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Discussion Starter · #1 ·
This is part of a message to Tsunami. I was thinking that the symptoms he described for the die-back of his red Ludwigia did not sound like nitrogen deficiency, but his observations were that in a high light tank, these symptoms developed whenever he let his nitrates get below the 5-10 ppm range.


When they grow plants hydroponically to show nutrient deficiencies by witholding a different nutrient in each culture, they always have high concentrations of all the other nutrients so that the deficiency symptoms that develop are sure to be only those related to the witheld element. I wonder if, in the aquarium, when one nutrient becomes limiting and others may not be in high concentration, you might get multiple deficiency symptoms caused indirectly by the one limiting nutrient. The deficiency of the other nutrients could be secondarily caused by the deficiency symptoms of the primary limiting nutrient impairing uptake of other nutrients. For example, if calcium deficiency causes root tips to die, then wouldn't the damaged roots be much less able to take up other nutrients?

I would think that nitrogen deficiency would be less likely to impair uptake of other nutrients than most deficiencies, however. One thing I have seen over and over again, is that if my plants get low on nitrigen, they grow lots more roots. Nitrogen deficiency is commonlly encountered by plants living in their natural envrionments, and probably phosphorus deficiency also. Plants do not seem to be harmed by deficiencies of these two nutrients nearly as much as they are harmed by deficiencies of others.

For me, iron is the most perplexing nutrient. Aquarium plants seem to differ widely in their ability to take it up. There may be some plants that are still mildly deficient even when the iron in the water column from chelated iron, is 1 or 2 ppm. I have seen what looks like potassium deficiency in Hygrophila, developed when there is plenty of potassium present according to my LaMotte kit, disappear, when I added more chelated iron. I suspect that in many aquatic habitats, iron availability is quite high because anaerobic water seeps in from the soil, loaded with reduced iron compounds that precipitate out right on the leaves and stems of the plants.
 

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Paul, I agree about the lower nutrients besides the one in question.

NO3 and NH4 sources need to be addressed also.
N and P seem to be the bigger players, K+ less so.

Fe is funny.
I think that many, but not all plants need both a source in the water column and a source in the substrate to do well.

The reason is that the transport _without_ the aid of evapotransportion in emergent or terrestrial plants, might be slow/too slow.

The shoot organs have to trasport in down to the roots for growth or the roots have to transport it up to the shoots.

Fe is chealted by the plants after it takes it in as Fe2+. This seems like a tough way to move this nutrient around.

This is one of those nutrients I will say needs to be in both locations no matter what if you use CO2.

Regards,
Tom Barr
 

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From my experience, nitrogen is probably one of the most important nutrients for determining uptake. When this nutrient drops to zero, PO4 uptake slows down considerably. The aquarium, as a whole, stalls. A lot of plants decline --especially fast growing, nutrient sponges like Heteranthera zosterifolia. At high light levels (3-4 w/g), zero nitrates for more than 24 hours is lethal for a lot of plants. Micranthemum umbrosum and Heteranthera zosterifolia became completely transparent. Rotala macrandra stunted, and the leaves became ragged.

However, holding nitrate at 0 in a tank with 4 w/g is not the same as holding nitrate at 0 in a tank with 2 w/g. With lower lighting levels, uptake slows down and the plants don't seem to need the higher nutrient concentrations to be healthy. A decent fish load is basically all that is needed to grow healthy plants as far as N and P are concerned. I believe this is why I had such great success as a beginner with 2 w/g when I never dosed phosphate or nitrate. I had a flourite substrate, DIY CO2, and added Kent Water Plant Supplement for Fe/K/micros --that was it. I grew Rotala macrandra, Heteranthera zosterifolia, Rotala wallichii, Alternanthera reineckii, Glossostigma elatinoides, etc very well. Those were the good old days. And then I increased my lighting to 4 w/g and realized that I had to add a lot of other nutrients in a lot larger quantities to get the same results. :)

Carlos
 

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Discussion Starter · #4 ·
Here is a picture of nitrogen deficient Hygrophila polysperma. This was grown at 4 watts per gallon. The typical symptoms of nitrogen deficiency---almost the same in all plants---are shown here. The leaves are pale, but the older leaves do not die unless the deficiency is extreme and long lasting. Growth is virtually stopped in this plant. As the deficiency developed, the plant put a lot of growth into the roots. There are more roots than a plant this size would have if it were not deficient. Nitrogen deficiency is less damaging to plants than some other deficiencies, probably because nitrogen deficiency is common in natural settings. This is not severe deficiency, but often plants in natural settings will respond with a growth spurt when given nitrogen.
 

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