Palmate compound leaf: the
leaflets branch from the petiole
i.e. they are attached to a
common point at the tip of the
petiole e.g. silk cotton (Bombax
ceiba (Asian)/Ceiba pentandra
(American).
There are various types
according to the number of
leaflets e.g.
• Unifoliate: possess only one
leaflet at the tip of the petiole e.g.
Citrus sp
• Bifoliate: has two leaflets e.g.
Cassia rotundata
• Trifoliate: has three leaflets e.g.
Vigna sp, Calopogonium sp
• Multifoliate/Digitately
compound: has about 5 leaflets
e.g. Bombax
Bombax leaf
3. Phyllotaxy/Leaf arrangement
Phyllotaxy is the arrangement of
leaves on the stem or branch.
This is usually of
several types:
Alternate: a single leaf arises at
each node in alternate manner,
as in china rose (Hibiscus rosa-
sinensis), mustard and sun
flower (Helianthus sp.) plants.
Opposite: a pair of leaves arise
at each node and lie opposite to
each other as in Akra (Calotropis
sp.) and guava (Psidium
guajava) plants.
Whorled: Three or more leaves
arise at a node and form a whorl
e.g. Mexican oleander, (Thevetia
peruviana), Alstonia sp.
Rosulate: The leaves arrange
themselves in a ring-like (spiral)
pattern around the stem, they
have a circular arrangement e.g.
Aloe polyphylla.
Rosulate
4. Petiole/Leaf stalk
This is the part that attaches the
leaf blade to the stem. It could
be:
• Petiolated: the leaf has a stalk
or petiole which attaches it to the
stem e.g. celery, mango etc.
• Pulvinus: a swollen base that
attaches the leaf to the stem e.g.
Mimosa pudica
• Winged petiole: the petiole has
a wing-like extension from the
base e.g. Tietie (Pullinia pinnata;
Sapindaceae)
• Sessile/apetiolated- The leaf
does not have a petiole and is
directly attached to the stem e.g.
Euphorbia sp.
winged leaf pulvinus leaf
5. Shape of the Leaf
blade/Lamina
It is the most conspicuous part of
the leaf and it is the main
photosynthetic part of the plant.
The blade forms/shapes are
diverse.
• Elliptical: the margins are
symmetrically curved and oval, it
is widest at the center e.g. apple,
orange, corn lily (Veratrum
californicum)
• Lanceolate: the leaf has lance
shape, it is longer than broad,
round at the base and widens
above it at about ⅓ from the
base and narrows/pointed at the
apex e.g. mango (Mangifera
indica), masquerade tree
(Polyalthia longifolia)
• Linear: the leaf is long, flat,
narrow, it is longer than broader,
has parallel sides. They may also
exhibit a distinct twist along their
vertical axes e.g. grasses
• Acicular: long leaf, narrow,
cylindrical and needle like e.g.
onion (Allium cepa)
• Ovate: egg-shaped,
symmetrically curved, widest
below the middle e.g. orange
(Citrus sp.), goat weed
(Ageratum conyzoides)
• Obovate: Cashew (Anacardium
occidentale)
• Cordate: heart-shaped e.g.
morning glory (Ipomoea
involucrata), Ipomoea
batatas, water lily (Nymphaea
odorata).
• Spatulate: Spoon-shaped e.g.
Water oak (Quercus nigra)
• Falcate: sickle-shaped or boat
shaped e.g. Eucalyptus, Sickle
shaped leaf (Bulbophyllum
falcatum)
• Sagittate: has an arrow-head
shape with its basal lobes
pointing downwards e.g. Taro,
old cocoyam (Colocasia
esulentum)
• Hastate: arrow shaped with two
spreading lobes at the base,
heart of Jesus (Caladium bicolor)
• Cuneate: wedge shape; water
cabbage/ water lettuce (Pistia
statiotes)
• Orbiculate: circular outline or
round shaped e.g. giant
pigweed/black pigweed
(Trianthema portulacastrum)
• Peltate: shield-shaped, petiole
is attached at the center of the
leaf e.g.
• Reniform: Kidney shaped leaf
e.g. Geranium (Pelargonium sp.)
6. Leaf margin
Based on the serration on the
edge of the leaf blade, the leaf
margin may be entire/smooth or
indented
• Smooth: This type of leaf
margin is called ‘entire’ leaf
margin and is smooth and even
all around the leaf edge. They
neither have lobe nor teeth e.g.
guava
• Sinuate: Have strongly/deeply
wavy margins with shallow
rounded divisions e.g. white oak
(Quercus alba); English oak (Q.
robur)
• Dentate: They have square or
rectangular teeth along the
margin that point outward
ascending to the mid rib e.g.
watermelon, siam weed
(Chromolaena odorata)
• Serrated/toothed: Have sharp,
saw-teeth shaped margins
ascending/pointing to the apex
e.g. hibiscus (H. Rosa-sinensis)
• Undulate: Wavy, curling from
the front
to the back of the leaf e.g.
Polyalthia
• Lobed: the leaf blade is divided
but the division doesn’t reach the
midrib e.g. Ranunculus
• Ciliate: The margin bears hair
e.g. Cleome vicosa
• Crenate: the margin has
shallow indentations (about 1/3
the distance to the midrib) e.g.
Bryophyllum
• Cleft: indentation towards the
midrib (more than halfway to the
midrib) e.g. papaya
• Doubly serrate: twice serrated,
have both small and larger
serrations e.g. red alder
7. Leaf apex
• Acute: margin straight to
convex, becoming gradually to
form an acute angle e.g.
Chromolaena odorata Siam
weed
• Obtuse: has round apex;
straight to
convex, forming a terminal angle
more than 90
• Acuminate: margin straight to
convex, sharply pointed forming
a terminal angle of less than 45
• Apiculate: slightly curled
• Caudate: acuminate with
concave margins
• Aristate: the apex is prolonged
into a stiff & straight extension
• Cirrhose: has coiled or tendril
flexuous apex
• Truncate: apex ends as if it is
cut in a straight line
• Mucronate: sharp, point as a
result of midrib elongation
• Emarginated: Truncate or
obtuse apex with a deep notch
• Retuse: rounded or obtuse with
a central shallow indentation
• Subobtuse: imperfectly or less
than completely obtuse
8. Leaf base
• Acute/cuneate: leaf blade ends
abruptly on the petiole e.g.
Mango
• Obtuse/round: blade forms a
smooth curve before ending on
the petiole e.g. Ixora
• Attenuate: blade tappers
gradually at the petiole e.g.
cottonwood
• Cordate: the base of the leaf is
drawn into two round lobes
before joining the petiole, heart
shaped base e.g. Black
cottonwood.
• Oblique/asymmetrical: the base
of the blade is unequal and they
join the petiole at different points
e.g. slippery elm
Modifications of Leaves
Leaves are often modified to
perform functions other than
photosynthesis. They are
converted into:
• tendrils for climbing as in peas
• spines for defence as in cacti
• store food e.g. the fleshy leaves
of onion and garlic
• Traps: Leaves of certain
insectivorous plants such as
pitcher plant, venus-fly trap
