Fast movements of plants. Insectivorous plants

you are: Fast movements of plants

Many insectivorous plants meet in marshy areas the low maintenance of nitrogen in soil. These plants satisfy a part of the requirement for nitrogen, catching insects leaves and digesting then extraction. This inversion of more usual relations between animals and plants intrigued many researchers, including Charlza of Darwin. The simple experiments made by its have shown, how the meat diet (tab. 13.1) is salutary for insectivorous plants.

Darwin investigated in essence all aspects of behaviour of these surprising plants, beginning from their methods of capture of extraction to chemical features of process of its digestion. Its witty experiences, carefully collected given and brilliant conclusions should admire all biologists. Some of its books are specified in the bibliography in the end of this chapter.

The Insectivorous plants which have been found out among mushrooms and in six families pokrytosemennyh, can use passive (like a sticky paper) or the active mechanism of catching of insects (fig. 13.5). Passive traps usually chasheobraznye and deep. To an insect who has flown or has crept in one of them, it is difficult to get out so quickly to avoid damage by a sour secret and not to be killed by digestive enzymes containing in it. In such traps the sheet surface is covered by mucous substance, obezdvizhivajushchim an insect. Such substances, mainly carbohydrates, are synthesised by ferruterous cages on a surface of sheet and deduced from a cage sekretornymi by vials diktiosom. Some insectivorous plants, for example rosjanka (Drosera), use as ' a sticky paper ', and the active mechanism of catching: the insects who have got to a sticky secret, beat legs and wings, irritating thus touch cages of hairs being nearby.

These hairs cover an insect and result it in contact to the ferruterous cages allocating strong acids and gidroliticheskie enzymes. Trap movements are rather slow

At plants with the combined is passive-active mechanism of catching of insects and much faster at such plants, as a Venus flycatcher (Dionaea) which at catching of insects is necessary exclusively on trap movements.

The Trap at Dionaea consists of the sheet, forming two blade with a number of hairs on edge and three trigger hairs located on the top surface in the form of a triangle (fig. 13.6). The mechanical irritation of one of trigger hairs causes the one and only potential of action which extends on hair and blade cages, raising in result of a cage of the blade which change of volume causes its movement.

Two consecutive potentials of action are necessary For trap closing or even more if the interval between two potentials is more 15 with. This condition (like necessity of some consecutive days for a photoperiodic induction) assumes presence of primitive type ' memories '. The plant still ' remembers ' the first potential of action if the second follows the first quickly enough, but this ' the memory trace ' is soon erased. Apparently, one potential of action leads to increase in quantity of any substance supervising movement. Level of this substance which should collapse in due course, after one irritation still remains podporogovym. But if the second potential of action comes earlier, than this level will essentially decrease, concentration of substance will exceed a threshold of excitation and there will be a reaction.

Trap Movement occurs extremely quickly, as well as should be that it was possible to catch an insect. All process, including stimulus transformation, a signal transmission and trap closing, comes to the end less than through 0,1 with the ambassador of sufficient irritation. Closing of a trap at Dionaea as well as at niktinasticheskih plants, it is supervised by changes of volume of key motor cages; however it is not clear, whether play To +, С1- or other inorganic ions a considerable role in regulation their tourist's mountain.

The Double irritation does not conduct to full closing of a trap. Therefore very small insects can creep out between hairs and escape. But if the insect touches a touch hair each time is raised new potential of action, the trap is closed more densely and secretion of acids and digestive enzymes with ferruterous hairs on the top surface of sheet is stimulated. Thus, the resisting insect accelerates own  destruction

The Trap at Dionaea remains closed until all body of an insect, except its skeleton, will not be digested; if the insect large, it can last week and more. If the trap was closed as a result of irritation by any not food object (not an insect) or short-term mechanical influence, it can already open again in some hours. Thus, as has concluded Darwin, products of digestion hold a trap of the closed. When the food will be digested also a trap again will open, leaves again will appear in horizontal position, optimum for photosynthesis. Thus, for lack of meat food the plant comes back to avtotrofnomu, to a photosynthetic food.