Tree physiological processes

Knowledge of the functions of individual organs and parts of a tree as well as knowledge of the physiological processes taking place in them is the basis for the proper performance of many treatments related to tree care.

Transport of water and mineral salts - ascending current. Uptake is one of the basic life processes of trees, conduction and excretion (transpiration) water. Taking water with mineral salts dissolved in it is a very complicated and not fully explained process. In the root cells there is an osmotic pressure with a force of up to several atmospheres, which allows you to overcome the suction force of the soil, which normally does not exceed a few atmospheres. This pressure difference enables the roots to take up water. Saline soils, however, can have a suction force of up to 30, and even 100 atmosphere. The soil substrate in cities can often show a high concentration of various salts, which makes water uptake by the roots difficult.

Root pressure is an important force that enables water to conduct vertically. Its values ​​are 1-2 atmospheres. This is enough to raise the water in the vessels above 10 m. In the period of the so-called "juicing", root pressure is the main factor that moves the water. The cutting of the vessels in the sapwood causes the known phenomenon of spring "crying". During this period, the ascending current solution contains, in addition to water and mineral salts, some spare nutrients (carbohydrates, amino acids, enzymes etc.), moved to developing leafy buds. Therefore, no pruning should be made during this period. In the period of strong sunlight, both in early spring and in autumn, and even in winter, there may be a phenomenon of "crying"; in such a case, the maintenance work must be stopped.

In active wood, water moves with considerable speed, reaching up to 50 m/hr. This is possible due to the transpiration of large amounts of water through the leaves.

In leafy trees, transpiration is the main factor that causes water to move, causing an increase in cell sap concentration and an increase in leaf suction power. E.g 200000 During a sunny day, birch leaves evaporate on average 60-70 l of water, in extreme cases, even up to 400 l. Assesses itself, that a hectare of forest transpires 1500-2000 m3 of water annually. On an annual basis 1 m2 of beech leaves transpires 50-60 l of water, which is roughly 1/3 annual rainfall on 1 m2 of soil surface. Centennial beech stands transpire an amount corresponding to 210-290 mm of annual rainfall, spruce 170-320, and pine 50-100. The daily transpiration of 50-year-old stands from one hectare in summer may show significant differences. For example. birch and larch stands transpire amounts corresponding to 4-7 mm of precipitation, beech 3,8, Douglas fir 5,3, spruce 4,3 and pine 2,3.

In comparison to other plants, trees are characterized by low water consumption needed for production 1 gram of organic matter, i.e.. have a low transpiration rate; oak 344, birch 317, pine 300, larch 257, spruce 231, Douglas fir 173, buk 169, while the rye 680, and flax 905.

Transport of assimilates - downdraft. The organic substances produced in the leaves must be delivered to the branches, the trunk and roots as an energy material, building and spare. Transport within the parenchyma should be distinguished here (for short distances) and through the screen tubes (over long distances). The mechanism and chemistry of these processes have so far been known only fragmentarily. The knowledge of the descending current mechanism is of particular importance for the proper performance of tree care treatments. The initial stage of assimilate movement are enzymatic processes at the photosynthetic site - in the leaves - that ensure the breakdown of starch into sugars with small molecules, water-soluble. The transport of assimilates takes place mainly in the sieve tubes. Radial displacement into the gulp, wood and core provide core rays. The circumferential movement is strongly limited, especially in conifers, due to the lack of transverse connections between the sieves. This is due, inter alia, to the slower formation of healing tissue around wounds in conifers than in deciduous trees. The need to shape the treated wounds also depends on the method of transporting assimilates.

Photosynthesis and respiration. The leaf is the organ and site of the most important biochemical process on Earth - photosynthesis (the so-called. carbon dioxide assimilation). It is present in chloroplasts containing a green dye - chlorophyll. The main function of chlorophyll is to absorb solar energy (luminous) and converting it into chemical energy, necessary for the synthesis of organic compounds. The essence of photosynthesis is the production of a glucose molecule from carbon dioxide and water using solar energy according to the following, a very simplified equation:

Within an hour 1 m2 of leaf area produces approx 1 g of glucose.

All living parts of the tree must breathe. Respiration (dissimilation) is a process that releases energy "stored" in chemical compounds and converts it into a form useful for the cell. The breathing process works according to the following pattern:

This energy is needed for all life processes. The sum of the energy released during dissimilation processes is on average 1/10 energy accumulated in the process of assimilation. The equalization of values ​​of these two processes is called the compensation point. If the amount of energy used in the process of breathing exceeds the amount of energy obtained in the process of assimilation, then a given part of the crown die off. This phenomenon occurs in heavily shaded branches.

Beneficial results from the basic life processes discussed above, mainly the microclimatic importance of trees. The crowns with healthy leaves ensure maximum performance of these sanitary functions. At the same time healthy, a profusely leafy crown is a prerequisite for good tree growth and development.

Whereas photosynthesis occurs almost exclusively in the corona, respiration, as previously mentioned, takes place in all living parts of the plant. Intensive breathing processes take place in the trunk and in the roots. Any factors that limit the breathing process negatively affect the entire tree. Roots breathing very often is difficult due to covering the soil with various impermeable or poorly permeable surfaces..


One thought on “Tree physiological processes”

  1. I am looking for a transpiration factor for birch and that's how I found this page.
    Unfortunately, the coefficients, which you provide for trees are completely different than that given by Dębski in the table.
    Can you provide the source you used ?
    oak – 613 l / kg
    spruce – 242
    pine – 123

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