Tissues and the Primary Growth of Stems

Angiosperms

Flowering plants are classified as the Division Magnoliophyta, informally as ________

Several groups within Magnoliophyta

• Basal angiosperms

• Eudicots (broadleaf plants)

• Monocots (narrow-leaved)

Two types of plant bodies

• Primary plant body

• Secondary plant body

Primary plant body

Is herbaceous

Secondary plant body

Is woody

Types of Plant Cell

• Parenchyma

• Collenchyma

• Screlenchyma

Parenchyma cells

Have only thin primary walls

Parenchyma tissue

A mass of parenchyma cells forms _________

Special parenchyma

• Chlorenchyma

• Glandular cells

• Transfer cells

• Phloem

Chlorenchyma

• Are photosynthetic parenchyma cells. walls allow light and carbon dioxide to pass through to the chloroplast

• Pigmented cells are parenchyma.

Chlorenchyma

Secretes Nectar, Fragrances, Mucilage, Resins, Oils

Chlorenchyma

• Mediate short-distance transport of material.

• They have a large, extensive plasma membrane with numerous molecular pumps.

Phloem

• Is parenchyma tissue that conducts nutrients over long distances.

• Some parenchyma cells function by dying at maturity to form open areas

Collenchyma cells

• Have a primary wall that is thin in some areas and thickened in others.

• This allows plasticity

Chlorenchyma

Tends to exist beneath epidermis and supporting vascular bodies

Screlenchyma

• Has a primary wall and a thick secondary wall that is usually lignified.

• These walls are elastic

• Supports the plant by its strength.

• Usually dead at maturity

Two types of Screlenchyma

• Conductive

• Mechanical

Fibers

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

Shoot

A stem with included leaves

Nodes

Where leaves are attached

Internodes

The region between nodes

Leaf axil

• The stem area just above the point where a leaf attaches

• Contains an axillary bud

Axillary bud

• Miniature shoot with a dormant apical meristem

• Several young leaves

Terminal bud

At the extreme tip of each stem

Phyllotaxy

Is the arrangement of leaves on the stem

Alternate phyllotaxy

One leaf is attached at each node

Opposite phyllotaxy

Two leaves attached at each node

Whorled phyllotaxy

Three or more leaves attached at each node

Distichous phyllotaxy

Leaves arranged in two rows when viewed from above

Decussate phyllotaxy

Leaves arranged in four rows when viewed from above

Spiral phyllotaxy

Eacch leaf is located slightly to the side of the ones immediately above and below it, and leaves form a spiral up the stem

Stolons

Have especially long and thin internodes allowing dispersal of daughter plants.

Modified Stems

• Rhizome

• Tuber

• Phylloclades

• Stolon

• Corm

• Bulb

Rhizome

Fleshy, non-green underground stems (e.g. gingers)

Tuber

Swollen tip of underground lateral stem (e.g. potato)

Phylloclades

Succulent stems, leaves modified into spines (e.g. cactus and euphorbia)

Stolon

Creeping horizontal plant stem that forms new plants along its length (e.g. airplane plant)

Corm

Vertical thick stems with thin, papery leaves (e.g

gladioluses)

Bulb

Condensed discoid stem with fleshy scale leaves (e.g. onions and garlic)

Epidermis

• Is the outermost surface of an 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

Outer tangential walls are coated with waterproof cutin.

Cuticle

Builds up as a layer

Stomata

Gas exchange is allowed by ________.

Guard cells

Are a pair of cells that border the stomatal pore.

Stomatal pore

Is the hole between the guard cells through which gases can pass.

Trichomes (hair)

Some epidermal cells elongate outward and become _______.

Cortex

• Is 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

Vascular Tissues

Are responsible for the conduction of materials

throughout the plant.

Two types of Vascular Tissues in Plants

• Xylem

• Phloem

Xylem

• Conducts water and minerals

• Is dead and hollow at maturity.

Phloem

• Distributes sugars and minerals

• Remains alive at maturity.

Two types of xylem cells

• Tracheids

• Vessel elements

  • Collectively referred to as tracheary elements

Circular bordered pits

The most derived and strongest tracheary elements have _______.

Pits

Are weaks points in the wall

Border

Weakness is reduced by a _______ of extra wall material.

Pit membranes

Water moves between tracheids through _________.

Perforations

Form between vertically stacked vessel elements.

Vessel

A stack of vessel elements

Phloem has two types of conducting cells

• Sieve cells

• Sieve tube members

Sieve element

The term “_______” refers to either.

Sieve cell

• Is similar in shaped to a tracheid

• Sieve areas are distributed over its surface.

• Found in older fossils and in nonflowering vascular plants

Sieve tube members

• Are similar to the vessel members of the xylem

• All angiosperms have sieve tubes.

Albuminous cell

Sieve cells are associated with _______.

Companion cells

Sieve tube members are controlled by ________.

Xylem and phloem

▪ Occur together in vascular bundles inerior to the cortex.

▪ Arrangement of bundles differs between monocots and other angiosperms

Collateral

Xylem and phloem run parallel to each other.

Eudicots stems

Vascular bundles are arranged in one ring surrounding the pith.

Monocots

They are distributed as a complex network throughout the inner part of the stem.

Primary Xylem

The xylem of a vascular bundle

Primary Phloem

The phloem of a vascular bundle

Apical meristem

Region is known as _______.

Subapical meristems

Contain cells dividing and growing, producing cells for the region below.

Metaxylem

Some of the elongating cells will differentiate and mature into ______.

Protophloem

Exterior cells mature as _______.

Metaphloem

Cells closest to the metaxylem become _______.

Protoderm

Is epidermal cells that are in the early stages of differentiation

Provascular tissues

Young xylem and phloem cells are ________.

Ground meristems

The equivalent stages of pith and cortex are _____.

Primary tissues

Are produced by apical meristems

Primary growth

Is the growth and tissue formation that results from apical meristem activity