As winter approaches, the length of the day shortens, the temperature drops, and plants, including trees, can detect this change.
It is worth pointing out that leaves don’t
drop to the ground because they are dying ―
rather, the tree initiates an active process of clever recycling called senescence. A tree, like an oak for example, would struggle to survive through a harsh winter if it retained its canopy of leaves. ( ① )
It would risk damage from strong winter winds and would lose more water from its leaves than it could draw up from the frozen ground. ( ② )
If it didn’t
blow over, it would die of thirst. ( ③ )
It signals to them that it is time to lose their leaves. ( ④ )
First, however, trees carefully suck all of the useful nutrients out of the leaves and then, with surgical precision, block up that pathway into the leaves. ( ⑤ )
That blocked pathway at the base of the leaf stem creates a weakness and, in the wind, the leaves snap off and fall to the ground. * senescence: 노화
