Question

To what does the term ‘Green Revolution’ refer? Using your knowledge of gibberellin biosynthesis and perception, discuss how this hormone has been shown to be the key to the semi-dwarfed nature of the plants of the ‘Green Revolution’.

Answer 1

Green Revolution is the improvement of crops through required modifications at genetic level of plants to obtain increased yields of the crops. Semi - dwarf rice crops are modified in such a way to produce high yields of rice crops IR8 variety to overcome food scarcity problem worldwide. The IR8 rice crop mutants for sd1 gene are semi dwarf or short plants. The sd1 gene encodes for gibberellin biosynthesis. Gibberellin is a plant hormone that stimulates plant growth by cell elongation and cell division.

The sd1 mutant IR8 rice crops produced low amounts of gibberellin levels and as result these crops appear short in height. The sd1 gene encodes an oxidase enzymethat plays a major role in the biosynthesis of the plant hormone gibberellin. Exposure of sdi mutant plants to gibberellin had shown positive response and plants could grow to normal height. The mutant plants aredetected with low amounts of gibberellin precursors and this could be due to new GA20ox gene and deletion associated with the gene. The sd1 mutantation was found to be preserved by wild type plants encoding GA20ox-2 gene and this gene enables the plants to synthesize gibberellins and resume to normal growth.

In this aspect, green revolution is defined as improvement of crops with alteration of genes and enzymes and exposure to plant hormones that can improve the crop yields.