Question

Inflorescence consisting of acropetally arranged sessile, bisexual flowers on an elongated axis is called

• A. spike
• B. raceme
• C. catkin
• D. spadix

Answer 1

The correct option is A spike

Spike: In this type of racemose inflorescence, the main axis remains elongated and acropetal i.e., older flowers are at the base and younger ones at the tip. The flowers are sessile, without pedicel or stalk, e.g., Piper longum (long pepper), Achyranthes (chaff flower), Amaranthus (amaranth), Justicia adhatoda (Malabar nut), etc.

Raceme: The main axis is unbranched, elongated and bears pedicellate flowers laterally in acropetal succession. Examples: Brassica campestris (mustard), Raphanus sativus (radish), Crotalaria retusa (rattleweed), Cleome viscosa (Asian spider flower), Antirrhinum majus (snapdragon), Convallaria majalis (lily of the valley).

Catkin: It is a modified spike with a drooping central axis. It contains unisexual sessile flowers arranged closely on the peduncle. Flowers have inconspicuous petals and scaly bracts. Examples: Morus alba (mulberry), Betula (birches), Quercus (oak), Salix (willows), etc.

Spadix: This is also a modification of spike inflorescence having numerous sessile unisexual flowers and a fleshy axis, which remains enclosed by one or more large, brightly coloured bracts, the spathes. This inflorescence is found only in monocotyledonous plants. Examples: Present in the plants of family Araceae (arums), Musaceae, Palmaceae.