Cell types and tissues

What is a tissue in a plant?1

An aggregate of cells that function as a unit.

What is a simple tissue?

A tissue composed of cells that are all of the same type.

What is a complex tissue?

A tissue composed of more than one cell type.

What are the three main functions of plant tissues?

Structural support, protective covering, and transport of water and nutrients.

What is a meristem?

A site in the plant body where new cells form and the complex processes of growth and differentiation are initiated.

What is the shoot system?

The aboveground part of a vascular plant, including stems, leaves, buds, flowers, and fruits.

What is the root system?

The belowground part of a vascular plant, composed of main roots and branches.

What is the function of the cell wall in plant cells?

Provides rigidity and support to each cell.

What is pectin's role in plant tissues?

It's a material that glues plant cells together, contributing to the plant's strength and flexibility.

What are the three main tissue systems in plants?

Ground tissue system, vascular tissue system, and dermal tissue system.

What is the ground tissue system?

The most extensive tissue system, especially in leaves (mesophyll) and young green stems (pith and cortex).

What is the vascular tissue system?

Contains xylem (transports water and solutes) and phloem (transports sugars) throughout the plant.

What is the dermal tissue system?

(Epidermis and periderm) Covers and protects the plant surface.

Name the three types of simple tissues.

Parenchyma, collenchyma, and sclerenchyma.

Describe parenchyma cells.

Usually somewhat spherical or elongated living cells with thin primary cell walls involved in photosynthesis, respiration, storage, and secretion. They can also be reprogrammed.

What is lignin and what does it do?

A polymer embedded in some cell walls, making them impermeable to water and rigid.

What is the cortex in plants?

The region between the plant's epidermal and vascular tissues in most stems and roots, often composed of parenchyma tissue.

What is the pith in plants?

Usually composed of storage parenchyma cells and lies at the center of many stems, inside the cylinder of vascular tissues.

What is the mesophyll?

The parenchyma tissue that makes up the bulk of most leaves and is the site of most photosynthesis and water storage in leaves.

What are transfer cells?

Modified parenchyma cells with many cell wall ingrowths that improve short-distance transport of water and minerals.

Describe collenchyma tissue.

A simple tissue specialized to support young stems and leaf petioles. Its living cells have unevenly thickened, flexible cell walls.

Describe sclerenchyma tissue.

A rigid simple tissue that supports the weight of plant organs. Its cells (fibers and sclereids) often have thick, lignified secondary cell walls and are usually dead at maturity.

What are fibers (in plants)?

A type of sclerenchyma cell that is long and narrow with thick, pitted cell walls and tapered ends, often providing strength and support.

What are sclereids (in plants)?

A type of sclerenchyma cell with variable shapes (e.g., stone cells) and thick cell walls, contributing to rigidity.

What is xylem?

A complex vascular tissue that transports water and dissolved minerals throughout the plant. It contains tracheids, vessel members, fibers, and parenchyma cells.

What are tracheids and vessel members?

The water-conducting cells of xylem, also known as tracheary elements. They are dead at maturity and have thickened, often lignified, cell walls. Vessel members connect to form vessels.

What are vascular bundles?

Discrete bundles containing xylem and phloem found in leaves and young stems.

What is the vascular cylinder?

The central region of a young root containing the primary xylem and phloem.

What is primary xylem?

Xylem that is formed in the root and shoot apex very early in organ development.

What is secondary xylem?

Xylem that forms later in the development of stems and roots, organized in cylindrical patterns.

What are pits in plant cell walls?

Thin areas in the secondary cell walls (primary wall remains) that allow for water exchange between adjacent cells. They can be simple or bordered.

What is a vessel (in plants)?

A series of vessel members connected end to end, forming a continuous tube for water transport.

What is phloem?

A complex vascular tissue that transports sugars (produced by photosynthesis) throughout the plant. In angiosperms, it includes sieve-tube members, companion cells, parenchyma, and sometimes fibers and sclereids.

What are sieve-tube members?

The main conducting cells of the phloem in angiosperms, connected end to end to form sieve tubes. They lack a nucleus at maturity.

What are companion cells?

Living cells connected to sieve-tube members by plasmodesmata, thought to regulate their metabolism and play a role in loading and unloading phloem.

What are sieve areas and sieve plates?

Sieve areas are clusters of pores in the walls of sieve-tube members. A sieve plate is one or more sieve areas on the end wall of a sieve-tube member.

What is P-protein?

A complex of proteins found in the sieve-tube members of angiosperms.

What is callose?

A carbohydrate that can be deposited around the pores in sieve areas, especially in response to aging, wounding, or stress, to limit cell sap loss.

What are sieve cells and albuminous cells?

In gymnosperms and ferns, sieve cells are the conducting elements of phloem (similar to sieve-tube members but lacking sieve plates), and albuminous cells are associated companion cells.

What is the epidermis?

The outer protective covering of the plant, usually one layer of cells, composed of epidermal cells, guard cells, and trichomes.

What is the cuticle?

A waxy, impermeable layer (made of cutin) covering the outer walls of epidermal cells in most plant parts (except shoot apex and root cap), preventing water loss.

What are guard cells?

Specialized epidermal cells, usually crescent-shaped and containing chloroplasts, that occur in pairs surrounding a pore (stoma) and regulate gas exchang

What is a stoma (plural stomata)?

A pore in the epidermis surrounded by two guard cells, through which gases enter and leave the plant.

What are trichomes?

Epidermal outgrowths (hairs) that can be single-celled or multicellular and have various functions (e.g., root hairs for water absorption, leaf hairs for protection).

What is the periderm?

A protective secondary tissue that replaces the epidermis in older stems and roots. It consists of phellem (cork), phellogen (cork cambium), and phelloderm.

What is phellem (cork)?

The outermost layer of the periderm, composed of dead cells with suberin in their walls, providing protection.

What is phellogen (cork cambium)?

A layer of dividing cells in the periderm that produces phellem to the outside and phelloderm to the inside.

What is phelloderm?

A layer of parenchymalike cells formed to the inside of the phellogen in the periderm.

What are secretory tissues?

Tissues that produce and secrete various materials, found mostly in leaves and stems, and can be single cells or complex multicellular structures (e.g., laticifers).

What is growth in plants?

The irreversible increase in size that comes from both cell division and cell enlargement.

What is cell differentiation in plants?

The changes that a cell undergoes structurally and biochemically so that it can perform a specialized function.

What are apical meristems?

Meristems located at the tips of branches (shoot apical meristem - SAM) and roots (root apical meristem - RAM), responsible for primary growth (increase in length) and the ultimate source of all cells in the plant.

What are primary meristems?

Meristems that originate in apical meristems (protoderm, procambium, and ground meristem) and differentiate into the primary tissues, also contributing to the elongation of the root and shoot.

What are the three primary meristems and what tissues do they produce?

• Protoderm: Differentiates into the epidermis.

• Procambium: Differentiates into the primary xylem and primary phloem.

• Ground meristem: Differentiates into the pith and cortex of stems and roots and the mesophyll of leaves.

What are secondary meristems?

Meristems (vascular cambium and cork cambium) that produce the secondary tissues responsible for secondary growth (increase in thickness or girth).

what is the role of meristems in the plant body?

they are the origin of different cell types and tissues

which tissue is most extensive in leaves and young green stems

ground tissue system

which of the following best describes the characteristics of scelerids

they are dead at maturity with thick, lignified secondary cell walls

what type of plants use sieve cells rather than sieve-tube members

Gymnosperms and ferns

how do guard cells differ from other epidermal cells?

they contain chloroplasts and have a crescent shape

What distinguishes intercalary meristems from other types of meristems?

they occur within the stem to regulate its elongation

What is the primary role of sieve-tube members in the phloem?

transport sugars throughout the plant

What is the function of callose in the phloem?

It limits the loss of cell sap from injured cells.