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root hairs, optimal growth

> > > This doesn't jive with my experiences with massive plant growth using
> > > gravel substrates, undergravel filters and Dupla fertilizers. 
> > 
> > You are assuming that your Dupla substrates are infertile. If your
> > substrate helps to grow better aquatic plants, it can only be because
> > is fertile. Any other theories?
> "Infertile" is your definition, not mine. Maybe we need some new
definitions or 
> terms that aren't quite so loaded with implication. How about:
>   Dupla-style: "just right"
>   Fertile: "loaded time bomb"

I believe you fellas are speaking of two different things here:  optimal
growth and fertility.  Just because two substrates contain equivalent
mineral nutrient content does not mean they will provide for equivalent
growth rates.  A gravel substrate usually prevents the formation of root
hairs.  I do not think this prohibits "lush growth" but this is just not
optimal (whatever the heck optimal means).  If you consider that your
average crop plant (say corn or wheat....gasp, land plants in this forum?)
only expresses about 20% of its calculated genetic yield potential under
field conditions (I have no clue who modeled this, but the unreferenced
reference appears in Taiz and Zeigler, Fund. Pl. Phys.  1992), you can see
how difficult it would be to define what is optimal growth.  Definitely an
interesting discussion (probably for another forum).

Dennis J. Harney
...finally snowing in SW Ohio.......
Miami University Botany Dept, Plant Physiology.