Plants need water to produce leaves. In trees, this process is looked after by an extended system of waterways depending on how high the plant is growing. Keeping all this going needs a lot of energy. So energy conservation is key to what is going on.
The mechanism in trees to allow moisture being transported against gravity is far more complex than many would think. Transporting water to the very tips of the leaves is a sophisticated system. A loose comparison with the complexity of the artery system as found in the human body would not be too far off the mark. But there is a marked difference. Humans cheat by using a pump: The heart.
Consider the extraordinary route droplets of moisture collected from the soil have to take to reach the uppermost branches of a 200 ft beech tree. The energy doesn't come from a pumping mechanism hidden in its roots or trunk. The roots serve mainly as an anchor for the tree in the ground and allow it to stand upright. The energy comes from microscopic root hairs found at the extremity of the tree's vast root system.
The water from the soil eventually finds its way to the leaves, where it is converted to sugars and starches by the action of sunlight (photosynthesis) and using carbon dioxide drawn from the atmosphere. At the base of each leaf is found a group of cells called ‘abscission cells’ through which the tubes carrying this water pass and through which they return the converted sugars back to the tree to sustain its growth and health.
It is these cells that swell and choke the transport tubes thereby cutting off the flow from leaf to tree. The result is the coloration of leaves and their fall that we experience spectacularly each autumn. The cause that triggers this kamikaze effect is still not understood by botanists. The common view is that lower soil temperatures shut off the osmotic process that takes in moisture through the root hairs, thereby cutting off vital nutrients to the tree.
Yet the higher temperatures we have experienced with late summers and early winters contradict this theory. In fact, deciduous trees across the country shed their leaves in September and October regardless of the weather’s volatility, just as they have done for millions of years.
Weaker sunlight is also thought to have an effect on the two-way transport of water and sugars between leaf to tree by closing down photosynthesis. However, we seem to be having more sunny days than we had throughout much of the summer, yet we see beech trees closing down for the winter, displaying glorious gold foliage.
What is certain is that trees do not waste energy in performing unnecessary tasks. Beech saplings in plantations will retain their leaves throughout winter to protect the young plants from the ravages of winter. As beech hedges are trimmed regularly, and thus emulate the vulnerable sapling in as much as they are never allowed to reach full growth, they too retain their leaves.
Consider the extraordinary route droplets of moisture collected from the soil have to take to reach the uppermost branches of a 200 ft beech tree. The energy doesn't come from a pumping mechanism hidden in its roots or trunk. The roots serve mainly as an anchor for the tree in the ground and allow it to stand upright. The energy comes from microscopic root hairs found at the extremity of the tree's vast root system.
The water from the soil eventually finds its way to the leaves, where it is converted to sugars and starches by the action of sunlight (photosynthesis) and using carbon dioxide drawn from the atmosphere. At the base of each leaf is found a group of cells called ‘abscission cells’ through which the tubes carrying this water pass and through which they return the converted sugars back to the tree to sustain its growth and health.
It is these cells that swell and choke the transport tubes thereby cutting off the flow from leaf to tree. The result is the coloration of leaves and their fall that we experience spectacularly each autumn. The cause that triggers this kamikaze effect is still not understood by botanists. The common view is that lower soil temperatures shut off the osmotic process that takes in moisture through the root hairs, thereby cutting off vital nutrients to the tree.
Yet the higher temperatures we have experienced with late summers and early winters contradict this theory. In fact, deciduous trees across the country shed their leaves in September and October regardless of the weather’s volatility, just as they have done for millions of years.
Weaker sunlight is also thought to have an effect on the two-way transport of water and sugars between leaf to tree by closing down photosynthesis. However, we seem to be having more sunny days than we had throughout much of the summer, yet we see beech trees closing down for the winter, displaying glorious gold foliage.
What is certain is that trees do not waste energy in performing unnecessary tasks. Beech saplings in plantations will retain their leaves throughout winter to protect the young plants from the ravages of winter. As beech hedges are trimmed regularly, and thus emulate the vulnerable sapling in as much as they are never allowed to reach full growth, they too retain their leaves.
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Hi, great reading your post
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