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Green Eusteralis
Hi Paul. Good to see you at the AGA conference this year.
Paul wrote: "I did research on nitrogen and phosphorus deficiencies in
various aquatic plants back in the 60's, and I found that the plants I
studied could tolerate even extreme phosphate deficiency without any
die-back. The plants just got small and dark colored. They never lost any
leaves. Tissue contents expressed as % of dry weight were as low as 0.07 in
highly deficient plants. Critical values (where growth just begins to be
phosphorus limited) were right around 0.15%, Luxury consumption was as high
as 0.71%."
In my recent fooling around, I found that if I stopped dosing PO4 altogether
and reduced the amount of fish food introduced into the tank while keeping
all other nutrients present in a high light CO2 injected tank that the ES
leaves would turn a very strange bright purple color and actually fall off
at the whorl nodes. I also found if I stopped the experiment after the
first few whorls of bright purple leaves and started supplementing phosphate
again that the new growth would be green but the old purple leaves would not
recover. After a week or two the purple leaves would fall off leaving the
stem.
To a lay person it seems as if the phosphate is not being transported within
the plant after the phosphate deficient leaves grow in. I recall you
mentioning to me over lunch at the AGA conference in 2000 that many plants
show extraordinary ability to grab phosphate and that phosphate can be
transported within plant tissue fairly easily. Would you expect a phosphate
deficient leaf to recover and grab phosphate once it becomes available?
Regards, Steve Dixon
San Francisco