Wednesday 13 December 2017

Helicopter seeds a good example of evolution at work

By Jim Hurley - Nature Trail

The 'helicopter' seeds of the Sycamore tree are now tumbling down in great profusion.
The 'helicopter' seeds of the Sycamore tree are now tumbling down in great profusion.

The first British-designed helicopter to fly and serve with the Royal Air Force was the 'Sycamore' so called, of course, as the rotation of the search and rescue craft was reminiscent of the rotating motion of the seeds of the Sycamore tree that are now tumbling down in great profusion.

The Sycamore is a member of the maple family of trees and is the most common representative of that family in Europe. It is not native to Ireland. Following its introduction here it became fully naturalised and spread rapidly so that it is now one of our most abundant tree species found in a wide variety of habitats.

Some regard the alien tree from mainland Europe as a weed but whether you love it or loath it, it is so widespread, so abundant and so successful at spreading its seed that it is here to stay and is now an integral part of the countryside.

Flowers on Sycamore trees are greenish-yellow in colour and are pretty unremarkable unless searched for among the fresh green foliage during the late spring. The fruit that follows is more obvious and is in two parts, each part bearing a single seed. Most remarkable is the long wing that develops from the style of the female flower.

The two wings diverge with the two seeds loosely joined in the middle. Sometimes the two fall together; sometimes they fall singly. As a fruit falls at this time of year, gravity pulls it down, the air resists the movement and pushes the single rotor up causing the wing to rotate and the fruit to helicopter itself away from the parent tree.

If it lands on fertile ground with soft soil, the fall from a height will often ensure that the seed is firmly stuck into the ground with its now redundant wing standing erect above it. Seeds are unlikely to grow immediately under the parent tree so the best helicopters that pilot their precious cargo of genes farthest from the parent tree stand the best chance of survival.

By that simple means or success or failure, nature selects the best helicoptering genes to survive and the less proficient to perish. Natural selection and evolution are not mere academic ideas, they are realities that are being acted out at present in tens of thousands of waysides, back gardens and public parks as countless millions of Sycamore fruits and seeds are dispersed throughout the countryside.

Wexford People

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