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, but its pruning-harvest activity alters source-sink balance leading to leaf-flushing disturbance. Gibberellin is expected to promote faster recovery and enhance flushing in post-pruning kaffir lime, thus, present study aimed to determine optimal gibberellin concentration and its impact on leaf-flushing growth and phenology. The experiment was conducted at an open field (coordinates: -6.9316851, 107.775863, 718 m asl) in a randomized complete block design with six gibberellin concentrations, namely G0 = control (no gibberellin), G1 = 200 ppm, G2 = 400 ppm, G3 = 600 ppm, G4 = 800 ppm, and G5 = 1000 ppm. Results showed that gibberellin application via foliar feeding significantly enlarged leaf and flush performances, compared to the control. The optimal gibberellin concentration is 600 ppm, which increases leaf and flush size by 82% and 100%, respectively, although it also results in a near threefold increase in spike size. Exogenous gibberellin application also 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.