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Experiments With Growth Hormones Added to Plants

Experiments on plants, involving the addition of growth hormones, often show how different conditions affect how fast a plant grows. Some variables used in experiments are temperature, light and exposure to various elements. Experiments with growth hormones lead to the development of fertilizers and herbicides for various types of plants. Knowing how a plant grows is the key to knowing either how to improve it or how to stop it.

History
- In 1880, Charles Darwin discovered auxins, compounds that have the ability to induce cell elongation in stems. He performed an experiment that suggested the tip of a coleoptile was responsible for perceiving light and producing a signal that traveled through the stem. The coleoptile is the plant tissue that makes a plant to bend toward light. Adding auxins to the coleoptiles stimulates growth in some plants. It also delays fruit ripening to allow the fruit to become larger. Adding auxins to plant roots increases the absorption and transport functions of the roots, resulting in larger, stronger plants.
Hormone Types
- In addition to auxins and gibberllins, other natural and synthetic hormones stimulate or stunt plant growth. Scientists are able to reverse the effects of plant growth hormones in order to stunt growth. The altered growth substances exist in many herbicides for controlling broad-leaved plants in lawns. Cytokinins are plant hormones that stimulate cell division in a plant. Two cytokinins occur naturally: zeatin and isopentenyl adenine. The response a plant has to zeatin or isopentenyl depends on the location and concentration of the hormone. Abscisic acid is a hormone used to help plants deal with extreme weather conditions. Ethylene is a gaseous hormone responsible for ripening fruit.
Plant Tissue
- Experiments involving plant growth hormones require the use of plant tissue cultures. Researchers use a variety of methods for obtaining plant tissues. Cultures allow researchers to study the role of hormones, plant molecular biology and gene regulation. Experiments often result in innovative ideas applied in plant science and agriculture. Using aceptic techniques means taking all precautions necessary to exclude invading microorganisms during an experiment.
Experiment Ideas
- A plant growth hormone called gibberellin elongates cells within stem internodes of a plant. Use of this hormone was in response to a disease infecting rice plants in Japan in 1809. When tested on cabbage plants, it induced them to grow up to two meters tall, according to Jeanette Baker of the University of Southern Illinois, Carbondale. Ms. Baker suggests expansions of this experiment would add valuable information. Experiment ideas are treatment times and results from varying the amount of hormones use.

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