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Don't believe everything you read...?

While browsing through my local Barnes & Noble bookstore, I happened to pick up 
a thin paper-bound book called 'Aquatic Plant Handbook", published by Barron's.  
This book made some claims which I found astounding, because they seem to 
contradict the assembled wisdom available through this mailing list.  I have 
paraphrased some of these, and would be interested in reading any comments.

The parts I found particularly amazing are followed by a (!).

1. Both Echinodorus and Cryptocoryne are marsh plants, not true aquatics (!).  
Being marsh plants, they are unable to absorb nitrogen through their leaves, and 
must be fertilized at the root (!).

2. Aquatic plants are only able to absorb nitrogen in the form of ammonium, and 
are unable to metabolize either nitrite OR NITRATE (!).  The book goes on to 
state that utilization of nitrate is ONLY characteristic of terrestrial plant 
life.  It doesn't say anything about a plant's ability to metabolize ammonia 
(vs. ammonium), other than saying to keep pH under 7.0 so that you never have 

3. If nitrate builds up in the water, it will actually stunt plant growth unless 
also accompanied by increased levels of light (!).  As a result, plants which 
are growing vigorously under low to moderate light may suddenly stop all growth, 
despite the addition of trace elements, etc.

Although I am sceptical of all of these claims, I can't help but wonder if #2 
might explain why I have a tank full of growing plants, but can't seem to keep 
my nitrate below 30 ppm.  I have a moderate fish load, but try not to overfeed 
them; I am in the process of building a 4-light hood (bringing me up to 3W/gal), 
hoping to increase plant metabolism.