Ask a Teacher

Search



IN PNEUMATOPHORES[SPECIOUS OF SHOE FLOWER]THE BUD COMES IN THE ROOT. WHY IS IT SO?
Pneumatophores (breathing roots) of Avicennia (Family Verbenaceae/Avicenniaceae) are pencil-like projections that form in the open mud flat of the mangrove swamp. These structures are thought to be important for oxygenating roots that grow in the anaerobic mud.
An aerial root may be defined as a root which, for part of the day at least, is exposed to the air. The mangrove mud is rather anaerobic (oxygen poor) and unstable and different plants have root adaptations to cope with these conditions.
Pneumatophores are erect roots that are some form of upward appendage or extension of the underground root system. Because these roots are exposed at least part of the day and not submerged underwater, the root system can obtain oxygen in an otherwise anaerobic substrate. It is not a species of shoe flower.
Virtually all mangroves share two common reproductive strategies: dispersal by means of water and vivipary.
Members of the Rhizophoraceae family (Rhizophora, Bruguiera and Ceriops species) have an intriguing viviparous method for successfully reproducing themselves. Vivipary means that the embryo develops continuously while attached to the parent tree and during dispersal. They may grow in place, attached to the parent tree, for one to three years, reaching lengths of up to one meter, before breaking off from the parent and falling into the water.
These seedlings (propagule) then travel in an intriguing way. In buoyant sea water they lie horizontally and move quickly. On reaching fresher (brackish) water however, they turn vertically, roots down and lead buds up, making it easier for them to lodge in the mud at a suitable, less salty. Once lodged in the mud they quickly produce additional roots and begin to grow.
Some other species (Avicennia and Aegiceras) also produce live seedlings but these are still contained within the seed coat when it drops from the plant. The seed of Avicennia floats until this coat drops.


comments powered by Disqus