Biology XI Content
The arrangement and distribution of flower in the axis of plant is called inflorescence. The supporting stalk in inflorescence is known as peduncle. The supporting stalk of individual flower is called pedicel.
Solitary terminal is the inflorescence in which single flower of the terminal part of growth.
Solitary axillary: If single flower develops from the axis of leaves and branches of plant, then the inflorescence will be solitary axillary.
Based on the mode of distribution and origination of flower, in plant, inflorescence can be categorized as:
In this type of inflorescene, the main axis of inflorescene does not terminate in flower but continuous to scene does not terminate in flower but continuous to grow and fives flowers laterally. The flower at lower or outer side is older and upper or inner flowers are younger. It is termed as arrangement of flowers in zeropetal or centripetal succession.It is of further following types:
In this inflorescene, the main axis is long and bears laterally flowers of equal length. E.g. mustard.
It consists of a long laterally like in racemose. E.g. Amarenthus, etc
- Catluin or Amentum:
In catluim, the flowers are arranged like that of spike but consists of more compactly arranged and unisexual flowers. The axis is long and pendulous. All the flowers of certain mature at the same time and fall as a unit. E.g. Mulberry,etc.
It is also like spike but axis is fleshly and whole axis is enclosed by one or more large bracts called spathes. E.g. banana. The upper part of it consists of flowers.
The arrangement of flowers in corymb is like in spike but the main axis is short and the pedicals of flowers are of varying length so that they are on the same level. E.g. candytuft. In some cases, the main axis is long and upper flower form corymb whereas lower form raceme. E.g. mustard.
It consists of a very short axis. All the flowers have long stalk arising from the same point e.g. Cantella.In some cases, a flower is represented by an umber and is called compound umbel. It is foung in Coriandrum.
- Head or capitulum
In this inflorescene, the main axis is compressed and forms a convex structure called receptacle. On the receptacle, sessile less flowers (florets) are arranged in a centripetal order. The whole inflorescene is surrounded by an involucre of bracts. The members of family compositae like sunflower, marigold, etc bear it.
In this type of inflorescene, the growing point is used up to form a flower. The further growth occurs by lateral branches which also end in flowers. The different types of cymose inflorescene are mentioned below:
The main axis ends in a flower and only are lateral bud grows and again ends in a flower. It is of two types:
- Helicoid: The successive lateral branches arise in the same side so that the flowers are borne only in one side. E.g.Drosesaea and Begonia etc.
- Scorpiod: In this type the flowers are borne alternately on both sides.
- Dichasial or Biparous Cyme
In this type, the main axis is terminated in a flower and lateral branches also terminate in a flower and lateral branches also terminate in a flower. This process can repeat for number times. E.g. Spegula etc
In this type, the main axis ends in a flower and number of branches arise from its lateral side. E.g. Calotropis etc.