lathyrus_long

Tissue culture is also used without genetic engineering. Orchid flasking is the classic example, since the seedlings require an external source of energy. A symbiotic fungus provides that in nature, but it's easier to replace that with the usual agar medium.

Many other species can be propagated conventionally, but will grow faster in tissue culture. That's typically referred to as micropropagation, and widely used for aroids (like here), flytraps, cactus, etc. It's also common for aquarium plants, I think because that eliminates the risk of introducing pests.

It's not fundamentally incompatible, but non-proprietary hybrids are extremely rare. The effort to maintain the two parents and do the cross is much greater than that of saving seed from an open-pollinated variety, so very few growers will undertake that even given the chance. Even if multiple growers do, the smaller population of plants in each of the pure lines increases the chance of significant divergence between sites, at which point the multiple production sites implicitly become multiple different varieties.

Anyone interested here might also wish to read Carol Deppe's "Breed Your Own Vegetable Varieties". She's a Harvard-trained geneticist and amateur vegetable breeder, with special interest in open-pollinated varieties derived from proprietary F1 hybrids. Her book extensively discusses the underlying biology, the practical breeding process, and the legal situation of such work.

You could say that a log scale is useful only when the variable can be usefully regarded as the exponential of something, and I think you'd be tautologically right. That exponential structure just shows up very often, whether from human sensory perception, or from linear systems math, or from economics, or from many other causes.

I generally prefer log units to linear percentages for anything like a scale factor or a ratio. A lot of stuff comes out cleaner and more symmetric, for example because (1 + 0.10)*(1 - 0.10) isn't equal to one exactly, but exp(0.1)*exp(-0.1) is. The case for that in the university chart seems slightly pedantic but fine to me.

Log scales are also widely used for physical quantities that humans can't directly perceive, like radio-frequency electric fields. The logarithmic nature of human perception provides an additional benefit in some cases, but it's not the sole or primary benefit. For example, the amplitude response of any linear differential equation to a sinusoidally varying input is (roughly, at low Q, etc.) piecewise linear vs. frequency on a log-log Bode plot. It has no similarly useful structure on a linear plot. That structure is relevant to all manner of problems in electromagnetics, optics, acoustics, dynamics in mechanics, and other areas. Any introductory course in signals and systems will cover it.

That's not very relevant to this university chart, though. For a simpler example, stock price charts are sometimes logarithmic. On such a chart, if I buy a constant dollar amount and then sell it, I'll make the same dollar gain or loss for any buy and sell points the same vertical distance apart. I believe this chart's creator was thinking of an analogous property; the labels are placed in pairs geometrically equidistant from 0%, since (1 + 0.25)*(1 - 0.2) = (1 + 0.5)*(1 - 0.333...) = 1. I believe the rounding to 34% and not 33% is a mistake, but that the scale is otherwise fine.

That's a question of why Fourier transforms are important though, not just how they're defined and computed. The next-level answer is presumably that sinusoids (or complex exponentials in general) are the eigenfunctions of general linear time-invariant systems, i.e. that if the input to an LTI system is exp(j*w*t), then its output will be A*exp(j*w*t) for some complex constant A. Some other comments here already alluded to that, noting that sinusoids are good for solving linear differential equations (which are LTI systems), or that the sum of two sinusoids of the same frequency shifted in time (which is an LTI operation, since addition and time shift are both LTI) is another sinusoid of that same frequency.

LTI systems closely model many practical systems, including the tuning forks and flutes that give our intuition of what a "pure tone" means. I guess there's a level after that noting that conservation laws lead to LTI systems. I guess there's further levels too, but I'm not a physicist.

That eigenfunction property means we can describe the response of any LTI system to a sinusoid (again, complex exponential in general) at a given frequency by a single complex scalar, whose magnitude represents a gain and whose phase represents a phase shift. No other set of basis functions has this property, thus the special importance of a Fourier transform.

We could write a perfectly meaningful transform using any set of basis functions, not just sinusoids (and e.g. the graphics people often do, and call them wavelets). But if we place one of those non-sinusoidal basis functions at the input of an LTI system, then the output will in general be the sum of infinitely many different basis functions, not describable by any finite number of scalars. This makes those non-sinusoidal basis functions much less useful in modeling LTI systems.

As others note, it's exactly a change in basis. In particular, it's an orthonormal basis, meaning that the dot product (correlation) between a basis function and itself is one, and between any two different basis functions is zero. This gives some intuition for why the forward and inverse transforms look so similar, in the same way that the inverse of an orthonormal matrix (like a rotation matrix) is just its transpose.

This article doesn't say, but vertical farms almost always grow hydroponically, using sterilized inert media (like coir) or inherently sterile inert media (like rockwool). The water and fertilizer are delivered together by drip irrigation. Some farms may instead use no medium at all, like in NFT or DWC. With precise control over the plant nutrition, this can achieve higher yields per square foot than soil, making optimal use of the expensive indoor space. (I think grains are particularly unsuitable crops though, per my other comments here.)

In theory it's possible to run completely free of insects, with cleanroom-like precautions, and I think some facilities do. I think it's more common to live with some level of insect pests though, since it's so hard to avoid introductions and so destructive when they occur--with no natural predators, they can multiply far faster than in nature. That implies some level of pesticides, deliberately introduced predatory insects (which are particularly effective indoors, since they can't fly away), etc.

It's more complicated than that, since the wavelength distribution matters--we can effectively transform green photons that the plant would have reflected into red or blue photons that it will absorb. (The plant still benefits from some green light, but less than in sunlight.) We can also supply each plant with its exact optimal PPFD and DLI. For example, lettuce may be grown under shade cloth, deliberately wasting much of the incident sunlight, because the extra light won't make it grow faster and will make it taste bitter. In a vertical farm, we can just set the LED current and spacing wherever we want.

I've heard that 1 m^2 of modern solar panels will support >1 m^2 of a low-light crop (like lettuce, unlike grain) under modern LEDs. I haven't done the math myself, and this obviously varies with climate. I think vertical farms (growing entirely by artificial light) are still uneconomic vs. greenhouses almost everywhere, per my other comment here. Supplemental artificial light in a greenhouse is of course highly economic in many climates, and Dutch growers have been using it for decades.

The cost to heat or cool a vertical farm should be lower than for a greenhouse with equivalent growing area, since it's got lower surface-area-to-volume ratio and doesn't need to be transparent. That may be important for stuff like high-end strawberries, where tight control of the day-night temperature swing enables higher sugar content. I again wouldn't expect a useful benefit for grains, though.

The objections are to vertical farms for grain, not vertical farms in general. Leafy greens are ideal candidates for indoor growing by artificial light, since they need relatively little light and are quickly perishable. The savings in transportation and waste may thus offset the costs of electricity, lights, and other capital equipment. I think even those economics are usually marginal now, and such vertical farms are usually profitable only if they can sell their produce at a premium due to real or perceived better quality (outside unusual locations like the far North). But there's still room for improvement in LED efficiency, automation, etc., so maybe it will cross over.

The economics for grain are much worse--the plants need much more light, and the product is easily dried, stored, and transported. The processing is also highly automated already. Here's an article with some (dismal) numbers:

https://www.pnas.org/doi/10.1073/pnas.2002655117

Tomatoes, peppers, lettuce, culinary herbs, and many other plant species are grown profitably under hydroponic conditions. This is especially common in colder climates, to maximize the yield per square foot in expensive greenhouses. It's sometimes economic even outdoors though, like in regions with poor soil or scarce water, or to mitigate some (but not all) pests and pathogens. Here's a paper studying the economics of hydroponic greenhouse tomatoes in Florida:

https://svaec.ifas.ufl.edu/media/svaecifasufledu/docs/pdf/ag...

The theory is the same regardless of the plant species, but irrigation equipment and consumables targeting the cannabis industry tend to be quite expensive, sometimes because the higher-value crop justified that, sometimes for no good reason. The lighting requirements for cannabis are also unusual (very high PPFD, controlled photoperiod for non-autoflowering strains), so the greenhouses would need some reconfiguration. So the capital investment doesn't go to zero, but it's a big markdown.

A lot of graduates of top agronomy and horticulture programs (Cornell, etc.) also seem to have ended up in cannabis, I assume because the money was good. It will probably be better for society overall if this crash redirects their efforts to the food supply, though sad for them personally--vegetable growers are paid quite badly, even by the already dismal standards of the life sciences.

I'm not sure that's how I perceive capsaicin myself; but the guy who bred the Carolina Reaper is a recovering addict (in the usual sense, street drugs and alcohol), and he certainly describes his creations in similar terms:

https://honeysucklemag.com/smokin-ed-currie-peppers-addictio...

I think that's seed potato production, where the consistency and lack of pathogens justifies the extra cost. Here's a manual:

https://cipotato.org/wp-content/uploads/2014/08/005447.pdf

It would be possible to grow potatoes for human consumption with a similar system, but I don't think it's currently economic.

What do you mean by "sludge"? Typical hydroponic solution just looks like water, thus the name. The fertilizers used are higher purity ("greenhouse grade", "ultra-soluble", etc.) than those applied to soil, since impurities risk clogging the fertigation equipment.

High calorie and/or high fiber foods require complex rhizospheres which is currently only found in healthy soil.

What is your source for this claim? Major grains (wheat, corn, rice, etc.) grow fine hydroponically--I've actually seen modern conventional agriculture described derisively as a hydroponic system using the sterilized natural soil as its inert medium. That description seems basically correct to me, though I don't think it's necessarily bad. Production of grains in systems analogous to hydroponic vegetable production would certainly be possible, just currently uneconomic:

https://www.pnas.org/doi/10.1073/pnas.2002655117

The major benefit of hydroponics is in achieving very high yield per acre. This is important e.g. when growing perishable vegetables in expensive greenhouses near densely-populated areas. For grains that are readily dried, stored, and shipped, it's currently far cheaper to cultivate more acres in remote areas at lower yield per acre.

The "petrochemical" claim is also confusing. The point of hydroponics is that the plant gets nutrients from the solution, not from the inert substrate. Typical hydroponic substrates may be plant-based (e.g. coir) or not (e.g. rockwool), but in neither case are they providing significant fertility, nor making significant use of petrochemicals. Obviously their energy inputs for production and transportation often come from petroleum; but that's true for almost any human activity today, including organic agriculture. A few niche applications do use petrochemical-based substrates (e.g. phenolic foam), but very rarely.

The synthetic nitrogen fertilizers dissolved in the nutrient solution often use hydrogen from natural gas, since that's the cheapest source, but could use any other source of hydrogen (e.g., electrolysis of water) instead. Here's an article studying those economics:

https://www.frontiersin.org/articles/10.3389/fenrg.2021.5808...

Surely this relationship is noteworthy only to the extent it's potentially a causality? The authors are careful not to make explicit claims, but most discussion here is about that possibility. The title of this HN submission is too ("could negate"), though the title of the paper itself is more cautious.

After more carefully reading the paper, I think the premise of my original comment was completely wrong though. The study apparently had no information on whether the participants were eating conventional or organic produce. Rather, they categorized by type of fruit or vegetable, converting the average results of tests for residues to a score from 0 (best) to 6 (worst) with a somewhat arbitrary heuristic. For example, grapefruit scored 0, and spinach scored 6.

That eliminates the spurious correlation I speculated about, though others may exist; it would be interesting to know which specific fruits and vegetables accounted for most of the effect. That heuristic also increases the risk of data dredging; I wonder how many versions they tried before they got their result. As to the residues, it seems they considered all pesticides equally, even though some are strongly suspected to be much more dangerous than others. It would be interesting to repeat the analysis considering only residues of those suspected to be most (or least) dangerous, to see if their effect gets bigger (or smaller).

Conventional vs organic is not clear cut.

Certainly agreed. Note that the guidelines I linked above do permit certain synthetic pesticides, despite their somewhat confusing use of the word "conventional" in the text that I quoted. For example, cyflumetofen is synthetic, and it's in their lowest-risk category. Copper hydroxide products are permitted under OMRI organic guidelines, but forbidden or restricted here.

I generally like the idea of more restrictive voluntary guidelines based only on safety to the ecosystem and consumer, and not on naturalness like for "organic". I haven't seen much commercial uptake, though.

A matter of degree, maybe. Certainly there's a degree of understanding that's cheaper than just blind heavy spraying, and that any grower would thus be foolish not to obtain. I've often seen "IPM" used to refer to systems that went beyond that though, incurring higher cost for lower ecological impact. For example, the guidelines linked below note explicitly that

Practices contained in this protocol are considerably more expensive than conventional programs that rely on highly toxic pesticides.

https://ipminstitute.org/wp-content/uploads/2022/04/Red-Toma...

https://ipminstitute.org/wp-content/uploads/2022/04/Red-Toma...

I think my supermarket apples were just plain "IPM" though, not a specific set of guidelines like that. Those guidelines seem like a tough sell overall, hard to succinctly explain the benefits to the average consumer.

Many American cities have "community gardens" equivalent to the European allotments. Mine will provide a few hundred square feet to any resident for a nominal fee, for the exclusive use of that resident with some basic restrictions (noncommercial, grow mostly edible plants, etc.).

I've seen fruit marked as "IPM" in my local grocery store. That refers to integrated pest management, a general philosophy of controlling pests through understanding of their physiology, behavior, and interaction with the artificially-managed ecosystem, sometimes using synthetic chemical pesticides but in the smallest quantities that achieve the desired effect.

http://ipm.ucanr.edu/

I don't believe use of the term is regulated, though. So in practice that may just be a nicer-sounding synonym for "conventional".

I've heard of facilities with short crop cycles (greens, herbs, etc.) running totally bug-free with zero pesticides, with air showers at the entrance and careful segregation so that one introduction doesn't ruin their whole crop, etc. I don't think that's common, though.

There's usually bugs. It's common to deliberately introduce predatory insects, which control the pests in the same way as in nature, with the additional benefit that they can't fly away if the pest population gets too low. Chemical pesticides are also widely used, both organic and non-organic.

Hydroponic crops are especially vulnerable to sucking pests (aphids, whiteflies, etc.), because of the large amounts of tender new growth. Without controls or natural predators, their population can just explode, much worse than anything you'd get outdoors.

The p values are small enough that the correlation seems likely to be real, even after lots of dredging through that dataset. I'm less sure about the causality, though. It's also possible they've just discovered that richer people (a) live longer, and (b) like organic produce. They controlled for various factors (note 1 on table 2), but none that seem like usefully strong proxies for income or wealth.

Other kinds of fruit have higher sugar content; jujube is reportedly highest, reaching thirties or even forties. For a strawberry 13-14 is quite good, though. Here's a sophisticated amateur who managed to hit 14.5 (with lower average):

https://old.reddit.com/r/Hydroponics/comments/t8wx66/strawbe...

Also that price is for "11 medium berries or eight large berries", and has now dropped to $20. That's still a bit ridiculous, though it's not clear to me what fraction of their harvest is actually saleable at the high price.

They applied "nutrient solution of 0.125× strength MS nutrient solution, pH 5.7 (Murashige and Skoog)". The salts in that make a typical complete hydroponic fertilizer.

https://en.wikipedia.org/wiki/Murashige_and_Skoog_medium

Huh, quoting:

While they're easily cultivated from seed and grown in nurseries both in the United States and in Asia, the large, old, wild-harvested Dudleya are considered luxury items by collectors overseas and command high prices, sources said. Imperfections inflicted by the elements are a plus.

A lot of the Dudleya on Etsy sure do look irregular in a way that suggests wild collection. A few sellers claim explicitly that theirs are greenhouse-grown, and indeed have nice perfect rosettes. Most sellers are silent on the provenance of their plants.

I guess the issue hasn't gotten enough attention for markets in wealthy countries to make rules. Some basic paperwork (e.g., "seller must provide address of grower, and grower must permit audit") wouldn't eliminate demand for poached plants, but would probably decrease it by a lot.

If customers still want the irregular branched look, then that could be achieved deliberately in the greenhouse, with pruning and maybe PGRs (plant hormones). Probably at least five years from propagation to sale, though. Tissue culture lets the grower convert a single plant into an almost unlimited number of individuals very quickly, but each individual still grows at a normal rate thereafter.

Maybe, but I've never heard of anyone buying a wild-collected orchid from a species where commercially tissue-cultured specimens were available. Beyond the ethical question, greenhouse specimens tend to be more perfect, to carry fewer exotic pests and pathogens, and of course to be far cheaper. If such specimens were available of these Conophytums, then I'd guess almost all the illicit demand would disappear.

A few people report some success with tissue culture in that genus, e.g. (use Sci-Hub)

http://www.bioone.org/doi/pdf/10.25223/brad.n1.1983.a8

https://www.jstor.org/stable/42790034

A highly paywalled article seems to say this hasn't been commercially viable yet, though:

https://www.google.com/search?q=%22Inability+to+mass+produce...

Probably if demand remains high, someone will figure out a protocol and the price will come down. It would probably still take years to grow the plantlets to marketable size, though. Otherwise it looks like various nurseries are propagating them traditionally, but that will take even longer.

The usual cheap RO systems operate from household water pressure only. They fill a pressure tank at the output, allowing the purified water to be dispensed from a faucet. The pressure across the membrane is that input pressure minus the tank pressure. That's relatively low, so the efficiency is poor, wasting perhaps four gallons for every gallon of pure water.

You can improve the efficiency with an electric booster pump, or with a "permeate pump" that recovers energy from the exiting waste water, or by simply filling a pitcher with no pressure tank. I'd expect that even the most wasteful systems are still a small share of a typical household's total water consumption though, assuming they're used only for drinking and cooking water.

"Soilless Culture: Theory and Practice" is a pretty good textbook. I also recommend the USDA's

https://www.fs.usda.gov/treesearch/pubs/46345

That's not about hydroponics, but the theory behind sophisticated growing in containers of soil-like potting mix is almost the same.

I grow mostly by sunlight on my balcony. I've also got some white LM301B lights, which seem very popular among those growing by artificial light only. Greenhouse growers supplementing sunlight still seem to prefer red-blue. You could tell a story like "some intermediate wavelengths will improve yield, and you can get them either from white LEDs or from the sun", though I'm not sure how rigorous the evidence is for that.

I don't think there's much about plant hormone use that's specific to hydroponics. People use rooting hormone and foliar sprays of plant growth regulators and such, but they do that in soil too.

Sophisticated growers routinely get lab tests that provide a breakdown by element of the leaves, fruit, or other parts of the plant. This is mostly to assess plant health, but also gives an indication of the nutritional value to humans.

It's possible to manipulate the element breakdown of the edible parts of the plant over a surprisingly wide range with an appropriate nutrient solution. For example, they grow low-potassium vegetables for people at risk of hyperkalemia:

https://www.mdpi.com/2311-7524/7/4/87/pdf

Of course the lab test doesn't indicate whether the elements are in a form available to humans. I'm not aware of any biochemical mechanisms by which hydroponic vegetables with the same element breakdown would be less nutritious, though I'm not sure how you'd prove none exist.

Nothing exciting--the plants drain into a 1020 tray, and a pump sucks up the leachate. The pump feeds into a waste bucket, through a sample cup that contains pH and EC electrodes. (It would be more common for the leachate just to drain by gravity, but the pumps made best use of my limited balcony space.)