Irritation in plants.

The plants do not possess nervous system. Their behaviour is basa in local responses of the various organs of the body to specific environmental stimuli.

The plants do not possess nervous system. The outbreak of the plant is geared himself, so that increases their chance of fotosintetizar. The roots grow so that they meet with an efficient consumption of water and minerals. The flowers are geared to promote opportunities for flowering and seed germination is regulated to increase opportunities for future development.

These activities require complex integration and how it coordinates and regulates plant growth, comprising chemical messengers called hormones. These are not produced in specialized glands special as in animals if not groups of non-specialized cells, usually meristematic tissue that is located at ends of the root, stem and branches and the buds axial where outbreaks leaves Of these places will be carried by Liberians to the site where act, the main effects of plant hormones are to regulate plant growth: start flowering and fruit production; stimulate the formation of roots warning; inhibit leaf fall and fruits.

The action of plant hormones was observed by Charles Darwin and Francis in the last century and now already know some of them are known in their chemical composition and form of activity.

Fototropismo: It produces a response towards the light (light stimulus), and implies a growth of vegetation. The roots have a negative fototropismo, because growing up in the opposite direction to light. Leaves and stems are moving in the direction of light.

Geotropismo: It manifests itself depending on the severity. The stem and leaves grow in the direction opposite to gravity, thus presenting a negative geotropismo. The roots grow in the sense of seriousness, have a geotropismo positive, sometimes negative geotropismo presents the root, when there is more water in the soil surface in depth. In this case, the roots tend to grow toward the source of water in the soil surface in depth. In this situation, the roots tend to grow toward the water source, in response to Hidrotropismo.


Tigmotropismo: The vines or climbing plants depend on a carrier, whether these plants or other surfaces. The tendency to climb responds to contact with such media.

Circadian rhythms: changes are experienced by plants in line with environmental stimuli and according to some predetermined biological stimuli. Inside they have, for example, photojournalist and seasonal movements, which are responses of plants to changes in sunlight between day and night and between some stations and others. These changes are manifested in the different position of the leaves, in the closing night of flowers, the flowering period, the germination of seeds, etc..

B. - Nastia -:

There are movements of plant organs, particularly leaves and petals, in response to external stimuli. These movements, unlike the tropism are not addressed in the same direction as the stimulus and do not present an increase in plant mass. It produces a movement without guidance and passenger, since the plant back to its original position after a short time.

There are several kinds of nasties: sismonastias and quimionastias.

the sismonastias: That occurs when the stimuli are beaten or shaken to a plant, as when for example. Mimosa pudica commonly known as cat's claw, to be touched its leaves are folded and taken shrinking their appearance withered leaves on the stem as if closing or changing movements of leaves from plants to possess a carnivorous insects on them.

The quimionastias or response to stimulation of certain substances, usually water, and fotonastias, or responses to light stimuli, like when the leaves of the acacia or clover vary their position at dusk, while the sandiego night opens its flowers and the daisies close to the sun set.

c. - Circadian rhythm and watches

These changes experienced by plants in line with environmental stimuli and according to some stimuli biological prederminados. Inside they have, for example, photojournalist and seasonal movements, which are responses of plants to changes in sunlight between day and night and between stations and others. These changes are manifested in the different position of the leaves, in the closing night of flowers, flowering period, the germination of seeds, etc.. It was carried out because the plants have photoreceptor proteins, called fitocromo, that trigger female hormones, including being auxins. The light and temperature seem to be the most external stimuli that affect these changes.

How can a plant spinach distinguish one day 14 hours a day from 13.5 hours?. The measurement of photoperiod requires on the one hand, photoreceptors that can distinguish the day and night, on the other hand, a mechanism to measure the hours of darkness. As for the photoreceptors, which is known both as fitocromo criptocromos are involved. The outstanding issue is, how plants measure the length of time darkness?

This question leads us to another group of readily observable phenomena. Some plant species have flowers that open in the morning and closes at dusk. Other extend their leaves to sunlight and folded into the stem at night. Example: The leaves of the plant vinagrillo that folds its leaves at night.

A recent hypothesis, but even without evidence, is that "movements of sleep" prevent the leaves absorb the light that reflects the moon at night very clear, protecting phenomena photojournalist. These movements continue daytime although the plants are kept in constant light conditions. All are biologists now agree that circadian rhythms are endogenous, or originate within the agency itself and are controlled by what is known as biological clock.

"The response to environmental stimuli plants in this mediated by hormones."