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.
Yes, exactly. I use it for aquarium plants. You can start with a $20 culture from the store and turn it into 100 starter plants over a couple months or so. I love densely planted tanks, and the whole process is just fun and fascinating. If you’ve got the gear already, it’s worth playing around and learning something new.
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.
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.
> piecewise linear vs. frequency on a log-log Bode plot. It has no similarly useful structure on a linear plot.
log-log graphs are not the same as a log graph. A log-log graph is useful for turning monomials into lines, which is exactly what a Bode plot is. But this is a good point. Maybe "exponential function" is the wrong terminology. "Function with an exponent" is more apt.
> stock price charts are sometimes logarithmic.
Stock price charts are logarithmic when the movement of a stock is exponential over the time frame being looked at. Stock prices, in general, are kind of related to perception as well. A $4 stock that moves +/- $2 is perceived very differently than a $100 stock that moves +/- $2. The perception of a price delta is relative to the current price, not the absolute dollar amount of the movement. This is why stock prices exhibit compound returns, which is of course an exponential function.
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.
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.
you're still fertilizing then, its just in the liquid you're using. I suppose that helps against nitrogen runoff which is bad for water bodies so thats a plus.
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:
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:
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:
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.