Chapter 36

The Vascular Cambium produces ________________________.

Phloem to the OUTSIDE and Xylem to the INSIDE

Meristems

Found in shoot and root apices, as well as other parts. Meristem cells are undifferentiated cells that can divide indefinitely and give rise to many types of differentiated cells.

QUESTION: Root cortex cells are produced by?

Ground Meristem

Secondary Growth In Woody vs. Nonwoody Plants

Although it increases girth in many nonwoody plants, its effects are most dramatic in woody plants, which have 2 lateral meristems: 1) cork cambium, which contributes to the outer bark, and 2) vascular cambium which produces secondary vascular tissue.

Primary Meristems

Any of the 3 meristems produced by the apical meristem. They give rise to ground, dermal, and vascular tissue. They include: Protoderm, Procambium,

Secondary Growth

Increase in diameter due to lateral meristems.

Shoot System

Stems and leaves. Flowers, other reproductive organs, and ultimately, fruits and seeds are also formed on the shoot.

Transpiration (xylem)

The loss of water vapor by plants; most transpiration occurs through the stomata.

What Constitutes the Palisade Mesophyll?

Tightly packed rows of Chlorenchyma.

The 3 Primary Meristems

1) Protoderm, 2) Procambium, 3) ground meristem

Features of Plant Cells Used in to Distinguish Them

1) Vacuole Size 2) Thickness of secretions in the cell wall 3) Whether cells are alive at maturity 4) thickness of their cellulose cell walls

Definition: Dermal Tissue

A type of tissue that forms the outer layer of the body and is in contact with the environment; it has a protective function.

Sieve-Tube Member

All lack nucleus at maturity. Possessed by most Angiosperms. Each member is assocaiated with an adjacent, specialized parenchyma cell known as a "companion cell". "Companion Cells" carry out some of the metabolic functions needed to maintain the associated sieve-tube member, b/c it lacks a nucleus.

Food Conduction Accomplished by What Cells? (phloem)

By two kinds of elongated cells: Sieve Cells and Sieve-Tube members. Both have clusters of pores known as sieve areas b/c the cell walls resemble sieves. Unlike Pits in xylem, which contain primary cell walls, phloem pores are completely open.

Meristems: Overview

Clusters of small cells w/ dense cytoplasm and proportionately large nuclei that act as stem cells do in animals. That is, one cell divides to give rise to 2 cells, of which 1 remains meristematic, while the other undergoes differentiation and contributes to the plant body.

Epidermal Cells

Collectively forms the outermost layer of the primary plant body; includes specialized cells such as trichomes and guard cells.

QUESTION: Tough, flexible, elongated living ground tissue cells are called?

Collenchyma

Definition: Vascular Tissue

Conducts fluids and dissolved substances throughout the plant body.

Vascular Tissue: Xylem

Conducts water and dissolved minerals. Usually contains a combination of "Vessels", which are continuous tubes formed from dead, hollow, cylindrical cells arranged end-to-end, and "Tracheids", which are dead cells that taper at the ends and overlap one another. In woody plants, mature xylem,secondary xylem, constitutes most of the woody material in plants. Transpiration. In addition to conducting water, dissolved, minerals, and inorganic ions throughout the plant, xylem supports the plant body.

Ground Tissue

Consists primarily of thin-walled "parenchyma cells" that function in storage, photosynthesis, and secretion. Other ground tissue, composed of "collenchyma cells" and "sclerenchyma cells", provide support and protection.

Primary Tissues

Derived from apical meristems.

Roots, shoots, and leaves all contain 3 basic types of tissue:

Dermal, ground, and vascular tissue.

Stomata Functions

Dual Function: 1) exchange of O and CO2 gases essential for photosynthesis 2) diffusion of water in vapor form, enabling transport of water and minerals from the roots to the leaves.

In roots, the inner layer of the cortex is called the ___________?

Endodermis

Vascular Cambium

Forms b/n the xylem and phloem in vascular bundles, adding secondary vascular tissue to both of its sides. Xylem is added to the inside of the vascular cambium, and phloem to the outside.

Lignin

Found in secondary cell walls of Sclerenchyma. It is a highly branched polymer that makes cell walls rigid. It is an important component of wood.

Sclerenchyma Cells

Have tough, thick walls. Unlike collenchyma and parenchyma, they are typically dead at maturity. Their secondary cell walls are often impregnated with lignin, a highly branched polymer that makes cell walls more rigid. Found in: 1) Fibers, 2) sclereids (variable in shape but often branched)>

Tracheids (xylem)

In some plants, e.g. GYMNOSPERMS, Tracheids are the only water-conducting cells present

Lateral Meristems

In woody plants, they produce an increase in root and shoot diameter. Give rise to secondary tissues: the vascular cambium and cork cambium

Cutin

In young plants, a fatty layer produced by the epidermis that forms the cuticle (a waxy/fatty, non-cellular layer).

Monocot leaves

Its mesophyll is not differentiated into Spongy and Palisade layers and there is little distinction b/n the Upper and Lower Epidermis.

Vascular Tissue: Phloem

Located toward the outer part of roots and stems. It is the principal food-conducting tissue in vascular plants.

Eudicot LEaves

Loosely arranged Spongy Mesophyll b/n the Palisade Mesophyll and the Lower Epidermis, with pockets of air (function in gas exchange and passage of water vapor from the leaves)

In Plant Cells with a Secondary Cell Wall, why is the Primary Cell Wall always on the outside of the cell wall?

New cellulose is always being produced by the cell and deposited adjacent to the plasma membrane.z

Stomata

Occur in epidermis of leaves and sometimes on stems or fruits. In many plants, are more numerous on the lower epidermis of the leaf (helps minimize water loss).

Guard Cells

Paired, sausage-shaped cells flanking a stoma (plural = stomata). They open and close stomata. Unlike other epidermal cells, they contain chloroplasts.

QUESTION: What are the most common cells found in plants?

Parenchyma Cells

QUESTION: The stalk at the base of a leaf is called?

Petiole

Dermal Tissue

Primarily epidermis, is one layer thick in most plants, and it forms an outer protective covering.

Most plant cells have at least one cell wall called the _______________

Primary Cell Wall

Primary Xylem and Secondary Xylem

Primary Xylem: derived from the procambium produced by the apical meristem Secondary Xylem: formed by the vascular cambium, a lateral meristem. Wood consists of secondary xylem.

Both plant meristem and animal stem cells share:

Retinoblastoma gene, which determines whether a cell continues dividing or differentiates.

4 Regions in Developing Roots

Root Cap, Zone of Cell Division, Zone of Elongation, and Zone of Maturation.

The 2 Systems of the Plant Body:

Root System and Shoot System.

Intercalary Meristems

Seen in horsetails and corn, a type of meristem that arises in stem internodes (spaces b/n leaf attachments), adding to internode lengths.

Companion Cells/

Specialized parenchyma cell. In angiosperms, a common initial cell divides asymmetrically to produce a sieve-tube member cell and its companion cell. Companion cells have all the components of normal parenchyma cells, including nuclei. Numerous plasmodesmata (cytoplasmic connections b/n adjacent cells) connect their cytoplasm with that of the associated sieve-tube members.

Phloem Transports ... Xylem Trasports ...

Sucrose, amino acids, and hormones. Minerals and water.

Collenchyma Cells

Supporting tissue. Often found in regions of primary growth in stems and in some leaves. Like parenchyma cells, have living protoplasts, lack secondary cell walls, and may live for many years. Cell walls vary in thickness.

Vessel members (xylem)

Tend to be shorter and wider than tracheids. Both vessel members and tracheids have thick, lignified secondary walls and no living protoplasts at maturity. They conduct H2O more efficiently than the overlapping strands of tracheids. Lignin is produced by the cell and secreted to strengthen the celluolose cell walls before the protoplasts dies.

The Outer Bark of a Tree is produce by _____________.

The Cork Cambium

Parenchyma Cells

The most common type of plant cell; characterized by large vacuoles, thin cell walls, and functional nuclei. Function: storage of food and water, photosynthesis, and secretion. Most abundant in primary tissues.

Primary Plant Body

The part of a plant consisting of young, soft shoots and roots derived from apical meristems.

Zone of Cell Division

The part of the young root that includes the root apical meristem and the cells just posterior to it. The cells divide every 12 - 37 hours.

Protoderm

The primary meristem that forms the EPIDERMIS.

Ground Meristem

The primary meristem which differentiates further into ground tissue.

Procambium

The primary meristem which produces primary VASCULAR tissues (primary xylem and primary phloem)

Trichomes

They are cellular or multicellular hairlike outgrowths of the epidermis; glandular trichomes secrete oils or other substances that deter insects. Vary greatly in form. Reduce evaporation by covering stomata openings. Protect leaves from high intensity light and UV radiation and can buffer against temp. fluctuations.

Definition: Ground Tissue

Tissue whose functions include support, storage, secretion, and photosynthesis. May consist of many cell types.

Secondary Tissues

Tissues formed from lateral meristems, which comprise most of the trunk, branches, and older roots of trees and shrubs. Collectively called the "Secondary Plant Body".

Root Hairs

Tubular extensions of individual epidermal cells, occur in a zone just behind the tips of young, growing roots. Greatly increase the surface area for absorption. Is an extension of an epidermal cell and not a separate cell. Keep the root in intimate contact with the surrounding soil particles.