What are sub aerial stem modifications? Explain the types of sub aerial stem modifications?

Explanation

Sub aerial stem found in plants with weak stem in which branches lie horizontally on the ground. These are meant for vegetative propagation. Types of sub aerial stem modifications:
1. Runner: Slender, prostrate branch creeping on the ground and rooting at the nodes. Eg: Centella, Oxalis.

2. Stolon : Slender, lateral branch originating from the base of the stem. But it first grows obliquely above the ground, produces a loop and bends down towards the ground. When touches the ground it produces roots and becomes an independent plantlet. Eg: Mentha piperita, Fragaria.

3. Sucker: Sucker develops from a underground stem and grows obliquely upwards and gives rise to a separate plantlet or new plant. Eg: Chrysanthemum.

4. Offset: Offset is similar to runner but found in aquatic plants especially in rosette leaved forms. A short thick lateral branch arises from the lower axil and grows horizontally leafless for a short 1 distance, then it produces a bunch of rosette leaves and root at nodes. Eg: Eichhornia.