BIO421: Tissues and Primary Growth of Stems

Angiosperm

also called as flowering plants

most diverse group of plants

Division Magnoliophyta

the scientific name for the group commonly knowns as angiosperms or flowery plants

Basal angiosperms

flowering plants which diverged from the lineage leading to most flowering plants.

Eudicots

also called as broadleaf plants

clades of flowering plants which are mainly characterized by having two-seed leaves upon germination

Monocots

also called narrowd-leaved

flowering plants with one seed leaf or a cotyledon emerging from their embryo

2 types of plant bodies

1. Primary plant body is herbaceous.

2. Secondary plant body is woody

Herbs

Plants that never become woody and covered in plant.

Often annuals

Can be monocot or eudicot

3 basic types of cells and tissues

Parenchyma, Collenchyma, Sclerenchyma

Parenchyma

have thin cell walls

forms parenchyma tissues

Parenchyma tissues

Type of simple permanent tissue that makes a major part of the ground tissues in plants

Metabolically active

Most remain alive after they mature

4 special parenchyma

Chlorenchyma

Glandular Cells

Transfers cells

Phloem

Chlorenchyma

stores chlorophyll; photosynthetic

Glandular Cells

secretes nectar, fragrances, mucilage, resins, and oils

store and secrete secondary metabolites in a species- and cultivar-specific fashion

Transfer cells

Mediate short-distance transport of material

have large, extensive plasma membrane with numerous molecular pumps

secondary wall ingrowths

Phloem

conducts nutrients over long-distance

some function by dying at maturity to form open areas

Collenchyma

have a primary wall that is thin in some areas and thickened in others; allows plasticity

often occur in the outer part of the stem or leaf stalks

Sclerenchyma

primary wall and a thick secondary wall that is usually lignified; walls are elastic

Supports the plant by its strength

Usually dead at maturity

two types of sclerenchyma

Mechanical sclerenchyma and Conducting sclerenchyma

Mechanical Sclerenchyma

nonconducting

fibers are long and flexible

sclereids are short, isodiametric (cuboidal), inflexible, and brittle

Conducting Sclerenchyma

transports water

tracheary elements of the xylem

includes tracheids and vessel elements

Epidermis

outermost surface of a herbaceous stem

Single layer of parenchyma cells

All interchange of material between a plant and its environment occurs by means of its epidermis.

Functions in protection and preventing water loss.

Cutin

waterproof material that coats outer tangential walls.

Cuticle

a layer built by cutin; prevents desiccation but also prevents gas exchange.

Stomata

allows gas exchange; water is lost through stomata.

Guard Cells

pair of cells that border the stomatal pore.

Swell by absorbing water; the pore between them opens, permitting entry of carbon dioxide and exit of oxygen.

Can regulate when the pore opens and closes.

Closed after sunset or during periods of water stress.

Stomatal Pore

hole between the guard cells through which gasses can pass.

Trichomes

(hairs) epidermal cells that elongate outward

Deters herbivory, minimize water loss, protect from over exposure to sunlight, can act as secretory glands

Cortex

interior to the epidermis

Often homogenous, composed of photosynthetic parenchyma and sometimes collenchyma.

Cells are typically tightly fitted, but some plants have a cortex of aerenchyma, loosely packed with large intercellular air spaces.

Stele Region

where the vascular bundles are located.

Ground Tissues

Inner tissues that serve different purposes: Parenchyma, Collenchyma, Sclerenchyma

Vascular Tissues

transports water, minerals, and sugars into the plant

Xylem

transports water and minerals upward from roots to all aerial parts; dead and hollow at maturity.

Tracheary Elements

Tracheids and vessel elements with secondary walls

Pit Membranes

where water moves between tracheids.

Phloem

carries sugars and various organic compounds throughout the plant; remains alive at maturity.

Two Types of Conducting Cells/Sieve Elements

Sieve Cells and Sieve Tube Members

Eudicot Stem Vascular Bundle Arrangement

Arranged in one ring surrounding the Pith

Monocot Stem Vascular Bundle Arrangement

Distributed as a complex network throughout the inner part of the stem

Herbs

Primary body only

All cells mature into epidermis, ground tissue, or vascular tissue

Only live a few months. often annuals

Can be monocots or eudicots

Woody Plants

With a secondary body

Have cells that continue to divide and produce new cells*

Produces wood** and bark***

Produced by lateral meristems (cork and vascular cambium)

Vascular Cambium

a sheet of non-maturing cells along the vascular bundles.

Secondary Xylem

produced in the inner side of the vascular cambium and becomes wood.

Secondary Phloem

produced in the outer side of the vascular cambium and becomes part of the bark.

STEM

Supports the leaves and fruits

Transports water and stores starch

Either herbaceous or woody