights from Medicinal Plants Lecture 6, which focuses on the roles of secondary thickening and growth in dicot and monocot stems and leaves. Led by Dr. Amal F. Soliman and Dr. Walaa Safwat, this lecture delves into the intricate structures that differentiate these plant types. Understand the importance of vascular cambium and cork cambium in secondary growth processes.

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