Auxins: History, Bioassay, Function, Uses, Topics
What Are Auxins?
Auxins are a class of phytohormones that, among others, exert a key role in controlling various phenomena in plant development, such as cell elongation, the formation of roots, and mechanisms of response relating to light and gravity. Auxin activity and potency information are very important for both basic knowledge of the biology of plants and practical applications in agriculture and horticulture. The bioassays of auxins, standardized methods which quantify their biological activity by observation of their action on plant growth, are briefly expatiated upon in the following article. In line with this, it goes on to discuss more about the working principles of auxin bioassays, standard methods employed, and their meaning in plant science.
Bioassays: An Understanding
A bioassay is an analytical procedure that measures the potency or effect of a substance by its effect on living organisms, including plants. The type of response measured may be based on this approach: either quantal or quantitative, based on a binary or continuous measured response. In the case of auxins, bioassays are used to test for the growth-promoting effects of these hormones on plant tissues.
Principle Of Auxin Bioassay
It is founded on the principle of auxin bioassays: plant tissues are treated with a known concentration, and the ensuing growth response is measured. In many instances, this potency of the auxin is expressed in comparison to a standard reference to quantify its effectiveness. Various parameters can be used as a measure of the response, such as changes in the growth rate, curvature, or root development.
Standard Methods Of Auxin Bioassay
Several methods that are standardized because of their universality are used in estimating the activity of auxins. The most prominent of these is the Avena curvature test, which estimates the degree of curvature of oat (Avena sativa) coleoptiles responsive to applied auxins.
Avena Curvature Test
Procedure: In this test, oat seedlings are cut at the tip to remove the apical meristem, which is the source of auxin. Auxin solutions of different concentrations are applied to the cut surfaces and left for a certain specified period. Later, the degree of curvature of the coleoptile is measured.
Interpretation: The curvature is proportional to the concentration of applied auxin. The greater the degree of curvature, the higher the concentration of auxin that exerts growth-promoting effects.
Other Bioassay Techniques
Root Growth Bioassay: This technique involves treating the base of plant cuttings with auxin and quantifying root growth over time. The number and length of the roots are measured as a function of auxin activity.
Seed Germination Bioassay: This is a bioassay whereby the seeds get treated with auxin solutions and see the rate of germination and its speed. This technique shows that auxin is essential for seedling establishment.
Importance Of The Auxin Bioassays
The auxin bioassays are important for various uses:
Research Applications: They give valuable insights into the physiological activities of auxins in plant development, including their effects on phototropism-growth towards light and gravitropism-growth in response to gravity.
Agricultural Practices: The knowledge of auxin activity can be extended to agricultural practices, like the application of rooting hormones on cuttings, thinning of fruits, or the conditions that optimize plant growth.
Environmental Studies: Bioassays are also applied to quantify changes in auxin activity as a way to measure the effect of environmental pollutants on plant growth.
Limitations Of Auxin Bioassays
Even though auxin bioassays have been very useful, they also have several limitations:
Variability: Different plant species, and sometimes even cultivars within a particular species may vary in their response to auxin treatments and thus create variability in the results.
Complexity of Interactions: The interactions of auxins with other classes of plant hormones complicate the isolation of their actions in bioassays without considering the involvement of other growth regulators.
Recommended video on Auxin Bioassay
Frequently Asked Questions (FAQs)
Some limitations exist in the variability of the plant responses and the complexity of the interactions between the action of auxins and other plant hormones that may mislead results and their interpretations.
The Avena curvature test is a standardized bioassay that expresses the degree of curvature of oat coleoptiles caused by auxins, thus showing auxin activity.
They are important for understanding the physiological roles of plant hormones and assessing environmental impacts, as well as developing agricultural practices.
The potency of auxin is determined by applying plant tissues to known concentrations of auxin and observing the resultant growth responses, which include curvature or root development.