Aerial root - Types of Aerial Roots - Encyclopedia II

This plant organ that is found in so many diverse plant families has different specializations that suit the habitats which the plants can grow in. In general growth form, they can be technically classed as negatively geomorphic (grows from the stem up and away from the ground) or positively geomorphic grows down to the ground.

In the case of the Banyan tree, also known as the strangler fig, the tree begins as a small aerial plant, and grows down and around the stem of its host until it reaches the ground. The roots sprout branches along the way, and eventually when soil is reached, will uptake nutrients in a more typical fashion. Non-parasitic ivy plants use their aerial roots to cling to host plants, rocks, or houses.

These specialized aerial roots enable plants to breath air in habitats that have waterlogged soil. The roots may grown down from the stem, or up from typical roots. Some botanists classify these as aerating roots rather than aerial roots, if they come up from soil. This is a good example of the living nature of plant taxonomy, that different experts hold opposing views on the subject. The surface of these roots are covered with lenticels which take up air into spongy tissue which in turn uses osmotic pathways to spread the needed oxygen throughout the plant as needed.

These roots are found in parasitic plants, where aerial roots become cemented to the host plant via a sticky attachment disc before intruding into the tissues of the host. Mistletoe is a good example of this.

Adapted from the Wikipedia article "Types of Aerial Roots", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki/Main_Page