Racemose Inflorescence and Its Types MCQ - Practice Questions with Answers

Racemose Inflorescence and Its Types - Category A

Racemose Inflorescence:

• It is also called the indeterminate or indefinite inflorescence.
• The main axis continues to grow and never ends in a flower.
• The flowers occur acropetally, that is, oldest flower towards the base and gradually the youngest flowers the apex.
• The flowers can also occur centripetally, that is,  the oldest flower towards the margin and the youngest one at the centre.

Category A: Main axis elongated

1. Raceme: 

• Main axis grows indefinitely
• Flowers are pedicellate and are borne directly on the main axis
• Flowers are borne acropetally.
• Examples - Mustard, Caesalpinia 
• Some plants produce complex raceme called raceme of racemes or panicle.
• The maix axis produces branches and flowers are borne on these branches.
• Examples - Gulmohar, Radish

2. Spike:

• The main axis is elongated.
• The flowers are sessile and are borne on the main axis directly.
• Examples - Amaranthus, Bottlebrush, etc
• A small spike with a few small bracteate flowers is called the spikelet.
• Examples - Oats and grasses.
• A compound spike is the one in which the main axis is branched and the branches bear spikes or spikelets.
• It is called the spike of spikelets.
• Example - Wheat

3. Catkin:

• The main axis is elongated.
• It is a specialised spike.
• The axis is long and pendulous.
• The pendulous axis bears clusters of sessile flowers.
• Flowers are unisexual.
• Example - Mulberry, Acalypha, Populus
   

4. Spadix:

• The main axis is elongated.
• It is a specialised spike with a fleshy axis.
• The entire inflorescence is surrounded by a large bract called spathe.
• Flowers are unisexual and plants and monoecious.
• The female flowers are present towards the base.
• The male flowers are present towards the apex.
• In between the male and female flowers, sterile flowers are present.
• The terminal end of the axis is called appendix.
• The appendix and spathe attract the pollinators,
• It is a characteristic feature of the Arum family.

Racemose Inflorescence and Its Types - Category B and C

Category B - Main axis shortened

1. Corymb:

• It is a modified raceme.
• The main axis is shortened.
• The lower or older flowers have large pedicels.
• The upper or younger flowers have smaller pedicels.
• Due to this all the flowers appear to be at the same level.
• This make whole inflorescence conspicuous and noticeable to the pollinators.
• Examples - Candytuft, Cherry, Quisqualis, etc.
• In compound corymb, the main axis is branched and the flowers are borne on these branches, e.g., Pyrus.

2. Umbel:

• It is a modified raceme.
• The main axis is severely reduced.
• The flowers have pedicels of an equal length and appear to develop at the same point.
• Each flower arises in the axil of a bract.
• These bracts fuse to form a whorl called involucre.
• Umbel inflorescence resembles a loose head of pedicellate flowers that are arranged centripetally, that is, the older flowers towards the periphery and the younger ones towards the centre.
• It is a characteristic of the family Umbelliferae or Apiaceae.
• In compound umbel, the reduced main axis branches and the individual umber are borne on these branches.
• For example, coriander.

Category C: Main Axis Flattened

Racemose Capitulum or Racemose Head:

• The main axis is flattened.
• It appears like a flat disc and is called receptacle.
• A large number of sessile flowers are borne on the receptacle in a centripetal succession.
• Whorl of bracts called involucre is present.
• This inflorescence is an evolved form of umbel inflorescence.
• The individual flowers in the capitulum are called florets.
• The peripheral florets are called ray florets.
• The central florets are called disc florets.
• For example, Sunflower.