Railway Science (Biology – Plant Kingdom)

Through Lenticels - A porous tissue in the stem of a woody plant that allows gas exchange between the atmosphere and the internal tissues.
Osmosis - A process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one.
Stomata - cell structures in the epidermis of tree leaves and needles that are involved in the exchange of carbon dioxide and water between plants and the atmosphere.

Photosynthesis - Process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar. Equation - 6CO₂ (Carbon dioxide) + 6H₂O (Water) → C₆H₁₂O₆ (Glucose) + 6O₂ (Oxygen). During daytime, plants take in carbon dioxide and give out oxygen, and during the night it is vice-versa.

A monohybrid cross is a cross between two organisms with different variations at one genetic locus of interest. It is responsible for the inheritance of genes. Dihybrid Cross - It is a type of genetic cross between two individuals with either homozygous or heterozygous genotypes of two characters or traits.

Main Root Types- Tap Root (a main central root upon which root hairs are attached), Fibrous Root (bushy roots in which thin, moderately branching roots grow from the stem). Functions of RootAbsorption, Anchoring, Storage, etc.

Active transport is a mode of transportation in plants, which uses stored energy to move the particles against the concentration gradient. A concentration gradient occurs when the concentration of particles is higher in one area than another.
In passive transport, particles will diffuse down a concentration gradient, from areas of higher concentration to areas of lower concentration, until they are evenly spaced.

Advantages of Transpiration - Removal of excess water, cooling effect, distribution of mineral salts, helps in better development of root system, maintains the shape and structure of plant parts by keeping cells turgid, and supplies water for photosynthesis.
Disadvantages of Transpiration - Wilting or loss of turgidity is quite common during noon due to transpiration being higher than the rate of water absorption, transpiration reduces availability of water inside the plant and hence reduces the growth.

In mitochondria, aerobic respiration of pyruvate produces carbon dioxide and water. Pyruvate (a-keto propanoic acid) is produced at the end of the glycolysis process and is a key intermediate in various metabolic pathways such as gluconeogenesis, fermentation, cellular respiration, fatty acid synthesis, etc. It provides energy to the living cells through Krebs cycle.

In plants the waste products are stored in cellular vacuoles. In a plant waste materials are often stored in old xylem in the form of gums and resins. In plants, the vacuole is crucial for growth and development and has a variety of functions, including storage and transport, intracellular environmental stability, and response to injury.

Vascular tissue: Two kinds of vascular tissue occur in plants - xylem (distributes water and dissolved minerals, from the roots to the leaves) and phloem (brings food downward from the leaves to the roots).
Sclerenchyma tissue: It makes the plant hard and stiff. A permanent and simple type of plant tissue that does not undergo cell division and lacks intercellular spaces.
Meristematic tissue: Made up of a group of cells that divide continuously to form new cells. Parenchyma tissue: It consists of relatively unspecialised cells with thin cell walls. They are living cells. Large intercellular spaces are found in this tissue. This tissue generally stores food.

Other ways in which plants can excrete carbon dioxide which is produced during the process of respiration also gets removed through stomata. Some waste products are stored as resins and gums, especially in old xylem. Excretion in animals - In Amoeba (and other single celled animals), the waste material carbon dioxide is removed by diffusion through the cell membrane, but nitrogenous wastes (like ammonia) and excess water are removed by the contractile vacuole. In earthworm, the tubular structures called nephridia are the excretory organs. In addition to nephridia, the moist skin of earthworms also acts as an excretory organ.