the Organization of fabrics. Leaves

you are: the Organization of fabrics

In a cone of increase of a stalk periodically as a result of cellular division there are the groups of cages turning to a sheet rudiment. Such sheet rudiments look like in the beginning small bugorkov, formed by fabric layers. The part meristemy remains in a sheet bosom (a corner between sheet and a stalk) and gives rise to a kidney put here. From kidneys the runaways in turn bearing leaves or under corresponding conditions tsvetki can then develop. The nature of a put kidney often depends on temperature and from light exposure.

The First formed kidneys almost always give oblistvennye runaways. At some kinds of plants in stem knot one kidney, and at others - two, three and more is put. At a single bookmark consistently developing leaves often settle down on a stalk on a spiral; two kidneys give usually suprotivno the located leaves. Character listoraspolozhenija depends on a kind of a plant and is defined genetically.

The Order of an arrangement of leaves on a stalk (fillotaksis); can be expressed in fraction. Listoraspolozhenie 2/5 means, for example, that, moving on a stalk from sheet with which there is begun the account, to the sheet sitting directly over it, we will receive two turns of a spiral and that on these two turns is necessary five leaves.

The Most extreme cages on the top and bottom party sheet bugorka are differentiated in cages epidermisa, covered with a surface the film impregnated with wax - kutikuloj.

This film, a little nontight for water, protects leaves from drying. In epidermise is available, especially on the bottom party of sheet, a great number specialised, so-called closing, cages which, changing in appropriate way the form, thereby regulate opening and closing ustichnyh cracks. From that, are how much widely open ustitsa, gas exchange depends (i.e. An exchange of water steams, oxygen, dioxide of carbon and other gases) between internal space of sheet and air surrounding sheet. Between epidermisom the top and bottom party of sheet the photosynthesizing fabric of sheet - mezofill which sometimes name also hlorenhimoj because its cages contain a great number hloroplastov is concluded. Hlorenhima shares on palisadnuju and spongy. Cages of the first are packed densely and their longitudinal axes are perpendicular sheet surfaces; cages of the second are located ryhlo, and mezhkletniki are informed directly with ustichnymi cracks.

The Photosynthesizing fabric of sheet the spending bunches consisting of cages ksilemy and floemy penetrate numerous ' veins ', or. On these cages water and mineral substances arrive in sheet, and photosynthesis products are deduced from it. All these spending bunches are connected finally with the median vein of sheet passing through it chereshok and incorporating to the main vascular system of a plant.