The leaves of woody plants consist of the stalk or petiole and the lamina or blade. The petiole facilitates movement and positioning of the leaf. The blade is the part where photosynthesis, respiration and transpiration take place.
Atmospheric carbon dioxide is the tree's main source of food. Together with water and by the means of chlorophyll and radiant energy from the sun it is processed by the leaf cells into organic compounds that go into building the major part of the tree's organs. This process is known as photosynthesis.
Because the amount of carbon dioxide in the air is very low (0.03 per cent on average), the tree has to process great quantities of air. This must take place on the greatest possible leaf surface, which is why the leaves of woody plants are so thin, and why a mature tree has tens or hundreds of thousands of them.
To make the most of the sun's energy the leaves are spread out as advantageously as possible, this being aided both by the complex network of branches and by the varying lengths and positions of the stalks.
In comparison with non-woody plants they have the great advantage of height and longevity. Before man introduced intensive land cultivation most of the Earth's surface was covered with forests. Even today the forest would soon reclaim the land, should man cease to tend and cultivate it. This is borne out not only by examples in tropical Africa and southeast Asia, but also by all the lands in Europe that have been left lying fallow.
Only where insufficient rainfall, high temperatures or severe winters and frozen soil prevent the growth of trees do they leave such areas to grass, shrubs and succulents.
Atmospheric carbon dioxide is the tree's main source of food. Together with water and by the means of chlorophyll and radiant energy from the sun it is processed by the leaf cells into organic compounds that go into building the major part of the tree's organs. This process is known as photosynthesis.
Because the amount of carbon dioxide in the air is very low (0.03 per cent on average), the tree has to process great quantities of air. This must take place on the greatest possible leaf surface, which is why the leaves of woody plants are so thin, and why a mature tree has tens or hundreds of thousands of them.
To make the most of the sun's energy the leaves are spread out as advantageously as possible, this being aided both by the complex network of branches and by the varying lengths and positions of the stalks.
In comparison with non-woody plants they have the great advantage of height and longevity. Before man introduced intensive land cultivation most of the Earth's surface was covered with forests. Even today the forest would soon reclaim the land, should man cease to tend and cultivate it. This is borne out not only by examples in tropical Africa and southeast Asia, but also by all the lands in Europe that have been left lying fallow.
Only where insufficient rainfall, high temperatures or severe winters and frozen soil prevent the growth of trees do they leave such areas to grass, shrubs and succulents.
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When a garden seems a part of the house visually, plan the garden so that its style match that of the inside.
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