Too busy to grow

[iann]

This Ariocarpus kotschoubeyanus subsp. sladkovskyi wasn't growing too well so I thought I'd repot and see if the roots are OK. I guess the roots are OK, saving for a rainy day, but not letting much go for growth.

sladkovskyi-0715.jpg (59.2 KiB) Viewed 2231 times

[tumamoc]

Woah .

[adetheproducer]

That is one fat root. Epic growth.

[CactusFanDan]

Well you never know when the drought's gonna come. Perhaps this is the botanical equivalent of a hoarder.

[DaveW]

Juan Acosta (Spiniflores) did an interesting experiment on compost or soil types on the production of tuberous roots, which you can see here if you look at Spiniflores posts for Jan 20th and 28th, 2010:-

viewtopic.php?p=140000&sid=90b1b04f5100 ... 565ad8126c" onclick="window.open(this.href);return false;

I was talking to a friend at the BCSS Convention who regularly visits habitat and he remarked that in the case of Eriosyce some varieties separated from the species by Ritter through having tuberous rather than fibrous roots are often illusory (Neoporteria wagenknechtii v. napina, Thelocephala longirapa =
T. malleolata etc) since both tuberous and fibrous rooted plants can often be found in the same population solely depending in what soil they are growing in.

He also remarked to me that he knew somebody who grew all their plants in peat and he had produced Thelocephala esmeraldana's 2.5" diameter in quite a short time, a size that was quite out of character to the normal size of plants growing in habitat or mineral potting mixes. It's obvious then why the Continental nurserymen use peat since as it produces larger saleable top growth quicker since you can't charge extra for larger hidden tuberous roots!

Of course tuberous roots are a feature of many species, but they seem to be produced to a greater extent in mineral soils (but with less above ground growth) than in humus rich ones that produce more fibrous roots, but far more top growth above soil level. But how extra fertilisation with mineral soils effects tuberous root growth, something they would not get in habitat alters matters only experimentation would prove.

I see in "The Soil Hexalogue" promoting mineral mixes they only recommend weak fertilisation once a year to keep the plants in character, the plants deriving all else they need from the mineral mix itself:-

http://www.cactiguide.com/pdf_docs/hexalog-engl.pdf" onclick="window.open(this.href);return false;

[Steve Johnson]

My apologies for hijacking your thread, Ian, but I couldn't pass up this one...

I see in "The Soil Hexalogue" promoting mineral mixes they only recommend weak fertilisation once a year to keep the plants in character, the plants deriving all else they need from the mineral mix itself:-

The more I read through the Hexalogue, the less impressed I am about a few assertions which apparently haven't been thought through very well:

1. A salient feature of cacti in the desert is vigorous thunderstorm activity, which takes Nitrogen in the air and fixes it in water as Nitric acid. Does rain still yield a weak Nitric acid solution when there's no lightning in the area? And what about stored rainwater? If it maintains a pH lower than 7, then perhaps stored rainwater would be a sufficient Nitrogen source for watering cacti when they're in growth. These are questions that would have to be answered by someone who knows the chemistry behind it. For those of us who can't rely on rainwater anyway, the issue is a moot point since our cacti get Nitrogen only through fertilizers.

2. While the desert isn't exactly teeming with insect and animal life, things do poop and die out there. The resulting decomposition in desert soils is a much more readily available source of nutrients than anything cactus roots will absorb through the breakdown of minerals. Seems like the author is assuming facts not in evidence unless he happens to know that the chemical composition of the minerals he discusses would provide Phosphorus and Potassium. Even if these minerals could theoretically be a source of P and K, I'm still skeptical of the whole idea.

Weak fertilization? Yes, because overfed cacti won't do well over time. But once a year??!!?? I wouldn't recommend subjecting cacti to that kind of treatment, even if they're being grown in a mineral mix.

[CactusFanDan]

Ariocarpus associate with rock-digesting bacteria in the wild and in cultivation, which help the plants to obtain nutrients from what would otherwise be an environment with scant resources. Perhaps these bacteria have a role in fixing atmospheric nitrogen for the plants too. In the second issue of Xerophilia, a very successful grower of Ariocarpus shows his Ariocarpus which have been grown in a pure mineral mix without fertilisation for over a decade. They look like very healthy plants as well. However, he states that seedling Ariocarpus might require some fertilisation at the beginning of their life.

As for fertilisation, I haven't fertilised any of my plants in over a year, however I do add a bit of time release fertiliser to my soil mix. All my plants look healthy (or I think they do )

[LophoFan]

That is one fat root. Wow!! This sort of happened with one of my baby L. albertos, but nothing like this. They weren't really growing so I pulled one out and the root was about the size of the top.

Here it is next to a young A. caput-medusae seedling. Nothing really special, but I thought it was cool.

P4120015.JPG (11.46 KiB) Viewed 2136 times

I love fat tap roots. One reason why I switched to a mineral mixture for my slow growers recently. Good job

[DaveW]

Roy Mottram of Whitestone Nurseries in the UK used to grow in a mineral mixture he called "Whitestone One Eleven" indicating his mix formula of using Grog (a baked clay product they add to pottery clay to improve it, which is virtually akin to Cat Litter or Seramis) plus coarse sand. Anyway I went round his nursery in the past and he showed me a small bed in one corner of a greenhouse composed of this and said it had not had any fertiliser for many years only plain water, but the plants still grew healthy and well. He thought cacti might even be able to fix atmospheric nitrogen as being the explanation, but how feasible that is I don't know.

"The small cactus Mammillaria fraileana is a pioneer rock-colonizing plant harbouring endophytic bacteria with the potential for nitrogen fixation and rock weathering (phosphate solubilization and rock degradation)."

A quote from the following link:-

"Some habitats like this cactus community in the Sonoran Desert, rely on nitrogen-fixing bacteria at the base of the food chain as the source of nitrogen for maintenance of cell material. Every plant in this scene depends ultimately on biological nitrogen fixation."

http://textbookofbacteriology.net/Impact.html" onclick="window.open(this.href);return false;

http://books.google.co.uk/books?id=DISM ... en&f=false" onclick="window.open(this.href);return false;

The interesting question is do we need to fertilize our plants in pots because these bacteria are missing from our potting mixes, particularly if we sterilize the soils, or are we fertilizing when there is no need to do so?

I believe water stored in a water butt for a few days is not the same as falling rain since it's fertilizer value gradually evaporates?

[Saxicola]

Roy Mottram of Whitestone Nurseries in the UK used to grow in a mineral mixture he called "Whitestone One Eleven" indicating his mix formula of using Grog (a baked clay product they add to pottery clay to improve it, which is virtually akin to Cat Litter or Seramis) plus coarse sand. Anyway I went round his nursery in the past and he showed me a small bed in one corner of a greenhouse composed of this and said it had not had any fertiliser for many years only plain water, but the plants still grew healthy and well. He thought cacti might even be able to fix atmospheric nitrogen as being the explanation, but how feasible that is I don't know.

"The small cactus Mammillaria fraileana is a pioneer rock-colonizing plant harbouring endophytic bacteria with the potential for nitrogen fixation and rock weathering (phosphate solubilization and rock degradation)."

A quote from the following link:-

"Some habitats like this cactus community in the Sonoran Desert, rely on nitrogen-fixing bacteria at the base of the food chain as the source of nitrogen for maintenance of cell material. Every plant in this scene depends ultimately on biological nitrogen fixation."

http://textbookofbacteriology.net/Impact.html" onclick="window.open(this.href);return false;

http://books.google.co.uk/books?id=DISM ... en&f=false" onclick="window.open(this.href);return false;

The interesting question is do we need to fertilize our plants in pots because these bacteria are missing from our potting mixes, particularly if we sterilize the soils, or are we fertilizing when there is no need to do so?

I believe water stored in a water butt for a few days is not the same as falling rain since it's fertilizer value gradually evaporates?

That quote is somewhat misleading. As far as I know there are no cacti that fix nitrogen. However, Legumes are very common in these environments and they are famous for nitrogen fixation. So I think what the quote is getting at is the legumes (well, the bacteria in the nodules at least) fix more nitrogen than they use, leaching some into the soil, which other plants (cacti included) take advantage of.

[DaveW]

Evidently similar bacteria can exist in cactus roots:-

http://www.redorbit.com/news/science/17 ... are_rocks/" onclick="window.open(this.href);return false;

A quote in the following link says:-

"There is an abundant supply of nitrogen in the earth's atmosphere - nearly 79% in the form of N2 gas. However, N2 is unavailable for use by most organisms because there is a triple bond between the two nitrogen atoms, making the molecule almost inert. In order for nitrogen to be used for growth it must be "fixed" (combined) in the form of ammonium (NH4) or nitrate (NO3) ions. The weathering of rocks releases these ions so slowly that it has a negligible effect on the availability of fixed nitrogen."

"The photosynthetic cyanobacteria often live as free-living organisms in pioneer habitats such as desert soils (see cyanobacteria) or as symbionts with lichens in other pioneer habitats."

http://archive.bio.ed.ac.uk/jdeacon/mic ... trogen.htm" onclick="window.open(this.href);return false;

However if cacti's bacteria speed up the breakdown of rocks they would also speed up the supply of nitrogen to the roots?

You say:-

"So I think what the quote is getting at is the legumes (well, the bacteria in the nodules at least) fix more nitrogen than they use."

Therefore it is not the legumes fixing nitrogen but the bacteria they host, or for other plants that are found in the soils around them. As the bacteria in cacti digest rock it is feasible in doing so they release any nitrates in it. Therefore Roy's observation in a way was correct, the symbiotic bacteria in cacti were breaking down and releasing nitrates in the baked clay rather than fixing atmospheric nitrogen, therefore it did not require the aid of any nitrogen fixing plant to do so, or any supplied by fertilizer?

[iann]

Nitrates in rocks? Extremely rare and almost always derived from a (geologically) recent organic source such as guano. There are no common mineral sources of soluble nitrogen, or non-soluble sources that could be weathered into soluble forms. Only in extreme arid locations (only the Atacama so far as I'm aware) can nitrogen minerals persist for any length of time, simply because they are extremely soluble. Nitrogen is a plant nutrient unlike all others and derives from a totally separate source, often referred to as the nitrogen cycle and always involving a living component. This is now supplemented by man-made soluble nitrogen sources, essentially agricultural pollution.

Rainwater is also a poor source of nitrogen, although it may be significant in a desert environment where other sources are almost non-existent. Rainwater contains only a few ppm of dissolved nitrogen, perhaps as high as 10ppm for short periods in extreme cases. Tapwater is usually a better source of nitrogen, routinely 20ppm or higher in densely populated areas, largely due to agricultural runoff. In some more isolated locations, tapwater nitrogen content may be nearly as low as rainwater. The US federal limit for nitrates in drinking water is 45ppm, in the UK it is 50ppm.

Also, rainwater is not acidic because of dissolved nitrogen. The major cause is carbon dioxide. This used to be supplemented by nitrogen- and sulphur-based pollution, aka acid rain, but really not much now in western countries. For example, thirty years ago nitrogen pollution contributed about a third of the acidicty in rainwater in the highly populated states of the US, but now it is more like a tenth. This means that rainwater pH is similar throughout the world (maybe still serious acid rain in some third world countries? China?), usually close to pH 5, occasionally lower due to pollution. Less common is alkaline rain caused by wind-blown limestone particles. This obviously only occurs in particular locations (looking at no-one in particular, Texas) and even then not all the time.

[iann]

Back to the original subject, I suspect that growth was being hurt because the top of the taproot was exposed above the soil. I've buried it completely now and I'll keep my fingers crossed.

[DaveW]

Found these:-

http://www.google.co.uk/url?sa=t&rct=j& ... P1UMFHRgUQ" onclick="window.open(this.href);return false;

http://www.npr.org/2011/09/06/140206913 ... k-nitrogen" onclick="window.open(this.href);return false;

http://www.scientificamerican.com/artic ... -microbes/" onclick="window.open(this.href);return false;

Some claim it is the bacteria addociated with cacti that provide the nitrogen through atmospheric fixation, however the links above seem to indicate the previous assumption rock based nitrogen was not available may be wrong:-

"We were working in the desert, when we observed that many individual cacti grew in sheer rocks," says Dr Yoav Bashan, a biologist at the Northwestern Center for Biological Research in La Paz, Mexico.

"They looked good and green in habitats where usually plants do not grow."

The enigma, says Dr Bashan, is that plants need minerals and nitrogen to survive. We believe that we have found a new symbiosis between bacteria and plants. But neither are available from rock, which binds in minerals and contains no accessible nitrogen.

"The only explanation that we could think of is involvement of microorganisms assisting the plant to grow, fixing nitrogen and dissolving mineral."

"We looked for them and found them."

http://news.bbc.co.uk/earth/hi/earth_ne ... 209687.stm" onclick="window.open(this.href);return false;

[DaveW]

As said on the other thread I have just been re-potting my Eriosyce and here's an Eriosyce (Thelocephala) nuda seedling Jens sent me the other year which has not produced much above ground growth, but now I know why. My thumb for scale, the above ground stem is 1.5cm (5/8th inch) diameter.

nuds.jpg (93.41 KiB) Viewed 1984 times

Not quite as great a root to stem proportions as Ian's Ariocarpus, but you can see why they are called "earth cacti" since most of the plant is underground in the dry season in habitat when the root contracts and pulls the head down to soil level or below it.