
MORPHOLOGY OF FLOWERING PLANTS
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In palmately compound leaves, the
leaflets are attached at a common point, i.e.,
at the tip of petiole, as in silk cotton.
5.3.3 Phyllotaxy
Phyllotaxy is the pattern of arrangement of
leaves on the stem or branch. This is usually
of three types – alternate, opposite and
whorled (Figure 5.9). In alternate type of
phyllotaxy, a single leaf arises at each node
in alternate manner, as in china rose,
mustard and sun flower plants. In opposite
type, a pair of leaves arise at each node and
lie opposite to each other as in Calotropis
and guava plants. If more than two leaves
arise at a node and form a whorl, it is called
whorled, as in Alstonia.
5.3.4 Modifications of Leaves
Leaves are often modified to perform
functions other than photosynthesis. They
are converted into tendrils for climbing as
in peas or into spines for defence as in cacti
(Figure 5.10 a, b). The fleshy leaves of onion
and garlic store food (Figure 5.10c). In some
plants such as Australian acacia, the leaves
are small and short-lived. The petioles in
these plants expand, become green and
synthesise food. Leaves of certain
insectivorous plants such as pitcher plant,
venus-fly trap are also modified leaves.
5.4 THE INFLORESCENCE
A flower is a modified shoot wherein the shoot
apical meristem changes to floral meristem.
Internodes do not elongate and the axis gets
condensed. The apex produces different
kinds of floral appendages laterally at
successive nodes instead of leaves. When a
shoot tip transforms into a flower, it is always
solitary. The arrangement of flowers on the
Figure 5.10 Modifications of leaf for :
(a) support: tendril (b) protection:
spines (c) storage: fleshy leaves
(c) Onion
Fleshy
leaves
Leaf
tendril
(a) Pea
(b) Cactus
Leaves
modified
into spines
Figure 5.9 Different types of phyllotaxy :
(a) Alternate (b) Opposite
(c) Whorled
(c) Alstonia
(a) China rose
(b) Guava