Collenchyma and Sclerenchyma Tissues

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Questions and Answers

What is the primary function of collenchyma tissue in plants?

To provide rigidity and support throughout the plant body

To enable flexibility and support elongation in growing parts (correct)

To store nutrients and water in mature organs

To facilitate photosynthesis in green tissues

In which parts of the plant is collenchyma tissue primarily produced?

In woody tissues of mature plants

Shoot tips and young petioles (correct)

Subterranean shoots and flowers

Mature roots and older stems

What role do turgid parenchyma and collenchyma play in plant structure?

They function like air pressure and tire to provide stability. (correct)

They work independently to support the plant.

They primarily store water and nutrients for the plant.

They enhance photosynthesis by increasing surface area.

Why is sclerenchyma tissue unsuitable for growing shoot tips?

Its rigidity prevents elongation of the shoot. Signup and view all the answers

What characteristic distinguishes sclerenchyma tissue from collenchyma tissue?

Sclerenchyma has primary and secondary cell walls that are strongly thickened Signup and view all the answers

What is the main characteristic of sclereids?

They are brittle and often dead at maturity. Signup and view all the answers

Which type of sclereid is commonly referred to as stone cells?

Brachysclereids Signup and view all the answers

What type of fibers are found in the xylem of plants?

Xylary fibers Signup and view all the answers

Which type of sclerenchyma is responsible for conducting water in vascular plants?

Tracheids Signup and view all the answers

What is the primary function of fibers in plants?

Providing structural support Signup and view all the answers

Which type of fiber is most commonly found in phloem?

Extraxylary fibers Signup and view all the answers

Which type of sclereid is characterized by a star shape?

Astrosclereids Signup and view all the answers

Which of the following types of cells are typically found underneath the epidermis in young stems?

Collenchyma cells Signup and view all the answers

What is the primary function of glandular hairs in carnivorous plants?

Prey attraction and digestion Signup and view all the answers

Which of the following substances is typically exuded through hydathodes?

Excess salts Signup and view all the answers

What structural feature connects the cells of glandular hairs?

Plasmodesmata Signup and view all the answers

What is the phenomenon called when water droplets are exuded from the edges of leaves?

Guttation Signup and view all the answers

What is the primary function of xylem tissue in vascular plants?

Conducts water and soluble minerals Signup and view all the answers

In plants, what is the main challenge related to nutrient transport?

Roots can take up sugars but not water. Signup and view all the answers

Which structure in xylem helps facilitate the movement of water sideways?

Pits Signup and view all the answers

What key characteristic allows xylem vessels to prevent collapse under pressure?

Lignin content Signup and view all the answers

Which type of xylem cell is characterized by bordered pits?

Tracheids Signup and view all the answers

What type of tissue primarily transports sugars in plants?

Phloem Signup and view all the answers

What shapes can guard cells take?

Bean- or kidney-shaped Signup and view all the answers

What triggers the opening of the stomatal pore?

Increase in the potassium and sugar content in guard cells Signup and view all the answers

What is the main function of the subsidiary cells in relation to stomata?

Assisting in the opening and closing of stomatal pores Signup and view all the answers

How does the uneven thickening of guard cell walls affect their function?

It facilitates the opening of the stomatal pore during swelling Signup and view all the answers

What distinguishes trichomes from papillae?

Trichomes can be branched or unbranched, whereas papillae are outgrowths of epidermal cells Signup and view all the answers

What primary role do the hairs and trichomes play in plants?

Protecting against intense transpiration and herbivores Signup and view all the answers

Which type of trichome is specifically known for aiding drought resistance?

Squamiform hairs Signup and view all the answers

What is the appearance of guard cells when they are turgid and the stomatal pore is open?

Thick and swollen Signup and view all the answers

Study Notes

Collenchyma Tissue

Found in strands near the stem surface, along leaf veins, and near vascular bundles
Provides strength and flexibility
Cell walls exhibit plasticity and retain their shape even after tension or pressure is removed
Responsible for elongating root tips and providing flexibility in vining plants
Works with turgid parenchyma, similar to how air pressure works in a tire
Requires more glucose for production
Primarily produced in shoot tips and young petioles
Not present in subterranean roots and shoots

Sclerenchyma Tissue

Cells have both primary and secondary cell walls, which are strong and hard due to extreme thickening and lignification
Cells are often dead
Exhibits elasticity
Provides support and storage
Develops mainly in mature organs that have stopped growing
Supports growing and elongating plant parts, and some cells mature into sclerenchyma once the organ has matured (e.g., leaves)
Not useful in growing shoot tips because its rigidity would inhibit elongation
Two types: mechanical sclerenchyma and conducting sclerenchyma

Mechanical Sclerenchyma

Includes sclereids and fibers
Sclereids are short, somewhat cuboidal cells common in the shells of nuts and seeds
Fibers are long, tapered cells that often occur in groups or clumps, particularly abundant in the wood and bark of flowering plants
Sclereids:
- Isodiametric, often dead at maturity
- Brittle and inflexible
- Form hard and impenetrable surfaces, such as the shells of coconuts and seeds
- Flexibility would be disadvantageous

Types of Sclereids

Brachysclereids: Isodiametric or elongated, also called stone cells (found in the fleshy edible part of fruits)
Macrosclereids: Rod-like, found in the epidermal cells of seed coats
Osteosclereids: Bone-like with lobed ends, found in the seed coat of pisum (peas)
Astrosclereids: Star-shaped, found in the petioles of some plants
Trichosclereids: Hard, needle-like branched cells, serve as protection from herbivores
Filiform: Long cylindrical cells, found in the palisade and spongy parenchyma of olive leaves

Mechanical Sclereids: Fibers

Long and flexible, with many types dead at maturity while others remain alive and are involved in storage
Found in the wood of most flowering plants
Their strength supports trees and their flexibility allows them to sway in the wind

Types of Fibers

Surface fibers: Found on fruit walls and seed coats (e.g., coconuts)
Xylary fibers/wood fibers: Located in the xylem of plants
Extraxylary fibers/bast fibers: Located external to the xylem, the most common are phloem fibers

Conducting Sclerenchyma

Tracheids: Long, narrow cells with tapered ends, contain no perforations, dead at maturity, found in vascular plants
Vessel elements: Short and wide, with rather perpendicular end walls, must contain one or two perforations, dead at maturity, found almost exclusively in flowering plants and a few ferns, horsetails, and gymnosperms

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Description

Explore the characteristics and functions of collenchyma and sclerenchyma tissues in plants. Understand their roles in providing support, flexibility, and strength, as well as their unique cellular structures. Delve into how these tissues contribute to the overall growth and development of plants.