The Venus flytrap, Dionaea muscipula, is probably the most famous of carnivorous plants, and for good reason. The spike-toothed traps that snap closed fast enough to capture fast-flying insects are unique among plants. Not only do they move quickly -- they're among the fastest things in the plant kingdom -- they do so only at a very, very precise trigger.
When an insect lands on the flytrap's trap (actually a modified leaf), it brushes against tiny hairs on the leaf surface. Touching those hairs triggers the trap, and it snaps shut. At first, there's still a little gap between the "teeth" of the trap, though, which lets very small prey escape -- that way, the plant doesn't have to waste its energy digesting something too small to be of any use. When too small a bug triggers the trap and then escapes, the trap can open back up within 12 hours. There's no need to waste time and digestive juices on a useless gnat.
If the trapped bug is big enough, though, it won't be able to slip out. Instead, it'll just keep squirming inside the trap: the continued pressure on the hairs tells the plant to seal the trap completely, pushing its edges together until it's a watertight pocket. Once that has happened, the plant releases digestive juices into the pocket. These juices break down and dissolve all the soft parts of the bug so that the plant can absorb the nutrients in it. Once this is finished, about 10 days later, the bug is nothing but an empty exoskeleton. The trap then opens back up, letting the bug-husk fall away and getting ready for its next meal.
Tuesday, January 31, 2012
Monday, January 30, 2012
Carnivory Week: When plants get hungry
Everyone knows that carnivorous plants exist. Even if their sheer weirdness and amazing capabilities hadn't already brought them into classrooms, Little Shop of Horrors would have cemented them firmly in the popular consciousness. One thing that's rarely discussed, though, is exactly why a plant would resort to carnivory. Why bother catching and eating animals when you're a plant and can already make all your own food?
The answer is simple: minerals. Carnivorous plants are as good at photosynthesis as any other species, but photosynthesis only makes sugar. They still need soil nutrients -- nitrogen, phosphorus, potassium, and a host of other trace minerals -- for the same reason that people need our vitamins. Most plants get their nutrients from the soil, where the stuff is abundant; farmers and gardeners add minerals, in the form of fertilizer, to help their crops thrive.
On its own, though, a plant can't very well pop down to Home Depot and buy itself a bag of fertilizer. When the soil lacks important minerals, what's a plant to do? Some species have found ways to conserve or reuse scarce nutrients, making a little go a long way. Others have found ways of making their own: legumes can pull nitrogen right out of the air (and that's a subject for another post). Carnivorous plants do neither. Instead, they just let their prey bring the goods right to them.
When a plant traps and digests, say, a fly, it gets to suck up all the nutrients in that bug's body. There's nitrogen in the protein of its muscles, potassium in its nerves to let them fire, phosphorus down the very backbone of its DNA, and much more. A single fly can save the plant from a startling amount of malnutrition. Carnivorous plants aren't just being vicious: like any carnivore, they're only trying to survive.
This week, look for posts on the wonders of four different carnivorous plants: the literal hair-triggers of the Venus flytrap, the booby traps set by pitcher plants, the gluey hairs on sundews, and the vacuum suction of the bladderwort.
The answer is simple: minerals. Carnivorous plants are as good at photosynthesis as any other species, but photosynthesis only makes sugar. They still need soil nutrients -- nitrogen, phosphorus, potassium, and a host of other trace minerals -- for the same reason that people need our vitamins. Most plants get their nutrients from the soil, where the stuff is abundant; farmers and gardeners add minerals, in the form of fertilizer, to help their crops thrive.
On its own, though, a plant can't very well pop down to Home Depot and buy itself a bag of fertilizer. When the soil lacks important minerals, what's a plant to do? Some species have found ways to conserve or reuse scarce nutrients, making a little go a long way. Others have found ways of making their own: legumes can pull nitrogen right out of the air (and that's a subject for another post). Carnivorous plants do neither. Instead, they just let their prey bring the goods right to them.
When a plant traps and digests, say, a fly, it gets to suck up all the nutrients in that bug's body. There's nitrogen in the protein of its muscles, potassium in its nerves to let them fire, phosphorus down the very backbone of its DNA, and much more. A single fly can save the plant from a startling amount of malnutrition. Carnivorous plants aren't just being vicious: like any carnivore, they're only trying to survive.
This week, look for posts on the wonders of four different carnivorous plants: the literal hair-triggers of the Venus flytrap, the booby traps set by pitcher plants, the gluey hairs on sundews, and the vacuum suction of the bladderwort.
Friday, January 27, 2012
Going bananas for a seed, any seed
Wild bananas (Musa spp.) are, not to put too fine a point on it, nearly inedible. Their seeds are enormous: a wild banana fruit has only a thin layer of pulp between the peel and the huge hard seed. Obviously, something has changed between the wild type and the virtually-seedless, soft, sweet bananas sold in every American grocery store. In fact, it took decades of selective breeding to shrink the seeds that far. There are dozens of banana varieties now, most of them sweet and pulpy, with seeds that could easily dance on the head of a pin.
Seeds that small, unfortunately, are reproductively useless. They'll almost never sprout. Commercial banana growers have no desire to extract millions of minute seeds from their crop just to grow one or two new banana plants... so they don't. Bananas aren't grown from seed: they're propagated by cloning. To get a new banana plant, the farmer cuts a root sucker from the parent plant's corm and grows it to fruiting size in wet sand.
Because all commercial bananas are grown this way, commercial farms are monocultures -- huge masses of clones. The bananas found in American supermarkets, for instance, are all from the Cavendish variety, and every Cavendish banana is genetically identical to all the others. When it comes to producing uniform bananas and growing them all the same way, that's a good thing. When it comes to disease resistance, though, it's very, very bad. Since there's no genetic variation in these plants, they all have the same immune system: a disease that can kill one Cavendish banana plant can kill any other.
We had an object lesson in the problem once, not too long ago. Before 1960, the Cavendish banana was a nobody: commercial banana-growers all used clones of the Gros Michel, a variety with tastier fruit that was easier to ship. It worked out nicely, right until the outbreak of Panama disease. Caused by a soil fungus, the disease ripped through banana plantations worldwide, rendering the Gros Michel virtually extinct. Worse, since the fungus persists in soil, the Gros Michel plantations couldn't just be replanted: the new plants died before they could ever bear fruit. If you've ever heard the song "Yes, We Have No Bananas", you have some idea of the effect Panama disease had on the world banana trade.
The Cavendish banana's fruit is inferior to the Gros Michel in practically every way, but it has one thing its predecessor never will: it's resistant to Panama disease. With Gros Michel plants dropping like flies, the Cavendish came to the rescue. It may not be the perfect fruit, but it can actually be grown commercially even in a Panama-disease-haunted world. It has replaced the Gros Michel now; it's grown worldwide, with millions of its clones producing millions of pounds of bananas each year.
What's wrong with this picture, though? The Cavendish is still a clone. If another disease develops that can take down one Cavendish, it can kill them all. For as long as our bananas are all cloned, we're inches from a repeat of the Gros Michel disaster. Monoculture just doesn't work in the long run.
Seeds that small, unfortunately, are reproductively useless. They'll almost never sprout. Commercial banana growers have no desire to extract millions of minute seeds from their crop just to grow one or two new banana plants... so they don't. Bananas aren't grown from seed: they're propagated by cloning. To get a new banana plant, the farmer cuts a root sucker from the parent plant's corm and grows it to fruiting size in wet sand.
Because all commercial bananas are grown this way, commercial farms are monocultures -- huge masses of clones. The bananas found in American supermarkets, for instance, are all from the Cavendish variety, and every Cavendish banana is genetically identical to all the others. When it comes to producing uniform bananas and growing them all the same way, that's a good thing. When it comes to disease resistance, though, it's very, very bad. Since there's no genetic variation in these plants, they all have the same immune system: a disease that can kill one Cavendish banana plant can kill any other.
We had an object lesson in the problem once, not too long ago. Before 1960, the Cavendish banana was a nobody: commercial banana-growers all used clones of the Gros Michel, a variety with tastier fruit that was easier to ship. It worked out nicely, right until the outbreak of Panama disease. Caused by a soil fungus, the disease ripped through banana plantations worldwide, rendering the Gros Michel virtually extinct. Worse, since the fungus persists in soil, the Gros Michel plantations couldn't just be replanted: the new plants died before they could ever bear fruit. If you've ever heard the song "Yes, We Have No Bananas", you have some idea of the effect Panama disease had on the world banana trade.
The Cavendish banana's fruit is inferior to the Gros Michel in practically every way, but it has one thing its predecessor never will: it's resistant to Panama disease. With Gros Michel plants dropping like flies, the Cavendish came to the rescue. It may not be the perfect fruit, but it can actually be grown commercially even in a Panama-disease-haunted world. It has replaced the Gros Michel now; it's grown worldwide, with millions of its clones producing millions of pounds of bananas each year.
What's wrong with this picture, though? The Cavendish is still a clone. If another disease develops that can take down one Cavendish, it can kill them all. For as long as our bananas are all cloned, we're inches from a repeat of the Gros Michel disaster. Monoculture just doesn't work in the long run.
Thursday, January 26, 2012
How American grapes saved French wine
The first two entries for this week discussed weird ways that plants clone themselves in the wild. The last two will deal with weird ways that plants can be cloned in cultivation, and with the effects -- good and bad -- of the ways we use them. The phenomena for Thursday and Friday don't really happen without human intervention, and you'll soon see why.
In the case of grafting, the reason is simply that plants don't usually come into natural contact that way. To graft two plants, a gardener cuts off a stem from one of them -- the scion -- at a sharp angle. He or she then slices a notch into the stem of another one -- the stock -- and sticks the scion's cut stem into the notch. If the layers inside the two stems are lined up properly, and they're tied into place and given time to heal, the two plants will actually fuse together and keep growing. All the parts of the stock plant will grow as is typical for its species, but the scion stem will grow as typical for its species.
Gardeners frequently use this technique to combine characteristics from different species into a single plant. Say that you graft a scion from a cherry tree onto a peach sapling, for instance. Once the hybrid tree matures, you can end up with a tree half of whose branches produce peaches while the other half produces cherries. Even better, graft the stem of a tomato onto a potato's roots: you'll get edible tomatoes above ground and edible potatoes below.
Alternately, if you're the European wine industry, you could use grafting to save your very livelihood.
The aphid Dakytlosphaira vitifoliae, AKA the grape phylloxera, is native to the eastern USA and is a parasite on grape vines. To the grape species native to the same places as phylloxera -- the riverbank grape Vitis riparia, the fox grape Vitis labrusca, and the summer grape Vitis aestivalis -- the aphid is a fairly minor pest. To the European grapevine, Vitis vinifera, though, phylloxera infestation is lethal. Early attempts at starting vineyards in America all failed spectacularly as soon as the aphid found them. The cause was unknown until much later: grape growers knew only that America was hostile to their vines.
Imagine the devastation, then, when phylloxera found its way to Europe. After 1863, when its effects were first recorded in France, it spread like wildfire and devastated the French wine industry. No one knew exactly what was happening. Chemical pesticides and fertilizers were of no use. Nothing worked at all until, in 1868, French botanists hypothesized phylloxera as a cause. Their hypothesis was confirmed in 1870. Now that the cause was known, all that was needed was some solution. Pesticides still didn't work. What was it, people wondered, that let the native American grapevines survive the blight that was massacring V. vinifera?
Actually, they decided, they didn't need to know precisely what it was, as long as the resistance transferred across a graft. By grafting scions from wine-producing V. vinifera cultivars onto rootstocks from resistant American V. aestivalis, viticulturists were able to develop vines that produced familiar European grapes but would not succumb to phylloxera. The wine industry was saved! The fiercer French purists disdained the inferior American stocks, fearing that their wine grapes would be contaminated, but it quickly became clear that there was no choice. It was either embrace the resistant species or be wiped out.
To this day, any viticulturist who wants to grow V. vinifera without the threat of massive phylloxera losses must use only grafted plants. Pesticides are still no use, and no resistant strain of pure V. vinifera has been developed. Winemakers still debate whether an un-grafted V. vinifera produces better wines than one with an American rootstock, but the point cannot be tested: phylloxera is all but ubiquitous now.
For all that their fruit is less popular than V. vinifera's, then, the humble native grapevines of America -- riverbank, fox, and summer grapes -- are responsible for virtually every vintage produced since the Great French Wine Blight. If you like your wine, thank a native grape!
In the case of grafting, the reason is simply that plants don't usually come into natural contact that way. To graft two plants, a gardener cuts off a stem from one of them -- the scion -- at a sharp angle. He or she then slices a notch into the stem of another one -- the stock -- and sticks the scion's cut stem into the notch. If the layers inside the two stems are lined up properly, and they're tied into place and given time to heal, the two plants will actually fuse together and keep growing. All the parts of the stock plant will grow as is typical for its species, but the scion stem will grow as typical for its species.
Gardeners frequently use this technique to combine characteristics from different species into a single plant. Say that you graft a scion from a cherry tree onto a peach sapling, for instance. Once the hybrid tree matures, you can end up with a tree half of whose branches produce peaches while the other half produces cherries. Even better, graft the stem of a tomato onto a potato's roots: you'll get edible tomatoes above ground and edible potatoes below.
Alternately, if you're the European wine industry, you could use grafting to save your very livelihood.
The aphid Dakytlosphaira vitifoliae, AKA the grape phylloxera, is native to the eastern USA and is a parasite on grape vines. To the grape species native to the same places as phylloxera -- the riverbank grape Vitis riparia, the fox grape Vitis labrusca, and the summer grape Vitis aestivalis -- the aphid is a fairly minor pest. To the European grapevine, Vitis vinifera, though, phylloxera infestation is lethal. Early attempts at starting vineyards in America all failed spectacularly as soon as the aphid found them. The cause was unknown until much later: grape growers knew only that America was hostile to their vines.
Imagine the devastation, then, when phylloxera found its way to Europe. After 1863, when its effects were first recorded in France, it spread like wildfire and devastated the French wine industry. No one knew exactly what was happening. Chemical pesticides and fertilizers were of no use. Nothing worked at all until, in 1868, French botanists hypothesized phylloxera as a cause. Their hypothesis was confirmed in 1870. Now that the cause was known, all that was needed was some solution. Pesticides still didn't work. What was it, people wondered, that let the native American grapevines survive the blight that was massacring V. vinifera?
Actually, they decided, they didn't need to know precisely what it was, as long as the resistance transferred across a graft. By grafting scions from wine-producing V. vinifera cultivars onto rootstocks from resistant American V. aestivalis, viticulturists were able to develop vines that produced familiar European grapes but would not succumb to phylloxera. The wine industry was saved! The fiercer French purists disdained the inferior American stocks, fearing that their wine grapes would be contaminated, but it quickly became clear that there was no choice. It was either embrace the resistant species or be wiped out.
To this day, any viticulturist who wants to grow V. vinifera without the threat of massive phylloxera losses must use only grafted plants. Pesticides are still no use, and no resistant strain of pure V. vinifera has been developed. Winemakers still debate whether an un-grafted V. vinifera produces better wines than one with an American rootstock, but the point cannot be tested: phylloxera is all but ubiquitous now.
For all that their fruit is less popular than V. vinifera's, then, the humble native grapevines of America -- riverbank, fox, and summer grapes -- are responsible for virtually every vintage produced since the Great French Wine Blight. If you like your wine, thank a native grape!
Wednesday, January 25, 2012
Mother-of-millions
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| A healthy adult B. daigremontianum |
Rather, the unusual thing about the mother-of-millions is the sheer number of plantlets and the odd place where they're produced. Most species that produce plantlets do so either from a modified stem (like the stolons of spider plants) or a modified flowering structure (like the bulbils that sometimes replace garlic's flowers). B. daigremontianum scoffs at that: its bulbils grow right on the leaves. From every notch in its serrated leaf edges springs a little green peg of leaf tissue, and from every peg springs a single tiny plantlet, complete with minute leaves and fine baby roots. A large, healthy mother-of-millions can produce hundreds of these clones at a time, and whenever one falls off the parent -- which can happen with as little stimulus as a nice fat raindrop, once the clones are mature enough -- it will eagerly take root and grow. The mother-of-millions is aptly named: under the right conditions, it spreads like a leafy green wildfire.
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| Tip of a B. daigremontianum leaf, plus 15 clones. Aww, look at their little bitty rootlets! |
Image sources: Wikimedia Commons.
- Anna. 2006. Kalanchoe daigremontiana. Retrieved January 24th, 2011, from Wikimedia Commons: <http://commons.wikimedia.org/wiki/File:Kalanchoe_daigremontiana.jpg>
- CrazyD. 2005. Bryophyllum daigremontianum nahaufnahme2. Retrieved January 24th, 2011, from Wikimedia Commons: <http://commons.wikimedia.org/wiki/File:Bryophyllum_daigremontianum_nahaufnahme2.jpg>
Tuesday, January 24, 2012
Rock gardens à la Cuisinart
Most plants are, to some extent or another, capable of vegetative reproduction. With a bit of rooting hormone and a bit of luck, the careful gardener can clone almost anything she'd care to grow. Some species are decidedly less difficult than others, though. Moth orchids (Phalaenopsis), for instance, take -- at best -- a lot of careful coaxing before they'll bud; but strawberries send out runners in all directions if the conditions are even halfway agreeable, and sometimes even when they're not. There's also the question of which parts of the plant are most readily reproductive. It's very difficult to grow a new moth orchid from anything other than the small plantlets ("keikis" to orchid fanciers) that it can occasionally produce from a flowering stem, but virtually any old leaf from an African violet will root readily if placed in soil, and willow branches will sprout new roots from either end if water so much as looks at them funny.
Strawberries, willows, and African violets all look like amateurs next to mosses, though. Most temperate moss species are so flexible and so reproductive that just about any part of them will root if separated from the whole. Chop them into tiny bits, and each part will simply grow into a new plant. Part of a leaf, or a millimeter-long bit of bare stem, can be enough.
This tendency is so strong that many mosses can quite literally recover from five rounds in a blender. If you put a chunk of dry moss in an ordinary kitchen blender with some room-temperature water and buttermilk, then spritz the resulting suspension over a rock and keep it moist, each tiny fragment will take root and grow into a whole new moss plant! Given enough time, you'll end up with a rock densely coated in the green stuff. The "moss milkshake" technique is widely-used among gardeners interested in these tiny plants, and you can even buy commercially-prepared milkshake starters if you don't want to get dirt in your only blender.
Strawberries, willows, and African violets all look like amateurs next to mosses, though. Most temperate moss species are so flexible and so reproductive that just about any part of them will root if separated from the whole. Chop them into tiny bits, and each part will simply grow into a new plant. Part of a leaf, or a millimeter-long bit of bare stem, can be enough.
This tendency is so strong that many mosses can quite literally recover from five rounds in a blender. If you put a chunk of dry moss in an ordinary kitchen blender with some room-temperature water and buttermilk, then spritz the resulting suspension over a rock and keep it moist, each tiny fragment will take root and grow into a whole new moss plant! Given enough time, you'll end up with a rock densely coated in the green stuff. The "moss milkshake" technique is widely-used among gardeners interested in these tiny plants, and you can even buy commercially-prepared milkshake starters if you don't want to get dirt in your only blender.
Monday, January 23, 2012
Week of the Clones: the ethics of vegetative reproduction
Is cloning ethical? That question is something of a hot-button issue in bioethics, especially as we get better at it. Forty years ago, we couldn't so much as clone a fruit fly; today, we can manage sheep and dogs, and biologists are ever honing our techniques. Soon, we may be able to clone human beings.
Oh, and did I mention that plants beat us to the punch by several hundred million years?
"Reproductive cloning", in the most precise sense, just means any form of reproduction where the offspring is genetically identical to the parent. In the most popularly familiar sense, this means the cloning of complex animals like, say, a sheep -- a process requiring a great deal of careful lab work. More broadly, though, it actually refers to any kind of asexual reproduction. Virtually all bacterial reproduction is clonal: when a cell divides, it is cloning itself. A great many animals reproduce asexually, too: when a planarian gets split in two and each end grows back into a complete individual, it is cloning itself.
Plants clone themselves all the time, both on their own and with human assistance. Most serious gardeners will, at some point, have propagated a favorite plant from cuttings or by dividing a clumping perennial: the resulting plants are clones of the original. When a tree produces root suckers, it is cloning itself. When a bulb (say, of an Asiatic lily or a garlic plant) produces smaller bulbs off its sides, it is cloning itself. Cloning is absolutely rampant in the plant world. It's called vegetative reproduction, and it's about as unusual as a rabbit having a litter of kits.
That said, the fact that plants clone themselves regularly doesn't make their methods of doing so any less interesting. The types of vegetative reproduction are as varied as plants themselves. This week, I'll be posting entries on vegetative reproduction both natural and artificial, in plants as diverse as mosses, bananas, grapes, and mother-of-thousands. Look for more coming up in the Week of the Clones!
Oh, and did I mention that plants beat us to the punch by several hundred million years?
"Reproductive cloning", in the most precise sense, just means any form of reproduction where the offspring is genetically identical to the parent. In the most popularly familiar sense, this means the cloning of complex animals like, say, a sheep -- a process requiring a great deal of careful lab work. More broadly, though, it actually refers to any kind of asexual reproduction. Virtually all bacterial reproduction is clonal: when a cell divides, it is cloning itself. A great many animals reproduce asexually, too: when a planarian gets split in two and each end grows back into a complete individual, it is cloning itself.
Plants clone themselves all the time, both on their own and with human assistance. Most serious gardeners will, at some point, have propagated a favorite plant from cuttings or by dividing a clumping perennial: the resulting plants are clones of the original. When a tree produces root suckers, it is cloning itself. When a bulb (say, of an Asiatic lily or a garlic plant) produces smaller bulbs off its sides, it is cloning itself. Cloning is absolutely rampant in the plant world. It's called vegetative reproduction, and it's about as unusual as a rabbit having a litter of kits.
That said, the fact that plants clone themselves regularly doesn't make their methods of doing so any less interesting. The types of vegetative reproduction are as varied as plants themselves. This week, I'll be posting entries on vegetative reproduction both natural and artificial, in plants as diverse as mosses, bananas, grapes, and mother-of-thousands. Look for more coming up in the Week of the Clones!
Friday, January 20, 2012
The tree with no name
The Douglas fir, Pseudotsuga menziesii, is widespread in the Pacific Northwest and the Rocky Mountains, and as such is quite important ecologically. It's not the least distinctive of trees, either, with its tall straight trunks and the conspicuous bracts like three-tailed ribbons poking out of its cones. For all that, though, this tree can be said to have no real name of its own! Both its common name and its Latin name are made entirely of references to other species.
Let's break that down, shall we? We'll start with the common name, "Douglas fir". "Douglas" refers to David Douglas, the botanist who first brought the species to Europe and more specifically to Scone Palace in Scotland. It's not a name for the plant itself -- it's a name for the man who made it famous. "Fir" is also a misnomer, since Pseudotsuga menziesii is not a true fir. True firs belong to the genus Abies; they have (among other things) upright cones that shatter as they ripen, no bracts on their cone-scales, and longer, softer needles that leave circular leaf-scars. Douglas "fir" has hanging cones that stay intact as they ripen, conspicuous bracts on the scales, and shorter, sharper needles that leave oval scars. "Douglas fir" is neither Douglas nor a fir.
The Latin name is no better. "Pseudotsuga" means "false hemlock": it states only that the species resembles the hemlock trees of genus Tsuga but is not in fact one of them. "menziesii" refers to Archibald Menzies, a globetrotting botanist of some renown, who was the first European to collect a great many North American plant species. Again, it's a name for a person, not the plant. "Pseudotsuga menziesii" is neither a Tsuga nor Menzies.
It has a few other names, but they are still not its own. An older Latin name, Pseudotsuga taxifolia, means "false hemlock with yew leaves". "Douglas pine" is no better than "Douglas fir": Pseudotsuga is no more a true pine than it is a true fir. "Oregon pine" is even worse, since the tree's natural range stretches well beyond Oregon.
This species has been formally known to Western science since at least 1889. You'd think that in over a hundred years, someone would at least have given it a name of its own.
Thanks to Barbara Ertter for pointing out this bit of trivia.
Sources: FNA, IPNI
Let's break that down, shall we? We'll start with the common name, "Douglas fir". "Douglas" refers to David Douglas, the botanist who first brought the species to Europe and more specifically to Scone Palace in Scotland. It's not a name for the plant itself -- it's a name for the man who made it famous. "Fir" is also a misnomer, since Pseudotsuga menziesii is not a true fir. True firs belong to the genus Abies; they have (among other things) upright cones that shatter as they ripen, no bracts on their cone-scales, and longer, softer needles that leave circular leaf-scars. Douglas "fir" has hanging cones that stay intact as they ripen, conspicuous bracts on the scales, and shorter, sharper needles that leave oval scars. "Douglas fir" is neither Douglas nor a fir.
The Latin name is no better. "Pseudotsuga" means "false hemlock": it states only that the species resembles the hemlock trees of genus Tsuga but is not in fact one of them. "menziesii" refers to Archibald Menzies, a globetrotting botanist of some renown, who was the first European to collect a great many North American plant species. Again, it's a name for a person, not the plant. "Pseudotsuga menziesii" is neither a Tsuga nor Menzies.
It has a few other names, but they are still not its own. An older Latin name, Pseudotsuga taxifolia, means "false hemlock with yew leaves". "Douglas pine" is no better than "Douglas fir": Pseudotsuga is no more a true pine than it is a true fir. "Oregon pine" is even worse, since the tree's natural range stretches well beyond Oregon.
This species has been formally known to Western science since at least 1889. You'd think that in over a hundred years, someone would at least have given it a name of its own.
Thanks to Barbara Ertter for pointing out this bit of trivia.
Sources: FNA, IPNI
Thursday, January 19, 2012
Back in my day, everybody had cones!
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| A Pinus longaeva, showing its age |
The oldest known bristlecone is a tree called "Methuselah", growing in eastern California. At the time it first sprouted, around 2800 BC, the Neolithic period was barely over. Mesopotamians had just invented the city, the Egyptians were developing hieroglyphic writing, and the potter's wheel was the height of technology. Imagine -- there is a single living thing that would remember all of that, if it could!
Image source:
Williams, Margaret. Pinus longaeva D.K. Bailey - Great Basin bristlecone pine. USDA-NRCS PLANTS Database. Retrieved 17 January 2012 from <http://plants.usda.gov/java/largeImage?imageID=pilo_002_avp.tif>. Used with permission.
Source: FNA
Wednesday, January 18, 2012
Coffee, please, with extra insecticide
Everything that a living thing does, it does for a reason. Evolution doesn't tolerate uselessness for very long: an organism that spends precious resources growing a body part, or indulging in a behavior, that doesn't enhance its fitness will eventually be out-competed by others that don't. (Vestigial structures are a matter for another post.)
Considered that way, caffeine doesn't make much sense. Why on Earth would a plant make a chemical whose only apparent purpose is to give humans a nice little buzz? In the wild, that doesn't get coffee or tea plants anything, does it? Actually, it does, because caffeine does more than make us jittery. To the plant, it's something else entirely -- a valuable insecticide.
Caffeine belongs to a large class of chemicals called alkaloids, a great many of which are made by a huge variety of plants for a number of different reasons. Whether or not you realize it, you're already familiar with quite a few alkaloids and their effects on humans. There's caffeine, of course; morphine, a valuable painkiller but also one of the key components of heroin; cocaine, a dangerous street drug; capsaicin, the stuff that makes peppers taste hot; and theobromine, the active ingredient in chocolate. All five of those serve the same general purpose in the plants that make them -- they scare off herbivores. Whether by producing an unpleasant taste, by making the herbivore's mouth burn, or by being lethally toxic, a plant full of alkaloids makes a less than satisfying meal.
Caffeine in particular, while essentially harmless to humans, is lethal to many insects. They are much less capable of metabolizing the substance: the same dose of caffeine that acts in humans as a mild central-nervous-system stimulant will paralyze or kill many insects. Even when it doesn't kill the pests outright, it immobilizes them for long enough that their own predators might find an easy meal.
None of this is any reason to swear off coffee or tea. You are not an insect, and the amounts of caffeine in your favorite beverage are thoroughly harmless. If you already stick to decaf, though, you can offer your caffeinated friends a new explanation: "I just don't like the taste of insecticide in the morning!"
Considered that way, caffeine doesn't make much sense. Why on Earth would a plant make a chemical whose only apparent purpose is to give humans a nice little buzz? In the wild, that doesn't get coffee or tea plants anything, does it? Actually, it does, because caffeine does more than make us jittery. To the plant, it's something else entirely -- a valuable insecticide.
Caffeine belongs to a large class of chemicals called alkaloids, a great many of which are made by a huge variety of plants for a number of different reasons. Whether or not you realize it, you're already familiar with quite a few alkaloids and their effects on humans. There's caffeine, of course; morphine, a valuable painkiller but also one of the key components of heroin; cocaine, a dangerous street drug; capsaicin, the stuff that makes peppers taste hot; and theobromine, the active ingredient in chocolate. All five of those serve the same general purpose in the plants that make them -- they scare off herbivores. Whether by producing an unpleasant taste, by making the herbivore's mouth burn, or by being lethally toxic, a plant full of alkaloids makes a less than satisfying meal.
Caffeine in particular, while essentially harmless to humans, is lethal to many insects. They are much less capable of metabolizing the substance: the same dose of caffeine that acts in humans as a mild central-nervous-system stimulant will paralyze or kill many insects. Even when it doesn't kill the pests outright, it immobilizes them for long enough that their own predators might find an easy meal.
None of this is any reason to swear off coffee or tea. You are not an insect, and the amounts of caffeine in your favorite beverage are thoroughly harmless. If you already stick to decaf, though, you can offer your caffeinated friends a new explanation: "I just don't like the taste of insecticide in the morning!"
Tuesday, January 17, 2012
Vivipary: a seed within a seed *
Take a good look at the photo below, and tell me: what's wrong with this picture?
If you pointed out the little green shoots, give yourself a pat on the back, because I'm pretty sure that corn isn't supposed to do that. The kernels usually wait until they're planted before they sprout. What we have here is a mutant plant, showing off a phenomenon called vivipary.
Want the explanation? Fruit is not, generally speaking, a particularly good place for a seed to sprout. Take apple trees, for instance. Apple seeds start out buried deep inside a sweet, fleshy ball of fruit: ideally, they shouldn't germinate until the apple has been eaten and its core discarded to rot. If they wait, they need only break through the relatively thin, brittle walls of the core, rather than having to expend lots of energy pushing out through the whole apple. Most importantly, if they wait til the apple is eaten, the animal that ate it has probably carried them a good ways away from the parent tree: they'll be able to grow without having to compete with Mom for sunlight and water.
Since nobody really benefits if a seed jumps the gun, plants have developed ways of keeping seeds quiet until it's time. In its fruits, the parent plant produces a hormone called abscisic acid, which suppresses germination and keeps the seed dormant. As long as the seed is inside the fruit, it gets a steady dose of the stuff and it stays dormant. Once the fruit is off the parent plant, though, and the seed broken out of the fruit, the abscisic acid stops flowing and the seed can sprout.
The trouble is that this system only works when both the parent plant can produce abscisic acid and the new seed is sensitive to it. Sometimes, one end or the other fails, and that's when vivipary happens. Corn sprouting on the cob! Pumpkin vines splitting your jack-o-lantern in two! Dogs and cats sleeping together! It's chaos!
Well, perhaps it's not as bad as that. The phenomenon is called vivipary -- "live-bearing", in the sense of an animal giving birth to live young -- and it's not common in the plant world, because it frankly doesn't work very well for the plants. Viviparous mutant strains are very useful in studying how abscisic acid works, but the naturally-occuring ones tend to die out fairly quickly. A few species, such as garlic and mangroves, have embraced vivipary as a way of getting around some reproductive limitation; mostly, though, it's not the norm.
Should you ever shuck an ear of corn and find a seedling inside, then, you let me know. You'll have a rare oddball on your hands, and I'll want to see it for myself!
Image source:
Hughes, Wayne. Corn4. 15 September 2005. Niches. Retrieved 16 January 2012 from <http://sparkleberrysprings.com/v-web/b2/?p=300>. Used with permission.
* All Inception jokes should be directed in person to Leonardo DiCaprio.
Image source:
Hughes, Wayne. Corn4. 15 September 2005. Niches. Retrieved 16 January 2012 from <http://sparkleberrysprings.com/v-web/b2/?p=300>. Used with permission.
* All Inception jokes should be directed in person to Leonardo DiCaprio.
Monday, January 16, 2012
Yes, Virginia, it really is a fruit
Fun botany fact of the day: A tomato is really a fruit, but it's also really a vegetable.
You've probably heard the first half of this one before, so let me actually explain it this time. Whether something is a fruit or a vegetable all depends on who you're asking. To a botanist, a tomato is a fruit; to a cook, it's a vegetable. The botanical definition of "fruit" and the culinary definition of "vegetable" refer to completely different, unrelated properties, so it's actually possible to be both a botanical fruit and a culinary vegetable at the same time.
A botanical fruit is the part of the plant that developed from the flower's ripened ovary (which almost always means that it contains seeds). Apples, peaches, pears, raspberries, oranges, kumquats, and durian are all botanical fruits and also culinary fruits. Tomatoes, squash, olives, green beans, bell peppers, corn kernels, wheat "berries", and pumpkins are also all botanical fruits, although they're culinary vegetables. Botanically, there's no such thing as a "vegetable".
A culinary fruit is a plant part that's sweet; a vegetable is a plant part that's not very sweet. Every culinary vegetable is some other plant part as defined botanically. Carrots and radishes are roots, lettuce and spinach are leaves, potatoes and yams are tubers, onions are bulbs, celery sticks are petioles (leaf-stalks), peas are seeds, and tomatoes are fruits. All of those are also vegetables. There's no contradiction there.
You've probably heard the first half of this one before, so let me actually explain it this time. Whether something is a fruit or a vegetable all depends on who you're asking. To a botanist, a tomato is a fruit; to a cook, it's a vegetable. The botanical definition of "fruit" and the culinary definition of "vegetable" refer to completely different, unrelated properties, so it's actually possible to be both a botanical fruit and a culinary vegetable at the same time.
A botanical fruit is the part of the plant that developed from the flower's ripened ovary (which almost always means that it contains seeds). Apples, peaches, pears, raspberries, oranges, kumquats, and durian are all botanical fruits and also culinary fruits. Tomatoes, squash, olives, green beans, bell peppers, corn kernels, wheat "berries", and pumpkins are also all botanical fruits, although they're culinary vegetables. Botanically, there's no such thing as a "vegetable".
A culinary fruit is a plant part that's sweet; a vegetable is a plant part that's not very sweet. Every culinary vegetable is some other plant part as defined botanically. Carrots and radishes are roots, lettuce and spinach are leaves, potatoes and yams are tubers, onions are bulbs, celery sticks are petioles (leaf-stalks), peas are seeds, and tomatoes are fruits. All of those are also vegetables. There's no contradiction there.
Friday, January 13, 2012
Cactus tenacity: Never, ever say die
Those readers who know me in real life probably know by now what a herbarium is, since I work with them every day. For the rest, think of a herbarium as a sort of reference library for plant specimens. Botanists go out and dig up or clip off samples of plants, then press them flat between newsprint and blotting paper, folding or clipping them to size if they're too large to fit in the press. The pressed, dried specimens are glued to 11x17" sheets of archival paper, given detailed labels, and filed in the herbarium's cabinets for later reference. In those dark, dry, cool cabinets, a properly-prepared specimen can last for literally hundreds of years.
Think back for a moment over that process, and you'll realize that by the time it's archived, the plant on a specimen sheet is well and truly dead. Dug up, washed off, sliced up, pressed flat, dried out, glued down, and then locked away in the dark for long stretches -- well, how many plants do you know of that can bounce back from that?
To my great surprise, I actually met one not long ago.
In the wild, Mammillaria tetrancistra -- the common fishhook cactus -- looks like a fat green cylinder densely studded with inch-long, hooked, needle-thin spines. On the herbarium sheet, it's still green on the outside, but the cut surfaces of its stems are vibrant Crayola shades of red and orange. Live or dried, it's a rather striking sight.
When I pulled out a folder of M. tetrancistra last month, though, I got a surprise that had nothing to do with color or spines. The specimen inside was over a year old, collected and dried in the summer of 2010. It should have been desiccated and preserved. Instead, it was sprouting.
Source: CIC Herbarium (accession CIC 39704)
Thursday, January 12, 2012
Cryptobiosis: a convenient "death"
Water is life. Nothing on earth can live in its total absence, and few organisms can go without it for very long. A human can survive only a week or so without drinking. A camel, with its water- and food-storing hump, can go much longer, but will still die of thirst when its stores run out. Some cacti can survive for a year on the water stored in their stems, replenishing it only in the desert's short rainy season.
There's more than one way to survive dryness, though. Camels and cacti use about the same amount of water all the time; when there's none to be had outside, they fall back on their internal stores. A spikemoss species called Selaginella lepidophylla has found another way.
When it's well-hydrated, S. lepidophylla is green and perky, with tiny leaves in scale-like patterns that conjure images of steamy Jurassic jungles. When there's no water around, though, it does what most ferns would do: it dehydrates and shrivels, its branches curling into a sad little desiccated clump. You'd think it truly dead, right until the rains return and it promptly earns its common name -- the resurrection fern.
That lifeless ball of brittle twigs sucks up the water with desperate greed, and then it unfurls. The brown leaves soften and go green again. In a few short hours, the resurrection fern comes right back to life. It will live like this, soaking up the water and the sun, for as long as the water lasts; then, just as it did before, it will dry out and "die." It can do this over and over, and it can survive in dry state for months or years on end.
The video below is a time-lapse of a store-bought resurrection fern rehydrating, over the course of about five hours. Watch and enjoy.
The phenomenon -- an organism tamping down its metabolism to wait for more hospitable conditions -- is called cryptobiosis. The most famous cryptobiotic organisms are all microscopic: bacteria in cryptobiotic cysts can hibernate for centuries in unlikely places like permafrost and bedrock, and encysted tardigrades (water bears) have been exposed to excessively lethal doses of radiation, and even to the vacuum of space, with no ill effects.
Compared to that, Selaginella lepidophylla may not seem impressive, but keep in mind that it's many orders of magnitude bigger than those champions. It's resurrection on a familiar scale, and it happens over and over again. Beat that, Lazarus.
Wednesday, January 11, 2012
Silly names: Holosteum
The members of Holosteum, a genus of plants otherwise known as jagged chickweeds, are all quite small and very fragile. The one species found in North America, Holosteum umbellatum, is a delicate little thing whose straight, upright flowering stems -- the tallest part of the plant -- top out at no more than about fourteen inches. It is easily knocked flat, trampled, or crushed. When it's pressed and dried for a herbarium specimen, it will fall apart if you even think about handling it roughly.
That fragility is proof positive that Carolus Linnaeus had a sense of humor. When he named the plant, he picked out an ironic Greek phrase: holos for "whole, entire" and osteon for "bone".
Yep. He basically named this little plant, whose skeleton crumples at the drop of a hat, the equivalent of "unbroken".
Source: FNA
Source: FNA
Monday, January 9, 2012
Silly names: Kodachrome bladderpod
Today's plant is Physaria tumulosa, a little member of the bean family with a very odd name. Its Latin name is normal enough, but its scientifically-accepted common name is -- I kid you not -- the Kodachrome bladderpod. That's straight out of the Flora of North America; it doesn't get much more official than that. I want to go and find one now, to see for myself where it got a name like that! Unfortunately, it's a species of conservation concern with a pretty limited range, so that might be harder than it sounds. At least it's in Utah, and not too far from me.
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Update: Barbara Ertter has pointed out that there's a more plausible explanation for the origin of this name. "Botanists can't take credit/blame for this one," she writes; "the common name is obviously derived from Kodachrome Basin, where there is even a Kodachrome Basin State Park." I stand corrected. As much fun as the idea of a ludicrously-colorful little Physaria was, I'll freely admit that a whole basin painted as bright as color film makes a delightful mental image too.
...I think I know where I'm going next time I visit Utah.
...I think I know where I'm going next time I visit Utah.
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