what are the tree leaves for ?

composed of roots that give it sitting in the soil and which extract water of soil and minerals, a trunk (or drum), which supports the crown, and where the sap flows, and crown, all the branches and leaves, to ensure exchange with the atmosphere. The purpose of the tree, if there is one, would be would to grow up and enlarge the trunk, to better carry the weight of the crown. For this, it must make the wood carbon structure (cellulose). Carbon is extracted from the air, the famous carbon dioxide (CO2) is naturally present (0.3%) and rejected by human activities. Not to be confused with carbon monoxide, which in turn, destroys forests. The separation of carbon from CO2is made by the leaves:

The leaves capture CO2and mineral ions through the stomata, located bellow (they are not blocked by dust). It has between 10 and 200 per mm ² (knowing that a tree is making a thousand square meters of mature leaves, what is the number of stomata? .... between 10 and 200 billion). The air sucked through the stomata is attacked by sap flowing through the leaves. The sap contains primarily water, pumped into the ground by the roots (aided by evaporation in the leaves because evaporation created a depression). If the air is saturated with moisture, the roots repress ground water, creating a local overpressure. In the presence of water (H2O), the CO2 molecule is broken into carbon and oxygen. Oxygen (O2) is released into the air. Carbon, hydrogen associated with water, produces carbohydrates (hydrocarbon, Hn-Cn). They are stored in the trunk (cambium), during the summer to prepare for the spring bloom and make future leaf essential to the continuity of the cycle. Some cells will turn into wood. The leave also carries the amino acid synthesis using nitrates captured in the ground.

To activate these reactions, the leaf needs, as in any factory, power: it is the energy of light is used, and the reaction activated by light is called photosynthesis. There comes a well known pigment, chlorophyll, which gives the leaf its green color. At night, photosynthesis stops and respiration is reversed: the leaves capture the oxygen and release some CO2. To produce one kg of carbon material, the leaves have to treat 4000 m3 of air (a cube of side 16 m). It is estimated, in temperate forests, timber production to 3.9 t / ha / year of logs, which are added to 1.2 t / ha / year of classes. After the death of trees, bacteria break down carbon and nitrogen, and restore them in the form of carbon dioxide, ammonium and nitrate.

To recognize some leaves : click here

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