Monocots: the origins and characteristics of class

Monocots on planet Earth appeared almost at the same time as the bipartite: since that time has passed more than a hundred million years.And that's about the way in which it happened, botanists are divided.Proponents argue a position that monocots evolved from the simple bipartite.They develop in damp places: in ponds, on the shores of lakes and rivers.But defenders of the second view believe that monocots originate from primitive representatives of their class.That is, it turns out that form, prior to modern flowers, can be grassy.

Palm, grasses and sedges - these three families were issued and disseminated by the end of the Cretaceous period.But bromeliads and orchids, perhaps the youngest.

Monocots belong to the class of angiosperms, the second largest.They account for about 60 000 species, birth - 2800, and families - 60. Of the total number of flowering plants make up a quarter of the monocots.At the boundary of 20-21 centuries, botanists have increased this class by crushing several previously identified families.Thus, for example, distributed lily.The most numerous family of orchids appeared, followed by grasses, sedge, palm.And the smallest number of species has Araceae - 2 500.

generally accepted, widely used around the world classification system monocotyledonous flowering plants developed in 1981 by a botanist from the United States - Arthur Cronquist.He pitched all monocots into five subclasses: kommelinidy, aretsidy, zingiberidy, alismatidy and liliidy.And each of them consisting of several more order, the number of which varies.

Monocotyledonous are Monocotyledones.A classification system developed by APG and giving the name of the group in English only, it corresponds to a class Monocots.

presented monocots mostly grasses and to a lesser extent - trees, shrubs and vines.Among them are many who prefer to marshland, ponds, breeding bulbs.The representatives of this family are present in all continents of the globe.

Russian name monocots obtained by the number of cotyledons.Although this method of determining is neither sufficiently robust or easily accessible.

first distinguish between monocots and dicots suggested in the 18th century English biologist John. Ray.He identified the following characteristics of the first class:

- Stems: rarely branched;closed their vascular bundles;vascular bundles are placed randomly on the cut.

- Leaves: mostly amplexicaul without stipules;usually narrow shape;venation arcuate or parallel.

- Root system: fibrous;adventitious roots very quickly replace the embryonic root.

- Cambium: absent, in connection with the stem thickens.

- Bud: monocotyledonous.

- Flowers: perianth consists of two at most - three-term interests;the same number of stamens;three carpel.

However, separately, each of these attributes can not clearly distinguish between bipartite and monocots.They only considered in combination, allow to accurately set the class.