subject: The Log Of The Tree [print this page] The sapwood is the younger part of the wood, is the last growth rings of the tree produced by the vascular cambium in the stem of a plant, which corresponds to single xylem functional. Sapwood is usually lighter in color.
It is the part of the log of the tree , which is below the cortex , including the most recent growth rings. Is lighter, less dense, more permeable and contains more moisture than the heartwood . Although a clear majority of its cells are dead, contains cells that remain physiologically active cells ( parenchyma ). Contributes to the functions of structural support, driving upward of sap and storage of reserve material. The death of the parenchyma causes the transformation of sapwood to heartwood, physiologically dead center of the trunk.
From the point of view of the timber industry , and especially the carpentry , the sapwood is a factor taken into account in each of the woods, so much so that in any technical report of any kind the first thing is referred to heartwood (central part of the trunk) and the sapwood, there are some timber if its sapwood were more resistant would be much appreciated, since the sapwood not normally serves to work it decays either before, to even have a completely different color, which is almost always white; This gives different uses.
In botany , catkin is an inflorescence racemose, usually hanging, characteristic of certain trees , especially in the subclass Hamamelidae , families Salicaceae and Fagaceae .
The catkin is a spike articulated at its base and consists of flowers of one sex, as there are male catkins, more elongated, and female catkins. The flowers are simple, without petals or sepals , the males are reduced to the stamens and the female stigma .
The catkins appear in spring , usually before the leaves .
In these kinds of plants , the pollination is anemophilous , this means that transport of pollen is very abundant, is done by the wind .
The pollen of some trees may be, for the human species, a source of allergies .
In botany , catkin is an inflorescence racemose, usually hanging, characteristic of certain trees , especially in the subclass Hamamelidae , families Salicaceae and Fagaceae .
The catkin is a spike articulated at its base and consists of flowers of one sex, as there are male catkins, more elongated, and female catkins. The flowers are simple, without petals or sepals , the males are reduced to the stamens and the female stigma .
The catkins appear in spring , usually before the leaves .
In these kinds of plants , the pollination is anemophilous , this means that transport of pollen is very abundant, is done by the wind .
The pollen of some trees may be, for the human species, a source of allergies .
In botany , called anthecium the box formed by two floral bracts : the lemma and palea in the spikelet of a grass . Inside the anthecium lies the flower , consisting of a gynoecium with ovary globose or pear-shaped bearing a short style and two stigmas feathery, the androecium , consisting generally of 3 stamens and lodculas or glumelulas, evolutionary remnants of a perianth that whose function anthecium open during flowering.
In plants angiosperms , the anther is the terminal part of the stamen of a flower . It is a structure homologous to the micro sporangium in other clades and is responsible for the production of pollen . The word comes from Greek Anteros , which means flowered, alluding to the visible presence of the anthers indicates the height of anthesis (flowering). The Maya Lobis, or so-called "water adept" worshiped a god with a anther rose to the head.
Each stamen is often founded on a piececillo called filament and an anther, attached laterally to the end of the filament. It is said that the anthers are extrorse if the filament is attached to the anther by its external face (farthest floral axis), and are called introrsas in the opposite case, less frequent.
The anther typical of angiosperms typically consists of two distinguishable parts, contiguous, called libraries , linked by an area called connective , which is also where the anther joins the filament. If the anther cut perpendicularly to its axis, it is noted that each anther containing one or two pollen sacs extending throughout its length.
The anther is a dehiscent structure, ie that is spontaneously broken to expose its contents, pollen. Each pollen sac is generally open by dehiscence (cut) longitudinal where will the pollen.
The yarn is processed into a sheet production of male spores (microspores) that are pollen grains. The pollen sacs are the microsporangia.
In a cross section of young anther, seen from the outside in the following layers:
Exotecio epidermis or thin and continuous. It can sometimes break or collapse or interrupted.
Endothecium mechanical or tissue, fibrous layer on the outer edges of the pollen sacs. Sometimes it continues in the connective.
2 to 4 layers or layers parietal parenchyma cells disappear soon crushed, or degenerate quickly.
Mat or nutritional tissue.
Asporogenous tissue or arquesporio constitutes each pollen sac . Tissue cells by mitotic divisions asporogenous form pollen mother cells or microsporocytes , rather large cells with enlarged nuclei.
Dehiscence occurs through the endothecium. Cells exhibit their walls unevenly thickened, lignified fillets wider towards the inside of the cell, where they join each other, but instead are thinned towards the outer face. For this reason, upon dehydration of the cells, they are shortened tangentially causing stresses that lead to opening of the anther.
