What is the economic significance of the photoperiod phenomenon?

Application of photoperiod in agricultural economic production.

1. Introduction: The introduction of seeds in areas with similar latitudes is easy to be successful. The northward migration of short-day plants was due to the extension of sunshine in the growing season, and the southward migration of long-day plants was due to the shortening of sunshine in the growing season, which had the effect of delaying development. On the contrary, the southward migration of short-day plants or the northward movement of long-day plants has the effect of promoting development.

When short-day plants are introduced, the effects of temperature and light length are superimposed on each other, and the impact on the early or delayed development period is more prominent, and it is not easy to succeed when the distance between north and south is long. The introduction of long-day plants from north to south is compensated by the influence of light and temperature, and it is generally easier to succeed. However, in areas with poor thermal conditions, the introduction of short-day plants from high latitudes is often conducive to frost avoidance and early maturation.

However, for crops that are mainly harvested with nutrients, it is necessary to prevent premature transformation to reproductive growth.

2. In the breeding work, the photoperiod is used to adjust the flowering period to achieve hybridization between varieties. The photoperiod effect can be used to make crops develop early, and it can also realize superproduction and shorten the breeding period.

3. Adjust the sowing period. Choosing the appropriate sowing date and transplanting date to match the natural sunshine and temperature with the requirements of the crop is the main condition for improving yield.

4. Floriculture. The flowering period can be artificially adjusted by using the photoperiod phenomenon to make the chrysanthemums of short-day plants bloom in any season.

It is of great help to the economy, and mankind has long used the knowledge of the phenomenon of photoperiod in production, medicine and education. The nursery network collects and organizes a wide range of applications, such as adjusting the light time to control the flowering time of flowers and the amount of eggs laid by chickens. Under natural conditions, the total length of the diurnal cycle is a fixed value (24 hours), and a certain period of light must correspond to a certain period of darkness.

Under artificial conditions, although it is possible to produce a combination of light and darkness of any length, in order to produce the desired effect, it is still necessary to roughly simulate the natural conditions to which organisms have adapted for a long time.

The photoperiod phenomenon of plants, insects and birds is more obvious, and there are many studies on them. This includes flowering, defoliation, dormancy of seeds and spores, and formation of tubers and roots. diapause, migration and morphology of insects; Migration, gonadal development, body fat accumulation and moulting of birds, etc. Organisms must have photosensitive mechanisms to respond to photoperiod:

Photosensitin is found in plants; In animals, the optic nerve as well as the pineal gland or other brain structures are the first stops of the reaction. Second, there is no important research in this area where there must be a time-measuring device (circadian clock) in order to determine whether the length of the light (or dark period) is appropriate. Finally, in the efferent part of the reaction, the plant may be through hormones; Animals contain both nerves and hormones.

The phenomenon of biological photoperiod is an evolutionary genetic trait that determines how a species responds to the photoperiod, but the actual response is affected by environmental conditions. Light experiments were carried out on the parent silkworms, but the reaction was manifested in the offspring. The length of light exposure can determine whether the offspring is diapaused. This shows that the complexity of the photoperiod phenomenon needs to be combined with physiology, genetics, ecology and other aspects to elucidate.

The photoperiod phenomenon is the response of organisms to the pattern of day-night photo-dark cycles. The flowering of most annual plants is determined by the length of hours of daily sunshine. In addition to flowering, the formation of roots and tubers, the shedding of leaves, and the dormancy of buds are also controlled by the photoperiod (the relative length of day and night of the day).

Physiological response characteristics of plants to periodic, especially diurnal and nocturnal changes in light and darkness and the length of light and dark time. In particular, some plants require a certain photoperiod to form flower buds. But other physiological activities are also affected by photoperiod.

The phenomenon of photoperiod refers to the ability of plants to perceive changes in the length of day and night and to make a series of physiological responses based on these changes.

During phylogeny, plants respond to changes in daylight length, and the apical meristem differentiates from vegetative growth to reproductive growth, a phenomenon called photoperiod phenomenon. In addition to the need for constant temperature induction, the differentiation and formation of plant flowers must undergo a certain photoperiod induction.

Ecological significance. In temperate zones, the seasonal variation in temperature is significant, with longer winters as latitude increases. Plants cannot reproduce offspring if they do not form seeds before the arrival of low temperatures and frosts. Many plants have developed the ability to sense the seasons in the course of long-term adaptation, with the length of day and night being less affected by climatic conditions.

For example, some plants originating in high latitudes often bloom and bear fruit under the condition that the sunshine changes from short to long after the spring warms, and long days are required for flowering. Some plants of low latitude origin, with short-day plant characteristics, bloom in the autumn when the day length gradually decreases, which is conducive to making the most of the longer warm periods at low latitudes.

In some areas where water is not the temperature but the water that determines plant growth, the plants that originated in the dry season in winter and the wet season in summer are more short-day, and the opposite is more likely to be long-day plants. In the same latitude, different responses to day length make different plants flower and bear fruit in different seasons, which is an important factor in determining the phenological period of plants.

The photoperiod phenomenon refers to the flowering and fruiting, defoliation and dormancy of plants, and the reproduction, hibernation, migration and moulting of animals, etc., which are the response to the regular changes in the length of sunlight.

The phenomenon of photoperiod was discovered by Garner and Allard in the United States.

The above phenomenon shows that plants bloom in a specific season, they think that there must be an environmental factor in the control of flowering, as we know, the main environmental factors are temperature, light, water, air, mineral nutrition, then with the season change is mainly temperature and light length, therefore, they tested the effect of sunshine length on tobacco flowering, and found that only when the daylight is shorter than 14 hours, tobacco blooms, otherwise it does not bloom.

Later, it was discovered that many plants require a certain length of sunlight to flower, such as winter wheat, spinach, radish, peas, heavenly fairies, etc., which is the discovery of the photoperiod phenomenon.

In 1920, Garner and Allard worked at the Beltsville Agricultural Experiment Station of the United States Department of Agriculture in Maryland, USA, and they found two phenomena that are difficult to explain, one is the tobacco variety Maryland Mammoth, which can reach a height of 3 5 meters in summer, but does not bloom, and if it is in a greenhouse in winter, it can bloom if it is less than 1 meter high; Another phenomenon is that a soybean variety is sown at different times in the spring, but blooms at the same time in the summer, although the vegetative size of the soybean varies at different sowing stages.

Geographic latitude

China is located in the northern hemisphere, the temperature is low in the short period of spring, and the plants are generally in the seedling stage, which has nothing to do with flowering temporarily. Autumn is a time when temperatures are warmer and suitable for plant growth, so the sunlight at this time can significantly affect the flowering of plants. The natural long sunshine period in summer, with high temperatures, is a suitable period for plant growth and development.

These two seasons of the year affect the flowering and fruiting of plants. At lower latitudes, temperatures are higher throughout the year, but there are no long-day conditions, so there are only short-day plants, which generally bud in early spring and bloom at any time of summer and autumn. Some plants can be multi-seasoned, such as rice; In the mid-latitudes, there are both long-day and short-day conditions, and the autumn temperature is high, so both long-day and short-day plants are distributed.

Long-day plants bloom in late spring and early summer, while short-day plants bloom in autumn; In the high latitude region (northeast of China), although there are long-day and short-day conditions, the seasonal variation of temperature is more obvious. In autumn, when the days are short, the temperature is already low and the plants cannot grow. Therefore, it is not possible to survive some plants that require longer sunlight.

The different types of photoperiod reactions in plants are the result of long-term adaptation to the environment. Because the same latitude on the earth is different in different seasons and between different latitudes in the same season, the regular distribution of plant photoperiod response types is formed.