[Photographs: Robyn Lee and J. Kenji Lopez-Alt]

I haven't always been comfortable with foie gras, though I've spent a good chunk of my life working with it. At first, the discomfort was with the taste. I tried it first as a teenager in the form of a cold terrine that tasted mostly of cat food to me. Then again, I also hated mayonnaise, brussels sprouts, and fish at the time, so my young opinion could hardly be trusted. Later on, as my culinary career expanded, I learned to love it.

I learned to appreciate how it spreads like the world's most decadent and flavorful butter when served cold as a torchon. I learned to appreciate how when it's served hot, it's crisp, sweet, and savory, and melts in your mouth like no other food in the world. And then I learned how it's produced. How in order to get the liver to expand to a good 600% of its natural size, the ducks must be force-fed in a practice known as gavage, wherein a long metal tube (like the one on the right) is forcibly inserted into the duck's mouth up to three times a day and a large amount of food is crammed into its gullet until the liver becomes so large that it takes up the vast majority of the bird's body cavity.

My immediate reaction was a slight gag, followed by revulsion, as I imagined the discomfort of having a tube shoved down my own throat. It's a fair and common reaction, though as I later learned, not the correct one. But we'll get to that.

Even if you haven't eaten foie, pretty much everyone is familiar with the abhorrent images of mistreated ducks peddled by PETA and sites like nofoiegras.org, and indeed they are truly disturbing. Ducks crammed into wire cages just big enough to stand in with their filth-encrusted heads sticking out a hole in the front. Their feathers are scraggly and wiry (if present at all), there's often blood coming out of their nostrils, and their faces and feathers are caked with vomit and corn meal. A duck drinks scummy water out of a communal trough running in front of it while just upstream one of its less fortuitous bunkmates sits dead with its head lolling sideways, half submerged in the cloudy green water.

I've no doubt that farms like this exist in the world, and it is a terrible, atrocious tragedy. If this is how all foieor even all meatis produced, I'd become a vegetarian today. But video or photographic footage of one badly managed farm or even a thousand badly managed farms does not prove that the production of foie gras, as a practice, is necessarily harmful to the health or mental well-being of a duck. Foie gras production should be judged not by the worst farms, but by the best, because those are the ones that I'm going to choose to buy my foie from if at all.

So the real question is: is the production of foie gras torturous under even the best of conditions?

Those on one side would answer yes. How could force feeding an animal ever be considered anything but torture? On the other hand are those who claim that American foie farms are positively idyllic with ducks waddling around spacious pens, even queuing up for their gavage, that for a duck, none of the things we consider uncomfortable stress them out in the least. But who's right?

To answer this question, me and a few fellow Serious Eaters (yes, including Dumpling) set out on a brisk fall morning for La Belle Farms in the idyllic Hudson Valley in what was promised to us as a 100% full-access, bottom to top tour of the operation. We'd be free to see anything we liked, no doors would be locked, and we'd be taking cameras and notebooks with us.

Owner Herman Lee, who immigrated from Hong Kong in 1973 to attend the Fashion Institute of Technology before going on to start Bella Poultry, one of the most well-respected chicken operations in the Northeast, began raising Moulard ducks for foie gras in 2000, after spending several years studying the industry both at home and abroad.

In his office, he seems comfortable, almost eager to get started, to show us what his farm does. We waste no time in getting down to the fabrication room, where teams of workers are just beginning to pull ducks out of a walk-in cooler. Freshly killed and plucked the day before, they're now ready to be eviscerated and broken down into their various parts.

With a red-coated USDA inspector watching their every move (the USDA inspector is there every day), the crew gets to work.

"We'll process about 500 ducks today," says Bob Ambrose, Herman's business partner and head of Bella Bella Gourmet, La Belle's value-added line of prepared foods. "The ducks are all stunned in electrified water before we slaughter them, so they're completely unconscious, then we air-chill them and allow them to dry overnight," he explains. The stunning makes for a quick, painless death, while air-chilling and drying prevents them from taking on any extra water weight, diluting the flavor of their relatively lean meat.

The animals are unloaded one at a time onto a conveyer belt where the skilled workers go at them, each one making a few vital cuts, assembly line-style. As the first liver is removed, Robyn, our intrepid photographer, gives an audible gasp. "Whoah, that's big!"

Indeed, if you've never seen a whole lobe of foie gras before, the size of it can be a bit shocking. Weighing in at around a pound, each liver is roughly the size of a small football. That's close to 10% of the duck's total body weight, and it takes up the vast majority of the lower half of its body. The livers are passed to a woman who sorts them into two different grades, depending on the amount of bruises and blemishes they have. Large, clean livers get the "A" designation, while the rest are sorted into "B" and "Petite" trays.

Bob is quick to point out that "any mishandling of the ducksrough treatment, that kind of thingwill cause bruising, reducing its price," he explains. "So we've got a strong incentive to be gentle with the birds." Duck handlers, who are mostly female (apparently ducks take better to women) work on an bonus-based program where their pay is bumped for every "A" grade lobe one of their charge produces. It's the first time I've heard of a farm that offers workers a monetary incentive to be gentler with the animals. Bob insists that it works, and that the most experienced feeders can increase the number of A lobes from the normal 55% up to over 70%.

At a wholesale price of around $30 a pound for A's, the liver is the most prized part of the duck, but it's hardly enough to sustain the business.

"We use and sell every part of the duck except the heads and feet," explains Bob. The breasts, known as magret are removed and individually packaged to be sold fresh to chefs and gourmet butchers. Some of them are cured and dried into duck prosciutto, or smoked to a sweet, ham-like flavor. The excess fat (of which there is plenty) gets rendered down and sold to restaurants. The legs are cooked in the traditional french confit style, while the wings are smoked and slow-cooked.

The entire processing room gets sprayed down and disinfected every day. Next door is the killing room, where the ducks are zipped assembly-line style from the stunning station to the killing/bleeding station to the machines that pluck their feathers, which resemble industrial-sized washing machines lined with rubber fingers. The room is absolutely spotless, the countertops and conveyor belts a gleaming stainless steel.

So far, so good. It's about as clean and organized an operation as I've ever seen in a farm. We put on full-length disposable jumpsuits to protect our street clothes along with face masks, hair nets, and rubber boots to protect the ducks from outside germs, and head towards the sheds where the ducks spend the bulk of their 3 1/2 month lives.*

*That's significantly longer than the 4 1/2 weeks a normal chicken spends on this earth before slaughter.

The real questions would be answered within the walls of these long, corrugated aluminum boxes. I'd consulted with a veterinarian and done some reading on the subject of illnesses in waterfowl, so even before we entered the shed, I had a good idea of what to look for to recognize sick or distressed birds. I wanted to be sure that I could judge for myself how well-off these ducks were.

Labored breathing, discharge from the nostrils, infected or cloudy eyes are all signs of sickness or stress. Bleeding beaks or feet and missing feathers would indicate rough treatment or fighting amongst themselves. I walked into the shed prepared for the worst, and instead was quite stunned.

Far from the cramped, cruel conditions shown in the videos and photographs I'd seen, here was an enormous shed, full of birds free to roam as they pleased. They congregated in groups, quietly quacking at each other, roamed freely over the sawdust-strewn floor, even stretched their wings for a flap now and then. Granted, it did smella distinct barnyard aroma with a hint of ammonia (the chicken shed we visited afterwards had a much stronger ammonia smell to it), but as anyone who's worked on an animal farm will tell you, all farms smell, just as before the introduction of modern plumbing, all cities smelled as well.

Incidentally, all the birds here are male. The female Moulards don't grow livers as well as males, and are therefore not as profitable. Like the other foie farms in this country, La Belle sends their female ducklings to Trinidad within weeks of hatching where they are raised for meat.

It's true, there could have been more natural sunlight (a few large screened windows with fans in them were spaced along each side of the structure), and the air could have been fresher, but all in all, asides from the truly free-range chickens I've seen in backyards and a few small farms in New England and New York, and some of the boutique chef-run "education center" style farms, these were probably the most well-accommodated farm animals I'd ever seen. When asked about the light and air situation, Herman explained that "the animals are kept off of antibiotics, so we have to keep them minimally exposed to the outdoors." They'd let them out if they could, but wild bird populations can easily introduce deadly bacteria to domestic flocks, he says.

The birds seemed to show a mild aversion to us, flocking together and giving us a wide berth as we walked through the shed. Chichi quickly spotted a single dead bird, which we inquired about. La Belle shows a mortality rate of around 1% in their ducks, which may seem large, but it's less than 1/5th the mortality of regular chicken or duck farms, and about 10 times lower than the mortality and injury rate of the backyard chickens I'm acquainted with.

Eventually the ducks became a little less edgy, and I was able to move in for a closer look. All signs pointed to completely healthy animals. Their beaks were clean, their eyes were bright, they had no trouble vocalizing, and their feathers were for the most part completely intact. They seemed to waddle around with a positive swagger, congregating at the water dripper and feeding stations.

The facts so far: for at least the first 12 weeks of their lives, these ducks are sitting pretty in a stress-free, spacious environment. The next shed is where the ducks spend their last 25 dayswhere the gavage takes place.

Before we went inside, we were told that this was the only part of the tour where we would not be allowed to take photographs or video. Ah, I thoughta sure sign that what we are about to see is going to put us off our lunches (or tasting menus, as the case may be). But Bob explains: It's not that they have anything to hide with the procedure itself, it's that they've recently began employing a new custom-designed piece of technology that they don't want the two competing farms to get their hands on. We'd see it in action in a moment.

We entered another long shed, this one filled from end to end with 5-foot by 7-foot pens, each one holding about 10 ducks. Again, the ducks tended to congregate together, leaving more than half of the space in their pen empty. Occasionally, one would waddle out of the group for a stretch. Just as in the other sheds, these ducks seemed healthy, albeit much larger (these guys were on their third week of gavage, just a few days away from slaughter).

We walked down row after row of pens until we got to one where a worker was just about to start feeding. At La Belle, the ducks are fed three times a day for a total of up to 240 grams of their custom-designed feed. As we watched, the workera petit womanclimbed into the pen and sat on an overturned box. One at a time, she pulled a duck towards her and held it between her legs with its neck arched upwards. She gently squeezed the base of the duck's neck ("checking to make sure that he's finished all his food from the last feeding," says Bob), then eases a flexible plastic tube down the ducks throat. A machine whirls, a small bulge forms where the food is deposited, and the duck walks off, giving its head one shake, but otherwise seemingly unaffected.

While most other farms in the world still use metal tubes to feed their duck, La Belle has recently switched to a custom-made flexible plastic version. This is the piece of technology that they didn't want us filming.

However, a quick search on YouTube turned up this video, which is not dissimilar from our own experience (this video shows geese in France):

According to Bob, when the feeder feels the duck's esophagus, if there's any food remaining, she'll skip that feeding. So while the ducks are technically force-fed, there is a level of built-in anatomical control so that the ducks can't take in any more food than they can physically handle. That's more respect than most fast food chains show for their human customers.

La Belle has also started a program to reduce their workers' load. Many farms require that the same feeder work with the same ducks for the entire gavage process to reduce stress on the animal. For a worker, this means three long feeding shifts per day, every day, for 25 days.

A few years ago, they discovered that it's not the actual worker that the ducks grow accustomed to, it's just their sight and smell. They found that by having two different workers wear the same set of clothes, the ducks would respond to the second as if they were still the first. In fact, after starting their workers on this split-shift system, production of A graded foie actually increased.

I wouldn't exactly say that the ducks were lining up to be fed, as has been suggested by some foie advocates, but they certainly didn't seem stressed. By all activists accounts, these ducks should have been so fattened that they could barely stand under their own power. I didn't see one duck vomit, nor did I see any that couldn't stand or walk due to the weight of their livers.

After the walking tour, we stopped back at the office for a tasting of a few of Bella Bella's products, as well as some straight-up fresh foie, seared on a George Foreman griddle, of all things. Of all the foie I've cooked in the world (and it's a lot), La Belle's has the unique property of being able to hold its shape well without rendering off too much fat, making it an ideal candidate for searing.

We finished the day eating our foie, talking to Herman and Bob about their business. Back home, I started doing some more research.

We'd seen the process from start to finish, and from all outward appearances, the ducks seem to live perfectly comfortable livesat least as well as you can expect for any farm animal. Certainly far better lives than the millions of cows and pigs and billions of chickens that are raised every year for our consumption. But the question I had was, why aren't they more uncomfortable? Why doesn't a duck struggle with its large liver or having a tube forced down its throat?

First off, the key to understanding this is to make a very conscious effort not to anthropomorphize the animals. As waterfowl, they are distinctly not human, and their physiology differs from ours in a few key ways. Let's take a look at the foie gras duck, shall we?

In this country, foie gras is produced exclusively from Moulard ducks. The offspring of a male Muscovy and a female Pekin duck, Moulards offer many physiological and temperamental advantages that make them ideal for producing foie, and I believe an understanding of the breed can help clear up a lot of misconceptions.

Muscovies are an incredibly hardy species. Though native to the tropical regions of South America, they are nevertheless able to adapt to temperate climates, and are even comfortable living in sub-zero conditions. As such, they are non-migratory. This is important, because it means that unlike migratory species, they don't ever have the need to gorge themselves to put on extra fat to carry them through long periods with no food. They are an aggressive species; Males attack each other with their bills and sharp claws on their feet. Despite this, they are prized for their well-flavored, lean meat. Their robust nature and tolerance of many climates make them quite easy to farm.

Pekin ducks (also known as Long Island ducks) on the other hand were originally bred in China from wild mallards, and thus have many of the characteristics of that migratory species. They are relatively petite birds who are quite gregarious. They enjoy hanging out in groups and will naturally stand together in very tight quarters, whether or not they have the space to roam around. Years of breeding have shrunk their wings and increased their breast size. Because of their plump stature, they can't jump much higher than your average womp-rat, and thus no longer migrate (which isn't to say they wouldn't waddle south for the winter, given the opportunity), but their inner organs and basic metabolism are still that of a migratory waterfowl.

When you cross a male Muscovy with a female Pekin, you get a Moulard, a hybrid that combines the more desirable behavioral features of the two species. First off, it's larger and more robust than either a Muscovy or Pekin, much in the way that a mule is bigger and stronger than either the horse or donkey it was bred from (Moulards are also sterile, like mules, and are often referred to as "mule ducks"). Like Pekins, they don't fly and are relatively gregarious, making group living and containment quite simple for farmers, and non-stressful and safe for the ducks. Their most important feature, howeverand this is importantis that like Muscovies, they don't have the urge to migrate, but like Pekins, they retain all of the interior anatomy necessary for the gorging that migration requires.

This is the real key to the safe and ethical production of foie gras.

You see, migration depends upon gorging. The rapid intake and metabolism of large quantities of food in order to store enough energy to fly south for the winter. So while during the warm summer months, a duck may be content paddling around eating weeds, bugs, and the occasional minnow, when the weather starts getting colder, it begins to eat in earnest, stuffing itself more frequently, and with larger prey. Unlike in humans where excess fat builds up mostly in large deposits just under the skin, with migratory birds, this excess fat builds up both under the skin, and in the liver.

Granted, the production of foie gras requires feeding a duck far more than it would naturally consume (though if you are to believe Dan Barber's fantastic TED talk, there are wild geese who would feed themselves to almost the same degree), but this is true of all farm animals. Cows, pigs, chickens, they all get far fatter from the rich feeds we give them than they'd ever get if left to their own devices. Does that make it cruel? I'd say no. As long as the animal shows no sign of stress or discomfortand the ducks we saw today certainly did notthen what harm is a few extra pounds?

What about the act of feeding? Surely the duck feels discomfort when a tube is slid down its throat?

Tony Bourdain likes to remind us that we see worse things committed against human beings on late night pay-per-view. And he's right: humans have a gag reflex. But ducks? Not so. I tried hard to find a good video online of a duck eating fish, but they are all too blurry or too annoying to watch. The closest I came is this video of a cormorant, another migratory waterfowl.

Watch closely as it swallows a spiky fish several times wider than its neck.

Incredible, right? And that, folks, is the reason why ducks don't struggle when a feeding tube deposits food in its throat. Its body is built for exactly the same type of stress in the wild.

Humans chew their food in their mouth until it breaks down into pieces small enough to swallow. Ducks, on the other hand, have no teeth in their mouth, and they don't chew. Instead, they swallow their food whole, storing it in the bottom of the esophagus in a stretchy pouch known as the crop. Eventually, the solid food works its way into a stomach and a sac-like organ called the gizzard. Throughout the day, a duck will swallow small rocks and pebbles, which get stored in the gizzard. Once food enters it, the muscular organ uses the pebbles as make-shift teeth, grinding up the food so the duck can digest it.

Because of this, their esophagi are custom-built for stretching. I had Bob send a few of them to the office where I tied off one end and filled it up, water-balloon style in order to see exactly how much a duck can hold in its crop. The four we tested stretched out to a little over a quart of liquid apiece, or around 950 gramsfar more than the 80 grams of meal they were fed at each serving.

Surely they'd have difficulty breathing with a tube down their throat though, right? Not so fast. Humans have a single passageway leading from their mouth down into their neck. From there, it divides into the esophagus, which leads to the stomach, and the trachea, which leads to the lungs. Separating these two passages is a little flap of muscle called the epiglottis. Try to force something past the epiglottis, and you trigger a gag reaction. It's intended to make sure that the wrong things don't end up in your stomach.

Ducks, on the other hand, have completely independent tracheas and esophagi. Their esophagus goes straight from the mouth to the crop, while the trachea runs from the lungs and out the end of the tongue. That's right: Ducks breathe through their tongues. The cartilage that surrounds their trachea (called the tracheal ring) is also a complete circle, as opposed to ours, which is C-shaped, making their trachea much sturdier and less prone to collapse. What this means is that you can place a feeding tube in a ducks throat, and it can sit there indefinitely, neither gagging, nor suffocating.

So there it is. The evidence is out there, and from what Bob and Herman tell me, they are more than happy to be transparent with their operations, to let people see what goes on inside their farm. They believe they've got nothing to hide, and so do I. So why is it that activists are so zealous about destroying foie gras operations? I've worked in restaurants that have been picketed by protestors, and they aren't a particularly friendly bunch. Threats have even been made against the lives of chefs and their families for serving it in their restaurants.

In large part, it's because foie gras is an easy target. There are only three foie farms in the country, and none of them have the money or government clout to defend themselves the way that the chicken or beef industry does. It's a food product that is marketed directly at the affluent, and the rich are always an easy target. As an occasional delicacy, it's also a food that's relatively easy for most people to give up.

Personally, I find this kind of protesting abhorrent. If you are going to protest anything, it should be the industrial production of eggs, where chickens are routinely kept in cages so small that they can't even turn around for an entire year. The problem, of course, is that you tell people to stop eating cheap eggs, and nobody will listen. The leaders of the anti-foie movement know this and use it to their advantage, using video and photographs taken from the worst of the farms (none of the ones in this country, for the record), and making it seem like all foie production is as despicable.

If you are against the confinement, slaughter, and eating of all animals, then that's a different argument to be had at a different time. But to single out foie as the worst of the worst is misguided at best, and downright manipulative at worst. Just as there are good eggs and bad eggs, good beef and bad beef, good chicken and bad chicken, so there is good foie and bad foie. We are especially lucky, because we happen to live in a country where all of the foie produced is good foie.

The only question left for me is whether to serve it hot or cold.

Read this article:
The Physiology of Foie: Why Foie Gras is Not Unethical ...

Plant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants.[1] Closely related fields include plant morphology (structure of plants), plant ecology (interactions with the environment), phytochemistry (biochemistry of plants), cell biology, genetics, biophysics and molecular biology.

Fundamental processes such as photosynthesis, respiration, plant nutrition, plant hormone functions, tropisms, nastic movements, photoperiodism, photomorphogenesis, circadian rhythms, environmental stress physiology, seed germination, dormancy and stomata function and transpiration, both parts of plant water relations, are studied by plant physiologists.

The field of plant physiology includes the study of all the internal activities of plantsthose chemical and physical processes associated with life as they occur in plants. This includes study at many levels of scale of size and time. At the smallest scale are molecular interactions of photosynthesis and internal diffusion of water, minerals, and nutrients. At the largest scale are the processes of plant development, seasonality, dormancy, and reproductive control. Major subdisciplines of plant physiology include phytochemistry (the study of the biochemistry of plants) and phytopathology (the study of disease in plants). The scope of plant physiology as a discipline may be divided into several major areas of research.

First, the study of phytochemistry (plant chemistry) is included within the domain of plant physiology. To function and survive, plants produce a wide array of chemical compounds not found in other organisms. Photosynthesis requires a large array of pigments, enzymes, and other compounds to function. Because they cannot move, plants must also defend themselves chemically from herbivores, pathogens and competition from other plants. They do this by producing toxins and foul-tasting or smelling chemicals. Other compounds defend plants against disease, permit survival during drought, and prepare plants for dormancy, while other compounds are used to attract pollinators or herbivores to spread ripe seeds.

Secondly, plant physiology includes the study of biological and chemical processes of individual plant cells. Plant cells have a number of features that distinguish them from cells of animals, and which lead to major differences in the way that plant life behaves and responds differently from animal life. For example, plant cells have a cell wall which restricts the shape of plant cells and thereby limits the flexibility and mobility of plants. Plant cells also contain chlorophyll, a chemical compound that interacts with light in a way that enables plants to manufacture their own nutrients rather than consuming other living things as animals do.

Thirdly, plant physiology deals with interactions between cells, tissues, and organs within a plant. Different cells and tissues are physically and chemically specialized to perform different functions. Roots and rhizoids function to anchor the plant and acquire minerals in the soil. Leaves catch light in order to manufacture nutrients. For both of these organs to remain living, minerals that the roots acquire must be transported to the leaves, and the nutrients manufactured in the leaves must be transported to the roots. Plants have developed a number of ways to achieve this transport, such as vascular tissue, and the functioning of the various modes of transport is studied by plant physiologists.

Fourthly, plant physiologists study the ways that plants control or regulate internal functions. Like animals, plants produce chemicals called hormones which are produced in one part of the plant to signal cells in another part of the plant to respond. Many flowering plants bloom at the appropriate time because of light-sensitive compounds that respond to the length of the night, a phenomenon known as photoperiodism. The ripening of fruit and loss of leaves in the winter are controlled in part by the production of the gas ethylene by the plant.

Finally, plant physiology includes the study of plant response to environmental conditions and their variation, a field known as environmental physiology. Stress from water loss, changes in air chemistry, or crowding by other plants can lead to changes in the way a plant functions. These changes may be affected by genetic, chemical, and physical factors.

The chemical elements of which plants are constructedprincipally carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, etc.are the same as for all other life forms animals, fungi, bacteria and even viruses. Only the details of the molecules into which they are assembled differs.

Despite this underlying similarity, plants produce a vast array of chemical compounds with unique properties which they use to cope with their environment. Pigments are used by plants to absorb or detect light, and are extracted by humans for use in dyes. Other plant products may be used for the manufacture of commercially important rubber or biofuel. Perhaps the most celebrated compounds from plants are those with pharmacological activity, such as salicylic acid from which aspirin is made, morphine, and digoxin. Drug companies spend billions of dollars each year researching plant compounds for potential medicinal benefits.

Plants require some nutrients, such as carbon and nitrogen, in large quantities to survive. Such nutrients are termed macronutrients, where the prefix macro- (large) refers to the quantity needed, not the size of the nutrient particles themselves. Other nutrients, called micronutrients, are required only in trace amounts for plants to remain healthy. Such micronutrients are usually absorbed as ions dissolved in water taken from the soil, though carnivorous plants acquire some of their micronutrients from captured prey.

The following tables list element nutrients essential to plants. Uses within plants are generalized.

Among the most important molecules for plant function are the pigments. Plant pigments include a variety of different kinds of molecules, including porphyrins, carotenoids, and anthocyanins. All biological pigments selectively absorb certain wavelengths of light while reflecting others. The light that is absorbed may be used by the plant to power chemical reactions, while the reflected wavelengths of light determine the color the pigment appears to the eye.

Chlorophyll is the primary pigment in plants; it is a porphyrin that absorbs red and blue wavelengths of light while reflecting green. It is the presence and relative abundance of chlorophyll that gives plants their green color. All land plants and green algae possess two forms of this pigment: chlorophyll a and chlorophyll b. Kelps, diatoms, and other photosynthetic heterokonts contain chlorophyll c instead of b, red algae possess chlorophyll a and " d". All chlorophylls serve as the primary means plants use to intercept light to fuel photosynthesis.

Carotenoids are red, orange, or yellow tetraterpenoids. They function as accessory pigments in plants, helping to fuel photosynthesis by gathering wavelengths of light not readily absorbed by chlorophyll. The most familiar carotenoids are carotene (an orange pigment found in carrots), lutein (a yellow pigment found in fruits and vegetables), and lycopene (the red pigment responsible for the color of tomatoes). Carotenoids have been shown to act as antioxidants and to promote healthy eyesight in humans.

Anthocyanins (literally "flower blue") are water-soluble flavonoid pigments that appear red to blue, according to pH. They occur in all tissues of higher plants, providing color in leaves, stems, roots, flowers, and fruits, though not always in sufficient quantities to be noticeable. Anthocyanins are most visible in the petals of flowers, where they may make up as much as 30% of the dry weight of the tissue.[2] They are also responsible for the purple color seen on the underside of tropical shade plants such as Tradescantia zebrina. In these plants, the anthocyanin catches light that has passed through the leaf and reflects it back towards regions bearing chlorophyll, in order to maximize the use of available light

Betalains are red or yellow pigments. Like anthocyanins they are water-soluble, but unlike anthocyanins they are indole-derived compounds synthesized from tyrosine. This class of pigments is found only in the Caryophyllales (including cactus and amaranth), and never co-occur in plants with anthocyanins. Betalains are responsible for the deep red color of beets, and are used commercially as food-coloring agents. Plant physiologists are uncertain of the function that betalains have in plants which possess them, but there is some preliminary evidence that they may have fungicidal properties.[3]

Plants produce hormones and other growth regulators which act to signal a physiological response in their tissues. They also produce compounds such as phytochrome that are sensitive to light and which serve to trigger growth or development in response to environmental signals.

Plant hormones, known as plant growth regulators (PGRs) or phytohormones, are chemicals that regulate a plant's growth. According to a standard animal definition, hormones are signal molecules produced at specific locations, that occur in very low concentrations, and cause altered processes in target cells at other locations. Unlike animals, plants lack specific hormone-producing tissues or organs. Plant hormones are often not transported to other parts of the plant and production is not limited to specific locations.

Plant hormones are chemicals that in small amounts promote and influence the growth, development and differentiation of cells and tissues. Hormones are vital to plant growth; affecting processes in plants from flowering to seed development, dormancy, and germination. They regulate which tissues grow upwards and which grow downwards, leaf formation and stem growth, fruit development and ripening, as well as leaf abscission and even plant death.

The most important plant hormones are abscissic acid (ABA), auxins, ethylene, gibberellins, and cytokinins, though there are many other substances that serve to regulate plant physiology.

While most people know that light is important for photosynthesis in plants, few realize that plant sensitivity to light plays a role in the control of plant structural development (morphogenesis). The use of light to control structural development is called photomorphogenesis, and is dependent upon the presence of specialized photoreceptors, which are chemical pigments capable of absorbing specific wavelengths of light.

Plants use four kinds of photoreceptors:[1]phytochrome, cryptochrome, a UV-B photoreceptor, and protochlorophyllide a. The first two of these, phytochrome and cryptochrome, are photoreceptor proteins, complex molecular structures formed by joining a protein with a light-sensitive pigment. Cryptochrome is also known as the UV-A photoreceptor, because it absorbs ultraviolet light in the long wave "A" region. The UV-B receptor is one or more compounds not yet identified with certainty, though some evidence suggests carotene or riboflavin as candidates.[4] Protochlorophyllide a, as its name suggests, is a chemical precursor of chlorophyll.

The most studied of the photoreceptors in plants is phytochrome. It is sensitive to light in the red and far-red region of the visible spectrum. Many flowering plants use it to regulate the time of flowering based on the length of day and night (photoperiodism) and to set circadian rhythms. It also regulates other responses including the germination of seeds, elongation of seedlings, the size, shape and number of leaves, the synthesis of chlorophyll, and the straightening of the epicotyl or hypocotyl hook of dicot seedlings.

Many flowering plants use the pigment phytochrome to sense seasonal changes in day length, which they take as signals to flower. This sensitivity to day length is termed photoperiodism. Broadly speaking, flowering plants can be classified as long day plants, short day plants, or day neutral plants, depending on their particular response to changes in day length. Long day plants require a certain minimum length of daylight to starts flowering, so these plants flower in the spring or summer. Conversely, short day plants flower when the length of daylight falls below a certain critical level. Day neutral plants do not initiate flowering based on photoperiodism, though some may use temperature sensitivity (vernalization) instead.

Although a short day plant cannot flower during the long days of summer, it is not actually the period of light exposure that limits flowering. Rather, a short day plant requires a minimal length of uninterrupted darkness in each 24-hour period (a short daylength) before floral development can begin. It has been determined experimentally that a short day plant (long night) does not flower if a flash of phytochrome activating light is used on the plant during the night.

Plants make use of the phytochrome system to sense day length or photoperiod. This fact is utilized by florists and greenhouse gardeners to control and even induce flowering out of season, such as the Poinsettia.

Paradoxically, the subdiscipline of environmental physiology is on the one hand a recent field of study in plant ecology and on the other hand one of the oldest.[1] Environmental physiology is the preferred name of the subdiscipline among plant physiologists, but it goes by a number of other names in the applied sciences. It is roughly synonymous with ecophysiology, crop ecology, horticulture and agronomy. The particular name applied to the subdiscipline is specific to the viewpoint and goals of research. Whatever name is applied, it deals with the ways in which plants respond to their environment and so overlaps with the field of ecology.

Environmental physiologists examine plant response to physical factors such as radiation (including light and ultraviolet radiation), temperature, fire, and wind. Of particular importance are water relations (which can be measured with the Pressure bomb) and the stress of drought or inundation, exchange of gases with the atmosphere, as well as the cycling of nutrients such as nitrogen and carbon.

Environmental physiologists also examine plant response to biological factors. This includes not only negative interactions, such as competition, herbivory, disease and parasitism, but also positive interactions, such as mutualism and pollination.

Plants may respond both to directional and non-directional stimuli. A response to a directional stimulus, such as gravity or sunlight, is called a tropism. A response to a nondirectional stimulus, such as temperature or humidity, is a nastic movement.

Tropisms in plants are the result of differential cell growth, in which the cells on one side of the plant elongates more than those on the other side, causing the part to bend toward the side with less growth. Among the common tropisms seen in plants is phototropism, the bending of the plant toward a source of light. Phototropism allows the plant to maximize light exposure in plants which require additional light for photosynthesis, or to minimize it in plants subjected to intense light and heat. Geotropism allows the roots of a plant to determine the direction of gravity and grow downwards. Tropisms generally result from an interaction between the environment and production of one or more plant hormones.

Nastic movements results from differential cell growth (e.g. epinasty and hiponasty), or from changes in turgor pressure within plant tissues (e.g., nyctinasty), which may occur rapidly. A familiar example is thigmonasty (response to touch) in the Venus fly trap, a carnivorous plant. The traps consist of modified leaf blades which bear sensitive trigger hairs. When the hairs are touched by an insect or other animal, the leaf folds shut. This mechanism allows the plant to trap and digest small insects for additional nutrients. Although the trap is rapidly shut by changes in internal cell pressures, the leaf must grow slowly to reset for a second opportunity to trap insects.[6]

Economically, one of the most important areas of research in environmental physiology is that of phytopathology, the study of diseases in plants and the manner in which plants resist or cope with infection. Plant are susceptible to the same kinds of disease organisms as animals, including viruses, bacteria, and fungi, as well as physical invasion by insects and roundworms.

Because the biology of plants differs with animals, their symptoms and responses are quite different. In some cases, a plant can simply shed infected leaves or flowers to prevent the spread of disease, in a process called abscission. Most animals do not have this option as a means of controlling disease. Plant diseases organisms themselves also differ from those causing disease in animals because plants cannot usually spread infection through casual physical contact. Plant pathogens tend to spread via spores or are carried by animal vectors.

One of the most important advances in the control of plant disease was the discovery of Bordeaux mixture in the nineteenth century. The mixture is the first known fungicide and is a combination of copper sulfate and lime. Application of the mixture served to inhibit the growth of downy mildew that threatened to seriously damage the French wine industry.[7]

Sir Francis Bacon published one of the first plant physiology experiments in 1627 in the book, Sylva Sylvarum. Bacon grew several terrestrial plants, including a rose, in water and concluded that soil was only needed to keep the plant upright. Jan Baptist van Helmont published what is considered the first quantitative experiment in plant physiology in 1648. He grew a willow tree for five years in a pot containing 200 pounds of oven-dry soil. The soil lost just two ounces of dry weight and van Helmont concluded that plants get all their weight from water, not soil. In 1699, John Woodward published experiments on growth of spearmint in different sources of water. He found that plants grew much better in water with soil added than in distilled water.

Stephen Hales is considered the Father of Plant Physiology for the many experiments in the 1727 book;[8] though Julius von Sachs unified the pieces of plant physiology and put them together as a discipline. His Lehrbuch der Botanik was the plant physiology bible of its time.[9]

Researchers discovered in the 1800s that plants absorb essential mineral nutrients as inorganic ions in water. In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When the mineral nutrients in the soil are dissolved in water, plant roots absorb nutrients readily, soil is no longer required for the plant to thrive. This observation is the basis for hydroponics, the growing of plants in a water solution rather than soil, which has become a standard technique in biological research, teaching lab exercises, crop production and as a hobby.

One of the leading journals in the field is Plant Physiology, started in 1926. All its back issues are available online for free.[1] Many other journals often carry plant physiology articles, including Physiologia Plantarum, Journal of Experimental Botany, American Journal of Botany, Annals of Botany, Journal of Plant Nutrition and Proceedings of the National Academy of Sciences.

In horticulture and agriculture along with food science, plant physiology is an important topic relating to fruits, vegetables, and other consumable parts of plants. Topics studied include: climatic requirements, fruit drop, nutrition, ripening, fruit set. The production of food crops also hinges on the study of plant physiology covering such topics as optimal planting and harvesting times and post harvest storage of plant products for human consumption and the production of secondary products like drugs and cosmetics.

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Plant physiology - Wikipedia, the free encyclopedia

Greg Ikonnikov and Dominique Yelle

Clin Anat.2009 Jan;22(1):99-113. Can J Anaesth.1993 Nov;40(11):1053-64.

An organized rhythmic contraction of the heart requires adequate propagation of electrical impulses along the conduction pathway. Of note, the impulses in the His-Purkinje system travel in such a way that papillary muscle contraction precedes that of the ventricles, thereby preventing regurgitation of blood flow through the AV valves.

Physiol Rev.2005 Oct;85(4):1205-53.

Heart Rhythm.2010 Jan;7(1):117-26.

Note: The different types of cardiac ion channels are discussed below, throughout the description of the phases of action potentials in different cardiac cells.

Physiol Rev.2005 Oct;85(4):1205-53.

Action potential: electrical stimulation created by a sequence of ion fluxes through specialized channels in the membrane (sarcolemma) of cardiomyocytes that leads to cardiac contraction.

The action potential in typical cardiomyocytes is composed of 5 phases (0-4), beginning and ending with phase 4.

Pharmacol Ther.2005 Jul;107(1):59-79. Drugs.2007;67 Suppl 2:15-24. (The funny current)

Table 1. Cardiac cell types displaying pacemaker behavior.

Pacemaker

Location

Inherent rate (beats per minute, BPM)

Sinoatrial (SA) node

Right atrium (RA) at junction with superior vena cava (SVC)

60-100 BPM

Atrioventricular (AV) node

RA at posteroinferior area of interatrial septum

40-60 BPM

Purkinje fibers and ventricular cardiomyocytes

Throughout the ventricles

20-40 BPM

The sequence of events for pacemaker action potential:

Nature.2002 Jan 10;415(6868):198-205.

Excitation-contraction coupling represents the process by which an electrical action potential leads to contraction of cardiac muscle cells. This is achieved by converting a chemical signal into mechanical energy via the action of contractile proteins.

Calcium is the crucial mediator that couples electrical excitation to physical contraction by cycling in and out of the myocytes cytosol during each action potential.

Main contractile elements:

Regulatory elements:

The initial influx of Ca2+ into myocytes through L-type Ca2+ channels during phase 2 of the action potential is insufficient to trigger contraction of myofibrils. This signal is amplified by the CICR mechanism, which triggers much greater release of Ca2+ from the sarcoplasmic reticulum.

As with myocyte contraction, this process is synchronized with the electrical activity of the cell.

Adv Physiol Educ.2011 Mar;35(1):28-32.

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Mechanics of Breathing

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Humans need a continuous supply of oxygen for cellular respiration, and they must get rid of excess carbon dioxide, the poisonous waste product of this process. Gas exchange supports this cellular respiration by constantly supplying oxygen and removing carbon dioxide. The oxygen we need is derived from the Earth's atmosphere, which is 21% oxygen. This oxygen in the air is exchanged in the body by the respiratory surface. In humans, the alveoli in the lungs serve as the surface for gas exchange.

Gas exchange in humans can be divided into five steps:

Other factors involved with respiration are:

Structure of the Human Respiratory System

The Nose - Usually air will enter the respiratory system through the nostrils. The nostrils then lead to open spaces in the nose called the nasal passages. The nasal passages serve as a moistener, a filter, and to warm upthe air before it reaches the lungs. The hairs existing within the nostrils prevents various foreign particles from entering.Different air passageways and the nasal passages are covered with a mucous membrane. Many of the cells which produce the cells that make up the membrane contain cilia. Others secrete a type a sticky fluid called mucus. The mucus and cilia collect dust, bacteria, and other particles in the air. The mucus also helps in moistening the air. Under the mucous membrane there are a large number of capillaries. The blood within these capillaries helps to warm the air as it passes through the nose. The nose serves three purposes. It warms, filters, and moistens the air before it reaches the lungs. You will obviously lose these special advantages if you breath through your mouth.

Pharynx and Larynx - Air travels from the nasal passages to the pharynx, or more commonly known as the throat. When the air leaves the pharynx it passes into the larynx, or the voice box. The voice box is constructed mainly of cartilage, which is a flexible connective tissue. The vocal chords are two pairs of membranes that are stretched across the inside of the larynx. As the air is expired, the vocal chords vibrate. Humans can control the vibrations of the vocal chords, which enables us to make sounds. Food and liquids are blocked from entering the opening of the larynx by the epiglottis to prevent people from choking during swallowing.

Trachea - The larynx goes directly into the trachea or the windpipe. The trachea is a tube approximately 12 centimeters in length and 2.5 centimeters wide. The trachea is kept open by rings of cartilage within its walls. Similar to the nasal passages, the trachea is covered with a ciliated mucous membrane. Usually the cilia move mucus and trapped foreign matter to the pharynx. After that, they leave the air passages and are normally swallowed. The respiratory system cannot deal with tobacco smoke very keenly. Smoking stops the cilia from moving. Just one cigarette slows their motion for about 20 minutes. Thetobacco smokeincreases the amount of mucus in the air passages. When smokers cough, their body is attempting to dispose of the extra mucus.

Bronchi - Around the center of the chest, the trachea divides into two cartilage-ringed tubes called bronchi. Also, this section of the respiratory system is lined with ciliated cells. The bronchi enter the lungs and spread into a treelike fashion into smaller tubes calle bronchial tubes.

Bronchioles - The bronchial tubes divide and then subdivide. By doing this their walls become thinner and have less and less cartilage. Eventually, they become a tiny group of tubes called bronchioles.

Alveoli - Each bronchiole ends in a tiny air chamber that looks like a bunch of grapes. Each chamber contains many cup-shaped cavities known as alveoli. The walls of the alveoli, which are only about one cell thick, are the respiratory surface. They are thin, moist, and are surrounded by several numbers of capillaries. The exchange of oxygen and carbon dioxide between blood and air occurs through these walls. The estimation is that lungs contain about 300 million alveoli. Their total surface area would be about 70 square meters. That is 40 times the surface area of the skin. Smoking makes it difficult for oxygen to be taken through the alveoli. When the cigarette smoke is inhaled, about one-third of the particles will remain within the alveoli. There are too many particles from smoking or from other sources of air pollution which can damage the walls in the alveoli. This causes a certain tissue to form. This tissue reduces the working area of the respiratory surface and leads to the disease called emphysema.

Breathing

Breathing consists of two phases, inspiration and expiration. During inspiration, the diaphragm and the intercostal muscles contract. The diaphragm moves downwards increasing the volume of the thoracic (chest) cavity, and the intercostal muscles pull the ribs up expanding the rib cage and further increasing this volume. This increase of volume lowers the air pressure in the alveoli to below atmospheric pressure. Because air always flows from a region of high pressure to a region of lower pressure, it rushes in through the respiratory tract and into the alveoli. This is called negative pressure breathing, changing the pressure inside the lungs relative to the pressure of the outside atmosphere. In contrast to inspiration, during expiration the diaphragm and intercostal muscles relax. This returns the thoracic cavity to it's original volume, increasing the air pressure in the lungs, and forcing the air out.

External Respiration

When a breath is taken, air passes in through the nostrils, through the nasal passages, into the pharynx, through the larynx, down the trachea, into one of the main bronchi, then into smaller bronchial tubules, through even smaller bronchioles, and into a microscopic air sac called an alveolus. It is here that external respiration occurs. Simply put, it is the exchange of oxygen and carbon dioxide between the air and the blood in the lungs. Blood enters the lungs via the pulmonary arteries. It then proceeds through arterioles and into the alveolar capillaries. Oxygen and carbon dioxide are exchanged between blood and the air. This blood then flows out of the alveolar capillaries, through venuoles, and back to the heart via the pulmonary veins. For an explanation as to why gasses are exchanged here, see partial pressure.

Gas Transport

If 100mL of plasma is exposed to an atmosphere with a pO2 of 100mm Hg, only 0.3mL of oxygen would be absorbed. However, if 100mL of bloodis exposed to the same atmosphere, about 19mL of oxygen would be absorbed. This is due to the presence of haemoglobin, the main means of oxygen transport in the body. The respiratory pigment haemoglobin is made up of an iron-containing porphyron, haem, combined with the protein globin. Each iron atom in haem is attached to four pyrole groups by covalent bonds. A fifth covalent bond of the iron is attached to the globin part of the molecule and the sixth covalent bond is available for combination with oxygen. There are four iron atoms in each hemoglobin molecule and therefore four heam groups.

Oxygen Transport -

In the loading and unloading of oxygen, there is a cooperation between these four haem groups. When oxygen binds to one of the groups, the others change shape slightly and their attraction to oxygen increases. The loading of the first oxygen, results in the rapid loading of the next three (forming oxyhemoglobin). At the other end, when one group unloads it's oxygen, the other three rapidly unload as their groups change shape again having less attraction for oxygen. This method of cooperative binding and release can be seen in the dissociation curve for hemoglobin. Over the range of oxygen concentrations where the curve has a steep slope, the slightest change in concentration will cause hemoglobin to load or unload a substantial amount of oxygen. Notice that the steep part of the curve corresponds to the range of oxygen concentrations found in the tissues. When the cells in a particular location begin to work harder, e.g. during exercise, oxygen concentration dips in that location, as the oxygen is used in cellular respiration. Because of the cooperation between the haem groups, this slight change in concentration is enough to cause a large increase in the amount of oxygen unloaded.

As with all proteins, hemoglobin's shape shift is sensitive to a variety of environmental conditions. A drop in pH lowers the attraction of hemoglobin to oxygen, an effect known as the Bohr shift. Because carbon dioxide reacts with water to produce carbonic acid, an active tissue will lower the pH of it's surroundings and encourage hemoglobin to give up extra oxygen, to be used in cellular respiration. Hemoglobin is a notable molecule for it's ability to transport oxygen from regions of supply to regions of demand.

Carbon Dioxide Transport - Out of the carbon dioxide released from respiring cells, 7% dissolves into the plasma, 23% binds to the multiple amino groups of hemoglobin (Caroxyhemoglobin), and 70% is carried as bicarbonate ions. Carbon dioxide created by respiring cells diffuses into the blood plasma and then into the red blood cells, where most of it is converted to bicarbonate ions. It first reacts with water forming carbonic acid, which then breaks down into H+ and CO3-. Most of the hydrogen ions that are produced attach to hemoglobin or other proteins.

Internal Respiration

The body tissues need the oxygen and have to get rid of the carbon dioxide, so the blood carried throughout the body exchanges oxygen and carbon dioxide with the body's tissues. Internal respiration is basically the exchange of gasses between the blood in the capillaries and the body's cells.

The respiratory center is gray matter in the pons and the upper Medulla, which is responsible for rhythmic respiration. This center can be divided into an inspiratory center and an expiratory center in the Medulla, an apneustic center in the lower and midpons and a pneumotaxic center in the rostral-most part of the pons. This respiratory center is very sensitive to the pCO2 in the arteries and to the pH level of the blood.The CO2 can be brought back to the lungs in three different ways; dissolved in plasma, as carboxyhemoglobin, or as carbonic acid. That particular form of acid is almost broken down immediately by carbonic hydrase into bicarbonate and hydrogen ions. This process is then reversed in the lungs so that water and carbon dioxide are exhaled. The Medulla Oblongata reacts to both CO2 and pH levels which triggers the breathing process so that more oxygen can enter the body to replace the oxygen that has been utilized. The Medulla Oblongata sends neural impulses down through the spinal chord and into the diaphragm. The impulse contracts down to the floor of the chest cavity, and at the same time there is a message sent to the chest muscles to expand causing a partial vacuum to be formed in the lungs. The partial vacuum will draw air into the lungs.

There are two other ways the Medulla Oblongata can be stimulated. The first type is when there is an oxygen debt (lack of oxygen reaching the muscles), andthis produces lactic acid which lowers the pH level.The Medulla Oblongata is then stimulated. If the pH rises it begins a process known as the Bohr shift. The Bohr shift is affected when there are extremely high oxygen and carbon dioxide pressures present in the human body. This factor causes difficulty for the oxygen and carbon dioxide to attach to hemoglobin. When the body is exposed to higher altitudes the oxygen will not attach to the hemoglobin properly, causing the oxygen level to drop and the person will black out. This theory also applies to divers who go to great depths, and the pressure of the oxygen becomes poisonous. These pressures are known as pO2 and pCO2, or partial pressures. The second type occurswhen the major arteries in the body called theaortic and carotid bodies, sense a lack of oxygen within the blood and they send messages to the Medulla Oblongata.

Various marine mammals have been found to have adapted special abilities which help in their respiratory processes, enabling them to remain down at great depths for long periods of time. The Weddell seal possesses some amazing abilities. It only stores 5% of its oxygen in its lungs, and keeps the remaining 70% of its oxygen circulating throughout the blood stream. Humans are only able to keep a small 51% of their oxygen circulating throughout the blood stream, while 36% of the oxygen is stored in the lungs. The explanation for this is that the Weddell seal has approximately twice the volume of blood per kilogram as humans. As well, the Weddell seal's spleen has the ability to store up to 24L of blood. It is believed that when the seal dives the spleen contracts causing the stored oxygen enriched blood to enter the blood stream. Also, these seals have a higher concentration of a certain protein found within the muscles known as myoglobin, which stores oxygen. The Weddell seal contains 25% of its oxygen in the muscles, while humans only keep about 12% of their oxygen within the muscles.

Not only does the Weddell seal store oxygen for long dives, but they consume it wisely as well. A diving reflex slows the pulse, and an overall reduction in oxygen consumption occurs due to this reduced heart rate. Regulatory mechamisms reroute blood to where it is needed most (brain, spinal cord, eyes, adrenal glands, and in some cases placenta) by constricting blood flow where it is not needed (mainly in the digestive system). Blood flow is restricted to muscles during long dives and they rely on oxygen stored in their myoglobin and make their ATP from fermentation rather then from respiration.

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Mechanics of Breathing - Breathing in Joy

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