A principal appendage of the stem On branches of a plant Arise from nodes Bear lateral buds in their axils Chief photosynthetic organ Developed in acropetal succession Exogenous in origin

1. LEAF
Fatima Zahra

2. LEAF
• A principal appendage
o Of the stem
o On branches of a plant
• Arise from nodes
• Bear lateral buds in their
axils
• Chief photosynthetic organ
• Developed in acropetal
succession
• Exogenous in origin

3. LEAF MORPHOLOGY
Each leaf consists of
 A green, flattened portion,
the lamina
 A petiole, that raises the
lamina to expose it to the
sunlight
 A leaf base, the part of the
leaf through which it is
attached to the stem
Leaf base

4. Chief Types of Leaves
 Foliage Leaves :
ordinary green leaves which carry out photosynthesis
 Cotyledonary Leaves :
 found in seeds and serve as food storage
 Absorb food from endosperms for the growing
embryo
 Scale Leaves :
 Small undeveloped leaves
 Usually sessile
 Rarely green
 Their function is usually protection

5. Chief Types of Leaves
Cotyledonary
Leaves
Foliage Leaf Scale Leaves

6. Chief Types of Leaves
 Bracts and Bracteoles :
 Leaves of flowering shoots
are known as bracts
 They may be
• Scale like or
• Green
 Bear one or more flowers
in their
 axils

7. Chief Types of Leaves
 Floral Leaves :
Specialized leaves which form the
parts of flower. They are
 Sepals
 Petals
 Stamens
 Carpels
They are arranged on thalamus.

8. Stipules
The paired outgrowth
developed at the base of leaves.
A leaf may be
 Stipulate
When stipule is present as in
Rosa indica
 Exstipulate
When stipule is absent as in
Ipomea
Ipomea
Rosa indica

9. Kinds of Stipules
 Scaly Stipules :
 Leafy Stipules :
 Free Lateral Stipules
:
 Petiolar or Adnate
Stipules :
 Axillary Stipules :
 Orcheate Stipules :
 Tendriller Stipules :
 Spinous Stipules:
as in peepal
as in pea
as in cotton
as in rose
as in Victoria
as in polygonum
as in smilax
as in Zizypus jujbe

10. 1. Scaly Stipules
 Small
 Membranous
 Scaly
 Protect young leaves in
bud
 They drop off as the bud
open.
 As in peepal

11. 2. Leafy Stipules
 Large
 Green
 Leaf like
 Manufacture food for
plants
 As in pea

12. 3. Free Lateral Stipules
 Small
 Green
 Standing freely at the base of
leaves one on each side
 As in cotton

13. 4. Petiolar or Adnate Stipules
 Fused laterally with the
petiole
 grow along its some
distance
 Giving winged appearance
 As in Rose.

14. 5. Axillary Stipules
 Stipules are fuse to form a single
stipule
 Lie between stem and petiole
 As in Victoria

15. 6. Orcheate Stipules
 The large stipules fuse
along their margins to
form a hollow tube
orchea
 They surrounds the
stem from node up to
certain height of
internode.
 As in polygonum

16. 7. Tendriller Stipules
 Stipules are modified
into tendrils
 As in Smilax

17. 8. Spinous Stipules
 Stipules are modified into
spines which act as
protective organs
 As in Zizypus jujube.

18. Insertion
Attachment of leaves to the stem or branches is called
insertion.
 Cauline :
If the leaves arise on main stem
 Ramal and Cauline :
If the leaves arise both on main stem and its branches,
e.g., in sunflower.
 Radical :
When leaves arise from a reduced stem e.g., in radish
and onion
Such leaves usually forms a rosette.

19. Insertion
Cauline
Radical
Ramal and
Cauline

20. Phyllotaxis
 The arrangement of leaves on stem is called
phyllotaxis
 Helps to avoid overcrowding of the leaves so that
all leaves get maximum light for photosynthesis
 The phyllotaxis may be:
 Alternate: e.g., Hibiscus rosa-sinensis
 Opposite:
a. Opposite decussate: e.g., Calotropis, Ocimum
b. Opposite superposed: e.g., Guava
 Whorled: e.g., Oleander, Alstonia,

21. Phyllotaxis
Alternate
Hibiscus rosa-
sinensis
Opposite superposed
Guava
Opposite
decussate
Calotropis
(Ak)
Whorled
1. Astonia 2.
Oleander

22. Venation
 Parallal Venation
 Found in monocots e.g., grasses, cereals, onion,
banana
a. Unicostate: If there is a single mid rib in the lamina
b. Multicostate: If more than one midribs are present in
the lamina
 Reticulate Venation
 Found in dicots
a. Unicostate: e.g., in Mango, Peepal etc.
b. Multicostate: e.g., in Castor oil

23. Venation
Unicostate Multicostate Unicostate Multicostate
Parallal Venation Reticulate Venation

24. Duration Of Leaves
 Caducuous:
If the leaves fall very early, as in Opentia
 Deciduous:
If the leaf fall at the end of growing season, as in
Dulbergia sissoo
 Persistent:
If the leaf remain functional on the plant for more
than one season, and the plant is called as
evergreen, as in mango etc.

25. Presence and Absence of
Petiole
 Petiolate:
When a leaf stalk or petiole is present, as in peepal
 Sessile:
When the petiole is absent. As in poppy.
 Sub-Sessile:
When the petiole is extremely small, as in Calotropis.
 Winged:
When the petiole has a small blade on its either side and
has a wing like shape. As in Citrus
 Peltate:
When the petiole is inserted at or near the centre of
lamina, as in lotus

26. Presence and Absence of
Petiole
Petiolate
Sub-Sessile
Sessile
Winged
Peltate

27. Kinds of Leaf
 Simple leaf:
When the leaf lamina is all in one piece e.g., in peepal
 Compound leaf:
 Pinnate Compound leaf
• Peripinnate: if the leaflets are even e.g., Cassia fistula
• Imperipinnate: when leaflets are odd e.g., Rosa indica
 Palmate Compound leaf
• Unifoliate: e.g., Citrus
• Bifoliate: e.g., Bauhinia yunnanensis
• Trifoliate: e.g., Oxalis
• Multifoliate: e.g., Alstonia

28. Kinds of Leaf
Peepal Rose
Cassia fistula
Bauhinia yunnanensis
Citrus
Astonia
Oxalis

29. Special Modification of
Leaves
 Leaf-Tendrils: as in grapes and
sweet pea
 Leaf-Spines: as in Berry
 Leaf-Pitcher: as in pitcher plant
 Leaf-Blade: as in bladder wort
 Phyllods: as in Australian
Acacias

30. Modifications
Leaf-
Tendrills Leaf-
Blades
Leaf-Pitcher
Leaf-Spines Phyllods