The leaf has three main parts - the leaf base, petiole, and lamina. The leaf base attaches the leaf to the stem, the petiole holds the blade and provides support, and the lamina is the expanded green part of the leaf containing veins and veinlets. Leaves can have parallel or reticulate venation patterns depending on the arrangement of veins. Leaves are either simple, pinnately compound, or palmately compound. Phyllotaxy refers to the arrangement of leaves on stems, which can be alternate, opposite, or whorled. Leaves are sometimes modified to perform functions other than photosynthesis, such as for climbing, defense, food storage, or to act as

2. 5.3 THE LEAF (vegetative organ)
•The leaf is a lateral ,generally flattened structure borne on
the stem.
•It consists of three parts leaf base, petiole and lamina .
• leaf base :-the attachment of leaf to its base .
•It has two lateral small leaf like structures called stipules.
•In leguminous plants leaf base becomes swollen and is
called pulvins.
•Petiole :-hold the blade to exposed light .
•Lamina:-green expanded part of leaf with veins and
veinlets.
• Veins:- provide rigidity to leaf blade and act as a channel
for transport of food and water
•Midrib:-middle prominent vein

3. 5.3.1 VENATION
• Venation:-The arrangement of veinlets in lamina of
leaf
• Reticulate:- veins forming a network.
• Parallel venation:-when veins run parallel to each
other within lamina
• Monocotyledonous plants show parallel venation
• Dicotyledonous plants show reticulate venation.

5. 5.3.2 TYPES OF LEAVES
• simple leaf:-when lamina of leaf is entire and
incision does not touch the midrib
• Pinnately compound leaf:-leaflet are present
on common axis rachis.
• Palmately compound leaf:-leaflet are attached
at tip of petiole .e.g. silk cotton.
• Compound leaf:- when incision of lamina
reach up to midrib breaking it into number of
leaflets.

7. 5.3.3 PHYLLOTAXY
• Phyllotaxy:-pattern of arrangements of leaf on
stem or branch.
• 3 types of phyllotaxy are:-
• Alternate:-single leaf arises at each node. single
leaf arises at alternate node .e.g. china rose.
• Opposite:- a pair of leaf arises at each node ad
lie opposite to each other. E.g.Calotropis.
• Whorled:-more than two leaf arises at each
node . E.g.Alstonia.

9. 5.3.4 MODIFICATION OF LEAVES
• Leaf are modified to perform function other than
photosynthesis.
• They are used for climbing and for defence .
• They are converted into tendrils for climbing e.g. pea.
• They are converted into spines for defence .e.g. Cacti
• The fleshy leaf of garlic store food.
• For those plant who bear shot leaf such as Australian
acacia the petiole in these plant expand and synthesise
food .
• Leaves of certain insectivorous plants such as pitcher
plant are modified leaves
• Venus fly trap are used as modified leaf.

10. Summing up
• Leaf:-lateral flattened surface
3 parts are:-leaf base ,petiole , lamina.
• Venation:- arrangement of veins and veinlets on lamina
of leaf
2 type are parallel, reticulate venation
• Types of leaf:-simple ,compound , pinnately compound
leaf, palmately compound leaf.
• Phyllotaxy:-arrangements of leaf on stem or branch.
3 types are opposite ,alternate ,whorled respectively.
• Flowers or their leaf are modified for :-
1.Sythesising food
2.Defence
3.Climbing
4.Pitcher plant and venus-fly trap are modified leaf