characteristics of Bryophytes

Bryophytes Bryophytes are non vascular land plants of moist habitat. They include about 960 genera and 24k species. The plant body of bryophyte is more differentiated than that of algae. These are the unique group of plants commonly regarded as 'amphibian of plant kingdom', intermediate between aquatic algae and terrestrial pteridophytes. Characteristics of Bryophytes 1. They grows generally in large numbers on wet soils, edges of rocks, walls, tree trunks etc., especially during spring season. 2. The dominant phase in the lifecycle of bryophyte is gametophyte. It is a thallus, i.e., not differentiated into root, stem and leaves. In majority of bryophytes the plant body is simple, dorsiventrally differentiated dichotomously branched thallus made up of parenchymatous tissue. They possess many hair like structures called rhizoids which fix them to the substratum. They help in the absorption of water and minerals. The vascular tissues are absent, conduction of water and food takes

Economic importance of green algae

1. Food: Many green algae such as Ulva, Caulerpa, Enteromorpha, Chlorella etc. used as food. Chlorella has highest percentage of protein or even more than in other vegetables or egg. It is said to contain all vitamins from A to D.  2. Antibiotics: An antibiotics called Chlorellin is extracted from Chlorella. It has marked effects against both Gram positive and Gram negative bacteria especially E. coli etc. Even Cladophora and Caulerpa also yield antibiotics. The alga like Chara and Nitella have larvicidal property. 3. Sewage treatment: Green unicellular algae such as Chlorella and Chlamydomonas are used in sewage treatment ponds. They show photosynthesis, remove carbon dioxide and release oxygen and make the sewage water habitable for many fishes and aerobic bacteria. 4. Green algae in space research: In recent years biologists used green alga(Chlorella) extensively in space flight trips. The algae can reuse carbon dioxide during the process of photosynthesis and release oxygen for the

characteristics of gymnosperms

Gymnosperms Gymnosperms are seed bearing plants without flower and fruits, represented by about 900 living species all over the world Characteristics of gymnosperms Gymnosperms are regarded as an intermediate group between the pteridophytes and angiosperms. They formed a dominant vegetation on the earth about 200 million years ago and now they have maintained their dominance in the colder regions. A few are in warmer climate also. The plants are with roots, stems and leaves. These plants bears naked seeds. All gymnosperms are perennial woody trees. Some of them are large and live for thousands if years. The roots are generally taproot, in some species mycorrhiza, corolloid roots and root with cyanobacteria are seen. The stems are branched or unbranched. The leaves may be simple or compound. In Cycas leaf is pinnate and persists for a few years and young leaves circinate venation. In Pinus leaves are needle like to reduce the surface area. Thick cuticle and sunken stomata in gymnosperms

Root apex and Quiescent Centre of Root Apical Meristem

Root apex During the later stages of development of embryo, the cells at the root pole become arranged in a pattern characteristic of the species. This group of cells comprises the apical meristem of the primary root. The cells of this region are all relatively undifferentiated and meristematic, densely protoplasmic and with large nuclei and they all undergo active division. The tissues of the mature root are eventually derived from a number of these cells of the apical meristem, which are termed initials. In contrast to the apical meristem of the shoot, that of the root produces cells not only towards the axis but also away from it, for it initiates the root cap and because of the presence of root cap the root meristem is not terminal but sub terminal in its position, in the sense that it is located beneath the root cap. The root apex also differs from the shoot meristem in that it forms not lateral appendages comparable to the leaves, and no branches. The root branches are usually in

secondary growth in dicot root

It is common in dicot roots except a few short lived herbs and submerged aquatics. In dicot roots, the meristematic tissue(cambium) is completely secondary in origin, secondary growth in dicot roots takes place by the formation of secondary tissue. Two types secondary tissue-the secondary vascular tissue and the periderm are produced during secondary growth. These are formed by the lateral meristems vascular cambium and cork cambium respectively. Origin and activities of vascular cambium The primary dicot roots lack cambium. The vascular cambium develops later as secondary meristem. It develops partially from conjunctive parenchyma and partially from pericycle. The conjunctive parenchyma and partially from pericycle. The conjunctive parenchyma cell lying on the inner side of the primary phloem bundles, becomes meristematic to form cambium strips. In the meantime, cells of the pericycle just outside the protoxylem also become meristematic. These join with the earlier formed cambial stri

structure and function of cell wall

The typical plant cell has three distinct regions. They are cell wall, protoplast and 3 vacuoles. A cell wall is the non living outer boundary of the cell of plants and fungi which encloses various living organelles and non living inclusions. One of the major differences between animal cell and plant cells is the possession of true cell walls by the plants. The chief structural component of cell wall is cellulose. In addition to cellulose, pectic compounds, hemicellulose, lignin, suberin, cutin, protein, fats etc. may also found in cell wall. A plant cell wall can be differentiated into three regions namely-middle lamella, primary wall, and secondary wall. 1) Middle lamella It is chiefly composed of calcium and magnesium pectate and is the amorphous region between two cells. The formation of middle lamella begins in the telophase stage of the cell division when fragments of endoplasmic reticulum and golgi apparatus migrate and accumulate in the middle region to form a cell plate. Middl