The Indian Express (Delhi Edition)
Ferocious Plants
For their survival, some plants kill, others even turn into parasites
Plants can be more ruthless than a hungry lion tackling a zebra. This usually happens in slow motion
W
E MIGHT think of plants as quiet, passive peaceniks, surviving on water, minerals, carbon dioxide and sunlight. But really, plants can be more ruthless than a hungry lion tackling a zebra. We don’t see what’s happening because it usually happens in super slow motion. A lion may kill in a matter of minutes but a plant takes its own sweet time…certainly not pleasant for its victim.
On the top of the list of ferocious plants are, of course, the carnivorous ones, from the renowned sundew family. One illustrious member is the Venus flytrap, which uses a deadly gin trap design in its leaves, backed up by a timing mechanism that ensures it doesn’t snap shut when say, a raindrop falls on it, but will, if it’s a fly. Naturally, there is bribery involved in the form of sweet sticky nectar — literally, a honey trap. And then, the truly evil part of the process begins — the slow dissolving of the frantic insect in digestive juices and enzymes.
There are a whole host of such plants, each with their own devious traps. Some like the notorious Nepenthes rajah may grow 41 cm high and 20 cm wide, its tankard-like bloom holding up to 3 litres of nectar-water, and another 2.5 litres of digestive juices, into which insects and thirsty rodents, lizards and small birds fall, drown and dissolve. But one small species of shrew has struck a deal with the plant: it sips the nectar and defecates in the tankard, supplying the plant with much-needed nitrogen.
In defence of these kattar carnivores, they grow in marshy, boggy areas that are low in nutrients. As long as they show that they are non-sentient, there’s
no deliberate cruelty involved because they are not aware of being so. Many other creatures use even more gross ways of consuming their meals: spiders inject enzymes which dissolve their victims’ insides and suck up the resultant smoothie (the victim is usually dead by now) and starfish extrude their stomachs over their victim, digest it and then draw it back into their bodies.
But plants can (and have to) be ferocious with other plants too. In dense forests, very little (as low as 2 per cent) sunlight reaches the forest floor. Without the sun, no plant can survive. So, every plant aims to get as high up in the forest canopy where its leaves, usually broad, can catch as much of the sun, as quickly, as possible. To do so, these lianas and vines will wind around other supporting plants and trees and throw lassos across trees to form bridges (useful for small animals). They are rooted in the ground and compete ferociously with the supporting plant for nutrients, water and sunlight. They stunt the host tree’s growth and ability to produce seeds.
One of the most notorious of this clan is the strangler figs — the banyan being one among them. A bird deposits a sticky seed high up in a tree, the seed puts down a root, and sends up a stalk, with leaves. More roots emerge, clasping and encasing the trunk of the host tree like a nest full of pythons, gradually garroting it, while up above its leaves successfully compete with the host tree’s leaves for sunlight. For the host tree, it is death by slow strangulation and as its trunk rots away. All that is left is a fretwork of freestanding prop roots, hollow at the centre; always a rather disconcerting sight. The banyan could be forgiven because it is a keystone species, (the kalpavriksh or the tree of life) and supports a host of insects, animals and birds providing shelter, shade, leaves and figs.
Epiphytes, like orchids, ferns and mosses are not quite as deadly. While they do grow from the trunks and branches of trees, using them for support, they get their sustenance from the leaf debris and rainwater that collects in the canopy. They are shallow-rooted and easily removed. As parents too, many plants have to be cruel to be kind. No tree or plant will permit its progeny to grow near it — if a seedling is dropped close to its parent, it will not be allowed to germinate until its parent dies because the mama plant hogs all the sunlight, water and food. So, parent plants have devised several ways to send their progeny far away. They may explode their seed pods like bombs (like the Himalayan balsam), scattering the seeds like buckshot or use sweet temptations in the form of juicy fruits that animals and birds (and us) can’t resist, so they are eaten and the seeds are deposited far away. They may equip their seedlings with wings or even parachutes that catch the faintest breezes.
Trees also use the ‘wood-wide-web’ to exchange nutrients via hyphae, filamentous fungi threads at the ends of their roots, helping each other in times of need. But they may also send poisons through these hyphae if they sense dangerous competition. Many plants are armed with thorns, prickles and poisons. Every plant has the right to defend itself!