External factors affecting the respiration of orchids

Within a certain limit, as the temperature increases, so does the intensity of respiration. The effect of temperature on respiration also has three basic points, namely, the lowest point, the most suitable point and the highest point of respiration.

Compared with photosynthesis, the lowest temperature of respiration is much lower, because as long as life goes on, there will be breathing. But if you are suddenly affected by low temperatures in the middle of summer, breathing may stop. However, the optimum temperature of respiration only indicates that the respiratory intensity of the orchid plant reaches the highest point at this time, but it is not necessarily beneficial to its whole life cycle. Because of the increase of respiratory intensity, sometimes cause unnecessary consumption of substances, so that the plant is damaged, such as high temperature and lack of light, respiration is greater than photosynthesis, which will affect the accumulation and growth of organic matter.

Oxygen is a necessary condition for the oxidation and decomposition of organic compounds in respiration. Under normal circumstances, the content of oxygen in the air is about 21%. If the content of oxygen does not change much, it does not have much effect on respiration. Only when the content of oxygen in the air is reduced to 1%-2%, the respiration will be significantly reduced. When the aboveground part of the plant is in contact with air, the general situation is that it will not feel the lack of oxygen and affect the respiration. However, the underground part of the plant is prone to oxygen deficiency, if the cultivation substrate ventilation is poor, air exchange is difficult, oxygen is difficult to enter the cultivation substrate, hypoxia is easy to occur. At the same time, the microbial activity in the cultivation substrate and the absorption of water and inorganic salts in the newspaper need to consume oxygen, which will affect the growth and normal respiration of the newspaper and the normal growth of the orchid plant.

Carbon dioxide concentration is the product of respiration, which can increase photosynthesis at a certain content, which is beneficial to plant growth. But high levels of carbon dioxide can reduce or inhibit respiration. In normal weather, the amount of carbon dioxide is very low (about 0.03%) and does not affect respiration. When the concentration of carbon dioxide increased to more than 1%-10%, the respiration was significantly inhibited. Due to the activity of roots and the respiration of microorganisms, a large amount of carbon dioxide is released in the cultivation substrate, especially in the summer and autumn high temperature season, if the cultivation substrate is poorly ventilated or hardened, the accumulation of carbon dioxide may be as high as 4% to 10%, or even higher. Therefore, the cultivation container should have air exchange holes, and there are a large number of pores in the cultivation substrate, which is easy to exchange with the atmosphere in order to ensure the normal respiration of the report system.

The amount of water in the water environment can affect the water content of plant cells. The water content of cells has a great effect on respiration, because all kinds of life activities can be carried out vigorously only when the protoplast is saturated with water. But roots, leaves and so on sometimes produce the opposite result. When the leaves wilt, their respiration is strongly active, which is due to the lack of water in the cells, the enhancement of the hydrolytic activity of enzymes, the hydrolysis of starch into soluble sugars, the increase of cell osmotic pressure and the increase of deep water power to adapt to the arid environment. However, soluble sugar is the matrix of respiration, and its increase leads to the enhancement of respiration.

Respiration is the center of plant metabolism, which is related to the whole life process of the plant. Respiration releases energy to supply the needs of plant growth and life, and promotes respiration, which can enhance the growth and development of plants. However, respiration consumes organic matter, and excessive respiration is not conducive to the accumulation of organic matter. In order to reduce the consumption of organic matter, respiration should be reduced as much as possible in the long-distance transportation of orchid plants or sorting out of the nursery for transportation.

Respiration can not only release energy to meet the needs of various physiological processes of plants, but also its intermediates are raw materials for the synthesis of a variety of important organic compounds. Respiration is the center of metabolism, which is conducive to plant absorption of nutrients, but also conducive to the transformation and transport of substances in orchid plants. The formation of new cells and organs and the growth of plants are closely related to respiration. The cultivation and management measures of the orchid plant are to ensure the normal respiration of the plant, such as keeping the cultivation substrate loose, easy drainage and good ventilation, so as to facilitate root respiration. Sometimes it is necessary to inhibit respiration, because excessive breathing can sometimes cause unnecessary consumption of organic matter.

90%-95% of the dry weight of orchid plants is synthesized by photosynthesis, the remaining organic matter except for respiratory consumption. The respiration intensity of leaves is equivalent to 5%-10% of photosynthetic intensity, but because photosynthesis is limited to leaves and carried out during the day, respiration is a process carried out by all living cells day and night, so that plants may consume 15%-25% of the total organic matter produced by photosynthesis in a day and night, and up to 30%-50% in extreme conditions. The rate of photosynthesis decreases or even stops in winter, and respiration can continue because its lowest temperature is lower than that of photosynthesis. When new buds sprout and pull out new leaves, photosynthesis is negligible to respiration. Therefore, in the process of orchid cultivation, in addition to improving light conditions to improve photosynthesis, respiration should also be controlled to reduce the consumption of photosynthates, facilitate the accumulation of dry matter and promote the growth and development of orchid forest.

In the hot summer, the photosynthesis was blocked and the respiration was enhanced due to the decrease of leaf water content, and the photosynthetic rate was weakened in the morning and evening, while the respiration was always strong, which inhibited the growth of orchid plants. Therefore, the degree of shade should be increased appropriately in hot summer, and measures should be taken to increase humidity and reduce leaf temperature to weaken respiration. Proper water supply is beneficial to the formation and transport of photosynthates and the growth of plants.

In the orchid room in winter, the photosynthesis of the orchid plant is weakened because of the weak light. At this time, if the indoor temperature is too high, respiration will be higher than photosynthesis, especially in rainy days, resulting in excessive consumption of organic matter. Therefore, the greenhouse in winter, affected by the climate, the temperature is easy to increase, which is disadvantageous to the growth of orchid plants. Measures must be taken to increase the light intensity, such as turning on the sun lamp, etc., when the light intensity increases, the temperature can be raised appropriately, but generally, it should not exceed 25 degrees in the day and 20 degrees in the evening. Therefore, in the orchid room configuration equipment, must be equipped with artificial light source. (Liu Zhongjian)