Question

How were gibberellins discovered? Explain two experiments in order to show the effects of gibberellin.

Answer 1

Hint: Gibberellins are promoting plant growth hormones. It is one of the longest known plant hormones. Talking about its discovery, it was discovered by the fungus Gibberella fujikuroi in the seedling.

Complete answer:
Gibberellin is a PGR reported widely around more than 100 samples of it. G3 was one of the first gibberellins to be discovered and remains the most intensively studied form.
In 1926, Eiichi Kurosawa, a Japanese botanist, while investigating the rice foolish seedling disease which was caused by Gibberella fujikuroi, a fungus. Later it was worked upon in the University of Tokyo triggering the symptoms of foolish seedling disease and was named 'GIBBERELLIN'.

EXPERIMENT 1:
Phaseolus seeding was taken in 3 Petri dishes separately. One was kept in the dark whereas the other two were kept in place having light. One of them is sprayed with a 20ppm solution of gibberellic acid. To calculate the result the stem growth of the seedling was measured and compared in each case.

OBSERVATION- Light is a source of energy thus helps the plants to grow and produce. Application of gibberellin can only be observed in plants growing in light. Reversal of light-induced inhibition of stem elongation reveals that gibberellin limits the growth in the plants kept in the dark and the one where it is not sprayed.

EXPERIMENT 2:
Let us again take the seedlings of Vigna that is grown in 2 Petri dishes. One is sprayed with a 20ppm gibberellin solution. The other is sprayed with distilled water. Observation for the above sample can be taken after a week's time. Calculate the height of the seedlings.

OBSERVATION: It can be clearly observed that height treated with gibberellin has a drastic increase trend than the one treated with distilled water.

Note: Gibberellin produces a wide range of physiological responses in plants. Their ability to cause an increase in length is used to increase the length of grape wine. They also are used to delay senescence. They also promote bolting (internode elongation just prior to flowering), in beets, cabbage and many more plants.