Role of gibberellins in regulation of source- sink relations under optimal and limiting environmental conditions

Gibberellins (GAs) are plant growth regulators that are known to stimulate physiological responses in plants and alter the source-sink metabolism through their effect on photosynthesis and sink formation. GAs promote fructose-1,6-biphosphatase and sucrose phosphate synthase and stimulate phloem loading. Photosynthate translocation from source to the developing sink is a major contributing factor towards increasing the sink strength, and GAs are the key regulators of the process through which the extracellular invertase involved in phloem unloading, carbohydrate partitioning and growth of sink tissues is induced. Gibberellic acid is the major contributor in the process of source and sink formation and is one of the most commonly studied GAs. Recent studies indicate that GA signalling is involved in adjustment of plants under limiting environmental conditions and maintains source-sink relation. This adjustment could be mediated through the influence of GA on the regulation of salicylic acid biosynthesis. Here we focus on the developments and understanding of integration of GA action with the metabolic process under optimal and limiting environmental conditions for maintaining source-sink relation. Further advances in the crosstalk between gibberellins and salicylic acid are discussed with reference to abiotic stress tolerance and source-sink relation.