MBC BIOLOGY

Growth is defined as the permanent increase in size of an organ or its parts in organisms like plants. Growth involves the energy requiring metabolic processes. Growth is followed by development. The development is about all the changes that occur in the life cycle of a plant from germination of the seed to senescence . The development in plants is controlled by different factors categorized as extrinsic and intrinsic factors . The extrinsic factors include light, temperature, water, oxygen, and nutrition, etc. The intrinsic factors are both the intracellular (genetic) or intercellular factors (chemicals such as plant growth regulators). Concept on seed germination Seed germination is the fundamental process by which different plants grow from a single seed into a complete plant. It brings about the sprouting of a seedling from a seed of angiosperms and gymnosperms. Process of seed germination The seed germination happens by four steps - imbibition, activation of enzymes, growth, a...

Q.N. 1. What are phytohormones?  Mention the different categories of plant hormones. Phytohormones are the chemicals that are produced by the plants to regulate their own growth and the development. They are produced in very low concentration and are transported to the various parts of the plant. They control the activities like cell division, enlargement, flowering, seed formation, dormancy and abscission. Based on their action, phytohormones are grouped as plant growth promoters and plant growth inhibitors . Plant growth inhibitors are abscisic acid and ethylene . Plant growth promoters Plant growth promoters are auxins , cytokinins , and gibberellins . Auxins Q.N. 2. What are auxins? List the physiological effects of auxins.   Auxins are plant growth regulators that are responsible for the elongation of the cells in the shoots. Auxin was isolated from the coleoptiles of oat seedlings by F. W. Went for the first time. Auxins are synthesized in the meristems and transport...