Download - 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 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