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Fe composition of plant tissues

An interesting bit of data from

Critical Fe limits for Pea plants 

       Fe-deficient < 75 g g-1 DW (chlorotic as used for chlorophyll) 
       Fe-sufficient 100 g g-1 DW (green and healthy) 
       Fe-toxic >500 g g-1 DW (necrotic spots on leaves)

In parts per million these are 0.075, 0.1 and 0.5 respectively. This is
a measure of the dry weight (DW) concentration in the plant tissues.
It's probably just coincidence that the common target for Fe
concentration in solution is 0.1 ppm. Plants are able to concentrate
iron several fold that in the environment.

The following oft quoted reference Feb, 1988 "Today's Aquarium, the
International Magazine of the Optimum Aquarium", ("Aquarium Heute" in
German), published by Aquadocumenta Verlag GmbH. gives the Fe
composition of aquatic plants as 15 ppm. It also states that plants are
able to concentrate Fe by a factor of 1000 although my quote of a quote
says '"Concen Factor" is how much plants can store beyond their needs
for growth, i.e., plants can store 1000 times more iron than they need.'

The range of tissue concentration for pea plants is less than 10 fold so
clearly plants are NOT able to store 1000 times their metabolic
requirement of Fe.
Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!