What are the effects of high and low temperatures on Chinese orchids?

The root system and stem and leaf growth of Chinese orchids are greatly affected by the temperature in the atmosphere and the medium. Generally, the most suitable temperature for Chinese orchid growth is 18°C to 28°C. High or low temperatures will affect the photosynthesis, respiration, transpiration, and the transport and storage of assimilated substances of Chinese orchids. When the temperature rises above the critical point for orchid root growth, root growth will stop due to excessively high temperature, root elongation and the water-absorbing capacity of the roots cease to function, the physiological functions of the plant decline, and over time the lifespan of the orchid plant will be shortened. High temperatures also damage root tissues and cause the secretion of the toxic substance ammonia, which poisons root cells and causes root cell death. Under high temperatures, the decomposition rate of organic matter in the medium accelerates, the medium enters a strongly redox state, and carbon oxides are thereby produced in large quantities. Harmful substances such as soluble ferrous iron, organic acids, methane, and ethylene will directly poison root cells. The root system and stem base will then, due to the harm caused by these harmful substances, develop reddish-brown and deep black symptoms, and in severe cases the root tissue will rot and die. When the temperature exceeds the growth critical point by too great a margin for Chinese orchids, high temperatures increase leaf transpiration, water in the plant body rapidly transpires out through the leaf stomata, root respiration accelerates, and the orchid roots must absorb large amounts of water through the root system in order to maintain the cell turgor pressure of the Chinese orchid, regulate the temperature inside the leaves, and keep them upright. If, under high temperatures, the orchid roots develop poorly or the medium has poor aeration, the leaves of the Chinese orchid lose large amounts of water from the plant body through transpiration due to the high temperature, and the water-absorbing capacity of the root system is affected by temperature and cannot take up water to replenish it. The Chinese orchid plant will then undergo temporary wilting due to lack of water. If this condition persists over the long term, the orchid plant will become wilted, and then turn into permanent wilt and die. This not only affects the growth of stems and leaves and the growth of the root system, but likewise the orchid plant will be severely harmed, further affecting the growth of new shoots, and even causing the death of the orchid plant. Therefore, how to use shading, ventilation, and humidification to lower the temperature is still a necessary means. When the temperature falls below the critical point for Chinese orchid growth, the cell membranes and metabolic enzymes of the Chinese orchid cells cannot endure the low temperature and are severely damaged, and the activity capacity of the root system is correspondingly reduced. At low temperatures, the respiration of the root system will slow down, or even stop functioning. The heat energy needed to absorb nutrients also cannot be fully obtained because low temperatures are accompanied by weak light. In addition, the root activity cannot function, so the absorption and transport of water and nutrients are both hindered. Photosynthetic products and storage amounts decrease, the bulb enlargement rate drops, and what is available is only enough to supply its own life needs, with no surplus nutrients to supply root growth. This causes the growth of the Chinese orchid plant to stall or enter a dormant state. Newly grown shoots also become smaller and smaller the more they are grown due to temperature limitations, and the number of leaves is also fewer than that of the original plant. Moreover, under low temperatures, the activity of microorganisms in the medium is affected by temperature and cannot normally decompose organic matter, nor can it, while decomposing organic matter, secrete beneficial substances that promote root elongation such as IAA and GA, as well as growth hormones, amino acids, ribose and other substances that promote root growth and root division, thereby slowing the absorption and transport capacity of orchid roots and reducing the amount of nutrient elements needed for leaf growth and development. The orchid roots thus lose the functions they should originally perform, age, rot, and die. In the scorching summer season, the daily sunshine duration often reaches 12 to 15 hours. Especially from noon to 2 hours in the afternoon, the PC transparent panels of the orchid room greatly absorb the radiant energy directly irradiated from the sun, and the accumulated temperature often reaches above 30°C. Hot air accumulates in the orchid room, the temperature rises greatly, and exceeds the critical point for Chinese orchid growth.CultivationIf the manager does not take cooling measures, the root growth of Chinese orchids will be harmed by high temperatures. Generally, during the high-temperature period in summer,Cultivationthe manager may install shade nets, increase ventilation equipment in the orchid room, set up flowing water below the orchid shed, spray water above the roof, or adopt various mechanical and physical humidification and cooling equipment to work in coordination with one another, which can achieve a cooling effect and allow Chinese orchids to grow in a suitable temperature environment, free from the effects of high temperatures. In this way, the root growth of Chinese orchids has a good environment, and only then can Chinese orchid plants of better quality and yield be cultivated. When the winter temperature falls below the critical point for Chinese orchid growth, the various tissues of the Chinese orchid will enter a dormant period to pass through the cold season. During dormancy, in order to maintain its own life needs, the Chinese orchid will consume the nutrients accumulated during its growth period. When the temperature falls below the minimum base point for the growth of the Chinese orchid plant, the plant cannot endure the icy air temperature, which causes great harm to the growth and development of the Chinese orchid plant and its ability to sprout the next generation. Generally, for Chinese orchid plants grown under cold winter temperatures, due to the influence of low temperatures, in order to maintain the continuity of life, the orchid plant itself will enter dormancy and consume the heat energy and nutrients stored in the plant body, and only when a temperature suitable for growth appears can it itself perform various functions. During this dormant consumption period, the plant has already consumed most of its nutrients, causing the newly grown orchid plant to be unable to obtain more nutrients from the mother plant to supply what is needed for cell division, and thus to become smaller. In addition, when the growth condition of the plant itself is poor, there are no surplus nutrients to supply root division, and the number of roots and root growth will be severely limited. During the low-temperature period in winter,Cultivationthe manager should keep the doors and windows of the orchid room tightly closed, leave only a small air inlet below the orchid room, and carry out ventilation work at around ten o'clock in the morning when the temperature outside the orchid room and the temperature inside the orchid room are equal, so that fresh air can enter the orchid room for gas exchange. When the temperature drops in the afternoon, in order to prevent the loss of heat energy accumulated from daytime sun exposure, the cultivation manager should close the doors and windows and avoid cold wind directly entering the orchid room and affecting the growth of the orchid plants. When the nighttime temperature falls below the critical point for Chinese orchid growth, the cultivator should install heating equipment, such as hot air and hot water cross-heating each other, to raise the temperature of the orchid room and maintain a temperature suitable for growth, helping the Chinese orchid plants pass through the cold dormant period, so that the Chinese orchids grow in the most suitable temperature and humidity environment. Only in this way can the growth of Chinese orchids be maintained and meet the needs of growth, avoiding the growth amount and growth vigor of Chinese orchids being limited due to insufficient accumulated temperature.