PL_LESSON 2: PLANT TISSUES

420

Plants began living on land ___ million years ago

Magnoliophyta

Flowering plants are classified as the division ___, informally as angiosperms

Basal angiosperms

Eudicots (broadleaf plants)

Monocots (narrow-leaved)

SEVERAL GROUPS WITHIN MAGNOLIOPHYTA

Herbaceous

Often annuals

Herbaceous

Soft, green, and non-woody

Herbaceous

Shorter life span than woody plants

Herbaceous

Ex. Cultural plants

Woody

secondary part body

Woody

Hard, tough textures. Have the characteristics of tree and a shrub

PARENCHYMA

Have only thin primary walls (for the function of transport)

PARENCHYMA

Metabolically active 

PARENCHYMA

Most remain alive after they mature

Transfer cells

mediate short distance transport of material; have a large, extensive plasma membrane with numerous molecular pumps.

Chlorenchyma

Glandular cells

Transfer cells

Phloem

Special parenchyma

CHLORENCHYMA CELLS

Photosynthetic parenchyma cells

CHLORENCHYMA CELLS

Thin walls allow light and carbon dioxide to pass through the chloroplasts

Conversion of sunlight into energy

Chlorophyll

pigment

Nectar - for sugar,

Fragrances - attract pollinators

Mucilage

Resins - protect themselves from fungi / insects

Oils

For defense of herbivores

GLANDULAR CELLS SECRETE

PHLOEM

Parenchyma tissue that conducts nutrients over long distances

PHLOEM

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

PHLOEM

Metabolically, these cells are relatively inexpensive to build

COLLENCHYMA

have a primary wall that is thin in some areas and thickened in others (uneven thickening - plasticity and flexibility)

COLLENCHYMA

tends to exists:

Beneath the epidermis

Supporting vascular bundles

SCLERENCHYMA

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

SCLERENCHYMA

Usually dead by maturity

SCLERENCHYMA

Presents in seeds, stems, roots, and leaves

SCLERENCHYMA

These walls are elastic and Supports the plant by its strength

Conductive

Mechanical

Two types of Sclerenchyma

Fibers, sclereids

MECHANICAL (non-conducting) SCLERENCHYMA

Fibers

long and flexible

Sclereids

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

SHOOT

Leaves are attached at nodes

Internodes

regions between nodes

THE AXIL

The stem area just above the point where a leaf attaches

THE AXIL

It contains

Axillary bud

Miniature shoot with dormant apical meristem

Several young leaves

terminal bud

At the extreme tip of each 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

PHYLLOTAXY

Arrangement of leaves on the stem

Distichous phyllotaxy

leaves arranged in two rows when viewed from above

Decussate phyllotaxy

leaves arranged in four rows when viewed from above

Spiral phyllotaxy

each 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.

Stolons

creeping horizontal plant stem that forms new plants along its length

airplane plant

Stolons

Bulbs

Short shoots with thick, fleshy leaves
Condensed discoid stem with fleshy scale leaves

Onion

bulbs

Corms

Vertical, thick stems with thin, papery leaves

Gladioluses

Corms

Rhizomes

Fleshy horizontal stems that allow a plant to spread underground

Ginger

Rhizomes

Tubers

Horizontal, like rhizomes, but grow for a short period and are mainly a means of storing nutrients.

Tubers

swollen tip of underground lateral stem

Potato

tuber

Phylloclades

succulent leaves modified into spines

cactus, euphorbia

Phylloclades

Epidermis

The outermost surface of an herbaceous stem.

Epidermis

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

cutin

Outer tangential walls are coated with waterproof ____

cuticle

cutin Builds up as a layer

Cuticle

prevents desiccation but also prevents gas exchange

stomata

Gas exchange is allowed by

Guard cells

are a pair of cells that border the stomatal pore

Stomatal pore

hole between the guard cells through which gases can pass.

Guard cells

swell by absorbing water. The pore between them opens, permitting entry of carbon dioxide and exit of oxygen.

stomata

Water is lost through

sunset or during periods of water stress

Guard cells regulate when the pores are open/closed. Closed after

trichomes (hairs)

Some epidermal cells elongate outward and become

Deter herbivory

Minimize water loss

Protect from over exposure to sunlight

Can act as secretory glands

Protective roles of trichomes

CORTEX

Interior to the epidermis

CORTEX

Often homogenous, composed of photosynthetic parenchyma and sometimes collenchyma

CORTEX

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

VASCULAR TISSUES

Responsible for the conduction of materials throughout the plant

XYLEM

Conducts water and minerals

XYLEM

Dead and hollow at maturity

Tracheids

Vessel elements

TWO TYPES OF XYLEM CELLS

tracheary elements

TWO TYPES OF XYLEM CELLS Collectively referred to as __

Annular thickenings

Helical thickening

Scalariform thickening

Reticulate thickening

Strength of cells due to the secondary cell walls

circular bordered pits

The most derived and strongest tracheary elements have _____

Pits

weak points in the wall

pit membranes

Water moves between tracheids through

Perforations

form between vertically stacked vessel elements

vessel

A stack of vessel elements

tracheids

All plants with vascular tissue have ___

leaf veins

tracheids found in____ of flowering plants

Sieve cells

Sieve tube members

Phloem has two types of conducting cells

PHLOEM

Develop from parenchyma cells that remain alive

Plasmodesmata

enlarge to become sieve pores

sieve cell

A ___ is similar in shaped to a tracheid

sieve tubes

All angiosperms have ___. Nonangiosperms do not

albuminous cells

Sieve cells are associated

companion cells

Sieve tube member are controlled by

Xylem and phloem

Occur together in vascular bundles interior to the cortex.

Collateral

xylem and phloem run parallel to each other.

one ring surrounding the pith.

In eudicot stems, vascular bundles are arranged in

Pith

central region of parenchyma similar to the cortex.

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

In monocots, they are