Different types of leavesDifferent types of leavesA typical leaf of a dicotyledonous plant consists of two main parts :
The blade is thin and expanded and is supported by a network of veins while the petiole is slender and connects the leaf to the stem.
The leaf blade varies greatly in shape and there are numerous terms to describe its general shape. These terms describe the leaf's
| general shape, | apex, | base, | margin, | and veins |
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The
leaf blade has two types of configuration. It may be in one unit, in which
case the leaf is called a simple leaf, or it may be divided into numerous small parts that
look like individual leaves and which form a compound leaf. It may be difficult to tell
whether one is looking at a simple leaf or the leaflet (pinna) of a compound leaf. The
distinction can be made by the fact that a leaf (simple or compound) has an axial
bud between the petiole and the stem.
The petiole of
a leaf may vary considerably and can be long, short, rounded or flat.
Some leaves have no petioles in which case they
are said to be sessile. At the base of the petiole in many leaves are small
leaf-like structures called stipules
e.g. in peas, beans and roses. Between the petiole and the stem is a bud of a potential
branch (an axial bud).
Leaves may be arranged on the stem in a variety of ways. The place on the stem from where the leaves grow is called a node and the part between the nodes is the internode. If only one leaf arises at a node the leaves are said to be alternate, if there are two leaves they are opposite and if there are more than two they are whorled.
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| Alternate leaves | Opposite leaves | Leaves in whorls |
