Page 15 - Lesson Notes-Morphologyof flowering plant

The Flower
The flower is the reproductive unit in the angiosperms. It is meant for sexual
reproduction. Morphologically, it is considered as a shoot bearing nodes and
modified floral leaves. A flowers is called modified shoot because the position of the
buds of both flower and shoot which is same and can be in terminal or axillary in
position.
Structure of Flower
A flower arises in the axil of a leaf like structure called bract. Flowers with bracts are
called bracteate and those without bracts are called ebracteate.
The terminal part of the axis of the flower is the receptacle or thalamus. The
receptacle contains sepals, petals, stamens and carpels. If the leaves are present on
the pedical, they are called bracteoles.

Parts of a Flower
A typical flower consists of four distinct parts the calyx, the corolla, the androecium
and the gynoecium. The calyx and corolla are accessory parts and the androecium
and gynoecium are essential parts.
These essential parts consist of two kinds of (male) sporophylls, the
microsporophyll (male) and the megasporophyll (female).
A flower can be unisexual or bisexual. It is borne on short or long axis. The axis
contains two regions the pedicel and the thalamus or receptacle.
The pedicel may be short, long or even absent. The thalamus is the swollen end of
the axis on which the floral whorls are arranged.
Different parts of flower are given below
i. Calyx
It is the outermost whorl of a flower. It is made up of units like sepals. The sepals are
generally green, leaf like and protect the flower in the bud stage, i.e., when floral in
bud condition. They have veins and stomata like ordinary leaves but are thicker in
nature. The sepals may be gamosepalous (sepals united), e.g., Caesalpinia or
polysepalous (sepals free), e.g., Crotalaria.
The sepals also prevent transpiration from inner parts of the flower. Coloured sepals
attract insects for pollination.
ii. Corolla
It is composed of petals. Petals are usually brightly coloured to attract insects for
pollination. Like calyx, corolla may also be gamopetalons (petals united) or