BIO 164 Lecture 4 - Ground Tissues: Parenchyma, Collenchyma, Sclerenchyma

Collenchyma

Derived from the Greek 'colla', meaning: glue, refers to the thick glistening wall characteristic of this tissue, this type of ground tissue has uneven cell thickenings: angular, lacunar, lamellar. It serves for support with flexibility (strong flexible cells) to a plant. They are closely related to parenchyma and differentiates usually from them. They have living protoplasts capable of resuming meristematic activity and have primary non-lignified cell wall. It retains active protoplasts and removes the wall thickenings.

Sclerenchyma

Derived from the Greek skleros, meaning "hard" and enchyma, an infusion, this tissue is composed of two types: sclereids and fibers. It has secondary lignified cell walls (causes death of the cells when deposited). It functions for mechanical support/inflexible support (may form strands). It is present in all parts of the plant. It is characterized by having long, elongated cells with admirably and evenly thickened cell wall.

Parenchyma

Derived from the Greek: para, beside, and en-chein, to pour (semiliquid substance "poured beside" other tissues that are formed earlier and are more solid.), this type of ground tissue is functionally classified according to its contents: chlorenchyma, storage, aerenchyma, water storage, and secretory. It is the main representative of the ground tissue system. It is found as a continuous tissue in plant organs (cortex, pith of stems, cortex of roots, ground tissue of petioles, mesophyll of leaves).

-Cactaceae -Aloe -Agave -Sansevieria -Peperomia

Give examples of succulent plants living in arid habitats.

-In the flesh of the fruits (brachysclereids) -In the endocarp (macrosclereids)

How are sclereids distributed in the fruits?

In seed coat epidermis or in layer(s) beneath epidermis (macrosclereids, osteosclereids)

How are sclereids distributed in the seeds of the plant?

-Continuous layer on the periphery of the vascular region -Groups of sclereids in pith (brachysclereids) -Astrosclereids in cortex

How are sclereids distributed in the stems?

-In mesophyll (diffuse) -Associated with ends of small veins (terminal) -Sometimes form part of epidermis (macrosclereids, trichosclereids, astrosclereids)

How are sclereids distributed throughout the leaves?

-Parenchyma forming vascular rays -Sclereids in mesophyll -Laticifers in parenchymatous tissue

In what ways are parenchyma associated with other cell types in morphologically heterogeneous tissue?

Transfer cells

A companion cell with numerous ingrowths of its wall, increasing the cell's surface area and enhancing the transfer of solutes between apoplast and symplast.

Osteosclereids

Also known as bone cells, this type of sclerenchyma is columnar in appearance with enlarged ends.

Trichosclereids

Also known as hairlike cells, these sclerenchyma tissue appears branched.

Macrosclereids

Also known as rod cells, this type of sclerenchyma is columnar in appearance.

Astrosclereids

Also known as star cells, this type of sclerenchyma has lobes or arms coming from the central body (star-shaped). They usually occur in the leaves.

Brachysclereids

Also known as stone cells, this type of sclerenchyma is isodiametric and elongated in appearance. They are round cells often present in the flesh of fruits.

Chlorenchyma

Also known as the assimilatory parenchyma, this type of parenchyma tissue contains numerous chloroplasts (plastids specialized for photosynthesis). They are greatly expressed in the mesophyll of leaves but can also occur in some types of stems in cortex, in piths, other green plant organs, and unripe fruits. Its cells are vacuolated and form extensive system of intercellular spaces.

Phloem fibers

An extraxylary fiber found in or associated with the phloem. Can be classified as primary or secondary phloem fibers.

Shape

Sclereids are classified based on what morphological feature?

-Wound healing -Regeneration

Stem cell parenchyma serves what particular purposes in the plant?

-Movement of water -Transport of food substances

These activities are played by parenchyma cell that occur in the xylem and phloem.

Tannins

These are a wide variety of chemical compounds stored in vacuoles of storage parenchyma that may interfere with digestive tracts of insect herbivores and inhibit microbial growth.

Glandular trichomes

These are epidermal outgrowths characterized by the presence of a head made of cells that have the ability to secrete or store large quantities of specialized metabolites.

-Some storage parenchyma (endosperm of the seeds of persimmon or coffee) -Endosperms of date palms -Wood -Transfer cells

These are examples of plant parts where you can find thickened and lignified parenchyma cells.

Air spaces

These are found in aerenchymatous tissue and are well developed in angiosperms growing in aquatic and semi-aquatic habitats or waterlogged soils.

Lacuna

These are large longitudinal aerenchyma found in leaves and stems of aquatic plants that differ structurally from that found in the roots. They are usually gas-filled and are continuous from roots to shoots. These enhances the diffusion of air from the leaves to the roots and enables wetland and waterlogged plants to maintain levels of oxygen sufficient to support respiration.

Fibers

These are long, extended cells often with tapering ends and have secondary thick walls that varies in the degree of lignification. The wall is hard and not hydrated as the wall in collenchyma.

Economic fibers

These are mostly phloem fibers that could be classified as soft fibers and are flexible because of the amount of lignin or hard fibers.

Simple pits

These are openings commonly found in secondary lignified cell walls of sclerenchyma.

Anthocyanins

These are plant pigments that give red, purple, and blue plants their rich coloring.

Aleurone grains

These are protein vacuoles that store proteins and are present in seeds.

Vascular tissue

These are special piping tissues that conduct water and sugars through the plant body. It comprises the xylem and phloem. This tissue conducts water and solutes between organs and also provides mechanical support.

Laticifers

These are specialized cells or ducts resembling vessels; they form branched networks of latex-secreting cells in the phloem and other parts of plants.

Elaioplasts (or lipid bodies)

These are specialized plastids in the cytoplasms of storage parenchyma which store lipids.

Lumen

These are the dead protoplasts of the sclerenchyma.

Hard fibers

These economic fibers are obtained from monocot leaves which have strongly lignified walls such as in Sansevieria (hemp) and Yucca.

-Photosynthesis -Assimilation -Respiration -Storage -Secretion

These essential activities is principally seated on this tissue.

Seed fibers

These fibers are obtained from cotton (Gossypium hirsitum), Coir (Cocos nucifera)

Leaf fibers

These fibers are obtained from the Abaca (Musa textilis).

Fibers from seed pods

These fibers are present from 'kapok' (Ceiba pentandra).

Stem fibers

These fibers are present in jutes (Corchorus capsularis), indian hemp (Cannabis sativa), and ramie (Boehmeria nivea)

Sclerified parenchyma

These parenchyma cells develop secondary walls (lignified) making it difficult to distinguish it from sclerenchyma.

-Pith and cortex of stems and roots -Mesophyll of the leaves -Flesh of succulent fruits -Endosperm of seeds

These plant parts consists largely or entirely of parenchyma cells.

Leaf fibers of monocots (with xylem) from corn and sugar cane

These plants are important in the paper making industry.

Sudan III or IV

These reagents are used in detecting lipid-containing organelles in a cell.

Fibers

These sclerenchyma tissue are long, slender cells, longer than wider, and form bundles.

Secretory canals (Internal cavities)

These structures is where secreted materials from secretory parenchyma gather.

Simple permanent tissues

These tissues compose the ground tissue system and are structurally and functionally similar.

-Chlorenchyma -Most storage cells

These types of parenchyma cells typically have thin and non-lignified cell walls.

Lamellar collenchyma

This collenchyma is characterized by having cell walls that are thickened in two opposite sides (inner and outer tangential walls). They can be found in the bark of trees.

Lacunar collenchyma

This collenchyma is characterized by having thickened cell walls that are adjacent to intercellular cavities. They can be found in water plants.

Annular collenchyma

This collenchyma is characterized by having thickened cell walls that are ring-like cross section. They are characterized by evenly thickened cell walls and are believed to be purely for support and structure in all directions, with no one side of the wall being thicker.

Angular collenchyma

This collenchyma tissue is characterized by thickness in the corners of the cells. They can be found in herbal parts of the plants.

Perivascular bundle fibers

This extraxylary fiber is present in either sheath or caps form (on side or two sides).

Chromoplasts

This is a type of plastid present in storage parenchyma that stores pigments that are responsible for the bright colors in fruit and flowers.

Idioblast

This is an isolated plant cell that differs from neighboring tissues. They have various functions such as storage of reserves, excretory materials, pigments, and minerals. They could contain oil, latex, gum, resin, tannin or pigments etc.

Polyhedral (Isodiametric)

This is the shape of a parenchyma cell which is characterized by having many sides or facets (approximately, 14 facets: polyhedron). They may also be elongated or lobed (cells vary in size).

Ground meristem

This meristematic tissue gives rise to the ground tissue system (Three tissue systems).

Root apical meristem

This meristematic tissue gives rise to the roots.

Shoot apical meristem

This meristematic tissue gives rise to the shoot.

Lysigenously

This method of formation of secretion is the result of cell lysis (e.g. secretion of volatile oils in the pericarp of citrus species).

Schizogenously

This method of formation of secretion is the result of the separation of the cell walls along the middle lamella (e.g. resin ducts of pines).

Ground Tissue

This packing and supportive tissue accounts for much of the bulk of the young plant. It also functions in food manufacture and storage. These tissues are also composed of cells which are structurally and functionally similar.

Secretory parenchyma

This parenchyma is rich in protoplasm that is rich in ribosomes, golgi bodies, and ER depending on type of secretion. Secretion may occur via external, epidermal structures, and within internal tissues. They are scattered among other cell types. Examples of secreted plant materials are tannins (secreted on idioblasts) and latex (secreted on laticifers).

Aerenchyma

This parenchyma tissue contains particularly large intercellular spaces/cavities (Air spaces) and is a characteristic of angiosperms growing in aquatic and semi-aquatic habitats or waterlogged soils such as rice. Deficiency of oxygen in such plants triggers the production of ethylene, which in turn induces programmed cell death and aerenchyma development. They may occur in the root, stem, and leaf as well. Roots contain air spaces to conduct oxygen from air down into the roots. Root cells are tolerant to ethanol which is the waste product from anaerobic respiration by root cells when oxygen is lacking.

Water storage parenchyma

This parenchyma tissue is specialized for water storage. This tissue consists of living cells of particularly large size and usually with thin walls. They are often in rows and may be elongated like palisade cells. Water is absorbed in the form of mucilage. It is a form of drought adaptation strategy and is a characteristic of the ground tissues of succulent plants living in arid habitats such as Cactaceae, Aloe, Agave, Sansevieria, and Peperomia.

Flax

This plant is economically important as it is used in textiles (linen).

Endosperm of seeds

This plant part contains parenchyma cells that are very compact.

Fleshy roots

This plant part has storage parenchyma with abundant intercellular spaces.

Amido black

This reagent is used in staining protein-containing organelles in a cell.

I2KI

This reagent is used in staining starch-containing organelles in a cell.

Drought adaptation

This strategy is achieved by storing the rare but periodically high precipitation either in the stem or in the leaves.

Dermal Tissue

This tissue system forms the "skin" of the plant body, protecting it and preventing water loss. It is in contact with the environment. It facilitates water and ion uptake in roots and regulates gas exchange in leaves and stems.

Storage parenchyma

This type of parenchyma tissue is a characteristic of storage organs, so it occurs principally in roots, rhizomes, bulbs, tubers, seeds or cotyledons. They may contain special ergastic substances. These cells can store starch in amyloplasts (in seeds and underground storage organs), sugars in the form of sucrose accumulated in the vacuole, as in sugar beets, and proteins and fats in protein vacuoles (as in parenchyma in seeds or embryo). They may also contain chromoplasts (in flowers and fruits), anthocyanins or tannins in vacuoles, or may contain different types of crystals.

Xylary fibers

This type of sclerenchyma fiber is located in the xylem.

Extraxylary fibers

This type of sclerenchyma fiber is located outside the xylem tissue (phoem fibers and perivascular bundle fibers)..

Sclereids

This type of sclerenchyma tissue is isodiametric to elongated in appearance and is mostly embedded in ground tissues.

-Mostly with thin primary cell wall -Middle lamella may or may not be distinguishable -Plasmodesmata are common -Typically thin, non-lignified -Sometimes thickened, lignified

What are the characteristics of a parenchyma cell wall?

-Angular -Lacunar -Lamellar -Annular

What are the classifications of the collenchyma tissue?

-Cellulose -Pectin (hydrophilic bounded to water and in large amounts: 40%) -Hemicellulose

What are the components of a collenchyma cell wall?

-Chlorenchyma (Assimilatory parenchyma) -Storage -Aerenchyma -Water storage -Secretory

What are the functional classifications of the parenchyma tissue?

-Mechanical support -Inflexible support

What are the functions of the sclerenchyma tissue?

-Parenchyma -Collenchyma -Sclerenchyma

What are the three classifications of the ground tissues?

-Dermal Tissue -Ground Tissue -Vascular Tissue

What are the three tissue systems present in plants?

-Sclereids -Fibers

What are the two types of sclerenchyma tissue?

-In continuous masses as parenchyma tissue -Associated with other cell types in morphologically heterogeneous tissue

What are the ways a parenchyma tissue would occur?

Support in plant parts that do not elongate

What is the function of the sclerenchyma fibers?

-Supporting tissue of the growing organs (support of growing leaves and stems, capable of extension) -Support against mechanical stress

What is the main purpose of the collenchyma tissue?

-Mostly found in leaves and stems (less in roots) -Peripheral regions (directly beneath the epidermis or a few layers removed from it) -Forms a continuous layer around the circumference of the axis of stem and leaf petiole (may occur in strands) and on midribs.

Where do collenchyma occur?

Mesophyll

t is the ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis. It also has extensive intercellular spaces called aerenchyma.