Occurrence and evolution of Pteridophytes Pteridophyta is a group of ancient plants. They formed the dominant part of the earths during Palaeozoic and Mesozoic periods. Majority of Pteridophytes became extinct. They are preserved in the form of fossils or coal deposits. Only a few living Pteridophyta are left. General structure The vegetative plant body is a sporophyte in Pteridophytes. Sporophyte ...

Photoperiodism is the response of a plant to the relative length of light and dark periods to produce flower. The relative length of day and night to which a plant is exposed is called the photoeriod. Photoperiodism is a photobiological process – a process that involves absorption of light by a receptor (usually a pigment) that results in activation of ...

Physio Chemical Nature of Plasma Membrane The plasma membrane surrounds the cell. Chemically plasma membrane is composed of: Protein: 60 to 80% Phospholipids: 20 to 40% Cholesterol is in small amount Carbohydrates is in small amount Different models were put forward about the physiochemical nature of plasma membrane. Old Concepts Charles Overton: He found that the substances which dissolved in ...

PSILOPSIDA TYPE PSILOTUM Occurrence Psilotum is distributed in tropical and subtropical regions. It may grow as an epiphyte on the bark of trees. It also grows on soil where humus is abundantly available. General structure The plant body is sporophyte. The plant is a small shrub. The plant body is differentiated into rhizome and aerial branches. 1.  Rhizome: Rhizome is ...

STRUCTURE OF LEAF Different groups of plants hake different variations in the internal structure or foliage leaves. Hie leaves show different evolutionary adaptations for different environmental conditions. The leaf tissues are divided into three fundamental systems. These are epidermal. mesophyll and vascular tissues. Epidermis The leaf tissue is covered on both sides by epidermis. The epidermis is fully activated in ...

Physio-Chemical Nature of Cytoplasm The living content of the protoplasm between the plasma membrane and nucleus is called cytoplasm. Living content of eukaryotes is divided into nucleus and cytoplasm. These living contents (nucleus and cytoplasm) collectively forms protoplasm. The cytoplasm has four components: Cytomembrane System It consists of well-defined structures, such as endoplasmic reticulum, mitochondria, plastids, Golgi apparatus, vacuoles and ...

Peroxisome Peroxisomes are cytoplasmic organelles. De-Duve and co-workers isolated peroxisome from liver cells and some other tissues. They are present in both animals and plants. They are also found in protozoa, yeast and many types of cells of higher plant. Structure: Peroxisomes are enclosed in a single membrane. Their size is 0.5 μm in diameter. In some mammalian tissues peroxisomes ...

Vacuole Vacuoles are the compartments within the protoplast bounded by the membrane tonoplast containing sap (aqueous solution). Vacuoles are present in both plant and animal cells. Both they are most abundant in plant cell. In plants, they occupy major part of the cell. Thus, the remaining intracellular structures form a thin peripheral layer. The numbers of the vacuoles are different ...

Ribosomes Palade discovered ribosomes in 1953 in animals. Robinson and Brown discovered ribosomes in plant cells. Ribosomes are non-membranous bounded structures. Ribosomes are the sites where the cell synthesizes proteins according to genetic instructions. A bacterial cell may have a few thousand ribosomes. But a human liver cell has a few million ribosomes. Cells that have high protein synthesis have ...

Protein Structure And Function Proteins are polymers of .amino acids. The name of proteins is derived from the Greek word called prokios. It means first place. Proteins always contain atoms of carbon, hydrogen, nitrogen. oxygen, and sometimes sulfur. Proteins are composed of more than 50% of the dry weight of most cells. Amino Acids Amino acids are the building blocks ...