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re: Plant deficiency?

Jon Hammond wrote:

> In my old tank I noticed with the Hygro and some other stem plants that
> they would grow really well towards the top and lose the leaves toward
> the bottom giving them a funny appearance.  Could this be because they
> crowded eachother out from the light (it was pretty dense) and the
> bottom leaves just dropped off as a response? Or could it be some
> deficiency in my water (I havent been adding any aditional nutrients
> or c02 to this tank for a long time.. lots of fish mulm and stuff in
> it tho).


Plants dropping an excessive number of older leaves is probably either a
nutrient shortage or damage.  It's normal for plants to drop some of the
lower leaves, and some plants will drop all of their lower leaves if you
let their tops get out of water.

If the problem was a nutrient shortage, then any of the "mobile" nutrients
could be suspected.  There's a letter (or two) at TheKrib that gives a
breakdown between mobile and immobile nutrients.  Mobile nutrients are
those that the plant can drain out of old growth and relocate to supply
new growth when the supplies are short.  Among the majors, potassium and
nitrogen are both mobile.  I'm not sure about phosphorus.

A nitrogen shortage might be suspected if the plants were unnaturally
light green or yellow and especially if the older leaves rotted back from
the tip when they died.  A potassium shortage might be suspected if the
lower leaves developed holes and developed a corroded look before they
dropped off.  Other nutrients will have other symptoms.

Roger Miller