Where are the following hormones synthesized in plants (a) IAA (b) Gibberellins (c) Cytokinins
Answers
Auxins
The primary function of the auxin hormones is to elongate plant cells in the stem. For instance, auxins are the hormones responsible for phototropism, the growth of a plant toward the light. Phototropism results from the rapid elongation of cells on the dark side of the plant, which causes the plant to bend in the opposite direction. The acid growth hypothesis explains this occurrence by speculating that auxins trigger proton pumps in cell membranes, lowering the pH in the cell wall to such an extent that the hydrogen bonds holding its cellulose fibers together break apart. These broken bonds give the cell wall greater flex ibility and expandability, so that more water can enter the cell by diffusion, causing the cell itself to elongate.
Auxins are also responsible for adventitious root development, secondary growth in the vascular cambium, inhibition of lateral branching, and fruit development. In fact, seedless fruits can be artificially created by applying synthetic auxin to plants; this causes fruit to develop even though fertilization (and thus seed formation) has not occurred.
Cytokinins
The cytokinin hormones promote cell division and tissue growth, and depend upon the presence of auxins to determine the extent of their activity. When the ratio of cytokinins to auxins is relatively high, stem and leaf growth is stimulated. When, on the other hand, the ratio of cytokinins to auxins is relatively low, root growth is stimulated instead. The balance between these hormones ensures that the plant invests in both root and shoot growth, so that neither becomes too large or small for the other. Cytokinins are also involved in the development of chloroplasts, fruits, and flowers. In addition, they have been show n to delay senescence (aging), especially in leaves, which is one reason that florists use cytokinins on freshly cut flowers.
Gibberellins
Gibberellins stimulate growth, especially elongation of the stem, and can also end the dormancy period of seeds and buds by encouraging germination. Additionally, gibberellins play a role in root growth and differentiation, and produce an enzyme that pro motes the conversion of an embryo's starchy food supply into utilizable sugars. In some plants, these hormones are essential for flowering and fruit development.
Answer:
Auxins or IAA is a plant hormone that helps in the growth of the lateral buds. They are produced in the stems, buds and at the root tip pf the plant. This hormone helps in the promoting the cell elongation.
The auxins moves in the darker part of the cell in order to promote cell elongation larger than the corresponding cell that lies in the lighter part of the plant.
Gibberellins are acids that is found in the plant. These were the first hormone to be discovered in the plant. They are synthesized in the plastids of the plant. They can also be formed in the double membrane bound organelle where the food is stored in the plant cell.
Cytokins are found in the plant cell and is found in the meristematic regions of the plants. These hormones are responsible for the growth and development of the plants.