Botany Lecture - Chapter 6

ORIGIN OF A FOLIAGE LEAF

Leaf arises from the activity of leaf primordium

=leaf-like pegs of meristem

Physiological function

Photosynthesis

Transpiration – the process by which plant loses water to serve the following purposes:

a. Continuous uptake of water

b. Cooling effects

c. Controls degree of saturation of cell with water

Monocot leaf sheath and

ligules Dicot leaf with stipules

EXTERNAL STRUCTURE OF FOLIAGE LEAVES

LEAVES, FOOD AND DEATH

Artichoke

Cynara scolymus

Cabbage

Brassica oleracea

Celery

Apium graveolens

Spinach

Spinacia oleracea

Lettuce

Lactuca sativa

Onion

Allium cepa

LEAVES, FOOD AND DEATH

Herbs and spices

Basil

Ocimum basilicum

Bay leaves

Laurus nobilis

Marjoram

Origanum majorana

Parsley

Petroselinum crispum

Sage

Salvia officinalis

Tarragon

Artemisia dranunculus

LEAVES, FOOD AND DEATH

Flavoring mints

Spearmint

Mentha spicata

Peppermint

Mentha piperita

LEAVES, FOOD AND DEATH

Alkaloids

LEAVES, FOOD AND DEATH

Alkaloids – Nicotine

Tobacco

Nicotiana tabacum

Insecticides

Rotenone

Citronella

Waxes

Carnauba

Aromatic Oils

Medical uses

Aloe (Mild Topical Anesthetic)

LEAVES, FOOD AND DEATH

1. Nature of the blade

2. Venation pattern

3. Phyllotaxy

4. Leaf margin

5. Leaf apex

EXTERNAL STRUCTURE OF FOLIAGE LEAVES

Classification:

a.Simple – with one blade of just one part

b. compound- with a blade divided into leaflets or

pinnae or pinnule

Classification: Nature of the blade

Two types of compound leaves

Pinnately compound Palmately compound

Simple Pinnately compound

Bipinnately Compound Leaf

Caballero –

Caesalpinia pulcherrima

Tripinnately Compound Leaf

Palmately compound leaves – leaflets are

attached to the end of the petiole

Types of palmately

compound leaves:

1. Bifoliate – two

leaflets

2. Trifoliate- three

leaflets

3. Quadri/tetrafoliate –

four leaflets

4. Pentafoliate

compound – with 5

or more leaflets

Palmately compound

Phyllotaxy – arrangement of leaves on the stem

Phyllotaxy – arrangement of leaves on the stem

Alternate and whorled

Phyllotaxy – arrangement of leaves on the stem

Decussate

Phyllotaxy – arrangement of leaves on the stem

Fasciculate

Pine needles

Pinus sp. Asparagus officinalis

Venation- arrangement of veins on

the blade

Parallel Venation Veins parallel to the Midrib

Parallel Venation Veins acute angle to the Midrib

Parallel Venation Palmately parallel

Parallel Venation Veins perpendicular to the midrib

Netted Venation Pinnately netted

Netted Venation Palmately netted

Netted Venation Radiately netted

Internal Structure of Foliage Leaves

Internal Structure of Foliage Leaves Epidermis, Mesophyll and Vascular Tissues

Guard cells

Are kidney-shaped,

chlorophyllous epidermal cells

Guard cells and pore

Internal Structure of Foliage Leaves Epidermis

epidermis

mesophyll

epidermis

palisade

spongy

Dorsiventral or Bifacial Mesophyll

In horizontally oriented leaf

Internal Structure of Foliage Leaves Mesophyll

Internal Structure of Foliage Leaves Mesophyll

Bundle sheath

photosynthetic

Kranz Anatomy – Halo or Wreath Anatomy Chlorenchymatous cells surround a photosynthetic bundle

sheath.

Internal Structure of Foliage Leaves Monocot Leaf

Bulliform cells are

large vacuolated

epidermal cells that

inroll the leaf during

hot conditions. Present

only in monocot

epidermal cells.

Kranz anatomy is typical of monocot leaf that undergoes

C4 metabolism

Internal Structure of Foliage Leaves Vascular Tissues of Monocot leaf

Cross section of midrib – grape leaf

Internal Structure of Foliage Leaves Midrib of a dicot leaf

Pine needle leaf

Internal Structure of Foliage Leaves Pine needle leaf

Abscission zone –

detachment area

of leaves from the

stem

Senescence – leaf

aging due to

breakdown of

chlorophyll, sugars

and loss of

photosynthetic

ability

Internal Structure of Foliage Leaves Leaf aging

MORPHOLOGY AND ANATOMY OF OTHER LEAF TYPES

Succulent Leaves-thick and fleshy, reduced surface-

volume-ratio.

Senecio – spherical

succulent leaves

Dinteranthus – pair

of succulent leaves

Lithops – pair of translucent

leaves acting as optical fiber

MORPHOLOGY AND ANATOMY OF OTHER LEAF TYPES

Sclerophyllous foliage-

thick sclerenchyma, resistant to animals, fungi, freezing temp and UV,

verythick cuticle.

Agave

Yucca Barberry

MORPHOLOGY AND ANATOMY OF OTHER LEAF TYPES

Spines- no blade and needle-shaped

Cactus- spines are

axillary buds of small

leaves

Colitis- spines are stipules

MORPHOLOGY AND ANATOMY OF OTHER LEAF TYPES

Tendrils- sensing contact with other objects, no

lamina

Pea plant Squash plant

MORPHOLOGY AND ANATOMY OF OTHER LEAF TYPES

Insect traps- digest insects and obtain nitrogen for

their amino acid

Nepenthes- pitcher

plant Sundew- with

stalked glands

Venus’ flytrap –

traps insects

MORPHOLOGY AND ANATOMY OF OTHER LEAF TYPES

Adventitious buds- produce plantlets

Kalanchoe- with plantlets

along the leaf margin Sansiviera- reproduce by

leaf cutting

Modified leaves

Colored leaves – for attraction

Poinsettia

Mussaenda

Bougainvillea

Anthurium- colored spathe

Water hyacinth – aerenchymatous enlarged leaf base

MORPHOLOGY AND ANATOMY OF OTHER LEAF TYPES

Floats – aerenchymatous leaf base for buoyancy, support

Modified leaves

Supporting leaf bases “pseudotrunk”– for support

Modified leaves

Motile leaves – display “thigmonasty” sensitivity to

touch, for protection

Modified leaves

Expanded leaf-like petiole or stipule – added

photosynthesis

Suha leaf Rose leaf