All questions 1. Describe in full detail ONE of the plant hormones discussed in
ID: 146288 • Letter: A
Question
All questions 1. Describe in full detail ONE of the plant hormones discussed in class. Support your description by discussing the chemical nature, site of biosynthesis, transport, effects, and practical uses 2. Describe the mechanism by which coleoptiles bend toward the light. Support your answer with a discussion regarding type of hormone, environmental cues, and historical experimental evidence. 3. Explain how eukaryotic cells are thought to have evolved from prokaryotic cells. You must use these words in your essay, but are not limited to them: endosymbiotic, enfolding, phagocytosis, mitochondrion, chloroplasts, eukaryotic, bacterial endosymbiont. 4. Discuss in detail anything worth 5 points from the Kingdom Protista. (Example: roles played by algae in ecosystems around the world; distinctive cellular features of any 5 algae; life cycle of a slime mold; photosynthetic pigments of the different groups; carbohydrates reserves; etc.) 5. Compare and contrast the 3 Phyla of Fungi that were outlined in class. 6. Identify all the stages of the generalized fungi life cycle, both asexual and sexual.Explanation / Answer
1.
The plant hormones are the factors or signals that stimulate growth and development of plants. A plant hormone is a natural substance involved in the control of plant activities. The plant growth regulators are the chemically synthesized compounds similar to the natural plant hormones. The plant hormones are 5 types like auxins, gibberellins, cytokinins, ethylene and abscisic acid.
The auxins are plant hormones that act at cellular level and control their activities. Chemically Auxin is indole -3 - acetic acid (IAA) and it is involved in formation of leaves and flowers in a plant. Auxins contain an aromatic ring and a carboxylic acid group in its molecular structure. Auxins are actively transported from cell to cell in plants and theis mechanism is known as polar auxin transport. Endogenous auxins produced in plants include indole-3-acetic acid, 4-chloroindole-3-acetic acid, phenylacetic acid, indole-3-butyric acid, and indole-3-propionic acid. Synthetic auxin analogs include 1-naphthaleneacetic acid, 2,4-dichlorophenoxyacetic acid (2,4-D) are widely used agriculture. The auxin 2,4-D is useful as herbicide. The auxin synthesis in certain cells is dependent on tryptophan biosynthetic pathways. The phloem vessels tranport the auxins to various parts of plants. The functions of auxins include plant growth by the cell enlargement or elongation, photo and geotropism, epical dominance, flower initiation and development and root initiation, fruit set and abscission of plant parts.
Gibberellins are plant hormones that are involved in stimulation of the stem growth, cell division, cell elongation and control the enzyme secretion. They also cause flower initiation, fruit growth and maturation and senescence of plant parts. They promote the plant height and break the dormancy in seeds and buds.
Cytokinins are involved in the plant growth and development by inducing cell enlargement, tissue differentiation, different phases of flowering and fruiting, retardation of leaf senescence and breaking the dormancy of seeds. They along with auxins act to stimulate the differentiation of tissue. They also initiate the root development.
Ethylene is a gaseous molecule that causesa variety of responses of plants. It induces fruit ripening, useful to overcome the bud dormancy, induces the leaf abscission, flowering in pineapple plants and induces in root formation in stem cuttings.
Abscisic acid is a plant hormone and a complex inhibitory substance associated with dormant buds. The abscisic acid is invovled in regulation of the process of seed development and acts as a stress hormone by initiating cold and water stress responses in plants.