What is the effect of exogenous gibberellin application on leaf-flush growth, morphometry, and delayed phenology in post-pruning kaffir lime seedlings?

Kaffir lime (Citrus hystrix DC.) is a valuable aromatic leaf spice used in both the culinary and pharmaceutical industries. Its leaves are rich in aromatic compounds such as citronellal, citronellol, and linalool. However, frequent pruning for leaf harvesting alters the source‒sink balance, impacting subsequent flush growth. Gibberellin is widely used in citrus orchards for regulating reproductive growth and development, and it also plays a crucial role in vegetative growth by supporting seed germination and stem elongation. This study aims to determine the optimal gibberellin concentration and its impact on leaf-flush growth and phenology in post-pruning kaffir lime seedlings.

Exogenous gibberellin application via foliar feeding promotes rapid vegetative growth in kaffir lime seedlings. The optimal gibberellin concentration is 600ppm, which significantly increases leaf and flush size by 82% and 100%, respectively. However, it also results in a near threefold increase in spike size. Gibberellin application extends the flushing cycle by delaying leaf maturation, with higher concentrations prolonging developmental stages. This delay is linked to increased leaf morphometric response, potentially enhancing plant source capacity. The study concludes that gibberellin can accelerate recovery and enhance leaf-flushing in post-pruning kaffir lime seedlings, but its application also affects plant phenology by prolonging the flushing cycle.