Re: Why do roots exist?

The roots of aquatic plants are fully functional!!! Anyone who baldly 
states that they are merely for anchoring the plant underwater has a 
complete lack of understanding of basic aquatic plant physiology AND 
The reality is that rooted aquatic plants acquire the majority of their P 
from the sediment via their roots. The same goes for nitrogen. The reason 
is that N and P in natural systems are at a much greater concentration in 
the sediment than in the water. In addition, aquatic sediments are 
anaerobic which means that N and P are either in a more useable form 
(NH3-N) or solubilized and more available. The anaerobic sediment also 
reduces ferric iron, which is insoluble, to ferrous iron which is soluble 
and much more available for plant uptake.
There is also evidence which indicates the presence of a 'transpiration' 
stream in aquatic plants. This means that aquatic plant roots absorb 
water and can push it up into the foliage, thereby delivering nutrients 
to the upper parts of the plants.
Over the past century there have been a plethora of controlled, 
repeatable experiments carried out by reputable scientists which clearly 
show that aquatic plants grow better on a fertile substrate. In addition, 
recent studies have indicated, as mentioned above, that N,P and perhaps 
most other nutrients, can be supplied exclusively from the sediment via 
the roots (references upon request). Only Ca, Mg and K have been shown to 
be essential in the water column. Interestingly, there are even some 
aquatic plants which acquire the majority of their CO2 from the sediment!
So, the next time somebody tells you roots are non-functional, just walk 
away because they just dont know what theyre talking about.

Dr. dave.