Lovely, Lovely Leaves

Leaf arrangement

OppositeDecussate

Leaf arrangement

Alternate Basal rosette

Function and Shape

Leaf Venation

Net venationParallel venation

Petiole

Sessile leaves

Axillary Buds

Simple & Compound Leaves

NB. position ofaxillary bud

Leaf Sheath & Ligule (monocots)

Sheath

Ligule

•Intercalary meristemalso important inMonocots (esp.grasses)

New Leaves

Shoot apical meristem

The Epidermis

Glandular Trichomes

Dionaea

Drosera

Sarracenia

Basic Leaf Anatomy

Xylem

PhloemBundle sheath

Mesophyll

sub-stomatalchamber

Kranz Anatomy

Leaf c.s. through midrib

Leaf Abscission

Abscissionlayer

Cotyledons

•Mostly storage organs

Heterophylly

• Leaves may be quite different (e.g., in beans, juvenile leaves are entire, while adult leave are compound)

Xerophytes

•Thick cuticle•Sunken stomata•Reduced air spaces in mesophyll (succulent)•Trichomes – boundary layer humid•Multiple epidermal layers

Hydrophytes

•Thin cuticle•Lack characteristics for water conservation•Leaves often lobed (underwater)

Special Features• Bulbs• Tendrils• Plantlets• Insect traps

Kalanchoë