Dioxide of carbon which in the course of photosynthesis communicates in hloroplastah cages of leaves, finally turns to carbohydrates. In a kind disaharida sucrose of a molecule of these, carbohydrates is transported to other bodies of a plant.

Photosynthesis Products can temporarily be reserved in the form of starch in hloroplastah and lejkoplastah when intensity of photosynthesis exceeds speed of tap of its products to other bodies of a plant. However starch cannot be transported as that as it is insoluble in water. Redistribution of carbohydrates can occur only after transformation of starch into sucrose and in a smaller measure in others of sugar, or saharospirty (sorbite).

If traheidy and wood vessels form spending system for moving of water and some solutions of soil, in an elevated part of a plant other tubular system, floema, serves for delivery of the sucrose formed in leaves, to all other bodies of a plant. In early experiences with trees at which floema is in a bark, have been revealed, a site and the important role of the system responsible for distribution of sugar. If from a tree to remove a narrow strip of a bark on all circle of a trunk leaves remain for some time live as water to them arrives on ksileme, located in wood. However roots die off, as, they are deprived energy and carbon access. At the same time sugar necessary for them collects in the inflated bark over the ring cut out on a trunk. From here it is clear that photosynthesis products are transported from leaves to roots on a bark. The data of the chemical analysis has served as one more certificate, unique function of a bark. It has appeared that floema barks possesses the high maintenance of sugars whereas at juice ksilemy there are mainly mineral salts.

The Bark - the general name of dense external fabrics of a wood stalk which can be separated from the firm internal wood cylinder a thin layer of actively sharing cages making vascular kamby. From an outer side the bark is covered by a protective layer of dead cages of a stopper, obrazuemyh pith kambiem, lying directly under them. When under the pressure of an extending trunk an external bark rastreskivaetsja, this pith kamby postpones more than pith cages from lateral aspect, corking with that a crack formed at rastreskivanii. The bark Inside consists from floemnoj a fabric containing sitovidnye tubes. they represent thin-walled, extended, connected the end in the end live cages (fig. 3.6 see). Besides these tubes floema contains a significant amount of fibres and parenhimnyh the cages scattered among sitovidnyh of tubes. In young stalks and at many grassy plants floema is mainly on an outer side of a vascular bunch though at some kinds its site can be another.

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