Many physiological and ecological processes of plants have significant effects on their growth and development. Therefore, in modern plant physiological and ecological research, it is often necessary to make scientific and accurate determination of these indicators in order to better optimize production and guidance. Planting stem flow is one of the important physiological information of plants. It refers to the ascending liquid flow produced by plants under transpiration. Accurately obtaining information on plant stem flow can more accurately evaluate plant transpiration and water demand status information. Based on this, it provides scientific basis for the regulation of plant growth environment and water-saving irrigation. The following is a brief introduction to the common methods for measuring plant stem flow, and what are the advantages and disadvantages of each method?
1. The heat pulse (HPV) method of heat pulse (HPV) method is mainly suitable for measuring objects. The advantage is that after improvement, it has been able to measure low liquid flow and reverse flow, but the disadvantage is that it may be due to injury: weather Rapid changes in factors; the size of the xylem tube aperture; the degree of wetting of the stem flow, etc., produce some errors.
2, the trunk heat balance (THB) method of the trunk heat balance (THB) method is: if a certain amount of constant heat source is provided to a part of the stem, under the condition that a certain amount of stem flow flows in the stem, here The temperature of the stalk will tend to be fixed. Ideally, in the absence of heat loss, the amount of heat supplied should be equal to the amount of heat carried away by the stem flow. This argument constitutes the basis for the determination of stem flow by the heat balance method. This method is suitable for trees with large breast diameters. The advantage is that there is no need to calibrate the empirical formula, and it is determined that errors may occur due to the thermal storage of plant tissues.
3. Stem heat balance (SHB) method Stem heat balance (SHB) method is applicable to herbs and trees with small breast diameter. The advantage is sensitive and accurate. It can also get accurate results when the flow is very low. The disadvantage is that when the liquid flow is high. It will be overestimated; changes in the heat storage of the heated parts and long-term damage to the plants will cause certain errors.
4. Thermal diffusion (TD) method The stem heat balance (SHB) method is applicable to trees. The advantage is that the result is accurate and the instrument cost is low. The disadvantage is that the plant xylem stem flow is uneven in the stem direction and produces a certain error.
At present, with the development of science and technology, the determination of physiological and ecological indicators of plants, etc., will rely on professional plant physiological instruments, and the measurement of plant stem flow can also be used by professional instruments. It is a plant stem flow meter , and the instrument adopts heat dissipation probe method. Measuring the instantaneous stem flow density of the trunk, the liquid flow of the tree can be continuously observed for a long time, and the instrument is simple, accurate and efficient, and thus has been recognized and praised by plant physicists and agronomists.
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