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The concept of photoperiod , also mentioned as photoperiod (no accent on the I ), is used in the field of biology to name the daily time that a living being is exposed to light . During this period, various processes are carried out in the plant organism that allow the regulation of its biological functioning .

In a broad sense, it can be said that the notion of photoperiod covers both the time of exposure to light rays and the processes that this exposure produces in the plant. The alternation between day and night, solar cycles and changes in station determine the effects of the photoperiod.

Exposure to light influences the germination and in the developing of plant species: according to the number of hours a plant receives light , can grow more or less. The photoperiod causes a species to grow less in winter than in the rest of the year, for example, since the days are shorter and growth, in this context, is interrupted.

The light signals are recognized by the plants through receivers that capture and translate them, triggering various reactions. He phototropism It is one of the phenomena directly linked to the photoperiod.

It is possible to classify the different species of plants based on the way in which they respond to the photoperiod, since many of their activities are determined by the duration of the day (an example is the production of flowers). In this framework we can talk about the short day plants , whose flowering occurs only in the short days, or else it is then that this production process is accelerated; there are also the long day plants , which need a much greater exposure to sunlight.

There is a third class of plants, called neutral plants , whose response to the photoperiod is null; where appropriate, flowering occurs through autonomous mechanisms of regulation .

It is known as photoperiodic induction to a regulated process that takes place at the moment in which the leaves of a plant recognize the photoperiod through the use of the so-called receptors phytochromes and photoreceptors, and send signals to apical outbreak (the one that is produced from a bud terminal, that is to say, that it is in a tip) so that it begins to produce the flowers.

In greenhouses, the exposure of plants to light can be done artificially, as well as many other phenomena. The lighting installations in these spaces are divided into two well-defined types, according to their classification: on the one hand there are those that serve to photosynthetic assimilation , for which they are used lamps of sodium; In the case of photoperiod control, incandescent lamps are often used.

For crops of cut flowers (where we find the paniculata, kalanchoe and chrysanthemum, among others) lighting installations offer the possibility of controlling the duration of the photoperiod through the fusion between artificial light and a shade mesh, and the cycles are programmed for automated execution; for example, operators can determine that the lights remain on for ten minutes and then turn off, to turn on again twenty minutes later.

It is important to mention that the photoperiod also affects the animals . The environmental factors affect sexual behavior and, therefore, the reproduction and breeding of new specimens. In short, all living beings carry out their vital processes according to the conditions of the environment, both by light and by other variables.

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