Inflorescence - Racemose Inflorescence - Cymose Inflorescence & Alternation of Generation

It is the mode of branching of floral axis having a group of flowers. There are two types of inflorescence.

Racemose Inflorescence: 

    It is indefinite inflorescence. In Racemose, man axis called peduncle continues to grow. The flower develops in acropetal in acropeta succession. It means the old flowers are at the base while young flowers are at the tip of floral axis. The opening is centripetal.

Peduncle Elongated: 

• Racemose : It is an inflorescence in which flowers are pedicellated and bisexual. e.g. Brasica.
• Spike: It is an inflorescence in which flowers are sessile and bisexual. e.g. Amaranthus.
• Catkin: It is an inflorescence in which flowers are sessile and unisexual. e.g. Mulberry.
• Spadix: In this case flowers are covered by one or many large bracts called pathes.

Peduncle Shortened: 

• Corymb: It is an inflorescence in which flowers have pedicle of unequal length. The lower flower have long pedicle and upper have small pedicle so that all flowers are at the same level. e.g. lbreis.
• Umbel: It is an inflorescence in which all flowers have pedicle of same length, the pedicles appear to rise from common point. e.g. Coriander.

Peduncle Flattened: (head) (Capitulum)

     It is an inflorescence in which peduncle is flattened laterally expanded, with growing point in center. It has a mass of small sessile flowers called florets. It has one or more whorls of bracts at the base forming an involucre.

Florets are of two types.

• Ray Florets: These florets are strap shaped and are present at the margin.
• Disc-Florets: These florets are tubular and are present in the center. e.g. Sunflower, Zinnia, Marigiod etc.

Spikelet Inflorescence: This kind of florescence is found in many plants. It is a kind of racemose inflorescence. There are three bracts at its base called glumes. The lower two glumes are without flowers are called empty glumes. The third glume has flower in its axil and is called lemma. Just opposite to lemma there is small bractole called palae. Flowers are covered by their lemma and palea e.g. Wheat, rise, Coat etc.

Cymose Inflorescence

  In cymose inflorescence main axis soon stops growing i.e. it grow to a certain height. The flower develop in basipetal succession i.e. oldest flowers are at tip and young flower are at the base. The opening of flower is Centrifugal.

1. Uniporous Cymose: The main axis soon ends into a flower and producing only one lateral branch at a time ending in a flower. It has only two types.
2. Scorpioid Cymose: If successfully branches are produced on alternate side is called Scorpioid Cymose e.g. Cotton, Forget-me-not.
3. Helicoid Cymose: If the succeeding branches are produced on same side, it is called helicoid e.g. Sundew.
4. Biparous Cymose: The main axis soon ends into a flower and producing two flowers, this mode is followed by each succeeding flower. e.g. pink-night-jasmine.

Alternation of Generation

   In plants there are two generations called sporophyte and gametophyte. During life cycle of plant, sporophyte form gametophyte and it forms sporophyte, this is known as Alternation of Generation.

   Only in bryphytes the main plant is gametophyte, while in all other plants sporophyte is main plant while gametophyte is reduced.

Posted in: Botany