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.

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.

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...

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>

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>

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.