5.5.5 Gibberellin

Question 1

What is the experimental evidence for the role of gibberellin in stem elongation?

Answer 1

Gibberellins are a group of hormones that help plants grow by stimulating cell division and elongation in the stem

Dwarf plant varieties have been shown to have very low levels of gibberellins

This is often due to a mutation in a gene involved in the synthesis of gibberellins

Under experimental conditions, treating these dwarf varieties with gibberellins results in them growing to the same height as normal varieties

Some farmers apply gibberellin to shorter plants to stimulate growth

Question 2

What is the experimental evidence for the role of gibberellin in seed germination?

Answer 2

The fact that gibberellins stimulate germination and the breaking of dormancy has been shown by many experiments

For example:

Seeds of mutant varieties of the Arabidopsis plant that do not produce gibberellins can be induced to germinate if gibberellins are applied

Seeds of certain lettuce varieties that require light in order to germinate can be made to germinate in the dark if gibberellins are applied