Fig.21.1 Cyanobacteria Cellular Structure

REVIEW OF LOWER PHOTOTROPHS, FUNGI, HIGHER SPORE PLANTS AND THEIR MEDICINAL REPRESENTATIVES

(sense module 4)

Theme 21

LOWER PLANTS: CYANOBACTERIA AND ALGAE. REPRESENTATIVES, WHICH HAVE MEDICAL APPLICATIONS

RELEVANCE OF THE THEME:Knowledge of taxonomy and systematics, as well as general and specific features of lower plants are needed to identify diagnostic features of medicinal plants of systematic taxa.

TRAINING GOAL of the LESSON

GENERAL PURPOSE:Master the basics of taxonomy and systematics, and morpho - anatomical characteristics of lower plants.

SPECIFIC PURPOSE

TO KNOW:

1. The objectives, tasks and methods of botanical taxonomy, systematics and taxonomy basics necessary to classify plants.

2. General characteristics of lower plants.

3. Descriptions of separate representatives of bacteria and algae, which are medicinal plants.

BE ABLE TO:

Describe and identify representatives lower plants that are medicinal plants.

THE BASIC THEORETICAL TEMS OF INFORMATION

Class Cyanobacteriae—The Cyanobacteria (Blue-Green Bacteria)

In the past, algae as a group have been distinguished from other organisms in being photosynthetic, in having relatively simple structures, and, for those reproducing sexually, in having sex structures consisting of a single cell. As more became known about cellular details, however, it became apparent that the differences between the cyanobacteria (blue-green bacteria) (formerly known as the blue-green algae) and true algae are quite basic. Like all other members of Kingdom Bacteria, cyanobacteria have prokaryotic cells, while all algae that are assigned to Kingdom Protista have eukaryotic cells. Cyanobacteria, in fact, are so much like other true bacteria that biologists generally have abandoned the reference to them as algae and consider them true bacteria.

Fig.21.1 Cyanobacteria Cellular Structure

The main distinctions between organisms traditionally regarded as bacteria and cyanobacteria are:

(1) cyanobacteria have chlorophyll a, which is found in higher plants, and oxygenis produced when they undergo photosynthesis;

(2) cyanobacteria also have blue phycocyanin and red phycoerythrin pigments known as phycobilins;

(3) cyanobacteria are the only organisms that can both fix nitrogen and produce oxygen - a paradox, since nitrogen-fixation is essentially an anaerobic process.

Except for the prochlorobacteria, other bacteria capable of carrying on photosynthesis do not produce oxygen, and they do not have chlorophyll a.

Cyanobacteria are found in almost as diverse a variety of habitats as other true bacteria. They are common in temporary pools or ditches, particularly if the water is polluted. They are not found in acidic waters, but they are abundant in other fresh and marine waters around the globe, from the frozen lakes of Antarctica to warm tropical seas. In the open oceans, cyanobacteria are the principal photosynthetic organisms in plankton, the tiny cells of the cyanobacterium Synechococcus commonly occurring in concentrations of 10,000 cells per milliliter. Trichodesmium is a marine, filamentous, nitrogen-fixing cyanobacterium that forms extensive mucilage-producing colonies in some tropical waters. Other bacteria multiply in the mucilage and become food for protozoa.

The microscopic blue-greens have no membrane-bounded nucleus (prokaryotic, pro = before). [All plants and animals have membrane-bound cell organelles including nuclei (eukaryotic, eu = true).] The cell has a mucilaginous sheath of pectin that surrounds the cell wall and an inner cellulose wall. Cell contents (protoplasm) include nuclear material with DNA fibrils, chlorophyll a, and accessory pigments of blue (phycocyanins), red (phycoerythrin), orange (carotenes), and xanthophylls (yellow) colors. These pigments are involved in capture of light and subsequent formation of carbohydrates (photosynthesis). Cyanophycean starch is the storage product. Blue-green forms may be one cell (unicellular), colonial (cells held together by a gelatinous sheath), or filamentous (chains of cells called trichomes). They have nothread-like structures (flagella) for movement.

Date: 2016-01-03; view: 1167