Substantial K in rainforest through fall.

[TyroneGenade]

K and Na are not salts but metals. Many salts of K and Na are not hygroscopic. Whether or not a substance is hygroscopic has no bearing on its effect as a solute on osmotic pressure. Your comments about osmosis have no basis in science.

I concede that hydroscopy has nothing to do with calculating osmolarity. My point was that water follows Na and K ions. It will even happily descend out of the atmosphere to join the salt in your salt shaker.

See http://www.chem.purdue.edu/gchelp/howtosolveit/Solutions/osmoticpressure.html for the equation to calculate osmotic pressure. Notice the M for molar concentration of dissolved species. K+ and Na+ concentrations affect osmotic pressure. You are also going to start messing with membrane potentials and the ability of cells to move ions across their membranes.

Thank you Trithor the medical reply on Na+/K+ ion physiology. Plants maintain their turgor using K ions to move water around. See http://www.jstor.org/stable/56098 for an little article on how K concentrations are used to manipulate the flow of sap. Now what do you suppose would happen if the salts built up in the substrate and prevented the movement of water into the xylem? Will the plant be able to move water into the phloem with all that K stuck in its tissues? Yes, it could pump out the sugars and drag the water out of its cells that way but that would mean an increase in tissue salinity that would mess with protein function and kill the cell. I think we've had the discussion of K accumulating in the substrate before (several times)...

So we are all on the same page (from Webster's dictionary): toxic, containing or being poisonous material especially when capable of causing death or serious debilitation. Poison, a substance that can cause people or animals to die or to become very sick if it gets into their bodies especially by being swallowed. Too much salt will kill, ergo it is acting as a poison and is toxic.

Going back to Mulder's chart. If you decrease, for instance K, then Mg becomes more available and it acts synergistically with N. This means that you can drop the concentration of N if Mg is more available to help with its uptake. If the absolute concentration of K is the problem, causing toxicity, then by simply diluting high K fertilizers to safe K levels you can avoid the toxicity issues while promoting Mg uptake which will then increase N uptake.

Going back the articles that started this thread, note that N is very low in that rain water. N as nitrates and ammonia is, generally, very low in the environment. We don't need to give our plants massive amounts of N in the fertilizer. In the wide world outside of agriculture N is rarely a fraction of 10 ppm. (One of the greatest mysteries in the plant aquarium world is why we need to 10 ppm nitrate in our tanks to grow plants while you won't find even 0.1 ppm in rivers with luxuriant plant growth.) Simple dilution of the fertilizer may be all that is needed to avoid toxic K issues. We already accept this when we suggest to growers that they use commercial fertilizers as half and quarter strengths. What is more, when we suggest they fertilize weekly weakly (or is it weakly weekly?) we are buying into the idea that our fertilizers are too strong and we can get away with less.

A few years ago a commercial grower spoke at the Cape Orchid Society about his Cymbidiums (heavy feeders, as we all know). He was fertilizing 1/10th daily (1/10 of already 1/2 so 1/20th) and was getting Cymbidiums from seedlings to flowering size in 2-3 years. His chief gripe was that he was getting a lot of fertilizer burn at the leaf tips. Bloody efficient things these Cyms...

We all already accept that our fertilizers are too concentrated and orchids need weaker feeding. All we are now doing is arguing which is the biggest factor of the fertilizer problem: too much K or a lack of something else. I think the data is now pretty clear that the issue is too much K.

tt4n

 

[DavidCampen]

I concede that hydroscopy has nothing to do with calculating osmolarity. My point was that water follows Na and K ions. It will even happily descend out of the atmosphere to join the salt in your salt shaker.

See http://www.chem.purdue.edu/gchelp/howtosolveit/Solutions/osmoticpressure.html for the equation to calculate osmotic pressure. Notice the M for molar concentration of dissolved species. K+ and Na+ concentrations affect osmotic pressure. You are also going to start messing with membrane potentials and the ability of cells to move ions across their membranes.

tt4n

You had no point. Your words were complete nonsense. Water also follows (your terminology) Ca, Mg and NH4 ions; so what? And, your word "hydroscopy", if it is even a word, has nothing to do with hygroscopicity which is perhaps the word that you were trying to use.

 

[Rick]

this one seems to show that not much detrimental effect of high K on Dendrobium: Determining the Nutritional Requirements for Optimizing Flowering of the Nobile Dendrobiium as a Potted Orchid. M.S. thesis by Rebecca G. Bichsel (2006) I haven't had time to read it in details, but she seems to have used up to 400ppm of K, and her data seem not to show a strong detrimental effects. Has anyone read this, and noticed if there were some issues (i.e. something which doesn't apply for hobbyist culture) with this set of experiments???

Naoki

The actual rate of application (as per figuring the dose exposure) is difficult to understand.

Yes 0, 50,100,200 400ppm. I can deduce that the total duration of exposure to any regime is only 6,7,8 months. These are not hydoponic application but cannot determine the frequency of application (daily weekly monthly??) Only that at any given time 100 to 150 ml of nutrient solution was applied to the pot. The potting mix seems fairly open, so I would suspect they may have watered once or twice a week, but can't tell how much actually stayed in the pot.

Table 16 has the primary data of interest. For one thing nothing died (including the 0ppm application).

Everything made it to flowering the following year (at least 4 months after termination of fert application).

Most of the metrics show that the plants maxed out by 100 ppm K (no benefits beyond that). Although the chlorophyl content parameter was significantly better for the 0ppm K application while all other doses were about the same from 50 to 400 ppm.

So no acute toxicity effects after 6-8 months of unknown application frequency (although I suspect at least weekly) at concentrations through 400 ppm. But growth leveled out after 100 ppm.

Also ratio of NH4:NO3 varied with the K exposures, but even at the extremes there was still alot more NH4 entered into the system than you would ever get in MSU RO version. That could cause K deficiency at low concentrations N and offer protection from high K concentrations in these short term experiments.

 

[eteson]

IMO one of the easiest ways to prove detrimental effects of K is using in-vitro plants.
Is is quite easy to make a "standard" media and add the desired amount of Potassium Nitrate. (4 or 5 different concentrations).

I can add this test to the experiments already running.

 

[Stone]

IMO one of the easiest ways to prove detrimental effects of K is using in-vitro plants.
Is is quite easy to make a "standard" media and add the desired amount of Potassium Nitrate. (4 or 5 different concentrations).

I can add this test to the experiments already running.

I think that could be very instructive eteson! :clap: Anything which adds to our knowledge is very desirable.

 

[naoki]

Rick and Lance, you are right, those horticulture oriented papers use short-term experiments. But these do show that acute toxicity of K is rather rare even at the super-high K.

I thought the K-toxicity is mostly based on the correlation between cellular content of K vs Mg and Ca. This is well known (and in the Potash chapter Rick put the link), but is there a demonstration that this causes detrimental effects in a long term? We may have discussed it in the past (but there are too much stuff, and I can't remember everything). The shift in cellular content could be an adaptive response. Also plants have good buffering capacity (especially epiphytes), so the lower Mg and Ca might be within the range, and you may not get any phenotypic effects.

Mineral components in tissue seems to change drastically with age (e.g. more Ca in the older growth). This probably represents the change in the functionality (sexual reproduction for newer growth vs supporting the newer growth for older growth). K is a unique mineral because the majority of the molecules are not bound to a larger molecule in plants. So it is highly mobile. Mike's original papers show that canopy plants can easily get rid of K if they want to (really high enrichment of K in through fall). So I'm still puzzling about the actual mechanism how K might cause a long term "toxicity" (this topic is interesting because nobody knows the answer yet).

Eliseo's experiment would be interesting, but again, wouldn't you say that it is about the short-term effects? One issues is that the physiology of adult orchids are quite different from seedlings in flasks (e.g.,. it's shown that even the preference for NH4:NO3 can change).

 

[Stone]

Eliseo's experiment would be interesting, but again, wouldn't you say that it is about the short-term effects? One issues is that the physiology of adult orchids are quite different from seedlings in flasks (e.g.,. it's shown that even the preference for NH4:NO3 can change).

It should at least show us if high K relative to Ca and Mg reduces growth response in the seedlings compared to controls. Or alternatively, if low K concentrations increase it. I have doubts as whether the age of an orchid would drastically change any findings. However it is possible. Baby orchids do rely on mycorrhiza in the habitat for their nutrition which may differ in the P and N etc. available however older plants are less tied to this association.

It would also be interesting if we could compare epiphyte with terrestrial or at least bark epiphyte with humus grower such as Phrag or Paph or Masdevallia and Oncidium or Cattleya etc. as there does seem to be a small (probably insignificant) difference in the element ratios. Elisio??

 

[Rick]

Rick and Lance, you are right, those horticulture oriented papers use short-term experiments. But these do show that acute toxicity of K is rather rare even at the super-high K.

Not necessarily Naoki.

1) There is no 000 control, all the single 0 additions still have lots of the other 2 added. The absolute worst looking plant (closest to death) is 0 N, but 250ppm K and 200 ppm P. The 0 ppm K or 0 ppm P plants are way better looking than that 0N plant.

2) total mineral application of even the "control plants is XXX higher than we ever feed anyway.

3) even the lowest application of the target nutrient is still XXX more than environmentally relevant.

4) without tissue analysis all of the observed effects of what is deficient or excess are assumptions. Does the 0 ppm N plant look so crappy from N deficiency, K overdose, Ca or Mg deficiency form excess K uptake. No tissue concentrations were measured so the effects are all speculative.

Given the magnitude of the concentrations used in this paper (or the Wang papers) are really studies on the antagonistic interaction effects of NPK.

I'm not aware of any published truly controlled GH study with orchids working with either acute or chronic effects of NPK with environmentally relevant concentrations.

That's were looking to mother nature is our last resort for useful info. We know that beautiful healthy orchids grow just fine in the jungle with total (N+P+K+Ca+Mg) ppm of nutrient at < 50ppm. Which makes these optimization studies so crazy when they say things like " a minimum of 50 ppm K is needed to grow orchids", base on a result where the 0 K is receiving 100ppm N and 250ppm P.

 

[Rick]

Mike's original papers show that canopy plants can easily get rid of K if they want to (really high enrichment of K in through fall). So I'm still puzzling about the actual mechanism how K might cause a long term "toxicity" (this topic is interesting because nobody knows the answer yet).

Actually there is nothing in Mikes original paper that suggests a voluntary release of K from living tissue. And when you divide out for hectares and years, "massive amounts of K" is certainly not the reality of what's getting shifted around. The moss/lichen paper that I linked (which is forest data from one of the same (Southern China) locations as Mikes throughfall paper indicates that the increase in throughfall K is from the leaching of decomposing/degrading materials in the canopy. The papers I attached years ago on bromilead K uptake and the Zotz paper on leaf senescence (actually linked by Mike 2 years ago) show that epiphytes have no brakes on taking up K, and do everything they can to retain it during growth.

There seems to be adequate literature for crop plants that excess K causes detrimental effects due to calcium and magnesium deprivation. You could look at the rice or alfalfa literature for that.

 

[Rick]

The shift in cellular content could be an adaptive response.

Yes it is well known that luxury storage of K occurs in plants as an adaptive response to living in environments where K is rare.

 

[Rick]

Mineral components in tissue seems to change drastically with age (e.g. more Ca in the older growth).

I have not seen this demonstrated for plants where K is kept high during the entire growth cycle.

I have seen this for conditions where K is pulsed initially or allowed to decline after a single large application. But K is highly mobile in live leaf tissue at all times. Ca is not readily moved around . So as long as K is high its not going to allow Ca or Mg to build into mature leaves. (That Poole and Seeley study certainly did not show increasing Ca/Mg in mature leaves).

 

[Rick]

So I'm still puzzling about the actual mechanism how K might cause a long term "toxicity" (this topic is interesting because nobody knows the answer yet).

Nobody knows the mechanism or the symptoms?

What is your definition of long term "toxicity"?

Scroll down to the symptoms of deficiency and excess. Naoki this is old school.

http://www.ladyslipper.com/minnut.htm

 

[Stone]

QUOTE] I think the data is now pretty clear that the issue is too much K.

How could you possibly say that?

Where is it clear that the ''issue'' (and I don't even see the issue) is too much K??
Is the issue that orchids are stunted/dying/have poor roots/suffer from bacterial rots/suffer from insect attack/grow well for a while then collapse/don't do as well/don't grow as fast?

Forget about your data its just confusing you. With everything that has been said, there is still no proof that standard K formulations are any less beneficial than very low K ones. There is however vast amounts of proof that orchids can grow perfectly well WITH standard K formulations.

I can attribute all the above problems on bad culture. Too much watering, not enough water, too hot, too cold, not enough air, too much humidity, not enough humidity, feeding too much, feeding to little, ( yes that happens more often than you might think)! etc. etc. How do I know that these were the shortcomings?, because I have fixed all of them without reducing K. Ask any one who has grown orchids for 30 years or so and they will tell you the same thing.

Our club's best grower has won orchid species of the year (culture and quality) with Phrags, Paphs and others 3 or 4 times State wide. He uses an off the shelf fertilizer with high K.

And you say its pretty clear too much K is the issue? Show me the proof please!

As I have said, all the evidence points to the important factor being to determine any given species' tolerence to salinity. This varies greatly among different spp. eg. a twig epiphyte that relys mainly on tiny amounts of nutrients arriving in the mist and rain (no throughfall at all in some cases) to a huge Vanda on a tree trunk that can suck up everything which comes its way and do all the better for it. The ratios of elements changes very little.

I am willing to concede that some spp. which grow on limestone and have sparse tree cover may have evolved with less K in circulation and may perform better in cultivation with less. (Again no proof) An example might be the coastal Brachys?? But a quick look at Tanakas web sight tells you they can do extremely well with 30 30 30 spring summer and 10 30 30 fall.
He has plants in the same pot for 10 years with no loss of leaves. Is that long term enough for you?

So show me now where it is clear.

All this talk about osmotic pressure and plant physiology mechanisms is absolute nonsense. Stop over analysing and just talk to a good grower for your answers.

 

[naoki]

Thanks for the additional comments, Rick!

1) There is no 000 control, all the single 0 additions still have lots of the other 2 added. The absolute worst looking plant (closest to death) is 0 N, but 250ppm K and 200 ppm P. The 0 ppm K or 0 ppm P plants are way better looking than that 0N plant.

2) total mineral application of even the "control plants is XXX higher than we ever feed anyway.

3) even the lowest application of the target nutrient is still XXX more than environmentally relevant.

4) without tissue analysis all of the observed effects of what is deficient or excess are assumptions. Does the 0 ppm N plant look so crappy from N deficiency, K overdose, Ca or Mg deficiency form excess K uptake. No tissue concentrations were measured so the effects are all speculative.

Given the magnitude of the concentrations used in this paper (or the Wang papers) are really studies on the antagonistic interaction effects of NPK.

OK, you are right, it's not complete factorial desing, and they didn't have no fertilization treatment. However, from the pattern you see, it is difficult to see any detrimental effects, though. 100ppm K was better than 0 ppm K, then it reaches saturation above 100ppm K, but it is still a monotonic response (not a humped response). If there is a toxic effects, don't you expect that one of the higher ppm should show lower growth than the lower ppm K?

As a related note, this paper has tissue analysis of 0-fertilizer treatment vs reasonable fertilization (which would be probably super high-K in your definition). There are quite a few interesting points in this paper.

http://www.redalyc.org/pdf/1802/180215650014.pdf

It's not designed to test the proportion of fertilizer. In the normal fertilization (I wasn't sure about the exact dosage, maybe 100 total ppm for inorganic ones?, but I'm calling this "high-K" treatment), leaf K was pretty normal (not off the scale compared to no fertilizer), Ca is also within the range, Mg was a bit low. In no fertilizer treatment, it looks like there are some deprivation (or deficiency). Maybe you can interpret this better than me, though. Ca deficiency can be seen within the time of experiment.

I came across this paper when Mike was talking about organic-N vs NO3 vs NH4.

I'm not aware of any published truly controlled GH study with orchids working with either acute or chronic effects of NPK with environmentally relevant concentrations.

That's were looking to mother nature is our last resort for useful info. We know that beautiful healthy orchids grow just fine in the jungle with total (N+P+K+Ca+Mg) ppm of nutrient at < 50ppm. Which makes these optimization studies so crazy when they say things like " a minimum of 50 ppm K is needed to grow orchids", base on a result where the 0 K is receiving 100ppm N and 250ppm P.

Well, you are right, they are optimizing for quick growth, more and larger flowers. These may not be the optimization for us hobbyists, which you have been pointing out, and I agree with you. We may prefer very slow growth like in nature, but lower death rate. Low rate of fertilization (and nutrident deprivation) increase root:shoot ratio (Rodriguez et al. 2010 has some data), and this could be good for long term survival for our plants in artificial environment.

The moss/lichen paper that I linked (which is forest data from one of the same (Southern China) locations as Mikes throughfall paper indicates that the increase in throughfall K is from the leaching of decomposing/degrading materials in the canopy.

Oh, OK, I don't know well about nutrient cycling in ecosystem (other than N & P).

The papers I attached years ago on bromilead K uptake and the Zotz paper on leaf senescence (actually linked by Mike 2 years ago) show that epiphytes have no brakes on taking up K, and do everything they can to retain it during growth.

I think Poole and Sheehan's review also mentions it, but they seem to think orchids takes up Ca and Mg similarly (no mention of detrimental effect of accumulation, though).

Quotes from p.206:
"Cattleya and other genera were shown to absorb relatively high levels of K, Ca, Mg and several of the microelements (especially Mn, in older leaves). However, there is little evidence to date which indicates that the plants (1) require high levels of these elements, (2) utilize these nutrients rather than accumulating them, or (3) benefit (in terms of survival) from these levels. In fact, analyses of upper (acropetal) leaves and lower (basipetal) halves of one- and two-year-old Cattleya leaves of plants grown under poor fertilization practices in a fir-bark medium (Poole and Sheehan 1973b) indicate that at least Ca, Mg, and Mn are preferentially translocated to the upper halves of older leaves and accumulated. This physiological response may be necessary to reduce nutrient antagnosims or imbalances in the younger and meristematic tissues. Plants in this study exhibited severe chlorosis in the upper halves of two-year old and older leaves but only slight signs in the lower halves. The leaves could possibly be showing symptoms of K deficiency caused by low K levels coupled with relatively high concentrations of Ca and Mg, especially in the upper half of the leaf. The one year old leaves were a pale but acceptable green color...."

There seems to be adequate literature for crop plants that excess K causes detrimental effects due to calcium and magnesium deprivation. You could look at the rice or alfalfa literature for that.

Yes, but these are the case with extremely high level of K, right? Even though the orchids are tolerant (slow to respond, or buffered well) against nutrient deficiency, don't you expect to see Ca, Mg deficiency in those studies which uses unreasonably high amount of K? For example, Ca deficiency can be seen within 18mo of studies (with Peter's fertilizer).

I have seen this for conditions where K is pulsed initially or allowed to decline after a single large application. But K is highly mobile in live leaf tissue at all times. Ca is not readily moved around . So as long as K is high its not going to allow Ca or Mg to build into mature leaves. (That Poole and Seeley study certainly did not show increasing Ca/Mg in mature leaves).

Ca not phloem-mobile is something what I have been taught, too. But see the quotes above. Epiphytes might have slightly different mechanisms to enhance their nutrient efficiency. In both Catt and Phal, data suggested Ca could be mobile.

Quote from p.205 of PS review:
"Poole and Sheehan (1973, 1974) indicate that both Ca and Mn are preferentially translocated to and accumulated in mature leaves..."
So tissue analysis shows higher concentration of Ca and Mg and lower concentration of N and K in older leaves than in younger leaves. Poole and Sheehan (1974) showed similar pattern in Phal leaves (p.208 and Table 6-9 of PS review). Also in the same page, a interesting quote here: "The researchers were unable to obtain a growth response with increased levels of K, and it seems therefore that Phalaenopsis can accumulate a large amount of K in the leaves in apparent "luxury consumption"". So a small amount of K is good enough for Phals, but they didn't note the detrimental effect of K, neither.

Nobody knows the mechanism or the symptoms?

What is your definition of long term "toxicity"?

Scroll down to the symptoms of deficiency and excess. Naoki this is old school.

http://www.ladyslipper.com/minnut.htm

Rick, I'm not talking about the symptom of deficiency. At the physiological and cellular level, what processes explain what you consider to be working under K-lite principle. I think you are proposing that the long-term benefit of K-lite is higher Ca/Mg concentration in the cells. I think I might not be using the terminology correctly in the field of toxicology. But for a given growth index (coming up with this can be a challenge, but let's say survival rate), I would define that toxicity as the lower growth index with increase in K. Obviously, "toxicity" is influenced by other nutritional conditions, environments, genetics etc. But for a given whatever condition, can we really see reduced growth with increased K concentration. I'm sure we'll gradually understand the complex dynamics of epiphyte nutrition in the future.

I didn't mean to write a long essay reply, and I don't feel like proof-reading it now... (so sorry, if the post doesn't make any sense...)

 

[Stone]

We may prefer very slow growth like in nature, but lower death rate

Interesting stuff naoki but I'll just make a note that orchids don't grow slowly in nature. Many Paphs mature a new growth every year. Even emersonii according to Xavier. I'm feeding the hell out of my Phal schilleriana and although its very healthy it is still slow compared to what I would expect in the habitat. Maybe not hot enough??

 

[naoki]

Interesting stuff naoki but I'll just make a note that orchids don't grow slowly in nature. Many Paphs mature a new growth every year. Even emersonii according to Xavier. I'm feeding the hell out of my Phal schilleriana and although its very healthy it is still slow compared to what I would expect in the habitat. Maybe not hot enough??

I guess that maybe different species respond differently to cultivation? For example, Taiwan Phal industry can go from seed to seed at an amazing speed, right? Also, could the natural observation a bit biased? For example, we are more likely to find bigger plants, and it's less likely to find seedlings of 1-2 year old after pollination. Once the plant becomes established with lots of roots, then they look like that they are growing fast. So they can't be compared with 4 year old single growth, P. emersonii, in pots?

When I'm not screwing around in ST, I have to deal with non-orchid plants (as a professional plant evolutionary biologist/geneticist), and many plants, which I have dealt with in the last 20 years, grow much faster and larger in greenhouse once they are released from the intra- and inter-specific competition in the nature. We have followed growth of Alaskan Arabidopsis for 4-5 years in the field (I'm sure there is discovery bias toward larger plants even though we try hard not to do it). They could remain 5-10mm diameter in the field, but they grow to 70-120mm rapidly in the greenhouse (they don't look like a same species). But, maybe as you said, orchids could be an exception (or we don't know what we are doing).

This is a bit a trivial point, but after looking into Rick's comment about the through-fall, this is somewhat related:
http://coweeta.uga.edu/publications/publications/5th group/pdf/575.pdf
Obviously deciduous temperate forest is quite different from tropical rain forest. I don't completely understand this paper, but tree canopy can leach K from the leaves.

p.108 bottom:
"Comparisons of foliar leaching transfers to leaf nutrient burdens showed that K+ was leached in greatest quantities from foliage, followed by Mg2+, Ca2+ and PO4 3- (Table 10)."

 

[gonewild]

I'm feeding the hell out of my Phal schilleriana and although its very healthy it is still slow compared to what I would expect in the habitat. Maybe not hot enough??

Or maybe too much K.

 

[DavidCampen]

There seems to be adequate literature for crop plants that excess K causes detrimental effects due to calcium and magnesium deprivation. You could look at the rice or alfalfa literature for that.

The only paper that you have cited in this regard, IIRC, demonstrated that rice plants grown hydroponically with KCL concentrations in excess of 1000 ppm did poorly. How do you extrapolate this as evidence that K ion concentrations of 10 ppm are toxic to orchids? From the paper that you cited, it wasn't even clear if this was due to K ion toxicity or chloride toxicity.

 

[DavidCampen]

The paper ... I attached years ago on bromilead K uptake ... show that epiphytes have no brakes on taking up K

No, that paper shows exactly the opposite. Look at figure 2. The rubidium uptake rate does not change, does not increase, over a 2 order of magnitude change in the rubidium concentration. From a change in rubidium concentration equivalent to 8 ppm potassium to 800 ppm potassium the rate of rubidium uptake does not increase at all.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2924823/

 

[gonewild]

Excess potassium...
http://eprints.nwisrl.ars.usda.gov/917/1/652.pdf