Roots: Structure, Systems and Primary Growth
41 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

In a root undergoing secondary growth, from which primary tissue layer does the cork cambium typically originate?

  • Endodermis
  • Pericycle (correct)
  • Primary xylem
  • Primary phloem fibers

Which of the following cellular activities is the primary mechanism by which the pericycle increases in width during secondary growth?

  • Periclinal divisions (correct)
  • Anticlinal divisions
  • Development into fibers
  • Differentiation into sieve elements

During secondary growth in roots, what is the fate of the primary phloem's sieve elements as the periderm develops and the cortex is shed?

  • They differentiate into secondary xylem
  • They are absorbed back into the vascular cambium
  • They transform into cork cells
  • They are crushed and some develop into fibers (correct)

In the context of secondary root development, how does the vascular cambium initially form a continuous cylinder?

<p>Strips of vascular cambium form between the xylem and phloem and eventually merge. (D)</p> Signup and view all the answers

Where does cambium formation occur in the pericycle relative to the protoxylem poles during secondary root development?

<p>It forms opposite the protoxylem poles (C)</p> Signup and view all the answers

How does the root cap contribute to root function?

<p>By protecting the apical meristem from damage during soil penetration. (C)</p> Signup and view all the answers

In a eudicot root, what is the function of the endodermis?

<p>Regulation of the movement of water and minerals into the vascular cylinder. (D)</p> Signup and view all the answers

During seed germination, what is the role of the hypocotyl?

<p>To elongate and raise the cotyledons and shoot apex above the ground. (D)</p> Signup and view all the answers

What is the primary function of the zone of elongation in a plant root?

<p>To increase cell size, pushing the root tip further into the soil. (B)</p> Signup and view all the answers

A plant exhibits stunted growth and nutrient deficiency. Upon examining its root system, you observe a poorly developed taproot with minimal lateral branching. Which of the following is the most likely cause of these symptoms?

<p>Compacted soil, restricting root growth. (C)</p> Signup and view all the answers

A botanist discovers a new plant species with a unique root structure. Instead of growing downwards into the soil, the roots grow horizontally along the surface, extending far from the plant's base. What primary function are these roots MOST likely adapted for?

<p>Providing enhanced anchorage in unstable soils. (C)</p> Signup and view all the answers

If a plant's root system is composed primarily of adventitious roots, which of the following is LEAST likely to be true?

<p>The plant has a well-defined taproot. (D)</p> Signup and view all the answers

What is the primary function of the endodermis in plant roots?

<p>To regulate the movement of water and solutes into the vascular cylinder. (A)</p> Signup and view all the answers

In a typical eudicot root, where are the xylem and phloem located?

<p>In the center, forming a vascular cylinder. (C)</p> Signup and view all the answers

What is the pericycle's main role in plant roots?

<p>Formation of lateral roots. (D)</p> Signup and view all the answers

What is the differentiation pattern of xylem in primary roots described as 'exarch' mean?

<p>Xylem differentiates from the periphery inwards. (C)</p> Signup and view all the answers

What is the functional difference between protoxylem and metaxylem?

<p>Protoxylem develops earlier and can stretch as the root grows, while metaxylem develops later and is less flexible. (C)</p> Signup and view all the answers

In monocot roots, what is the core of the root typically composed of?

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

If a cross-section of a root shows the protoxylem located towards the periphery and the metaxylem towards the inside, what term describes this arrangement?

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

What tissue is primarily responsible for the storage of starch in roots?

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

How does the arrangement of vascular tissue differ between typical eudicot and monocot roots?

<p>Eudicots have a central vascular cylinder, while monocots have a core of parenchyma cells in the center. (A)</p> Signup and view all the answers

What is the origin of the vascular cambium in roots during secondary growth?

<p>The division of residual procambium between the primary xylem and phloem, along with pericyclic cells opposite the primary xylem. (D)</p> Signup and view all the answers

Which of the following describes the initial development of the vascular cambium's shape?

<p>It develops as isolated segments that eventually connect. (A)</p> Signup and view all the answers

What is the role of periclinal divisions in pericycle cells during the initiation of cork cambium?

<p>They spread around the circumference of the root, contributing to the formation of the periderm. (B)</p> Signup and view all the answers

How does the activity of the vascular cambium change the root's structure?

<p>It produces secondary xylem to the inside and secondary phloem to the outside, increasing the root's girth. (C)</p> Signup and view all the answers

Which of the following root tissues is retained from the primary growth stage even after secondary growth has occurred?

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

In contrast to the vascular cambium, what is the origin of the cork cambium?

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

Through divisions, the vascular cambium gives rise to what?

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

Where do the periclinal divisons occur for the initiation of the cork cambium?

<p>Outside the xylem poles (C)</p> Signup and view all the answers

What best describes the shape the vascular cambium eventually attains?

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

The periderm's creation relies on the initiation of what?

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

In a dicot root that has completed primary growth, which of the following tissues are fully differentiated?

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

How does the Casparian strip in the endodermis affect water and ion movement in roots?

<p>It blocks apoplastic movement and ensures all water and ions pass through the symplast. (D)</p> Signup and view all the answers

What is the origin of lateral roots within a plant root system?

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

What is the term used to describe the later-formed cells of the primary xylem?

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

What is the arrangement of vascular tissues in a triarch root?

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

In monocot roots such as corn, what term describes the arrangement of numerous xylem poles?

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

Which specialized cell wall feature is characteristic of the endodermis and controls water and solute uptake?

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

During the initiation of secondary growth in roots, what primary tissues give rise to the vascular cambium?

<p>Pericycle and residual procambium (C)</p> Signup and view all the answers

What is the primary chemical component of Casparian strips that makes them impermeable to water and ions?

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

What type of cell division is primarily responsible for the initiation of the vascular cambium during secondary growth?

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

Flashcards

Root Functions

Multicellular organs that anchor the plant, absorb water/minerals, and store nutrients.

Root Hairs

Small, hair-like extensions near the root tip that increase surface area for absorption.

Taproot System

A root system with one main vertical root and smaller lateral roots.

Fibrous Root System

A root system with many thin lateral roots and no main root.

Signup and view all the flashcards

Adventitious Roots

Roots that arise from stems or leaves, not from the primary root.

Signup and view all the flashcards

Root Cap

Protective layer covering the root tip that protects the apical meristem.

Signup and view all the flashcards

Endodermis

Innermost layer of the cortex that surrounds the vascular cylinder in roots.

Signup and view all the flashcards

Epidermis (Root)

Outermost layer of the root, providing protection.

Signup and view all the flashcards

Root Cortex

The layer of ground tissue in a root found between the epidermis and the vascular cylinder; it's role is storage.

Signup and view all the flashcards

Endodermis (Root)

Innermost layer of the cortex that surrounds the vascular cylinder, controlling water and nutrient uptake.

Signup and view all the flashcards

Vascular Cylinder

Central core of the root containing the xylem and phloem.

Signup and view all the flashcards

Pericycle

A layer of cells surrounding the vascular cylinder that gives rise to lateral roots.

Signup and view all the flashcards

Xylem (Root)

Vascular tissue that transports water and minerals upward from the roots.

Signup and view all the flashcards

Phloem (Root)

Vascular tissue that transports sugars (food) throughout the plant.

Signup and view all the flashcards

Exarch

Xylem differentiation starts from the periphery and moves inward.

Signup and view all the flashcards

Cork Cambium

A lateral meristem that produces the periderm, replacing the epidermis in stems and roots during secondary growth.

Signup and view all the flashcards

Root Cork Cambium Origin

In roots, it originates from the pericycle.

Signup and view all the flashcards

Secondary Growth (Roots)

Secondary growth is characterized by thickening due to lateral meristems.

Signup and view all the flashcards

Vascular Cambium (Root)

Forms strips between xylem and phloem, eventually becoming a cylinder producing secondary vascular tissues.

Signup and view all the flashcards

Periderm Formation (Root)

As secondary growth progresses, it's formed, and the cortex is shed off.

Signup and view all the flashcards

Metaxylem

Plant cells formed later during primary growth.

Signup and view all the flashcards

Triarch Root

A root with three (tri-) xylem poles.

Signup and view all the flashcards

Polyarch Root

A root with many xylem poles (poly-).

Signup and view all the flashcards

Casparian Strip

A waxy band in the endodermis cell walls; prevents apoplastic water movement.

Signup and view all the flashcards

Lateral Roots

Roots that arise from the pericycle.

Signup and view all the flashcards

Initiation of Secondary Growth

Procambium and pericycle cells begin dividing.

Signup and view all the flashcards

Vascular Cambium

The inner layer of dividing cells in the procambium during secondary growth.

Signup and view all the flashcards

Periclinal Divisions

The type of divisions made by cells in the procambium.

Signup and view all the flashcards

Vascular Cambium Origin

Vascular cambium arises from residual procambium between primary xylem and phloem.

Signup and view all the flashcards

Vascular Cambium Location

Located between primary xylem and phloem.

Signup and view all the flashcards

Circular Cambium

Vascular cambium becomes circular through cell division.

Signup and view all the flashcards

Pericycle Connection

Pericycle cells connect to cambium from residual procambium.

Signup and view all the flashcards

Cambium Function

Vascular cambium produces secondary xylem to its interior and secondary phloem to its exterior.

Signup and view all the flashcards

Cork Cambium Origin

Cork cambium arises in the pericycle.

Signup and view all the flashcards

What is Periderm

Collectively, the periderm is composed of cork cambium, cork, and phelloderm.

Signup and view all the flashcards

Study Notes

  • Roots are multicellular organs
  • Roots anchor the plant
  • Roots absorb minerals and water
  • Roots store organic nutrients

Origin and Structure of Roots

  • Elongating hypocotyl has formed a hook
  • The hook straightens out
  • This pushes the cotyledons and shoot apex above the ground
  • The stem-like axis (epicotyl) or shoot above the cotyledons becomes visible
  • It gives rise to foliage leaves

Root Systems

  • Taproot system: One main vertical root gives rise to lateral roots, or branch roots
  • Fibrous root system: Thin lateral roots with no main root
  • Adventitious roots: Arise from stems or leaves

Primary Growth of Roots

  • The root tip cap protects the apical meristem as the root pushes through soil.
  • Growth and development occur just behind the root tip, in three zones of cells: cell division, elongation, and maturation or differentiation.
  • The primary growth of roots produces the epidermis, ground tissue, and vascular tissue
  • Ground tissue fills the cortex region between the vascular cylinder and epidermis.
  • The innermost layer of the cortex is called the endodermis.
  • The stele is a vascular cylinder in most roots
  • Xylem differentiation in primary roots occurs from periphery inwards (centripetal) = exarch
  • The first cells to differentiate constitute the protoxylem
  • Later-formed cells constitute the metaxylem

Dicot vs Monocot

  • Dicot root has primary growth completed with fully differentiated Xylem and pholem.
  • The vascular cambium undergoes periclinal divisions and produces secondary xylem and pholem.
  • Pericyclic cells outside of the poles divide and connect to the cambium from residual procambium.

Endodermis

  • The thickened parts of cell walls contain the Casparian strips
  • The Casparian strips consist of a radial and tangenital wall
  • Casparian strips are impermeable to the passage of small molecules due to suberin
  • Suberin prevents the diffusion of water and ions out of the apoplast within the vascular cylinder
  • This occurs through the transverse and radial walls of the endodermal cells

Lateral Roots

  • Lateral roots arise from the pericycle
  • Lateral roots occur from the outermost cell layer in the vascular cylinder

Root Secondary Growth

  • Secondary growth begins in the residual procambium and parts of the pericyle.
  • The pericycle cells opposite the xylem poles initiate periclinal divisions.
  • The inner layer of cells is the vascular cambium
  • The outer layer remains as the pericycle

Cork Cambium

  • The periclinal division in the pericycle, which are not involved in the formation of the vascular cambium, occur not only outside the xylem poles
  • This spreads around the circumference of the root -> Cork Cambium

Atypical Secondary Growth

  • Atypical secondary growth in roots cause excessive development of parenchyma in the secondary xylem, produced by the normal cambium.
  • The parenchyma produced by additional cambia produce conducting elements

Specialized/modified roots

  • Storage roots
  • "Strangling” aerial roots
  • Buttress roots
  • Tap Roots
  • Prop roots
  • Pneumatophores enable root system to obtain oxygen by projecting above water
  • Photosynthetic roots
  • Root nodules develop as a result of a symbiotic relationship between rhizobial bacteria and the root hairs
  • Mycorrhiza is a fungi-plant root association

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Description

Overview of root systems: taproot, fibrous, and adventitious. Discussion of primary root growth, including the zones of cell division, elongation, and maturation. Examination of the ground and vascular tissues.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser