Plant Stem Growth and Meristems
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Questions and Answers

What type of cambium is formed between the xylem and phloem in dicot stems?

  • Vascular cambial ring
  • Interfascicular cambium
  • Intrafascicular cambium (correct)
  • Medullary cambium

Which type of initial is more abundant in the vascular cambium?

  • Medullary initials
  • Fusiform initials (correct)
  • Interfascicular initials
  • Ray initials

What is the primary outcome of the periclinal divisions in fusiform initials?

  • Formation of primary phloem
  • Formation of cambial cells only
  • Formation of primary xylem
  • Formation of secondary phloem and xylem (correct)

What happens to primary phloem during secondary growth?

<p>It is pushed towards the outside and gets crushed (C)</p> Signup and view all the answers

How many times more secondary xylem is formed compared to secondary phloem?

<p>8-10 times (B)</p> Signup and view all the answers

Which cells are responsible for forming the cambial ring?

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

What type of cambium develops from the cells of medullary rays?

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

What is the shape of fusiform initials in the vascular cambium?

<p>Long with pointed ends (B)</p> Signup and view all the answers

What type of meristem is responsible for primary growth in plants?

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

Secondary growth in plants primarily occurs due to which type of meristem?

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

Which type of vascular tissue is produced by the vascular cambium?

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

Which characteristic is true about secondary growth in plants?

<p>It leads to an increase in the plant's girth. (C)</p> Signup and view all the answers

What is the role of the cambium in secondary growth?

<p>It adds to the width of the plant. (A)</p> Signup and view all the answers

How do dicots differ from monocots regarding growth?

<p>Only dicots undergo secondary growth. (C)</p> Signup and view all the answers

Which component of vascular tissue primarily transports water and dissolved minerals?

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

What happens to the primary xylem and phloem during secondary growth?

<p>They are completely replaced by secondary tissues. (D)</p> Signup and view all the answers

What is the primary difference in the arrangement of xylem and phloem between monocots and dicots?

<p>Monocots have scattered bundles of xylem and phloem. (C)</p> Signup and view all the answers

Which type of cambium is responsible for the formation of secondary vascular tissues?

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

What is the primary growth in plants caused by?

<p>Division of apical meristems. (D)</p> Signup and view all the answers

Which statement accurately describes cambium activity in monocots?

<p>Cambium is absent in most monocots, preventing secondary growth. (B)</p> Signup and view all the answers

What does the activity of cambium primarily lead to in plant stems?

<p>Increase in stem diameter or girth. (B)</p> Signup and view all the answers

How does secondary growth occur in some monocots like Palm and Coconut?

<p>Through normal cambium activity. (B)</p> Signup and view all the answers

What are the roles of the two types of cambium in woody plant stems?

<p>Both types of cambium contribute to secondary xylem and phloem formation. (A)</p> Signup and view all the answers

What happens to the cambium cells each time they divide?

<p>One cell remains meristematic and the other differentiates. (C)</p> Signup and view all the answers

What happens to the primary tissues in the center of the stem during secondary growth?

<p>They degenerate due to pressure from secondary xylem. (B)</p> Signup and view all the answers

What characterizes heartwood compared to sapwood?

<p>Heartwood is darker and contains more waste materials. (B)</p> Signup and view all the answers

What is the main function of sapwood?

<p>Water conduction within the plant. (D)</p> Signup and view all the answers

What occurs to the cavities in heartwood that prevents water conduction?

<p>They are filled with waste materials. (A)</p> Signup and view all the answers

Tyloses play what role in the heartwood of a plant?

<p>They block the water conduction. (A)</p> Signup and view all the answers

Why is the destruction of sapwood detrimental to a plant?

<p>It blocks water conduction, causing plant death. (C)</p> Signup and view all the answers

Which of the following statements about heartwood is false?

<p>Heartwood conducts water effectively. (D)</p> Signup and view all the answers

What is the primary characteristic of the waste materials found in heartwood?

<p>They are antiseptic in nature. (B)</p> Signup and view all the answers

Flashcards

Apical Meristem

A type of plant tissue that is responsible for primary growth, allowing the plant to grow in length.

Lateral Meristem

A type of plant tissue that is responsible for secondary growth, allowing the plant to grow in width.

Primary Growth

Growth that occurs at the apical meristem, increasing the length of the plant.

Secondary Growth

Growth that occurs at the lateral meristem, increasing the girth or width of the plant.

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Vascular Cambium

A type of lateral meristem that produces secondary xylem and phloem.

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Cork Cambium

A type of lateral meristem that produces cork cells, which protect the plant from injury and disease.

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Xylem

A type of vascular tissue that transports water and dissolved minerals from the roots to the rest of the plant.

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Phloem

A type of vascular tissue that transports food (sugars) from the leaves to the rest of the plant.

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Monocot vascular bundles

In monocots, the xylem and phloem are arranged in scattered bundles throughout the stem.

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Dicot vascular bundles

In dicots, the xylem and phloem are arranged in concentric rings, with xylem on the inside and phloem on the outside.

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Cambium

A meristematic tissue responsible for lateral (outward) growth in plants.

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Monocot secondary growth

Secondary growth is usually absent in monocots due to the lack of cambium, but some exceptions exist like palm trees.

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Intrafascicular Cambium

A type of primary meristem located within the vascular bundle (between xylem and phloem).

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Interfascicular Cambium

A type of secondary lateral meristem found outside the vascular bundle, developing from medullary rays cells.

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Vascular Cambial Ring

A complete ring formed by the union of intrafascicular and interfascicular cambium, responsible for secondary growth.

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Fusiform Initials

Long, pointed cells within the vascular cambium that divide to produce secondary xylem and phloem.

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Ray Initials

Spherical cells in the vascular cambium that produce radial rays, responsible for lateral transport.

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Periclinal Division

A cell division where the plane of division is parallel to the longitudinal axis of a cell.

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Secondary Xylem vs. Secondary Phloem

Secondary xylem is formed more than secondary phloem due to hormonal factors, resulting in more wood than bark.

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Heartwood

The central, darker wood of a tree that is no longer actively transporting water. It primarily provides structural support and is resistant to decay.

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Sapwood

The outer, lighter-colored wood of a tree that actively transports water and nutrients. It is also the youngest wood.

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Tyloses

Bladder-like growths of parenchyma cells that protrude into the lumens of vessels and tracheids, blocking water transport in heartwood.

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What is the function of heartwood?

Heartwood primarily provides structural support for the tree and is resistant to decay, making it strong and durable.

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What happens when heartwood is destroyed?

The tree's vital functions are unaffected because the heartwood no longer transports water.

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What happens when sapwood is destroyed?

The tree will die because the sapwood is responsible for transporting water, which is essential for the tree's survival.

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Why does heartwood become darker?

Waste materials from decaying cells accumulate in the heartwood, giving it a darker color.

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Xylotomy

The study of wood.

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Study Notes

Plant Stem Growth

  • Plant stem growth occurs at meristems in the shoot system
  • Two types of meristems: apical and lateral
  • Apical meristems cause lengthwise growth
  • Lateral meristems cause outward (thicker) growth
  • Secondary growth is the increase in girth of stems/branches in some plants
  • Secondary growth is caused by lateral meristems called cambium
  • Two important types of cambium: vascular cambium and cork cambium
  • Vascular cambium creates more vascular tissue (xylem and phloem)
  • Xylem transports water and minerals
  • Phloem transports food
  • Secondary xylem and phloem increase plant width
  • Secondary growth occurs only in dicots, not monocots
  • Monocot stems have vascular bundles scattered throughout
  • Dicot stems have vascular bundles in rings (xylem inside, phloem outside)
  • Cambium is meristematic tissue for lateral growth; two types in woody stems, increasing diameter
  • Vascular cambium produces secondary vascular tissue (xylem and phloem)
  • Cork cambium forms the bark

Cambium Structure

  • Cambium is a single layer of cells
  • Cells divide parallel to epidermis
  • Cells differentiate into permanent tissue (xylem or phloem based on location)
  • Secondary growth in stems and roots of dicots and gymnosperms
  • Secondary growth in part of monocots but not common
  • Secondary growth in stems begins earlier in the stelar region
  • Early secondary growth forms a ring

Formation of Cambium Ring

  • Vascular bundles are xylem and phloem bundles in stems
  • Intrafascicular cambium is within vascular bundles (primary meristem)
  • Secondary growth causes interfascicular cambium to form as cells in medullary rays differentiate
  • Complete ring is formed from intrafascicular and interfascicular cambia (vascular cambium ring)
  • Two types of cells in vascular cambium ring: Fusiform and ray initials

Secondary Growth Details/Processes

  • Fusiform initials are long and pointed, while ray initials are spherical
  • Periclinal or tangential divisions occur in fusiform initials, parallel to longitudinal axis
  • Cells produced by division differentiate into secondary xylem (towards center) or secondary phloem (towards outside)
  • Secondary xylem and phloem formation pushes existing tissues (primary phloem, pith) outward or inward, respectively
  • Secondary xylem forms in greater amount than phloem in most plants
  • Secondary xylem formation blocks water transport
  • Sapwood (outer part of wood) carries water and nutrients, and is lighter in color
  • Heartwood (inner part) contains waste products, making the wood dark

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Secondary Growth in Plants PDF

Description

Explore the fascinating world of plant stem growth in this quiz. Learn about the roles of apical and lateral meristems, as well as the process of secondary growth and the significance of cambium in woody plants. Test your knowledge on how dicots and monocots differ in their stem structures and functions.

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