Question

What is Auxin bioassay?

Answer 1

Auxins are a potent growth stimulant produced by plants in their natural state. They enhance cell proliferation, stem and root development and are found in shoot and root apexes. They can also have a significant impact on plant alignment by accelerating cell division on one side of the plant in response to light from the sun and gravity.

Complete explanation
A bioassay is a method of determining a metabolic activity, such as a substance's developmental reaction, using a living medium, such as a plant or a plant portion. Auxin bioassay is a quantified test that determines the level of auxin required to generate the desired outcome as well as the magnitude of the effect.
One of the auxin bioassays is Root Growth Inhibition. In this assay, Cress seeds are sterilized and cultivated on damp filter paper. Root lengths are recorded when they reach a length of about cm. Half of the seedlings are placed in a test solution, while the others are left to grow on moistened paper.
After hours, the root lengths are evaluated. The seedlings in the test solution show very little root growth, whereas the control seedlings show regular root growth.

Note:
A bioassay measures the level of a particular substance, in this case auxin. Auxin is a substance that inhibits root extension and promotes the initiation of lateral roots. Application of very low amounts of auxin, possibly on those present at the root tip, can easily mimic the root tip's inhibitory influence on root growth. As a result, if inhibition occurs, it is due to auxin from the root tip.