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BIG ENCYCLOPEDIA FOR CHILDREN AND ADULTS
How does sap travel up the tree? Detailed answer
Directory / Big encyclopedia. Questions for quiz and self-education Did you know? How does sap travel up the tree? In humans and animals, blood circulates through the body driven by a powerful pump, which is the heart. Thus, each cell of the body receives all the substances necessary for its vital activity. Each part of the tree is also washed from the inside with a solution of nutrients in water - the sap of the plant. However, no tree has a heart. How, then, does the sap rise up the tree? Science still cannot give an exact answer to this question. None of the theories that exist today offers a complete and final explanation of this phenomenon. Therefore, scientists are inclined to think that the movement of sap along the tree is carried out under the influence of several forces acting simultaneously. The most widely accepted theory is osmotic pressure. The fact is that in all living organisms, a solution of nutrients enters the cells through thin membranes. This is because the concentration of dissolved substances on different sides of the membranes is different, and therefore, according to the laws of physics, it tends to equalize. Such a phenomenon (occurring, by the way, not only in wildlife) is called osmosis, and the difference in the concentrations of a substance on different sides of the membrane, which is the driving force of the process, is called osmotic pressure. Thus, the greater this concentration difference, the greater the amount of liquid transferred through the membrane. The water and mineral salts necessary for plants to sustain life are found in the soil. Since their content there is higher than in the roots of trees, osmotic pressure arises, forcing moisture with salts dissolved in it to penetrate into the plant. Due to the same effect, the juice rises up the root into the trunk and further to the rest of the tree. Mineral salts remain in the cells of the tree as the solution passes through them, and excess water evaporates from the leaves. There is another hypothesis in this regard. According to her, the movement of juice occurs due, firstly, to the evaporation of water from the leaves, and secondly, to the presence of "cohesion" of water. Cohesion is a force that causes a kind of "sticking" of one small particle of matter to another. According to this theory, when moisture evaporates from leaves, a vacuum occurs in their cells, and as a result, they begin to attract water from neighboring cells. The same thing happens there, and so on, until it reaches the roots, which absorb moisture (and with it nutrients) from the soil. As far as cohesion is concerned, it holds the water particles together as they move up the shaft, which keeps this flow uninterrupted. Author: Likum A.
What is embroidery? Embroidery is the art of sewing decorative stitches on fabric. This is a very ancient art. The remains of embroidered clothes were found during archaeological excavations of the ruins of Assyrian and Persian cities. The Old Testament describes the beauty of embroidery on the festive clothes of the Jews in biblical times. In the Middle Ages, embroidery reached great heights. The great Italian and Dutch artists drew blanks for tapestries, on which paintings were embroidered on biblical subjects. Noble women in their castles spent hours embroidering outfits for especially solemn occasions and bedspreads for the church altar. One of the most famous medieval embroideries is the Bayoq Tapestry depicting the Battle of Hastings. All the warriors, horses, griffins, phoenixes and monsters depicted on it are embroidered with woolen threads of eight shades on a linen cloth seventy meters long and almost fifty-five centimeters wide. In the XNUMXth century, embroideries became very expensive - more expensive than their weight in gold! In the XVIII-XIX centuries, the education of girls necessarily included learning the art of embroidery, which they practiced daily. They learned how to make various stitches on a piece of linen. Houses, animals, numbers, letters of the alphabet and even poems were embroidered on these samples. Finishing the embroidery, the girl indicated her name, age and the date when the work was completed. Each country had its own style of embroidery. In China and Japan, gold threads and silk were used for embroidery, with which dragons, flowers, birds and landscapes were embroidered on thin damask fabric. In warm countries such as Italy and Spain, embroideries were bright and cheerful in color and pattern. France and Switzerland were renowned for their fine workmanship. There, embroidery was often done with white thread on a white background. In the Balkan countries, clothes and bedding embroidered with bright ornaments were inherited from generation to generation.
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