Plant Structure Willow shoot. Monocot vs. Dicot Woody/herbaceousHerbaceous; never woody 75% of all angiosperms22% of all angiosperms -true of only flowering.

Plant Structure

Willow shoot

Monocot vs. Dicot

Woody/herbaceousHerbaceous; never woody

75% of all angiosperms22% of all angiosperms

-true of only flowering plants

-Eudicots: group of plants share a common pollen structure diff. from mono. and di.

Monocot Examples Dicot Examples

Palm Trees no wood

overlapping leaf bases

Corn

Peanut: not a nut legume!

Tomato

Monocot Seed Comes to Life!

Seed coat – From the wall of the embryo sack (mother tissue)Endosperm – Food supply containing 3 sets of chromosomes (2 from the mother and 1 from the father)Embryo – Immature plant

• Cotyledon – Seed leaf• Plumule – Shoot• Radicle – Root

Dicot Seed Comes to Life!• Seed coat – From embryo sack wall

and endosperm tissue (During development, the endosperm stops dividing and is absorbed into the embryonic tissues.)

• Embryo – Immature plant• Cotyledon – Food storing seed

leaf• Plumule – Shoot• Hypocotyl – Stem• Radicle – Root

Plant Parts

• Meristems– forever young tissues; divide actively throughout plant’s life– These cells divide to generate

additional cells: • Initials- generative cells that remain in

the meristem.• Derivatives- Those that are displaced

from the meristem and continue to divide for some time until the cells they produce begin to specialize within developing tissues.

– New cells created via mitosis and derivative cells pushed further and further away from initials

Plant Growth & Development

• Apical meristems: located at the tips of roots and in the buds of shoots– supply cells for the plant to grow in

length.

– Primary growth• initial root and shoot growth• produced by apical meristem• elongation occurs• restricted to youngest parts

of the plant (ex: tips of roots & shoots)

Locations of Meristematic Tissues

– Secondary growth: thickening of roots and shoots.• Produced by lateral

meristems • Develop in slightly older

regions of roots and shoots (ex: vascular and cork cambium)

• Lateral meristems: allow the plant to increase in girth (circumference)

Locations of Meristematic Tissues

Meristems

• Building a House

1. Foundation is laid

2. Construction of the frame

3. Installation of plumbing, heating, etc

4. Waterproof walls and roof

5. Food stored in appropriate places

• Building a plant1. Meristems give rise to

all tissues2. Three tissue systems

give rise to the major organs of a plant

3. Installation of the vascular tissue (plumbing)

4. Installation of dermal tissues– covering, skin

5. Installation of ground tissue– parenchyma

Types of Roots• Taproot

– Primary root– Able to grow deep

• Water absorption

– Ex: dandelion, carrots

• Fibrous Root– No root grows larger

than another– Prevents erosion– Ex: grasses, peas

• Root Cap: covers root tip & protects the meristem as the root pushes through the abrasive soil during primary growth.– The cap also secretes a lubricating slime.

• Growth in length is concentrated near the root’s tip, where three zones of cells at successive stages of primary growth are located.– zone of cell division– zone of elongation– zone of maturation

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Primary Growth in Roots

1. Dermal tissue• Epidermis/peridermis• Cuticle• Stoma• Trichomes

2. Vascular tissue (plumbing)

• Xylem• Phloem

3. Ground tissue • Cortex• Pith

Vascular Plant Organs are Composed of

3 Tissue Systems:

(outer protective

covering)

(everything else; energy

transformation, storage & support)

Dicot Root Monocot Root

Plant Shoot

Primary Growth of the Shoot

Stem Anatomy

Monocot StemDicot Stem

Anatomy of a Tree Trunk• After several years

of secondary growth, several zones are visible in a stem.

Leaf Anatomy

Typical Dicot Leaf X-Section

Palisade Parenchyma

Spongy Parenchyma

Vascular bundles

Epidermis

Cuticle

Stoma

Guard Cells

Typical Monocot Leaf X-Section

Xylem

Phloem

Bulliform Cells Stoma

EpidermisMidvein Vein Bundle sheath cell

Leaf Stomata: Allow Gas Exchange

Guard cells

Stoma

Plant Cell Structurecell wall

chloroplast

nucleus

central vacuole

Cell Wall Structure

middle lamella

primary cell wall

secondary cell wall

membranes that contain chloroplasts

Cell Wall Structure

plasmodesmata

• Microscopic channels in cell wall

• Allow for transport (proteins; used in phloem cells)

Plant Cell Types• Xylem

• Tracheids• Vessel elements

• Phloem• Sieve-tube

members• Companion cell

Vascular tissue:• runs continuous throughout the plant• transports materials between roots and

shoots.– Xylem transports water and dissolved minerals

upward from roots into the shoots. (water the xylem)

– Phloem transports food from the leaves to the roots and to non-photosynthetic parts of the shoot system. (feed the phloem)

Vascular Tissue

The water conducting elements of xylem are the tracheids and vessel elements.

Xylem

Xylem• Tracheids

–Characteristics• tapered elongated cells• connect to each other through pits• secondary cell walls strengthened with

lignin–Functions

• transport of water plus dissolved minerals• support

Xylem• Vessel Elements

–Characteristics• shorter and wider than tracheids• possess thinner cell walls than tracheids• Aligned end-to-end to form long

micropipes• dead at functional maturity

–Functions• transport of water plus dissolved

minerals• support

Water conducting cells of the xylem

• Food and minerals move through tubes formed by chains of cells, sieve-tube members.–sieve plates–companion cell

Phloem

Phloem• Sieve-tube Members

–Characteristics• living cells arranged end-to-end to form food-

conducting cells of the phloem• lack lignin in their cell walls• mature cells lack nuclei and other cellular

organelles• alive at functional maturity

–Functions• transport products of photosynthesis

Phloem• Companion Cells

–Characteristics• living cells adjacent to sieve-tube members• connected to sieve-tube members via

plasmodesmata–Functions

• support sieve-tube members• may assist in sugar loading into sieve-tube

members

Food conducting cells of the phloem