What environmental conditions affect Chinese orchids?

Chineseorchids' growth and development are determined both by the genetic factors of the mother plant and by environmental conditions. The quality of Chinese orchidcultivationis shown in how well the six major environmental factors required for the growth and development of Chinese orchids - light, temperature, water, air, soil - are properly coordinated to achieve thecultivationgoal. They cannot be considered in isolation, but under specific circumstances, one of these factors will always play a dominant role. (1) Light Light is a necessary condition for plant survival and is the energy source for plants to carry out photosynthesis, manufacture nutrients, and enhance their own growth. It mainly affects the entire process oforchidgrowth and development in three ways: light wave, light intensity, and light duration. A. Light of different wavelengths has different effects onorchidsat different growth stages, among which the main types of light are as follows: a. Red and orange light with a wavelength of 600-700nm is the light region most strongly absorbed by chlorophyll and where photosynthesis is most vigorous. Red light in particular can promote orchid growth, but red light alone will cause Chinese orchids to grow leggy, which is unsuitable for orchids valued for their variegation and broad leaves. b. Blue-violet light with a wavelength of 510-610nm is the light region more strongly absorbed by chlorophyll and xanthophyll. Among these, blue light is the main source for producing pigments and can also promote the absorption of phosphate fertilizer. It is indispensable for thickening stems and leaves, accelerating plant development, and regulating stomatal opening. Violet light mainly forms anthocyanins and inhibits the elongation of branches and leaves. B. The influence of light intensity on Chinese orchids Throughout the fourseasonsof the year, the illuminance in open ground at noon on a sunny summer day is about 100,000 LUX, and the illuminance in open ground at noon on a sunny winter day is about 25,000 LUX. In this region, cloudy and rainy days account for about 20%-30% of sunny days. Orchid leaves can carry out photosynthesis at an illuminance of 3000-5000 LUX. According to experiments, Cymbidium sinense requires an illuminance of about 5000 LUX, and variegated Cymbidium sinense requires about 4000 LUX. Narrow-leaved Chinese orchids require higher light intensity, up to 10,000 LUX. Therefore, under normal conditions, photosynthesis will not be hindered by insufficient light intensity, but light has many important relationships with the flowering period and flower color of Chinese orchids: if light is too strong during the flowering period, the flowering period will be shortened, while avoiding excessively strong light can appropriately extend the flowering period. Anthocyanin is the main pigment of orchidflowers. It is produced when light is strong and is not easily generated under weak scattered light, so the same variety of Chinese orchid will show great changes in flower color under different light intensities; that is, light intensity plays a role in inhibiting or promoting the formation of anthocyanin. In addition, excessively strong light is also unfavorable to the growth and development of orchid rhizomes (dragon roots). At present, some orchid growers use ordinary fluorescent lamps as artificial light sources. According to tests: ordinary fluorescent lamps have the most light at a wavelength of 500nm, which is yellow-green light. Moreover, at a distance of 20 cm from a 40-watt fluorescent lamp, only 400 LUX is measured, which is insufficient light intensity, and the heat generated by the lamp tube risks scorching orchid leaves. When using artificial light sources, they should be at least 60cm away from the leaf surface to prevent leaf damage. A 28-watt energy-saving lamp provides 2000 LUX, and a 35-watt energy-saving lamp can reach 3000 LUX. Simply adding a lampshade with high reflectivity can achieve the ideal light source of 4000-5000 LUX. In addition, for every 2 sq m, one 40W pure red and one 40W pure blue fluorescent lamp can be used as a group for light wave adjustment. When new shoots grow to seven or eight tenths mature, one purple lamp tube can be added. C. The influence of light duration on Chinese orchids We know that Chinese orchids, under effective light, convert carbon dioxide and water into carbohydrates through photosynthesis to meet their growth and reproductive needs. To better cultivate Chinese orchids, artificially extending light duration has been proven in the practice of many orchid growers to be a good method. However, Chinese orchids are divided into long-day and short-day types. Short-day Chinese orchids require daily sunshine duration below 12 hours, which is beneficial to their flower bud differentiation, such asCymbidium goeringii、Cymbidium kanran, and Cymbidium sinense. Long-day Chinese orchids require daily sunshine duration of 12 hours before they can form flower buds, such asFour SeasonsOrchid. However, if the sunshine duration is extended endlessly, it is instead unfavorable to the growth of Chinese orchids. This is because plants must go through a dark period for their cells to fully grow. If their limited dormancy period is terminated, it will lead to incomplete cell differentiation, and orchid seedlings cannot grow healthily. (2) Temperature The influence of temperature on the growth and development of Chinese orchids can be divided into air temperature and soil temperature (pot temperature), and both have equivalent effects on Chinese orchids. A. The influence of air temperature on Chinese orchids The most suitable temperature required by Chinese orchids throughout their life activities is about 18-25°C, but different varieties of Chinese orchids have different lowest limit temperatures for life activities. According to tests,Cymbidium goeringii。Cymbidium faberirequire a winter nighttime temperature of about 5°C and can tolerate temperatures below 0°C. Cymbidium sinense requires about 10°C, and below 5°C there is a risk of frost injury.Four SeasonsOrchidandCymbidium kanranfall between the above two major categories. Chinese orchids can tolerate a maximum temperature of about 50°C. There was once an experiment by orchid growers in our city who placed dozens of pots of various Chinese orchids in a high-temperature room at about 50°C during the day and about 40°C at night for more than 20 days, attempting to treat Chinese orchid viral disease. Although the orchids eventually had scorched flowers and rotten crowns, a few traces of fragrance still remained, which shows the heat tolerance of Chinese orchids. Within a certain range, the higher the temperature, the more vigorous photosynthesis becomes. Between 10-35°C, for every 10°C increase, respiration increases by 2-3 times. Under normal circumstances, high temperature promotes vegetative growth, while low temperature favors reproductive growth. For the same orchid, leaf buds are more tolerant of low temperature than flower buds, and roots are more tolerant of low temperature than stems. Duringcultivation, appropriately increasing the day-night temperature difference is beneficial to the size of orchid pseudobulbs, budding, and flower bud formation. B. The influence of soil temperature (pot temperature) on Chinese orchids Pot temperature has a great influence on seed germination, root development, and seedling growth. Only when there is sufficient heat in the pot can the root system better absorb water and nutrients from the soil. Generally, when the pot temperature is 3-6°C lower than the air temperature, the survival rate of small seedlings after planting is highest. Therefore, in winter, increasing pot temperature is more beneficial to the growth of Chinese orchids than increasing air temperature. (3) Water Water is an important component of plants, accounting for about 70%-90% of the fresh weight of Chinese orchids. It is an indispensable factor for all physiological activities of Chinese orchids. Without water, all physiological activities of orchidflowerswould stop, and the orchids would die. The moisture affecting the growth and development of Chinese orchids is mainly soil moisture and air humidity. A. The influence of soil moisture on Chinese orchids When watering, water is first absorbed by the particles of the potting medium and enters the interior of the particles, which is called absorbed water and cannot be used by plants. With continued watering, water is absorbed on the surface of particles and in the gaps, which is called capillary water and can be used by plants. After further watering, the water that flows freely in the soil is called gravitational water, which can quickly drain away under good drainage conditions. After gravitational water in the soil drains away, the water content contained is called field capacity. In Chinese orchid cultivation, it is appropriate to maintain the moisture of the potting medium at 60%-70% of field capacity. When it is greater than 80%, the space contained in the potting medium decreases, orchid root respiration is blocked and growth stops, and rot is likely. When the soil moisture is too dry, the concentration of the soil solution becomes too high, and root cells undergo reverse osmosis and die. In cultivation, soil moisture is generally controlled by the frequency of watering. It has different effects on different varieties, different leaf textures, different plants, different growth stages, different air temperatures, and so on. For example: fine-leaved Chinese orchids require relatively less water, while broad-leaved orchids require more water; those with thick and wrinkled leaves can be watered less, and increasing air humidity is sufficient; those with thin and flat leaves should be given a little more water and placed in a cooler, shadier place; strong plants with many roots have a large water uptake and can be given more water; weak and small plants with few roots do not easily grow roots when too wet; during the new shoot growth period, physiological activity is vigorous, so a little more water should be given; during the flowering period of mature plants, less water should be given, which can promote flower bud differentiation; during high-temperature periods, more water should be given to compensate for water evaporation, and during low-temperature periods, less water should be given. B. The influence of air humidity on Chinese orchids Although Chinese orchids belong to the terrestrial orchid group, their thick, stout, fleshy roots still give them some attributes of epiphytic orchids. During the growing process, relatively high air humidity is an important factor for successful cultivation, especially for the rough-skinned Chinese orchids that have become more popular in recent years. High-humidity air can not only allow the complete expression of the variegated characteristics of their new generations, but also increase the germination rate. According to observation, a humidity of about 80% is best for the growth of Chinese orchids. If air humidity is too high, seedlings and weak plants are prone to poor resistance and infection bypests and diseases. In particular, greenhouse cultivation should pay more attention to timely ventilation and control of air humidity. (4) Soil (potting medium) Among the factors that determine the success or failure of Chinese orchid cultivation, the potting medium is the primary factor. Only by fully understanding the different properties of potting media can they be improved and used well to grow orchids successfully. Traditional potting media for cultivating Chinese orchids mainly use: field soil, cow dung soil, baked soil, soaked mud, humus soil, pond mud, culture soil, and various other soils. They all have certain common problems: complex overall composition, difficulty in controlling nutrient element composition, difficulty in sterilization, difficulty in controlling the balance of water and air in the soil, and so on. We know that when the potting medium is well aerated, microorganisms in the medium are highly active and can transform organic matter in the medium into substances in a usable state for plant absorption. At the same time, sufficient air in the potting medium can promote root respiration and absorb more nutrients from the medium, and the fleshy roots of Chinese orchids have relatively high requirements for both air and water. Only by properly controlling the balance of water and air in the potting medium can the simultaneous needs of Chinese orchids for air and water be met, and only then can orchids be grown well. In recent years, through the continuous efforts of many Chinese orchid enthusiasts, various soilless cultivation methods have been widely applied in the orchid world. New types of potting media are emerging one after another. From tree fern fiber, sphagnum moss, broken tile pieces, red brick granules, pumice, weathered rock granules, volcanic rock granules to calcined clay granules, fired pond mud, Puli stone, Japanese orchid stone, and so on. There are all kinds, with Chinese and foreign products available in abundance, and all of them are based on the starting points of being light in weight, simple in composition, convenient for insect and sterilization, convenient for controlling nutrient element content, hygienic and clean, with good water permeability and aeration, and convenient for controlling the balance of water and air. According to observation: using fine granular potting medium (such as the size of a soybean) at about 2cm around the orchid crown is greatly beneficial to root development in Chinese orchids. In short, a potting medium that is neither loose nor tight, can both aerate and drain water while also retaining water and fertilizer, and has relatively coordinated water, fertilizer, air, and heat conditions is an ideal cultivation substrate for Chinese orchids. (5) Nutrient elements During the growth and development of Chinese orchids, they absorb carbon from carbon dioxide in the air and absorb hydrogen and oxygen from water. These 3 elements form the basic structural carbohydrates of plants, accounting for about 93% of the dry weight of plants. In addition, they also absorb mineral substances such as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, boron, manganese, copper, zinc, and barium from the potting medium. The first 6 elements are present in relatively large amounts in orchid plants and are also required in relatively large amounts. They are called macroelements. The latter several are present in smaller amounts and are called trace elements. Trace elements are required in even smaller amounts, but they have a great influence on various physiological activities and quality indicators of Chinese orchids, and they are both indispensable and cannot be excessive. a. Nitrogen (N): It is the main component for synthesizing proteins and chlorophyll in Chinese orchid plants. Applying nitrogen fertilizer can promote the growth of leaves and buds and make leaf color deeper, but when nitrogen fertilizer is excessive, it will cause leggy growth of orchid leaves, weaken disease resistance, delay flowering, make flowers small, and even cause hidden flowering, especially causing great harm to variegated orchids valued for their artistic colors. When nitrogen fertilizer is insufficient, cell walls are thick, growth speed is slow, leaf color is pale green, and the whole plant develops poorly. Usually, nitrogen fertilizer is applied in the early growth stage of orchid plants to promote leaf growth. At the same time, it also makes the roots grow larger. But if nitrogen fertilizer is applied in the later growth stage, the leaves grow large while the roots do not grow, so it must be applied cautiously when entering the flower bud stage. b. Phosphorus (P): It is an important component constituting the cell nucleus and protoplasm. Cell division of orchid plants, formation of chlorophyll, and maturation of pseudobulbs all require phosphorus. It can promote the differentiation and formation of leaf buds and flower buds, promote earlier flowering, enhance the developmental capacity of the root system, and also enhance the resistance of Chinese orchids to adverse environments andpests and diseases. During the vegetative growth period of seedlings, only an appropriate amount of phosphorus fertilizer is needed; after flower bud differentiation, more phosphorus fertilizer is required. If phosphorus is lacking, the growth of orchid rhizomes is immediately hindered. This causes orchid plants to become thin and weak, dark green, with purple leaf stalks and leaf drop, and weakened disease resistance. In addition, phosphorus deficiency also affects the absorption of nitrogen by orchid plants. C. Potassium (K): Its role is to dissolve nutrients, expand cells, and allow nutrients to permeate into various tissues. When potassium is sufficient, it promotes the toughness of orchid plants, making them less likely to lodge, promotes the formation of chlorophyll and the progress of photosynthesis. It can also enhance the drought tolerance, cold resistance, and disease resistance of orchid plants, and flower color can also be more vivid and lasting. When potassium content is insufficient, yellow-brown spots will appear between the leaf edges and veins. The tissue of pseudobulbs becomes weak and susceptible to disease infection, and in severe cases the growth of orchid plants may be hindered and stop. If potassium fertilizer is applied excessively, it will cause plants to be short, internodes to shorten, leaves to change color and wrinkle, and even orchid plants to wither and die. This is also commonly known as the problem of Eisgu. d. Calcium (Ca): It is one of the main components of the cell nucleus, and the growth of root tips and buds all require calcium. The role of calcium is opposite to that of potassium: it binds nutrients together to facilitate uptake by various tissues. Calcium and potassium have an antagonistic effect, so their contents must conform to a considerable proportion for plants to grow normally. e. Magnesium (Mg): It is a necessary component of chlorophyll, and its function is to regulate photosynthesis. f. Sulfur (S): It is a component of proteins and enzymes, and is also a constituent molecule of the waxy layer on the leaf surface of orchid plants. g. Elements such as iron, manganese, copper, and zinc are oxidation-reduction contact agents in plant bodies, and their role is to promote the formation of chlorophyll. h. The functions of elements such as chlorine, aluminum, and boron are similar to potassium, governing the transport of nutrients and water. If orchid plants lack these trace elements, it will lead to the death of shoot and root growth points, failure of flower buds to open, collapse and softening of vessels, and tissue necrosis or blackening. (6) Air Fresh air is an important condition for plants to carry out photosynthesis and respiration. In the natural environment, air contains 21% oxygen and 0.03% carbon dioxide, and the components of various gases maintain a certain proportion. In a greenhouse, however, the components of various gases vary greatly. If ventilation is not timely, harmful gases will increase and useful gases will decrease, affecting the normal growth and development of orchidflowers. Moreover, flowing air can not only continuously send carbon dioxide to the side of orchid leaves and maintain the balance of carbon dioxide concentration beside the leaves to facilitate orchid leaf respiration, but also greatly help regulate the balance of air humidity in a certain environment. In addition, salty sea breezes and waste gases emitted by factories, such as chlorine gas, sulfur dioxide, fluorine, and volatile gases from organic solvents, which are harmful gases that endanger orchid plants, should be noted during Chinese orchid cultivation. (Xiamen Orchid Association, Fujian Wu Pinglang)