Question

Bioassay for gibberellin is
A) Avena curvature test
B) Seed dormancy test
C) Dwarf maize test
D) Green leaf test

Answer 1

Gibberellin are group of tetracyclic diterpenoid compounds made up of four isoprene units with the ent-gibberellane structure that function as plant harmone which regulate growth by stem elongation, germination, dormancy, flowering, sex expression, enzyme induction and leaf and fruit senescence.

Complete answer:
Gibberellin promotes internal Einstein in dwarf plant species which are genetically engineered. Application of exogenous gibberellin to dwarf mutant’s restored normal, tall phenotypes. Gibberellin promotes internodal elongation by targeting the intercalary meristem and causes increase in both cell elongation and cell division. Therefore in dwarf maize test plants which are inhibited by the action of gibberellin is grown for certain age which results in the dwarf ness condition of plants, introduction of gibberellin to such plants results in the increase in height of the plant thus shows the action and requirements of gibberellin.

Additional information: Role of gibberellin in stem elongation in plants: The effects of gibberellins on stem elongation is very dramatic. gibberellin 1 is the biologically active gibberellin controlling stem elongation. The precursor of gibberellin 1 (gibberellin 19 - gibberellins) in higher plants is gibberellin 1(gibberellin 19- gibberellins). Enzyme gibberellic acid 3-oxidase ( functions as 3 beta-hydroxylase) catalyses the conversion of gibberellin20 to gibberellin1, by hydroxylation of carbon -3. Hence lack of enzyme gibberellic acid 3-oxidase causes dwarfism in plants. The active gibberellic acid 3-oxidase is encoded by le (mutant form of the enzyme) and thus can convert gibberellin20 to gibberellin1.

Hence the correct answer is option ‘C’.

Note: Avena curvature assay is to determine the role of auxin as auxin is responsible to respond to sunlight and creates bends in the plant. Bioassays are used to measure the biological activity and effects of a substance, like a hormone or drug, on a living organism.