The influence of the orchid-growing environment on the absorption of minerals by orchids and on orchid quality

TemperatureCultivationSubstrate temperature has a significant effect on the absorption of mineral elements. The speed at which roots absorb minerals increasesCultivationcontinuously as substrate temperature rises, but excessively high or excessively low temperatures will greatly reduce the amount of minerals absorbed. At low temperatures, the viscosity of cell protoplasm increases, which increases resistance to ions. Near 0 degrees, active absorption almost completely stops, and only passive absorption remains, so the absorption of mineral elements is very weak. Excessively high temperatures (above 30 degrees or even 40 degrees) will also weaken the roots' absorption of minerals, because high temperatures gradually deactivate enzymes, affect the normal metabolism of the roots, and also affect the absorption of minerals. Therefore, when humidity is too low and soil temperature is too high, water should be given or humidity increased as appropriate, using water to regulate temperature. Aeration conditionsCultivationWhen the substrate is heavy and sticky or has too much water, it will cause poor aeration for the orchid plant, affect the activity of the orchid's root system, and reduce the energy supplied for mineral absorption and transport, thereby lowering the orchid plant's ability to absorb mineral elements. This is because poor aeration directly affects root respiration. The pH of the growing substrate. pH affects the solubility of mineral salts, so it has a great influence on mineral absorption. When the alkalinity of the growing substrate solution increases, the solubility of iron, copper, zinc, calcium, magnesium and phosphorus decreases, and thus absorption is reduced. When the acidity of the solution increases, it can increase the solubility of various metal ions; although this is beneficial for plant use, they are easily leached away. The most suitable pH value for orchid growth should be maintained at neutral or slightly acidic. The concentration of the growing substrate solution. If the concentration is too high, it will lower the water potential of the growing substrate solution, affect water uptake by the roots, and at the same time hinder the plant's absorption of mineral elements. Therefore, when fertilizing, one should apply thin fertilizer frequently and lightly, so as to facilitate the effective use of the fertilizer. Interactions among ions. The presence of one ion affects the effectiveness of another; some show a promoting effect, for example, phosphorus and potassium can promote the absorption and use of nitrogen. An appropriate combination of nitrogen, phosphorus and potassium has a very good effect on increasing orchid plant growth. The presence or excess of some ions often inhibits the absorption and use of certain other ions, for example, too much phosphorus often causes symptoms of zinc deficiency. Therefore, the balance among ions should be considered when fertilizing. In addition, microbial activity in the growing substrate, light intensity, the growth condition of the root system itself, and so on all affect mineral absorption. During cultivation, the most suitable conditions for mineral absorption should be created as far as possible so that the orchid plants grow well. After mineral ions enter the roots, apart from some being retained by the root cells, most enter the xylem of the stele, and afterward one part is transformed into organic matter, but most still remain in the form of free ions and rise with transpiration to the organs above ground. Mineral ions absorbed by the roots can be transported upward in the phloem, and mineral ions absorbed by the leaves can be transported downward in the phloem. The main point is that the plant's phloem can transport mineral elements in both directions. The transpiration stream sends mineral elements to the parts that need minerals most, such as growing points, young leaves and other such parts, where they immediately take part in metabolic activities. Some elements take part in tissue composition, such as nitrogen and phosphorus taking part in the composition of protoplasm, and magnesium taking part in the composition of chlorophyll, and so on. Among mineral elements, some elements such as helium, phosphorus, potassium, magnesium and so on can move from parts with weaker metabolism to parts with stronger metabolism. When these elements are lacking in the environment, they can be transferred from old leaves to young leaves, ensuring the normal growth of the leaves. These elements are reused, and when these elements are lacking, the old leaves are the first to show symptoms. Therefore, during the cultivation of orchid plants, old leaves are often more prone to disease or to drying up under the influence of environmental factors. Elements that can be repeatedly used are mostly distributed in growing points and young leaves and other parts with relatively vigorous metabolism. There are also some elements, such as calcium, iron, boron, zinc, aluminum, copper and so on, which after being absorbed by the aboveground parts of the plant are fixed and cannot move, and cannot be reused. The older the plant organ, the greater the content of such elements; for example, the calcium content in old leaves is far greater than that in young leaves. Therefore, old leaves in orchid plants are relatively upright, while young leaves are relatively soft and drooping, and when the plant lacks these elements, symptoms are likely to occur in young leaves. Hence in orchid plants, new shoots and young leaves are more likely to "rot" and suffer "water damage." (Liu Zhongjian)