Name various plant hormones. Also give their physiological effects on plant growth and development.
Plant hormones are organic compounds which are synthesized by cells and tissues of plants called plant hormones/ phytohormones. They actively promote, or inhibit some factors and developmental processes of plants. Five major groups of plants hormones are present:-
1. Auxin:- it stimulates cell elongation in stems by the protein expansion, which has low pH, 4.5. The amount of xylem and phloem ratio is regulated by Auxin.
2. Gibberellins:- It promotes the internodal elongation of plants. It also helps in seed germination by activating vegetative growth of embryos in plants.
3. Cytokinin:- It involves the cell division in which formation, maintenance and growth of root apical meristem and shoot apical meristem by cytokinin’s both positive regulators in shoot apical meristem and negative regulators in root apical meristem. Also helps in chloroplast maturation.
4. Abscisic acid: It is also known as stress hormone which acts in the stress condition of a plant (example:- closing of stomata in extremely drought conditions). It also promotes the root and shoots growth with seed dormancy and germination, also includes wilting of leaves.
5. Ethylene: It is a gaseous hormone, present in almost every plant because it is responsible for many factors like flowering, fruit ripening, rooting and also for senescence (depends on its concentration).
You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table 10.3.
| Material medium |
Refractive index |
Material medium |
Refractive index |
| Air | 1.0003 | Canada Balsam |
1.53 |
| Ice | 1.31 | ||
| Water | 1.33 | Rock salt | 1.54 |
| Alcohol | 1.36 | ||
| Kerosene | 1.44 | Carbon disulphide |
1.63 |
| Fused quartz |
1.46 | ||
| Turpentine oil |
1.47 | Ruby | 1.71 |
| Benzene | 1.50 | Sapphire | 1.77 |
| Crown glass |
1.52 | Diamond | 2.42 |
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