The regulation of developmetantal and differentiation hormones

 In week 7, we were required to fill the teaching evaluation in the putrablast. We fill up the form and give the evaluation to the lecturers. After that, Dr Parameswari discussed the test 1 examination papers. We discussed the answer together the objective and the subjective questions. Through this, we can knew our mistake that we do during the test. Next, we learned about the plant growth regulators found in plants and explain their functions. Plant hormones are chemicals produced by plants that alter growth patterns and maintenance of the plant. Substance produced in a very low concentration and are mobile, both over short (diffusive) and long (mass-flow) distances. The plant hormones control cell activities by sending chemicals signals or messages to cells to do something or not to do the something, including activating the genes that code for specific enzymes or blocking gene transcription and plant hormones inhibit as well inhibit as promote cellular activities.

 
                                            Signal transduction in plants

After that, I had learned about hormones in plants. There are 5 classes of hormones in plants which are auxins, cytokinins, gibberillins, abscisic acid and lastly is ethylene. Auxins (plural of auxin /ˈɔːksɨn/) are a class of plant hormones (or plant growth substances) with some morphogen-like characteristics. Auxins have a cardinal role in coordination of many growth and behavioral processes in the plant's life cycle and are essential for plant body development. Auxins and their role in plant growth were first described by the Dutch scientist Frits Warmolt Went.^[1] Kenneth V. Thimann isolated this phytohormone and determined its chemical structure as indole-3-acetic acid (IAA). Went and Thimann co-authored a book on plant hormones, Phytohormones, in 1937. Auxin is increase the plasticity of plant cell walls and is involved in stem elongation. Auxin also enhances cell elongation.

                                                                                                                                                    auxin

    The main function of auxin is to help plants grow. Auxin stimulates plant cells to elongate, and the apical meristem of a plant is one of the main places that auxin is produced. This makes sense because the apical meristem is also the location that all the other parts of a plant grow from - the stem, leaves, and flowers.        

Then, I had read the lecture notes about phototropism. In phototropism, auxin migrates away from light. The stem will elongate faster on the extra auxin side.

                                                                                                         Phototropism

                                     
                                                               Gravitropism

Cytokines are a large group of proteins, peptides or glycoproteins that are secreted by specific cells of immune system. Cytokines are a category of signaling molecules that mediate and regulate immunity, inflammation and hematopoiesis. Cytokines are produced throughout the body by cells of diverse embryological origin. Cytokine is a general name; other names are defined based on their presumed function, cell of secretion, or target of action. For example, cytokines made by lymphocytes can also be referred to as lymphokines, while interleukins are made by one leukocyte and act on other leukocytes. And chemokines are cytokines with chemotactic activities. Cytokines may act on the cells that secrete them (autocrine action), on nearby cells (paracrine action), or in some instances on distant cells (endocrine action).

Cytokines generally function as intercellular messenger molecules that evoke particular biological activities after binding to a receptor on a responsive target cell.

                                                       Cytokinins

                                                                                               Auxin and Cytokinin interaction

Gibberellins are a group of plant hormones responsible for growth and development. Chemically speaking, gibberellins are actually acids. They are produced in the plastids of plant cells and are eventually transferred to the endoplasmic reticulum of the cell, where they are modified and prepared for use. Gibberellins are growth hormones that stimulate cell elongation and cause plants to grow taller. Gibberellins also have a role in other processes in plants, including stem elongation, germination, flowering, and fruit ripening. In humans, the pituitary gland secretes the human growth hormone at appropriate times; the plastids of a plant secrete gibberellin in a similar fashion. 

 Humans have glands that secrete hormones at different times to stimulate body processes such as growth, development, and the breaking down of sugars. Plants also have hormones that stimulate processes that are necessary for them to live. One hormone, abscisic acid, is involved in many developmental plant processes, including leaf abscission, responding to environmental stress, and inhibiting fruit ripening. Abscisic acid is produced in the roots of the plant as well as the terminal buds at the top of the plant. Abscisic acid is involved in several plant functions. Plants have openings on the bottom side of their leaves, known as stomata, that take in carbon dioxide and regulate water content. Abscisic acid has been found to function in the closing of these stomata during times when the plant does not require as much carbon dioxide or during drought times when the plant cannot afford to lose much water through transpiration. 

Ethylene is present in the tissues of ripening fruits, nodes of stems, senescent leaves, and flowers.

Functions of Ethylene

Leads to release of dormancy state
Stimulates shoot and root growth along with differentiation
Leaf and fruit abscission
Flower induction in Bromeliad
Stimulation of femaleness of dioecious flowers
Flower opening is stimulated
Flower and leaf senescence stimulation
Stimulation of Fruit ripening

After, i had learned about this, i knew the function of each every hormones. This topic is quite interesting because it is related in our daily life. Each hormones has their functions. I had found more interesting facts while I serching about all those 5 classes of hormones. Eventhough I did not like about the plants topic, but this topic has changed my perspective towards plants.