1 Umbel is racemose inflorescence-where stalked flower aggregate on a flat receptacle
2 In raceme the main axis is shortened and flowers are borne acropetally
3 Spadix is a pendulous spike with main axis much flattened
4 Spike is a racemose inflorescence having sessile flowers
Explanation:
D
Spike is a racemose inflorescence in which grows sessile flowers in the acropetal fashion, e.g. Achyranthes (Chiffon flower), Callistemon (Bottle brush), Adhatoda vasica, Amaranthus.
- The compound spike is known as the spike of spikelets. Sessile flowers (spikeletes) are present on the branched main axis, e.g.- Wheat, Barley, Sorghum, Oats etc.
Spike is a racemose inflorescence having sessile flowers.
In umbel flowers are arranged centripetally, In Raceme flowers are arranged acropetally. Spadix is modification of catkin in which the peduncle is thick and fleshy with upper part style.