Abstract
<title>Abstract</title> <p> Seasonal dependence of lime ( <italic>Citrus aurantifolia</italic> ) production poses significant challenges to year-round fruit supply and market stability. This two-year field study investigated the individual and interactive effects of paclobutrazol (PBZ) at four levels (0, 2.5, 5.0, and 7.5 g a.i. plant⁻¹) and photoperiod extension at three levels (natural, +2 h, and +4 h supplemental LED lighting) on winter flowering, fruit yield, and quality of lime cv. Binalebu-1 under subtropical conditions in Bangladesh. The experiment used a factorial randomized block design with five replications and repeated measurements over two seasons. Combined analysis revealed highly significant (P < 0.001) main effects for both factors across all parameters, with significant PBZ × Light interactions for fruit weight, leaf area, and shoot length. Increasing PBZ concentration progressively suppressed vegetative growth, while extended photoperiod further amplified reductions in shoot development and leaf area. Despite reduced leaf dimensions, chlorophyll density increased markedly under combined treatments, indicating enhanced photosynthetic efficiency. Reproductive parameters responded positively, with flowering advanced by 11.1 days and flower number increasing by 56.5% under the optimal combination. The treatment P3L3 (7.5 g a.i. PBZ with +4 h photoperiod) produced nearly four-fold increase in fruit number, 66.7% gain in fruit weight, and concurrent improvements in juice content, total soluble solids, and titratable acidity compared to untreated controls. Multivariate analyses confirmed tight phenotypic integration among traits, with strong negative associations between flowering time and overall productivity across treatments. This integrated PBZ-photoperiod strategy offers a robust approach for enhancing off-season lime production in tropical and subtropical regions. </p>