Railway Science (Biology – Plant Kingdom) (Part-II)

cotyledons - It is part of the embryo within the seed of a plant. Often when the seed germinates, or begins to grow, the cotyledon may become the first leaves of the seedling.
Ovule - An organ that forms the seeds of flowering plants. Radicle - The part of a plant embryo that develops into the primary root. Plumule - The rudimentary shoot or stem of an embryo plant.

Lignin - It provides rigidity and prevents bacterial infections. The lignified wall provides stiffness to sclerenchyma cells and aids in mechanical support. Sclerenchyma is one of the three types of ground, or fundamental, tissue in plants; the other two types are parenchyma (living thin-walled tissue) and collenchyma (living support tissue with irregular walls).
Cellulose: Comprising glucose units, it's the main plant cell wall component. Hemicellulose: Complex carb in cell wall matrix. Pectin: Polysaccharide aiding cell adhesion and gel-like texture in plant tissues.

Complex tissues are made of more than one type of cells. Xylem consists of tracheids, vessels, xylem parenchyma and xylem fibers. Tracheids and vessels are tubular structures. This allows them to transport water and minerals vertically.
Phloem is made up of five types of cells: sieve cells, sieve tubes, companion cells, phloem fibers and the phloem parenchyma. Phloem transports food from leaves to other parts of the plant.

Phloem: Vascular tissue in charge of transport and distribution of the organic nutrients. Its movement is bidirectional.
Xylem: Vascular tissue in plants which transports water and minerals from the roots to the leaves. Its movement is unidirectional.
Meristematic tissue is made up of a group of cells that divide continuously to form new cells.

From the region of maturation, some of the epidermal cells form very fine and delicate, thread-like structures called root hairs. These root hairs absorb water and minerals from the soil. Root cap - Thimble-like structure, which protects the tender apex of the root as it makes its way through the soil.

The phloem consists of parenchyma, fibers, sieve tubes, and companion cells. Phloem helps the bidirectional transport of food whereas xylem helps in the unidirectional transport of water.

The lignified wall provides stiffness to sclerenchyma cells and aids in mechanical support. Sclerenchyma cells have thick, lignified secondary cell walls. They are long and narrow structurally.

Xylem is to transport water from roots to stems and leaves, but it also transports nutrients. Parts of Xylem - tracheids, vessels, xylem parenchyma and xylem fibers. Tracheids and vessels are the conducting elements of Xylem. Xylem parenchyma - store food materials in the form of starch or fat, and other substances like tannins. Phloem - Transport food material from the leaf to other parts of the plants.

Meristematic tissue - The growth of plants occurs only in certain specific regions. This is because of the dividing tissue, also known as meristematic tissue. Depending on the region where they are present, meristematic tissues are classified as apical, lateral and intercalary.
New cells produced by meristem are initially like those of meristem itself, but as they grow and mature, their characteristics slowly change and they become differentiated as components of other tissues.

Cutin - It helps in the prevention of water loss through transpiration. Lignin - It is a complex polymer that is responsible for enhancing plant cell wall rigidity, hydrophobic properties and promotes minerals transport. Cellulose - A polysaccharide compound that gives rigidity to the cells.