Friday, August 10, 2012

It is possible, using only materials that can be found in the average garage or hardware store, to completely foil a plant's sense of gravity. You can grow plants in orbit from your backyard.

Wednesday, June 6, 2012

Glasswort by any other name: Salicornia

Yesterday we saw the most obvious way for a plant to deal with excess salt -- by taking it up and then immediately getting rid of it. That strategy works, as the dunegrasses' success can attest, but there's more than one way to peel an orange. Today, let's have a look at Salicornia, a genus with a lot of names (glasswort, pickleweed, sea pickle, marsh samphire, pousse-pierre...) and one interesting way of dealing with salt.
Salicornia virginica in flower.
The blossoms are those tiny
stringlike structures at the ends
of the branches.

Salicornia plants are odd-looking little things, though you might have to get close to see very much; most species don't get much larger than a foot tall. With their thick, succulent stems and tiny, scale-like leaves pulled in close, they look mostly leafless, and indeed the stems do most of their photosynthesis. Some species are edible, sold as a delicacy under the names "sea beans" or "samphire greens"; it's also been used in the glass industry, as a source of soda ash. These two uses, as a salty food and as a source of sodium carbonate, betray one important fact: mature Salicornia plants are chock full of salt. Yes, it's the same salt you're thinking -- sea salt, table salt, salt that sucks the water right out of living things.

How do they manage it without dying of dehydration? Glassworts, it turns out, have a special modification to their cells' vacuoles. Virtually every plant cell has a vacuole; it's essentially just a large membrane-bound bubble in the middle of the cell, which the cell uses to store water, control its size, and dump substances it doesn't want. For Salicornia, those substances include salt. It can keep salt locked up in the vacuole even when the concentrations inside are many times that of the rest of the cell, high enough that most plants couldn't keep the stuff contained and would die of dehydration. For these tough little oddballs, it isn't a problem; they just go on doing their thing with bubbles of saline death locked down right in the middle of every cell.

Hence their names: pickleweed for the salty flavor, sea pickle for the tolerance to ocean salinity, glasswort for being so rich in salt that the glass industry once used them as sodium collectors.


Image source: Folini, Franco. American Glasswort (Salicornia virginica) (6122382261). Retrieved 6 Oct 2014, from Wikimedia Commons: <http://commons.wikimedia.org/wiki/File:American_Glasswort_(Salicornia_virginica)_(6122382261).jpg>

Tuesday, June 5, 2012

A sparkling coat of death: saltwater cordgrass

Word-association time! Answer this question with the first thing that comes into your head: What does one do with watermelon seeds?

If you're like me, or like millions of other Americans who grew up where melons could be had, you probably answered something like "spit them". When we eat watermelons1, we eat a big bite of delicious fruit and are left with the inedible seeds. Those, we spit out. (If you're a kid and it's a lazy summer afternoon, you have contests to see who can spit them the farthest.) We've taken in the part that nourishes us (yum, watermelon!) and gotten rid of the part we don't need (ptui, seeds).

Now what if the seeds were poison, and watermelon were the only thing we had to eat? We'd be like  saltwater cordgrass (Spartina alterniflora). Native to the east coast of the USA, this plant grows in coastal sand dunes, where the only water available to it is thick with salt. In a habitat like that, most grasses quickly shrivel, drinking deep of seawater and still dying of dehydration. Spartina, though, thrives.

Spartina leaves. See the clumps of salt?
How does it manage? Like a person eating a slice of watermelon and spitting out the seeds, Spartina takes in seawater and actually spits out the salt. Specialized glands on its leaves exert a force stronger than osmosis, drawing the salt out of the water it sups, and excrete it onto the leaf surface in crystalline form. Until the rain washes them away, these crystals sit on the leaves and sparkle, visible to the naked eye.


Image source: Field Studies Council. "Spartina." Retrieved 10 Aug 2012 from <http://www.theseashore.org.uk/theseashore/Saltmarsh%20section/species/Spartina.html>

1. The older cultivars, not the new "seedless" ones.

Monday, June 4, 2012

Salt Lovers' Week: meet the halophytes

Water, water everywhere, nor any drop to drink... Coleridge knew it, sailors have always known it, and anyone who's been to the beach certainly knows it: salt water is no drop to drink. Water with as much salt as is found in seawater can, in fact, be lethal. It literally dehydrates the drinker,1 making you thirstier even as you guzzle it down. Humans can't survive on salt water.

Neither can plants, and for much the same reasons. Salt water dehydrates them just as it dehydrates us, sucking the moisture out of their tissues and leaving them to wilt and die. There's a reason that ancient armies would salt an enemy's farmland if they wanted to destroy it utterly: salted ground can't support crops. Not even barnyard weeds will grow in land seeded with salt.

Like virtually everything in biology, though, this prohibition isn't absolute. Salty ground is harsh and unforgiving, but many species of plants -- halophytes -- have grown to live in it anyway. Dunegrasses take up the salt, then spit it right back out. Glasswort takes it up, puts it aside, and lives with it anyway. Tamarisks can tolerate salt well enough to take over the salt-crusted desert waterholes of the American West. Some plants can even live fully immersed in extremely salty water -- they must have managed it, if they were to survive the primordial oceans.

This week, look for a post each day, each dealing with one of these extraordinary plants as it thumbs its nose at the killing salts.


1. By osmosis. If you have two aqueous solutions (things-dissolved-in-water) side-by-side, the water will tend to move from the less-concentrated to the more-concentrated one. The liquid in your tissues has less stuff dissolved in it than seawater does, so the salt water literally sucks the water out of your body. Nasty.

Friday, May 4, 2012

The largest herb in the world is the banana "tree". Since it never forms true wood, or even anything closely analogous to wood, it's not a tree but a herbaceous plant... admittedly, one that can grow to almost 8 meters tall!

Wednesday, May 2, 2012

What we call "a flower" isn't always just a flower. Often, it's actually a mass of several, tens, or even hundreds of tiny flowers -- an inflorescence -- condensed until it looks like one unit, sometimes with extra "petals" formed from tissues that aren't flowers at all. Jack-in-the-pulpit, dandelions and daisies, and poinsettias are all good examples of this particular weirdness.

Friday, April 27, 2012

Plants get sunburn, too, and it's bad for them for a lot of the same reasons that it's bad for us: it damages their DNA, frequently killing cells outright. To fight sunburn, they actually make natural sunscreens -- chemicals called flavonoids, which are transparent to visible light but opaque to dangerous UV.

Wednesday, April 25, 2012

The vast majority of wood is actually dead tissue -- but that doesn't mean it's not important. Just as hair or fingernails matter to a human, a tree would miss its wood very badly if the dead part were gone.

Tuesday, April 24, 2012

The delicate, translucent leaves of filmy ferns (family Hymenophyllaceae) are only one cell thick -- but some of them grow to over half a meter long!

Announcement: a new format

First off, I'd like to apologize for the Daily Cypsela's recent unannounced hiatus. It seems that a full-length post every day, on top of a full-time job and assorted other responsibilities, hobbies, etc., is more than I can really handle. As such, the Cypsela will, from now on, no longer be truly Daily. I really am sorry about that.

That does not, however, mean that this blog is to be abandoned. A full-length post every day may be too much, but a full-length one once or twice a week is completely manageable. Also, I plan to fill some of the gaps with entries even more like cypselae than the longer posts: little fun-fact sound bites, things that will fit into Facebook statuses or even tweets. Some of these mini-posts (tagged "cypsela") will be teasers for later full-length posts, in which I'll elaborate on some botanical wonder that the earlier blurb just pointed to.

We'll see how well the new schedule works out. Comments are, as always, very welcome.

And now, back to our semi-regularly-scheduled programming...

Wednesday, April 18, 2012

Hair-triggered suction traps: the bladderworts

A clump of Utricularia
vulgaris
 in flower.
Innocuous, right?
From above the water surface, a clump of bladderwort (Utricularia spp.) doesn't look much different from other common pondweeds like milfoil: a mass of feathery green leaves floating a little below the surface. In season, it lofts a cheery yellow or purple flower high above the water. It's a pleasant little denizen of its low-nutrient bog habitat.

Below the water, and at a much smaller scale, is where things get interesting. Look closely at those fine feathery leaves. Find the little rounded bladders that cling to them all over. Those aren't some kind of parasite -- they're part of the plant. In fact, they're its means of trapping prey.

The bladders, when they first develop, have a near vacuum inside. Their trap-door openings stay firmly shut, maintaining that suction-cup strain. Just outside the door, poking into the water like delicate whiskers, are one or more tiny hairs. Those hairs are fine triggers, poised, connected to the door.

When a water flea or tiny insect larva trundles by, brushing against those hairs -- snap! The trap door pops open, sucking water into the bladder, and the prey is swept along with it. The door snaps shut a fraction of a second later. By now, you can probably predict the end result: digestive enzymes, liquid bug, and the plant gets a very necessary dinner. Without the traps, the plant's growth slows dramatically, as it can't get enough nutrition from the acidic, nutrient-poor water of its native bogs.

Bladderwort traps are powerful things, especially for their size. If the plant is removed from the water (say, by a curious human), it often comes out with a spatter of audible crack! sounds: its traps springing shut on empty air.


Image source: Hillewaert, Hans. Utricularia vulgaris. Retrieved 17 Apr 2012, from Wikimedia Commons: <http://commons.wikimedia.org/wiki/File:Utricularia_vulgaris.jpg>

Tuesday, April 17, 2012

Sparkly but lethal: the sundews

The sundews, Drosera spp., set a wholly different sort of booby-trap for their prey. They do not move to trap it, not as dramatically as Venus flytraps do, but like Venus flytraps they depend on the hapless insect landing directly on their leaves.

Those leaves are beautiful, to the unwary: they sparkle in the light, giving the genus its common name. Those drops of liquid on their little stalks aren't just dew, though. For one thing, they're nectar-like, full of tasty sugar. Any hapless insect that lands to sip the bounty, though, will find out something else about them: they're sticky.


A Drosera capensis leaf bending to surround
and digest a trapped fly. Normally the leaves
are more or less straight.
A bug tricked into landing on a sundew leaf is quickly and effectively glued down, unable to free itself. Even if it only brushed one sticky droplet, the stalks bearing other droplets -- appropriately known as tentacles -- move towards it, glomming many other droplets onto its body. Some sundews can snap these tentacles into place in fractions of a second, faster than any prey can respond.

The prey's futile struggles inevitably kill it, either through exhaustion or through suffocation as the sticky lures clog its breathing. Slowly, then, the tentacles begin to tug on its body. The leaf curls inward around its trapped insect, and the glands that secreted the sugary lure start to secrete digestive enzymes. The prey is reduced to a nutrient soup, which the plant absorbs through other glands on the leaf surface. Dinnertime for the sundew.

Like all carnivores, though, these plants aren't being vicious. Drosera roots are effectively useless for nutrient uptake: without the nutrients they capture from their prey, they would sicken and die very quickly. It's all perfectly natural -- beautiful, even, in the fierce and sharp-edged way that nature so often is.



Image source: Elhardt, Noah. Drosera capensis bend. Retrieved April 16, 2012, from Wikimedia Commons: <http://commons.wikimedia.org/wiki/File:Drosera_capensis_bend.JPG>

Monday, April 16, 2012

Don't fall in: the pitcher plants

Nepenthes edwardsiana pitcher.
Steer clear, if you're a bug.
Venus flytraps are the most famous carnivorous plants, probably because they're so very active in their hunting. They're the only species that is. Most carnivorous plants don't set bear traps so much as booby traps, with the classic example being the pitcher plant.

Pitcher plants belong to five different genera in three different orders1, completely unrelated to each other, which is always a sign that something about them is adaptive (it works well enough to be "invented" independently). All of them share a common means of catching their little flying vitamin pills. They grow modified urn-shaped leaves -- "pitchers" -- with downward-pointing hairs or intricate grooves on their inner walls and a few milliliters of liquid in the bottom. The pitchers look or smell somehow enticing to their prey (some Nepenthes even produce sweet nectar as a lure), but the lure is just that: bait.

An insect that blunders into a pitcher plant's pitcher is usually doomed, as pitchers are very effective traps. Their walls are slippery and often grooved or covered with downward-pointing hairs, so that trying to climb out is like trying to force your way through a vertical hedge to climb a wall of slick ice. The trapped insect is forced into the pool of liquid at the bottom, where it eventually drowns.

Drowning isn't the end, though, because that liquid isn't just water. It's a solution of acid and digestive enzymes, much like the contents of a (much-diluted) human stomach. A drowned bug will be dissolved and digested over a period of days or weeks. The plant will absorb its nutrients through the walls of the pitcher, and hey presto! Dinner!

Contrary to popular belief, by the way, there is no such thing as a pitcher plant large enough to eat a human. The largest carnivorous plants in the world are pitcher plants -- Nepenthes rajah is the current champion -- but even they can't manage anything bigger than a small lizard or songbird.


Image source: Robinson, Alastair. Nepenthes edwardsiana entire ASR 052007 tambu. Retrieved April 16, 2012, from Wikimedia Commons: <http://en.wikipedia.org/wiki/File:Nepenthes_edwardsiana_entire_ASR_052007_tambu.jpg>

1. Nepenthes in the Caryophyllales; Heliamphora, Sarracenia, and Darlingtonia in the Ericales; and Cephalotus in the Oxalidales, in case anyone was wondering.

Monday, February 13, 2012

It's a leaf! It's a root! It's a... wait, what?

Tmesipteris elongata at Otira, New
Zealand. Looks pretty normal, right?
At a basic, developmental level, plants have only three types of tissue: leaves, roots, and stems. Everything else is modified from these. The trunk of a tree is just a modified stem. A potato's tuber is a modified stem, too. The grasping tendrils of ivies and peas are modified leaves. Each part of a flower -- each petal, sepal, stamen, and carpel -- is a modified leaf. I could go on for quite a while. Those three basic tissues have been modified into the whole dizzying variety of plant parts, and that is an enormously diverse variety indeed.

Sometimes, though, diversity isn't exactly what is needed, and plants simplify instead. Tmesipteris is a genus of unusual, "primitive" ferns, found only in a few scattered places in the South Pacific. To a casual eye, it looks as though it has all the usual parts of a fern -- roots, stems, leaves, and even the sort of spore capsules you'd expect on such an ancient lineage. It takes a much closer look, by which I mean microscopes and developmental analysis, to realize that something is odd there.

Those broad green structures along its stem, the ones that do most of its photosynthesizing? They're not leaves. The thready bits at its base, the ones that attach it to the bark where it lives? They're not roots.

Every single part of a Tmesipteris plant is, if you look closely enough, a modified stem.

At some point in the evolutionary past, this plant's ancestors found that leaves, roots, the whole shebang, were all -- for whatever reason -- unnecessary. As I pointed out before, evolution ditches unnecessary things pretty quickly. Why bother with leaves when you can just grow flat bits of stem, and they'll photosynthesize just fine? Why bother with roots when you can just grow thready stem-anchors, and they'll keep you nailed down just as well as you need? Other plants have found plenty of reasons to bother, but for Tmesipteris, there just wasn't a need. It's gotten along very well this way for something like 400 million years, thankyouverymuch, and it has no reason to change now.


Image source: Liefting, Alan [Public domain]. Tmesipteris elongata. Retrieved February 12, 2012, from Wikimedia Commons: <http://commons.wikimedia.org/wiki/File:Tmesipteris_elongata.jpg>

Wednesday, February 8, 2012

The elements of life

Plants are, in large part, literally defined by photosynthesis. It's practically alchemical, that ability to live on just air and water and sunshine. Yes, we know precisely how the process works -- it's a complex chain of chemical reactions whose details I won't discuss here -- but that doesn't remove the wonder. Photosynthesis produces the sugars that fuel a plant's metabolism and make up the building blocks of its structure. It is the source of well over 90% of a plant's mass.

Now consider this: that mass is mostly pulled out of thin air.

Let me explain, and bear with me for a minute. Photosynthesis, to make it simple, takes water from the soil and carbon dioxide from the air, then uses energy from light to pull an oxygen out of them and rearrange their remaining atoms into sugar. The overall chemical equation looks like this:

6CO2 + 6H2O + energy --> C6H12O6 + 6O2

Six molecules of carbon dioxide plus six of water plus energy are rearranged to give one molecule of glucose -- sugar -- and six of oxygen. There are quite a lot of intermediate steps, but this is what you get when you look only at what goes in (CO2, water, sun) and what comes out (sugar, oxygen).

The really fascinating thing, when you think about it, is where each of those atoms comes from and where it goes. All the carbon and oxygen atoms in the sugar come from CO2: the ones from water are thrown away as oxygen. Water only contributes hydrogen, which is important but not very heavy -- about 4% of the sugar's mass. Sunlight is absolutely crucial to the process, but it contributes energy, not matter. In the end, fully 96% of the sugar's mass comes from carbon dioxide.

That's what I mean when I say that most of a plant is made of thin air. Nearly 96% of its mass comes from just that. The rest comes from water, plus a fraction of a percent from trace minerals in the soil. Air, water, and soil, all of it held together with sunlight: it's the stuff of life.

That's not just true of plants, either. In virtually every biome on Earth, plants form the bottom of the food chain. The sugars they make provide energy for them, and for the herbivores that eat them, and for the carnivores that eat the herbivores, and so on. Almost every living thing is ultimately made of plant matter. We are made of plant matter: everything humans eat can be traced back to a plant.

When you get right down to it, then, all life on Earth is made of very simple things. We are air and water and a little bit of soil, all held together with sunlight.

Tuesday, January 31, 2012

A literal hair-trigger: Venus flytraps

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.

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.

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.

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!

Wednesday, January 25, 2012

Mother-of-millions

A healthy adult B. daigremontianum
Bryophyllum daigremontianum, AKA "mother-of-millions" and formerly known as Kalanchoe daigremontiana, has a rather unusual means of cloning itself. It's not unusual because it produces whole new plantlets -- root, stem, and leaf -- that are ready to grow the moment they fall off the parent. No, the production of complete plantlets isn't uncommon. Strawberries and spider-plants do that, and profusely, sending out questing plantlet-tipped runners (stolons) in every direction; and they're just two of the more familiar cases.

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.

Tip of a B. daigremontianum leaf, plus 15 clones.
Aww, look at their little bitty rootlets!
I keep a potted Bryophyllum daigremontianum in my living room. It needs a lot of sunlight but very little water, and thrives to the point that unless I keep it separated from my other houseplants, I am forever having to pluck freshly-rooted clones out of everyone else's soil. Anyone looking to adopt one of these need only let me know.


Image sources: Wikimedia Commons.

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.

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!

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

Thursday, January 19, 2012

Back in my day, everybody had cones!

A Pinus longaeva, showing its age
The intermountain bristlecone pine, Pinus longaeva, is thought to be the longest-lived tree in the world. One tree was estimated to be over 5,000 years old. It's not a common species, found in a few disjunct patches scattered through Nevada, California, and Utah; nor is it impressive in size or appearance like the giant sequoias or aspen forests. There are older single organisms out there, and larger ones: Pando, a quaking aspen forest in Utah that's all a single individual below ground, has been estimated to be over 80,000 years old. Still, for sheer age of a single trunk, you can't beat the bristlecone pine.

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!"

    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.

      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.

      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 tetrancista -- 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. tetrancista 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.

      Look closely at this photo, and especially where the arrows are pointing. Note the curls of sickly green stem coiling from the apex of that dried cactus pad. Their color isn't very healthy, but yours wouldn't be either if you'd been lying between sheets of paper in an opaque cabinet for fourteen months. There's a rootlet, too, sprouting from the base of the dried pad. They aren't growing very fast, but that's not surprising either, given that they're surviving on nothing but what food and water the cactus had stored on the day it was picked.


      Source: CIC Herbarium

      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

      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.

      Sources: FNA

      ---

      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.