Mushrooms, illnesses a plant and stability to illnesses. Phytotoxins

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We already noticed that the nature often advances the person in the ' inventions '. Do not make in this sense of an exception and herbicides. Many plants have own ' herbicides ', or phytotoxins with which they suppress growth of the competitors. The negative influence rendered by plants against each other by means of substances, allocated in environment, carries the name allelopatii. Generally examples allelopatii are observed in semidroughty areas because plentiful rains wash away water-soluble phytotoxins and facilitate also their microbic decomposition. About allelopatii absence nearby from the given type of plants of other plants competing to it testifies. The plant developing phytotoxin is frequent, is surrounded by a strip of the naked earth, and though on this naked earth of water, it is quite enough light and nutrients, other kinds of plants grow only on known distance from a phytotoxin source.

Phytotoxins can be flying or can extend by means of water. We will consider two examples to get acquainted with that and other situation. Salvia leucophylla (sage) is a small semibush with which in California meadows grow. Neither in thicket Salvia, nor of 1-2 m the grass does not grow in an adjoining zone in width. Even on distance of several metres from Salvia there are only separate copies of the grassy plants which growth is considerably oppressed. It was found out, as in air round bushes Salvia, and at soil near these plants there are two flying terpena - tsi-neol and camphor, toxic for the grassy plants, sharply suppressing germination of their seeds. Salvia allocates these terpeny in the end of spring when rains practically have already stopped. Terpeny are absorbed by soil particles and remain in soil throughout all long dry summer. When with approach of a season of rains seeds of grasses start to sprout, terpeny get into roots of sprouts, being dissolved in voskoobraznom kutine, covering their surface. Thus they suppress growth of young sprouts so strongly that those cannot survive any more if rainy weather is replaced again dry, and in local places it happens quite often. After several weeks of a rain terpeny in soil are not found out any more, however renewal of their formation upon termination of a season of rains restores again their level and provides constant domination Salvia. Roots Salvia form dense weight which absorbs almost all available water near to a soil surface that also complicates development of other plants.

The Wide set of substances is included by group of the phytotoxins extended by means of water. Californian chaparal consists from kustarnikovoj the vegetation occupying usually bottom part of dry slopes of mountain ridges. Dominates in this community Adenostoma fasciculatum, grassy plants here almost completely are absent. The phytotoxins collecting in soil chaparalja, get there not from a laying and not with root vydelenijami, and with the drops of a rain which are flowing down from leaves. They collect on leaves in dry weather and then are very quickly washed off from them even by the slight rain, and sometimes and during a fog. Therefore near to the plants developing phytotoxins, growth of grassy plants, and germination of their seeds is suppressed also. At research in sheet washouts 9 phenolic connections with phytotoxic properties were revealed. After cutting out of bushes toxic substances not for long remain in soil; Therefore thickets Adenostoma can keep dominating, caused allelopatiej position only in the event that their leaves are periodically washed by water. Other kinds of plants develop more proof toxins. For example, Arctostaphylos glan-dulosa forms proof phytotoxin which collects and in plant roots, and in a laying. Some kinds of oaks develop juglon - substance from a class hinonov, very strongly suppressing under the big trees growth of vegetation competing to them. In the past such natural phytotoxins practically were not considered as potential herbicides; however in due course we, probably, take, them on arms as these natural herbicides are valuable that they are harmless.