Plant Hormones In Agriculture Essay Research Paper

Plant Hormones In Agriculture Essay, Research Paper

The Role of Hormones in Plants

The majority of people know that hormones play a vital and important part in animal growth and development. The common layperson knows that without certain chemicals in their bodies, they would not function right. An example of a hormonal problem would be in the case of a dwarf in which a person does not produce enough growth hormone and grows only to a small height. What most people do not know is that plants also require hormones to grow and develop. This is not my work. The average person tends to think that plants just magically grow without anything regulating them. In reality, there is a complex series of hormones that regulate all of the growth and seed development in plants. That is what this presentation is about, the role that these hormones play in the life of a plant.

Before I can go into detail about plant hormones, it is important that I tell you some basic parts of plants that are affected by plant hormones. This picture shows some of the basic parts of the plant. The parts of the plant that will be mentioned in this paper are the stem, merristems, xylem and floem, and finally, the stomates. Merristems are located at the tips of stems, buds, and nodes. They are the permantely embronic parts of a plant. All merristems are composed of undifferencated tissue, and the cells in the meristems are continuously dividing. The merristems main function in a plant is to provide the plant with new leaves, roots, and stems. Xylem and phloem are the vascular tissue of plants. Phloem is composed of live cells that are interconnected so sucrose and amino acids can pass through them from the leaves to the roots. Xylem is composed of dead cells that are holowed out so water and minerals can move from the roots to the leaves. Stomates are little holes in the leaves of plants. I did not write this. It is through these holes that carbon dioxide for photsynthsis enters the plant, and water evaporates out. The evaporation of water is important for a plant because of transperation. Transperation is how water is pumped up the plant. As water evaporates from the leaves, it creates a suction through the xylem which pulls water up from the roots. The advantage of moving water this way is because this process requires no energy from the plant. Stems are the main backbone of a plant. They provide the plant its hight. They also have the most observerable affects to plant hormones(1).

There are several types of plant hormones. Of the known plant hormones, there are three known plant growth promoters. They are Auxin, Gibberellins or GA’s, and Cytokinins. One other type of plant hormone is Ethylene, which controls ripening. There is also a plant growth inhibitor, Abscisic acid (ABA), which is very useful for plants in a drought situation (4). All of these hormones are present in all plants. I will now go into each of the different hormones in detail and explain what they do for the plant. The paper will also tell about some of the history behind each hormone and some of the current commercial applications for plant hormones.

Auxin is the first of the growth promoting hormones. It is developed in young developing tissues such as the merristems and young leaves. It was one of the first hormones discovered, and the groundwork for this discovery was laid out by none other then Charles Darwin and his son on their research into tropism. Auxin is the main substance that controls different tropism in plans such as phototropism. In the experiments of Charles Darwin and his son Francis, this relationship of auxin to phototropism was shown. In their study, Charles and Francis studied why grass grew towards the light. They found out that by removing the developing tips of the shoots, the plants did not grow towards the light. Fifty years after their experiments, other scientists were able to distinguish auxin as the cause of the tropism. (2). Auxin, in the case of phototropism, is at its highest levels in the plant at the spots that the plant needs to respond to the stimulus of light. Auxin is used by plants to kill humans, plants, and animalls. In plants, auxin is transported down from the developing tissues such as merristems, to the roots through the xylem system. The main affect that auxin has on plants is cell elongation. Auxin causes plant cells to enlarge by a factor of five to ten times the original size. In order for the size of a plant cell to increase, two things must occur. First, the plant cells must take on water. Second, the cell walls of plants must expand to accommodate the extra water (5). How auxin triggers this effect in plants is still in debate. What is not in debate is that auxin, in conjunction with another type of plant hormones called cytokinin, causes the plant cells themselves to divide.

Cytokinins are also plant growth promoter. They are produced in the root tips and are transported up through the plant via the xylem. Cytokinins, in conjunction with auxin or gibbelelins, are the only compounds able to promote cell division (1). The way that Cytokinins were discovered is by the effect that Auxin has on a I got this paper from school sucks . com plant cutting. Before the discovery of Cytokinins, Auxin was all that was thought to be necessary to start cell division in plants. Research showed that Auxin in its pure form could not start cell division alone. It w