Effect of light on flowers

light intensity is the intensity of sunlight on the surface of an object. The intensity of light depends on the intensity of visible light. Under natural conditions, due to weather conditions, seasonal changes and different plant degrees, the light intensity has changed greatly. The light intensity is small on cloudy days, but large on sunny days. During the day, the light intensity is small in the morning and evening, and it is large at noon. In a year, the light intensity is low in winter and high in summer. When the plant density is high, the light intensity is low, and when the plant density is low, the light intensity is high.

light intensity has a great influence on the growth and development of plants, which directly affects the intensity of photosynthesis. In a certain range of light intensity, when other conditions are met, with the increase of light intensity, the intensity of photosynthesis also increases accordingly. However, when the light intensity exceeds the light saturation point, the light intensity increases again, but the photosynthesis intensity does not increase. When the light intensity is too strong, it will destroy the protoplasm and cause chlorophyll decomposition, or make the cells lose too much water and close the stomata, which will weaken or even stop photosynthesis. When the light intensity is weak, plants will stop growing when photosynthesis consumes less organic matter than respiration. Only when the light intensity can meet the requirements of photosynthesis can plants grow and develop normally.

the influence of sunshine time on the growth and development of plants

sunshine time refers to the number of hours from sunrise to sunset that directly irradiate the ground every day. The sunshine time that affects the growth and development of plants also includes twilight, because twilight can also make some plants carry out photosynthesis.

1. The illumination time affects the flowering of plants.

The light in the daytime alternates with darkness at night, that is, their duration has a great influence on the series of development processes of plants such as flowering, fruiting and dormancy. According to the photoperiod phenomenon of plants, plants can be divided into long-day crops, short-day crops and neutral crops. Long-day crops can only bloom when the sunshine length is longer than a certain time, and if it is shorter than a certain time, they will delay or not bloom. Short-day crops can bloom only after a certain time, while neutral crops can only bloom within a certain sunshine time range.

2. The illumination time affects the introduction of plants.

Long-day plants are planted in the north and moved to the south, and early-maturing varieties are selected. South species moved north, and later-maturing varieties were selected. Short-day plants are planted in the north and moved to the south, and the origin, late-maturing varieties and varieties with weak photosensitivity are selected. When the southern species move to the north, the varieties with early maturity and weak photosensitivity should be introduced. In the specific introduction, we should not only consider the length of light time, but also pay attention to the heat condition.

solar radiation affects the growth and development of plants by spectrum, light intensity, sunshine time, and solar radiation is the most direct and important meteorological factor affecting the growth and development of plants.

flowering of plants requires a certain sunshine length, which is the result of long-term adaptation of plants to their ecological environment during their development. Short-day plants originated in low latitudes (there is little difference between day and night in summer, but the day is shorter than that in high latitudes), while long-day plants originated in high latitudes (long days and short nights in summer). In the area near the equator, long-day plants generally cannot blossom and bear fruit, and only short-day plants are distributed; At high latitudes (above latitude 66.5), there is sunshine almost 24 hours in summer, and short-day plants cannot grow and develop, only long-day plants are distributed; In the mid-latitude zone, there are both long-day and short-day conditions, so both long-day plants and short-day plants can survive, but long-day plants mostly bloom in late spring and early summer, and short-day plants mostly bloom in autumn. . Most of the short-day plants are from tropical and subtropical regions with short sunshine time. Most plants with long sunshine are native to temperate and cold zones with long sunshine time in summer. If long-day plants are cultivated in the tropics, they will not bloom because of insufficient light. Similarly, short-day plants cultivated in temperate and cold regions will not bloom because of too long light time. This is of great significance to plant introduction and breeding. Because the south of China is located in the low latitude area, there are no long-day plants, only short-day plants; North China is located in the mid-latitude area, so there are both long-day plants and short-day plants; Long-day plants bloom in late spring and early summer, while short-day plants bloom in autumn; However, the northern part of Northeast China is in the high latitude area, because the temperature is already low in a short day, only some plants that require long sunshine can survive < P > As long as they bloom between the summer solstice and the winter solstice, they are called short-day plants, and the summer solstice and the winter solstice go through the autumnal equinox. For the northern hemisphere, before the autumnal equinox, the sun is in the northern hemisphere, and the higher the latitude, the longer the sunshine time. Jute, a short-day plant, blooms before the autumnal equinox, so the higher the latitude, the later it blooms, so that it cannot bloom. We need the stems of jute, which can't blossom and increase the yield. Those that need short sunshine to bloom are called short-day plants, such as chrysanthemum ~ petunia ~ marigold ~ crab claw orchid, etc. Those that need long-term sunlight to bloom are called diurnal plants, such as Dianthus ~ Violet ~ Daisy ~ hyacinthus orientalis, etc.

From the degree of plants' love for sunlight, we can see their primitive living environment: species living in open deserts and grasslands are called sunny plants, and if there is not enough strong sunlight, they will grow poorly or even shrink, such as sunflower ~ cosmos ~ cockscomb ~ cactus. However, plants living in the lower layer of dense forests rarely receive strong sunlight, and gradually adapt to the cloudy environment, but they don't adapt to the strong light, so they are called negative plants, and the representative plants are the vast majority of orchids ~ pineapples and foliage plants. < P > Most flowering plants like sunshine, because green plants absorb the energy of sunlight, assimilate carbon dioxide and water, make organic substances and release oxygen. This process is called "photosynthesis". Without light, there is no photosynthesis, and plants without photosynthesis cannot grow, so light is still the first factor to raise domestic plants.

The intensity of light is also closely related to flowering, which determines the number of flowers. For Xiyang plants, on the same plant, there are more flower buds formed on the branches with more light than those on the backlight side. In sunny years in summer, the flowers of flowering plants will be more lush in the second year.

the intensity of light determines the time when some flowers bloom. Flowers such as Scutellaria barbata and Oxalis only bloom at noon on sunny days. Evening primrose, jasmine and tuberose only emit fragrance in the evening. And the beautiful flowers of Epiphyllum exude fragrance at night. Morning glory is the most beautiful at sunrise in the morning.

the intensity of light affects the color. The colors of alpine tropical flowers are more vivid than those of flat flowers. Flowers of the same species are more colorful outdoors than indoors.

Generally, flowers are most suitable to grow and develop under the condition of 5% ~ 7% full sunlight. If the sunlight received is less than 5% full sunlight, the flowers will not grow well. If more than 7% of the total light will also inhibit the growth and development of flowers and trees. In winter indoors, if the light is insufficient for a long time, the plants will grow in vain, the internode distance will be lengthened, the flowering varieties will have less flowers, light colors, fragrant flowers, weak floral fragrance, poor tillering ability of flowers and trees, and their resistance will be weakened, making them susceptible to diseases and insect pests.

flowers have different requirements for light, which can be divided into positive flowers, neutral flowers and negative flowers.

1. Positive flowers:

This kind of flowers and trees generally prefer full sunlight and are not tolerant to shade. If the light is not enough, the flowers and trees will grow in vain, the branches will be thin, the flowers will become smaller, the colors will fade, and even they will not bloom. Most biennial herbaceous flowers, such as Scutellaria barbata, Asteraceae, Celosia cristata, Euphorbia zingiberensis and Cuiju, are all positive flowers. Another example is cactus and succulent plants, such as rat's paw and mountain shadow boxing, perennial flowers such as Lycopodium, Sedum, woody flowers such as Magnolia, Pomegranate, Lagerstroemia indica and Albizia Albizia, which are native to the sunny side of tropical, temperate and high mountains, are also sunshine-loving flowers.

2. Neutral flowers:

Neutral flowers like sunshine, but they can grow, blossom and bear fruit normally with a little shade. Most flowers belong to this category, such as hibiscus, gardenia, hydrangea, osmanthus, jasmine, platycodon grandiflorum, day lily and so on.

3. Negative flowers:

Most indoor foliage flowers and trees belong to this category. This kind of flowers and trees avoid direct sunlight in summer and require a certain degree of shade. Too much sunlight will cause the leaves to scorch. Such as Orchidaceae, Paeonia lactiflora, Hosta, etc. Flowers of Araceae require 8% shade; Rhododendron, camellia and begonia all require 5% shade to grow and develop normally. In addition, bromeliads, arrowheads, aquilegia, pouched peony, Hosta, etc. are also negative flowers. Some flowers, such as cyclamen, Erythrina macrophylla, Michelia, Gardenia, upside-down Admiralty, Clivia, etc., need shade in summer and sunshine in winter.

2. Long sunshine flowers, medium sunshine flowers and short sunshine flowers

Different kinds of flowers need more or less sunshine hours, which can be divided into:

1. Long sunshine flowers:

Most biennial flowers that bloom in early spring and early summer belong to this category. They need 14 to 16 hours of light every day to make flower buds differentiate and flowers open. If the light hours are insufficient, it will not bloom. For example, an annual grass flower, cosmos, is planted and germinated in spring under natural conditions, then grows nutritionally in long sunshine and blooms in autumn. If sowing is too late in spring, the plants will bloom in autumn even though they are short. The perennial flower Fulukou, which blooms in early spring, can bloom under long sunshine in spring after low temperature treatment in winter. After the low temperature stage of vernalization, the biennial autumn sowing grass flowers need some light to bloom. Such as pansy, calendula, bibcock flower, daisy, etc. Woody flowers such as white orchid, jasmine and Milan are also long-day flowers.

2. Mid-day flowers:

The effect of light duration on flowering is not obvious, and it can bloom normally under 6-1 hours of light every day. For example, carnation and hibiscus planted indoors, dahlia and rose planted outdoors can bloom all year round as long as the temperature is suitable and the nutrition is sufficient.

3. Short-day flowers: