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Tuesday, May 17, 2022

What happens when a tree explodes like a dynamite stick

It’s how several species prompt their seeds to leave home and germinate

Written by Ranjit Lal | New Delhi |
May 11, 2022 11:30:28 am
dandelionDandelion seed pod. (Source: WikiCommon)

Most (sensible) parents can’t wait for the day when their loutish teenagers finally decide to pack up and leave home because they “want to be independent” and live their own lives. Nor can most animal parents. Once the pup or kitty can fend for itself – it is turfed out of its parent’s territory. This is especially true of boys who can become obnoxious and pose a leadership challenge for their fathers. True, in some animals – like elephants – the girls remain with their mothers even when mature, but go out with roving boyfriends when the need arises. It’s easy for animals (and us) to move away – we just walk away. But how do plant parents get rid of their often hundreds if not thousands of young who like them are stuck in one place forever? They must, because some plant parents will not allow their progeny to mature if they stick around close to them – like parents who remain in helicopter mode all their lives. And sometimes, they have to literally kick butt to get rid of their clingy young. So how do these seeds get away?      

Well, like us they travel by air, by water and overland! They may parasail, flutter like drones, drift on the oceans for months together or hitch a lift with passing animals. A little while back, the silken seed pods of the silk cotton tree were wafting down everywhere: it’s worthwhile taking a close look at their beautiful and delicate design and construction. A whiff of breeze and it’s bye-bye mama, we’re off! And we’ve all experienced (or should have) the pleasure of blowing on a dandelion puffball and watched the tiny silk parachutes take off into the wild blue yonder; something filmmakers and photographers have used when they have a smitten, dreamy heroine around! 

Silk Cotton Tree Flowers of silk cotton tree. (Bombax Ceiba) (Source: WikiCommons)

Some seed pods of lianas growing in tropical forests are attached to tissue-thin membranous wings that are so aerodynamically perfect that they can float vast distances even in still air –and whose design our aerodynamic engineers are still trying to figure out. The seed pods of the sycamore are attached to helicopter-like vanes which spin when the seed falls free, taking it far away from its parent. 

As for the seafarers there is, of course, the coconut. Very helpfully, the parent – the tree – will lean towards the ocean or river as far as it can – and then drop its bombshell baby with the hope that the tide or current will catch it and bear it away. Heavy though it is, it floats and can do so without disintegrating for over three months by which time it is castaway on some distant shore where it can start a life of its own.

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Then, of course, there are the hippie-gypsies: those seed pods armed with hooks and burrs, or are just plain sticky which cling on to your clothes – or fur and travel with you, until you pull or scratch or shake them off. Walk through grassland or scrub and you’ll find your jeans covered with these seeds – all seeking a better life. Some of these can be really ferocious, getting their hooks deep into you, and drawing blood.

Some alas, show no desire to leave the comfort of their parents’ home – and literally have to be kicked out. Apparently, the Himalayan balsam is one such; the seeds stay put inside the pod, where like in a pressure cooker the pressure builds up – due to evaporation – then boom!. The fruit of the dynamite tree (Hura crepitans), explode like a stick of dynamite flinging its seeds 100 meters away. There are several species in Africa, which actually need fire to prompt the seeds to leave home and germinate. 

Perhaps the least prepossessing way of leaving home, which thousands of plants use – is literally by being eaten. With devious cunning, the parent plant will cover its beloved seeds with a sweet (often red, orange or yellow), juicy pulpy flesh – the fruit – which ripens in the sun, enticing monkeys, elephants, birds of all sorts, reptiles, ourselves et al to take a bite. Usually, the seed is just spat out – or makes the revolting journey through the steamy intestines of the predator and is evacuated from its nether end! What a way to make an entrance and start a new life! In fact, the seeds of some African acacias must go through this rite of passage – through the enormous gut of elephants in order to survive. The journey through this rumbling churning charnel of a tunnel kills beetle grubs which would otherwise kill the seeds themselves. And be warned, in many cases, such as in apples, while the fruit might by sweet and delicious, the seeds themselves are bitter and may be poisonous. Some seeds, like that of a mango I planted in the garden are lucky: they grow and are looked after and cosseted over every day. 

Of course, in many cases – like in pine trees – the cones fall beneath their parents towering mass. Here they must wait, until the parent tree dies and falls, and then there is a desperate race amongst the seedlings to shoot up and fill up the sky space that has just opened up, so they can get life-giving sunlight. In temperate countries, animals, like squirrels, will snatch up acorns and stash them away for the winter. They have formidable memories and will eventually retrieve (and eat) most of them, but some will get away, and begin to grow next summer. 

So yes, for some, leaving home is a breeze, for others Russian roulette, and yet others a trip up shit creek!

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