Monocotyledonous plants: the origin and characteristics of the class

Monocotyledonous plants on the planet Earth appeared almost at the same time as dicotyledons: since that time more than one hundred million years have passed. But about the way it happened, the botanists do not have a common opinion. Supporters of one position argue that monocotyledonous descended from the simplest dicotyledons. They developed in wet places: in reservoirs, on the shores of lakes, rivers. And the defenders of the second point of view believe that monocotyledonous plants originate from the most primitive representatives of their own class. That is, it turns out that the forms preceding the modern flowers could be herbaceous.

Palm, cereals and sedge - these three families formed and spread already towards the end of the Cretaceous period. But bromeliads and orchids, perhaps, are the youngest.

Monocotyledons belong to the class of angiosperms, the second largest. They count about 60 000 species, genera - 2 800, and families - 60. Of the total number of flowering plants, monocots make up a fourth. On the border of the 20-21 centuries, botanists increased this class due to the fragmentation of several previously isolated families. Thus, for example, the lily was distributed. The most numerous was the family of orchids, followed by cereals, sedge, palm. And the smallest number of species counts as arid - 2,500.

A common, widely used worldwide system for the classification of monocotyledonous flowering plants was developed in 1981 by a botanist from the USA, Arthur Kronkvist. He broke all monocotyledons into five subclasses: comelinids, arecids, zingiberides, alismatids and lilies. And each of them still consists of several orders, the number of which varies.

Monocots are Monocotyledones. And in the classification system developed by APG and giving names to groups exclusively in English, they correspond to the Monocots class.

Monocotyledons are represented mainly by grasses and to a lesser extent - by trees, bushes and vines. Among them there are a lot of those who prefer swampy terrain, ponds, bulbs multiply. Representatives of this family are present on all continents of the globe.

Russian monocotyledonous plants were given by the number of cotyledons. Although this method of determination is neither reliable nor readily available.

The first to distinguish monocotyledonous and dicotyledonous plants was proposed in the 18th century by the English biologist J. Ray. He defined the following characteristics of the first class:

- Stems: rarely branching; Their vascular bundles are closed; The conducting beams are arranged randomly on the cut.

- Leaves: mostly stem-like, without stipules; As a rule, a narrow form; Venation is arcuate or parallel.

- Root system: fibrous; The accessory roots very quickly replace the embryonic rootlet.

- Cambium: is absent, therefore the stem does not thicken.

- Embryo: monocotyled.

- Flowers: perianth consists of two, maximum - three-membered circles; The same number of stamens; Three carpels.

However, individually, each of these features can not clearly distinguish between bipartite and monocotyledonous plants. Only all of them, considered in the complex, allow to establish the class unerringly.