Question

A dwarf pea plant was treated with GA. The plant became tall. The treated plant was then crossed with a homozygous tall pea. The result in ${ F2 }$ are expected to be
(a) All tall
(b) Tall and dwarf 3 : 1 ratio
(c) $50\%$ tall
(d) All dwarf

Answer 1

Gibberellic acid (GA) is a plant growth regulator that helps in various physiological processes of the plants. It functions in the flowering, elongation of the stem, and germination of seeds in the plant and can inhibit growth by a specialized substance in most of the trees.

Complete answer:
When the dwarf plant is treated with Gibberellic acid (GA) then it will become tall. GA will increase the shoot length of the plant. This homozygous dwarf plant (tt) when becomes tall will result in the all tall plants in the ${ F1 }$ generation. When selfing of ${ F1 }$ is done it will result in the formation of both tall and dwarf plants in the ${ F2 }$ generation. The tall will and dwarf plants formed will be in the ratio 3 : 1. This ratio occurred even after the dwarf plants are treated with GA because GA can make dwarf plants taller physically but it cannot change its genetic constitution. These GA’s will help in the elongation of the internodes of the pants without interfering in the genetic constitution of the plants.
A cross between homozygous tall plant (TT) and homozygous dwarf (tt) plant results in the production of all tall hybrids (Tt) which are heterozygous. Here, even in heterozygous condition tallness is expressed then it is said to be the dominant character while its opposite factor is named the recessive factor (dwarfism) whose effect is masked by the presence of the dominant factor. The selfing of “Tt” will result in the ratio of 3:1 in the ${ F2 }$ generation.

So, the correct answer is ‘Tall and dwarf 3 : 1 ratio’.

Note:
The Gibberellin (GA) hormone was discovered from the fungus Fusarium moniliforme (Fujikuroi) in 1926 by Kurosawa while he was studying Foolish Seedling Disease that causes a strong elongation of the rice stem. Gibberella fujikuroi was the term from which Gibberellin was derived which is a hormone-producing fungus. It also helps in the prevention of seed and bud dormancy. Gibberellins are synthesized in plastids and then modified in the endoplasmic reticulum and cytoplasm.