People say that plants are insensate, unintelligent things. I beg to differ. Sure, they can’t play chess or compose music, but neither can a lot of people I know. Plants are very clever. They can’t move, but they can adapt to their environments. Survival is surely an intelligent skill.
I’m talking in particular about carnivorous plants. Most people have heard of the Venus Flytrap, but that is only one of about 630 species. Because they found themselves growing in environments that could not provide what they need to survive, they adapted instead of dying out. These plants get most of their nutrients by trapping and consuming little living creatures, mostly insects and bugs. They do this using five different kinds of trapping mechanisms: pitfall traps; flypaper traps; snap traps; bladder traps, and lobster-pot traps.
Pitcher plants are one kind of plant that use pitfall traps, which involve a rolled leaf with sealed margins. These leaves secrete bacteria or digestive enzymes which consume the creatures who investigate them. One type of plant from this group – the genus Nepenthes – has a plant who can devour small mammals and reptiles. The species sarracenia flava offers an enticing nectar that is laced with coniine, which is also found in hemlock, thus intoxicating its prey. Another of the members of this group is a bromeliad, related to the pineapple. Since it collects water in the “urns” formed by the leaves, it becomes a habitat for frogs and insects, as well as a breeding ground for bacteria. How multi-faceted is that – habitat, breeding ground, and food collection site?
Flypaper traps have leaves with a sticky mucilage. These leaves can trap small insects, such as gnats, but larger ones can usually get away. Some of the plants in this group are capable of moving their leaves by a chemical process in reaction to prey. Additionally, some of the plants in this group are only carnivorous while young, and it is thought that they need their prey specifically for flowering, and then they give up their evil ways.
Snap traps include the infamous Venus Flytrap. This group of plants has trigger hairs which, when bent by the weight of prey activate a mechanism that allows the lobes of the plant to snap shut in less than a second. So smart is this plant that it is able to identify true prey from a drop of water or dust. It waits for something that triggers it twice, 0.5 to 30 seconds apart, before it closes its lobes. As its prey struggles the lobes form a tight seal where digestion, a process that can take a week or two, takes place. The lobes become ineffective after three or four times.
Some plants suck. Literally. Bladder traps have long trigger hairs that, when touched, create a vacuum that draws in its victim, aided by water. Bladderworts have multiple bladders, and are often aquatic. One type of aquatic bladderwort actually regulates how many bladders it needs for its particular habitat. Intelligent and practical, to my mind.
A lobster-pot trap has inward-pointing bristles within its chambers that obstruct prey from exiting. Prey is forced to move to an inward stomach where digestion occurs. It devours aquatic protozoa. Because it also uses water to aid in trapping its prey, it may be evolutionarily related to bladder traps and their vacuum/water mechanisms.
Carnivorous plants can be cultivated with care. Because they developed in nutrient poor soils they are somewhat chalky, so common tap water can kill the plants from the build-up of minerals, in particular calcium. Therefore they need rainwater, distilled water, or water deionised by reverse osmosis. Because most of these plants come from bogs, giving them enough water is essential to their health and growth.
Carnivorous plants that are grown outdoors can usually feed themselves. Insects can be fed by hand as a supplement. If they catch no insects they will probably not die, but their growth will be stunted. They will die, however, if fed non-insect bits, such as hamburger or cheese bits. They are unable to digest these and the meat will rot, killing off the plant, or parts of it. Playing with their trapping devices will eventually kill them, too, so resist triggering them no matter how fascinating they are.
Most of these plants require bright light in order to synthesize pigments. Most also require high humidity, so place these plants on a saucer with pebbles and water. Since carnivorous plants are found all over the world except Antartica, most of them can survive cold temperatures. They require nutrient-poor soil, so a 3:1 mix of sphagnum peat (or coir) and horticultural sand is a good medium.
Oddly, carnivorous plants are susceptible to infestation from parasites like aphids or mealybugs, so these need to be cautiously removed, either by hand, alcohol or some other benign way. Grey Mold, which thrives in warm and humid conditions, is the biggest killer of these plants, and can be a deadly problem during winter. If the plants are kept cool and well-ventilated, and the leaves are dead-headed, this can be avoided.
A study from Tel Aviv University in 2009 states that secretions of the plants have compounds with anti-fungal properties which could lead to anti-fungal drugs for infections resistant to current ones.
Intelligence is open to interpretation according to your definition of it. As I learn more about animals, and now plants, my definition is becoming more and more open.