Photoperiodism and Flowering

Flowering is not a random process. Some plants bloom in the autumn, while others are in the middle of the summer, others in the middle of summer, others like chrysanthemums. These simple facts have been known for centuries; however, since 1920, some things can be understood about the relevant control mechanisms and many aspects are still not well known.

Photoperiodism and Flowering

The US Department of Agriculture's Laboratories in Beltsville, Maryland began an interest in the flowering process with the researches of WW Garner and HA Allard, working with tobacco plants. These researchers have found that a new type of mutant tobacco, Maryland mammoth, can grow exceptionally (up to 3 m); but they discovered that they could not bloom. Researchers have produced a new type of steeling and found that this variety can be blossomed in greenhouse in winter. Although flowering was not an issue that Garner and Allard originally worked on, they were interested in the question of why the varieties of Maryland mammoth could be blossomed in the greenhouse in the summer rather than in summer. Thus, they began a series of groundbreaking experiments in all botanical studies.
Even though creative researchers change all aspects of their research, they do not lose sight of a phenomenon and understand and understand its importance. Garner and Allard realized that the greenhouses in winter differed in terms of temperature, humidity, light intensity, day length and similar factors in summer. They then continued their experiments until they had discovered the day length factor in the possibility of carefully controlling these environmental factors by replacing one another by replacing one another. Researchers have found that the short days at the end of autumn and at the beginning of winter stimulate flowering of the Maryland mammoth.
These researchers have been able to keep the plants light for a certain time each day and expose them to short day conditions. On the other hand, they were able to prevent flowering by increasing the day length by lighting in winter.
Garner and Allard also experimented with soya bean Biloxi. They planted soybeans at two-week intervals from early May to July and found that all of the plants were flowered in September, even if the difference between growth periods was up to 60 days. As might be expected, plants were waiting for a signal from the environment. Garner and Allard were convinced that this signal was a short time.
Experiments with other species revealed that a large proportion of plants could be placed in one of three groups:
(1) Short-day plants (chrysanthemum, poinsettia, dahlia, dahlia, pıtrak, Altınçubuk and ambrosia), such as the aforementioned varieties of tobacco and soybeans, mostly in the autumn, when the length of day is below a certain critical value. ;
(2) Day length is long-day plants (lettuce, grains, crocus, hazan flower) that bloom especially when the summer exceeds a certain critical value;
(3) neutral-day plants (dandelions, sunflowers, carnations, pansy, tomatoes, corn, string beans) which are not affected by day length and can be bloomed on long days or short days.
This reaction, which Garner and Allard call photoperiodism, and which arises against the night length of day length, helps plants to determine their reproductive times. For example, some plants bind early seed; seedlings of these plants develop in the same year and spend the winter as young plants. Others bind late seeds and spend winter as seeds. Each strategy has certain benefits and costs, including the availability of water and light for seedlings that germinate at different times of the year. In addition, the cost of pollination is also added: since pollinators are scarce in spring, plants must offer large amounts of nectar to feed them. At the end of the summer, the market is enriched and pollination is cheap. Even if it's not the best flowering time for a species,

Is There A Flowering Hormone?

In 1936, in Russia, when MH Chailakhian began his experiments, it was supported by evidence that flowering was controlled by hormones. Chailakhian removed the leaves from the upper halves of chrysanthemums (short day plants); but leaves the leaves in the lower half. The investigator then blossomed when the leafless upper half exposed the lower half to shorter days.
After that, when the process was reversed by exposing the lower half to long days and the leafless upper half to short days, the plants were not bloomed. The investigator concluded that the length of the day does not have a direct effect on the flower buds, but instead leads to the production of a hormone that causes flowering in the leaves, to the buds. This theoretical hormone is called florigen.
Additional evidence of the presence of a movable stimulus, possibly a hormone, was obtained from inoculation trials with Xanthium = pide (another short-day plant). If a plant is inoculated from one plant to another and the first plant is exposed to a photo period (short days / long nights), and the other plant is exposed to a non-stimulating photoperiod (long days / short nights), the plant that is exposed to short days before it will bloom, after long time the plants will be bloom. Even if the second plant is not exposed to a stimulant photoperiod, a warning in the first plant probably reaches the second plant by vaccine and the plant is blossoming. The same results are obtained even if only one leaf is left in the plant that is exposed to the warning photoperiod. One leaf,
There is evidence that stimulation of flowering is similar in both short-day and long-day plants: in many cases, if a long-day plant and a short-day plant are inoculated together and then exposed to short days, both will be blossomed.
It is clear that some substances produced by the stimulated short-day plant have moved to the un-stimulated long-day plant and blossomed. Long-day plants and neutral plants or short-day plants and neutral plants can be encouraged to infuse both plants by grafting. The attempts to remove the ring indicate that the excitation is carried in the phloem.
In some plants the situation is a little more complicated. The leaves that are exposed in a photoperiod that does not generate any stimuli in this way actively block the flowering. An obstacle is placed on both sides of an Xanthium leaf, and if the base of the leaf is exposed in a photoperiod that stimulates the flowering and the tip is exposed in a photoperiod that does not stimulate the flowering, the nearest bud will give flowers. If the tip of the leaf is exposed to a stimulating photoperiod, and its pedestal is exposed in a non-stimulating photoperiod, the opposite of the above experiment, the bud does not bloom or the inflorescence becomes weak. Probably, at the end of the leaf, any hormone produced under stimulating conditions is disintegrated as it passes through the unstimulated base. 
If a leaf is exposed at a stimulating photoperiod and an unstimulated leaf is found between the stimulated leaf and the bud, this may indicate a inhibitory effect. The inhibition of Xanthium and other species may be local and impermeable, but there is evidence that in some species, such as strawberries, there may be a passive inhibitor.
The most prominent hypothesis that occurs in the above-mentioned trials about the explanation of flowering is that the synthesis of a hormone that stimulates flower development by being carried in the phloem is increased by photoperiod. A photoparotate that does not generate a warning stops production of this hormone in the leaves of many plants (but not all). So, under natural conditions, flower formation begins when the photoparine exceeds a critical value as the seasons change, and when it exceeds an equal value that interferes with hormone production by the leaves.
Although there have been very effective biochemical techniques in recent years, the continuous failure in the isolation of fluorogens is disappointing. Some biochemists working in this area doubt that an original flowering hormone can be found. Like many other plant functions, flowering is also thought to be controlled by the ratio of two or more hormones produced in the first roots. No matter what it starts, a complex program about the flowering process begins. As we have seen, the structure of the flower is very complex. In addition, the color and shape of the flower, opening time and odor are consistent with a certain class of pollinators. Pollen is not usually produced during periods when the egg is not capable of fertilization. This reduces the chance of self-fertilization. An unusual example of orchestration in flowering can be seen in woodoo lily. The complex blossom of this plant emits a bad smell that attracts Hungarian flies. These odors are spread in two different, dense, heat production cycles, each of which is initiated by the salicylic acid hormone (a close relative of acetyl salicaric acid, another plant hormone known as aspirin) and lasts for about two hours each. Lily emits the first fragrance and heat in the afternoon; flies go in and are arrested there; As they try to escape, they are transmitted to the pollen to be transported to the female organs. Propagated in two different, dense, heat generation circuits, each of which is initiated by the salicylic acid hormone (a close relative of acetyl salicylic acid, another plant hormone known as aspirin) and lasting for about two hours each. Lily emits the first fragrance and heat in the afternoon; flies go in and are arrested there; As they try to escape, they are transmitted to the pollen to be transported to the female organs. Propagated in two different, dense, heat generation circuits, each of which is initiated by the salicylic acid hormone (a close relative of acetyl salicylic acid, another plant hormone known as aspirin) and lasting for about two hours each. Lily emits the first fragrance and heat in the afternoon; flies go in and are arrested there; As they try to escape, they are transmitted to the pollen to be transported to the female organs.
The second heat increase (like the first, increases the normal temperature of the flower by 10-20 ° C) serves to stimulate the unresponsiveness of the flower to the overnight guest and to transmit signals to male organs, flies to be transmitted to the pollen. Thus, the fly is allowed to escape and take pollen to the other lily.
If flowering occurs as a result of exposure to the appropriate photoperiod, we need to learn how the photoperiod is defined and measured in the first place. Since the disruption of the dark period prevents the flowering of a short day (long night) plant and stimulates the flowering of a long day (short night) plant, the light itself must be defined by the plant. Which wavelengths of light are involved in this process?
US Department of Agriculture in Beltsville, Maryland, HA Borthwick, SB Hendricks et al. These researchers exposed the so-called Biloxi soybeans to different wavelengths of light and found that red light (at a wavelength of about 660 nm) at the most short day plants prevented flowering at the most, while the red light gave very good effect on the flowering of long-day plants. It was then found that the red-light light (about 730 nm wavelength) that the human eye could not see was reversed the effects of exposure to red light. When a short day (long-night) plant breaks down with a bright red light, that plant will not bloom; however, if,
Source: poxox blogs


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