What environmental and physiological factors does orchid cultivation require

1. Air pollutionOrchidsneed clean air; if the air is polluted, it will cause poor growth, corrosion and discoloration of the leaf surface, and even necrosis, as well as early flower fading, yellowing sepals, and so on. In severe cases, it can also lead to the death of the entire plant. 2. Humidity Being too humid not only makes plants susceptible to disease but also causes the plant to become soft; being too dry also leads to poor growth. 3. LightOrchidsshould not be suddenly exposed to strong sunlight. In addition, light that is too strong or too weak, and light duration that is too long or too short, will both cause poor growth. For example, light that is too strong can turn leaves yellow, mainly because under strong light the rate of chlorophyll destruction exceeds its synthesis; extremely strong light and sudden exposure can cause leaf scorch. For example, sunburn disease in vanilla is caused by direct scorching in sunlight, leading to chocolate-colored spots and cracks on the leaves, and sunscald can also invite infection by pathogenic bacteria. If light is insufficient, the leaves appear dark green; extreme insufficiency can also turn them yellow and cause poor growth. 4. Temperature If the temperature is too high, especially at night, it can cause the plant to drop leaves, become weak, grow poorly, and even die. If the temperature is too low, it will cause excessive chlorophyll, which likewise leads to poor growth, and in severe cases can also cause death. In addition, someorchidsrequire cyclical temperature changes, includingthe four seasonschanges and day-night changes; if these conditions are not met, they will not flower. 5. Fertilizer Too much fertilizer or fertilizer that is too concentrated will make the salt concentration in the soil substrate too high, causing large withered areas or dry leaf tips, commonly known as "burning to death." 6. Minerals As with other plants, the deficiency of certain elements can also cause orchids to show abnormal symptoms. For example, boron deficiency causes necrosis of the top leaves, blackening and death of the apical meristem, short and small roots, and stunted plants. Calcium deficiency causes newly grown organs to become deformed and fail to grow larger, yellowing and curling leaves, dry leaf tips, and poor root development. Chlorine deficiency causes leaf tip withering and bronzed leaves. Copper deficiency causes withering of the shoot apex and fading of leaves. Iron deficiency causes chlorosis, especially in newly grown organs, which become pale yellow or nearly white, particularly between the veins. Magnesium deficiency causes old leaves to turn yellow while the veins remain green; the entire leaf becomes brittle, fragile, and prone to falling off, and the plant grows poorly. Manganese deficiency causes mottled chlorosis of the leaves, with dark green veins and yellow or white interveinal areas, and the stems also become yellow-white. Molybdenum deficiency causes the leaf blade not to unfold and pale yellow chlorosis to appear. Nitrogen deficiency causes the plant to become slightly chlorotic and grow poorly. Phosphorus deficiency causes stunted plants, leaves turning dark green and purple, and anthocyanin along the veins. Potassium deficiency causes yellowing or necrosis of leaf margins, shrinking of the leaf surface between the veins, and stunted plants. Sulfur deficiency causes thin, weak stems, pale green to yellow leaves, and slow root growth. Zinc deficiency causes leaf chlorosis or necrosis, with upper leaves turning white, old leaves having whitish chlorotic stripes, and the plant becoming clustered in form. 7. Others Due to combined factors, including air pollution, unsuitable temperature and humidity, imbalanced fertilizer nutrients, as well as phytotoxicity and the plant's own physiological disorders (such as ethylene production), buds may wither and drop early, flowers may be incomplete and discolored, and aging may occur before maturity (mainly caused by ethylene), and so on. (Chen Xinqi, Ji Zhanhe)