In the system of plants all known plants are ordered according to the phyletic evolution. Among all organisms living today, viruses and bacteria belong to protista. As the viruses have no cells and metabolism, but only nucleus substance, they are not considered by some scientists to be real living beings. They penetrate like parasites into the cells of plants, animals (human) and bacteria and cause diseases, e.g., cold and kinds of cancer. The increase of viruses occurs in the host cells. The bacteria, on the contrary, have cells with simple organelles, but still no real nucleus.

Next step in the development of the living beings on our earth are living beings with real nucleus and developed organelles. The algae belong to them.

The algae are the oldest plants on earth. They have developed only a little and are simply built even today. Algae are single-cell or multicellular plants without differentiated tissues.

6.17 Algae

a – single-cell-spherically, b – multicellular-filamental, c – multicellular-branched

They live autotroph. The chlorophyll is responsible for the colouring for the photosynthesis which is in chloroplasts. The green algae store starch, their cell walls contain cellulose. Other groups of algae have, in addition, red, yellow or brown colorings and store other substances, e.g., oil. The importance of algae for food is increasing. They are used not only as a fertilizer for the ground and food for the farm animals, but also as food.

The algae still need water as environment. They are plants of the seas, lakes and rivers and live in humid places. They can reproduce by spores, asexual reproductive cells, or by gender cells. The male gender cells need water to be able to swim to the ova.

Among different systematic groups of algae the flagellates are known to have the most original forms. The flagellates, the protozoans and later the metazoeas developed from heterotrophen. The green flagellates, other algae and later the higher plants developed from autotrophen.

Fungi developed in parallel with algae from one-celled protozoa. They are either single-cell like the yeast or multicellular and then consist of thin fibers, mycelium. In the large part of fungi the cell walls contain not cellulose, but chitin, a material which is known, however, only from the animal kingdom. The multicellular fungi reproduce by spores. All fungi without exception live heterotroph. There are parasites among them. They cause diseases in plants (e.g., the real mildew on the leaves of useful plants), animals and people (e.g., skin diseases).

6.18 Mushrooms

a – yeast, b – mould c – pileate

Many fungy are saprophytes, e.g., yeast and mould. They grow in organic substance and diminish them. Yeasts are used in the production ofy bread, wine and beer, because by their fermentation alcohol is originated. Mould spoils food. The important medicine penicillin was received from mould penicillium notatum.

Mycelium of another fungus group is located in the roots of flowering plants with which these fungi live in symbiosis. The fungus supplies its symbiont with water and nutrient salt from the ground and takes, in return, carbohydrates which it cannot produce of water and carbon dioxide. Some mushrooms can be eaten, other are toxic.

Mosses can be found on humid ground. There are low, green land plants. They have the differentiation of tissues and the formation of organs.

6.19 Moss (a) and fern (b)

Ferns like seed plants have roots and sprouts. Both form sprouting plants. Their tissues and organs allow them to live on the ground. They are protected against too strong vaporisation. There are also trees among ferns.

Algae, mushrooms, mosses and ferns form spores for the asexual reproduction. They are called spore plants.

1.5 SEED PLANTS

Seed plants which are also called flowering plants are distinguished from the spore plants by the formation of blooms and seeds which serve the reproduction. Their male gender cells need no water to reach the female gender cells.

6.20 Gymnosperms

a – сonifer, male and female blooms, b – a part of a female bloom

Two main groups of seed plants are gymnosperms and angiosperms. Gymnosperms are plants in which the ovule freely lies on the carpel. In angiosperms the ovule is enclosed in the ovary. Gymnosperms appeared formerly in the phyletic evolution. The conifers important for the economy belong to gymnosperms. Their foliage leaves are mostly thin like needles. They have no fruits, but strobila in which the seeds are situated.

Angiosperms are divided into two groups: monocotyledonous and dicotyledonous.

As the name says, the embryo of monocotyledonous owns a cotyledon, which does not appear from the seed during the germination in this type of plants. Dicotyledonous have two cotyledons which in some kinds of those plants look like the first green leaves above the ground. While monocotyledonous have many roots beginning at the blooms of the sprouts, dicotyledonous generally have a main root with branch roots.

In the stalk cross section of monocotyledonous the vascular bundles lie untidily and have no cambium. In the stalk cross section of dicotyledonous the ring-shaped bundles lie regularly. Since these plants have cambium, secondary thickening is frequent. Trees with big diameter can thereby form.

The lamellose leaves of the monocotyledonous are mostly narrow and have parallel fibers. The lamellose leaves of the dicotyledonous are often wide conversely, their fibers make a net-shaped picture. Moreover, the sepals and petals of monocotyledonous are mostly of the same shape and colour. The number of sepals, petals, stamens and carpels equals to three, six etc. The blooms of the dicotyledonous are four or five.

The monocotyledonous were developed from elementary dicotyledonous.

Important dicotyledonous

Many of dicotyledonous as useful plants and they are important for food of people and farm animals.

Examples:

Legumes: Bean, peanut,

Rosaceae Family: Apple and other fruit,

Solanaceae Family: Potato, paprika, tobacco.

6.21 Features of monocotyledonous and dicotyledonous

Dicotyledonous include not only vegetables and fruits, but also medical plants, oil plants and forage plants.

Important monocotyledonous 

The important groups of grass and palms belong to monocotyledonous.

Big surfaces of Earth are covered with grass which basic food  for many animals and people. A grain, e.g., wheat, maize and rice, was developed for centuries from grass of the steppes.

The advantage of grain compared with the steppe grass are, above all, in the fact that they have bigger and more numerous grain. A grain contains beside the embryo a big pulp whose cells are filled with starch. Under the capsule there is a high-protein layer. By the processing of the grain this layer can be removed, so that very white flour is received. This, however, decreases the quality of food. The stalk of the grass is generally called halm.

In the warm areas of earth tilled sugarcane is a grass kind. Its stalks contain sugar juice which is received by pressing.

From different palms, however, fruit are used.  Palms are mostly trees with long trunks almost equally thick everywhere, with divided leaves at the top.

Constantly the quality and yield of useful plants are improved to create more favourable possibilities for people food.

1. Answer the questions using the information from the text:

1. How are viruses and bacteria distinguished?

2. What are algae?

3. How are single-cell algae and single-cell mushrooms distinguished from bacteria?

4. What is mycelium?

5. Where was penicillin received from?

6. What plants live heterotroph?

7. Which systematic groups are summarised as spore plants?

8. What is the difference between gymnosperms and angiosperms?

9. What angiosperms have four or five blossoms? Describe the features of these plants exactly.

2. Prepare an overview of the plant system and use the terms of the system from the text.

3. What features do algae, mushrooms, spore plants, gymnosperms, angiosperms have?

4. Compare different groups of the system of plants:

• bacteria – single-cell algae and mushrooms
• algae – mushrooms
• algae – mosses
• mosses – ferns
• spore plants – seem plants (flower plants)
• gymnosperms – angiosperms
• monocotyledonous  – dicotyledonous

5. Prepare a report about the system of plants.