Morphology of Flowering plants

Inflorescence

Have you ever wondered why some flowers bloom in bunches while some others bloom vertically? No, that is no magic! There is pure science behind it. As biology students, you must be aware of the term inflorescence. In this chapter, we will study more about inflorescence. We will also look at the various inflorescence types in different categories.

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What is Inflorescence?

Inflorescence is the arrangement of flowers on the floral axis. The flowers are arranged with respect to a fixed floral axis. We will look at the various types and arrangements of flowers now.

1) Racemose

In this type of inflorescence, the main axis continues to grow. It does not terminate in a flower and gives off flowers laterally in an acropetal manner (where old flowers are arranged lower side and young flowers are on the upper side). We can further divide it into:

  • Raceme: When peduncle or (main axis) is elongated and flowers are pedicellate. Eg. Radish, Mustard

Inflorescence

  • Spike: Here, the peduncle is elongated but flowers are sessile. Eg.Achyranthes.

Inflorescence

  • Catkin/Amentum: Here, the peduncle is thin, long and weak. The flowers are sessile and unisexual. Eg. Mulberry, Betula, Oak.
  • Spadix: In it, the peduncle is thick, long and fleshy. The flowers are small, sessile and unisexual. Examples include Colocasia, Maize, Aroids, Palms etc.
  • Corymb: In it, the peduncle is short and all flowers are present at the same level because the lower flower has much long pedicel than the upper one. eg. CandytuftInflorescence
  • Umbel: An inflorescence in which the flower stalks are of more or less equal in length, arise from the same point. At the base of flowers stalk, there is a whorl of bracts forming the involucre. Eg.Centella.
  • Capitulum/Racemose head (Anthodium): Here, the peduncle doesn’t grow. It becomes broad, flattened concave or convex.

Learn more about the Types and Parts of Flower here in more detail.

2) Cymose

In this type of inflorescence, the peduncle terminates in a flower.  Here, the older flowers are present at the upper portion and young buds are arranged towards the base. This arrangement is called as the basipetal succession. It is of the following types:

  • Uniparous cyme/Monochasial cyme: The peduncle ends in a flower producing lateral branch at a time It is of two types again: Helicoid cyme and Scorpioid cyme.
  • Dichasial or biparous cyme: In this type, peduncle ends in a flower and from the basal part of peduncle, two lateral branches arise. These also end in a flower and this same arrangement occurs on these lateral branches. Eg.  Bougainvillaea, Jasmine, Teak, Mirabilis.
  • Multiparous cyme/Polychasial: Here, the peduncle ends in a flower and from the base of it many lateral branches arise, which also terminate in flowers.

Now, we will look at some special types of Inflorescence.

Inflorescence Types

1) Cyathium

The bracts or the involucre fuse and form a cup-shaped structure on the margin. This houses the glands. In the central part of the cup-shaped structure, you can find the female flowers. These mature earlier. Due to the growth of pedicel, this comes out from the cup-shaped structure.

Small male flowers surround these female flowers. These are also found on Pedicel. The male flowers, which lie towards the centre, mature earlier than the flowers which are towards the periphery. This inflorescence is found in Euphorbiaceae family like Euphorbia, Poinsettia, Pedilanthus.

2) Verticillaster

We can find this type of inflorescence in Labiatae/Lamiaceae family, where the leaves are arranged in opposite manner on the stem. From the axil of each leaf, inflorescence develops. From the main axil, lateral axil arises, on which flowers you can find the flowers. Examples include Salvia, Ocimum, Coleus etc.

inflorescence types

3) Hypanthium

In this type of inflorescence, you can see the peduncle modified in narrow cup-like structure. At the base of the cup, the female flowers develop while towards mouth the male flower develops. All three types of flowers are present in this inflorescence. Eg. Banyan, Peepal etc.

Solved Example for You

Question: Write a note on Mixed Inflorescence.

Solution: In this arrangement, you can find the flowers arranged in both racemose and cymose manner on the same peduncle. It is further of two types:

  • Mixed spadix: eg: Banana
  • Cymose raceme or thyrsus: eg: Grapes
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