Journal of Advances in Biology & Biotechnology

Lettuce (Lactuca sativa L.), a cool-season leafy vegetable of high nutritional and medicinal value, is globally recognised as a premier salad crop. The present study was conducted during the Rabi seasons of 2023–24 and 2024–25 at SHUATS, Prayagraj, to evaluate the effect of Brassinolide (BR) application and plant spacing on growth and yield attributes of lettuce. The experiment followed a factorial randomised block design comprising five Brassinolide levels (0, 4, 8, 12, and 16 ppm) and three plant spacings (45×30 cm, 45×45 cm, and 45×60 cm), with 15 treatment combinations replicated thrice. The results revealed that the interaction of Brassinolide 0.01% SP @ 12 ppm with a spacing of 45 cm × 30 cm produced the highest yield, recording 360.72 and 404.47 q/ha in the first and second seasons, respectively, and the highest pooled yield of 382.60 q/ha. Yield improvement under Brassinolide 0.01% SP @ 12 ppm with a spacing of 45 cm × 30 cm resulted from optimal plant density combined with Brassinolide’s role in promoting cell elongation, leaf expansion, and photosynthesis. In contrast, the lowest yield was obtained in the control without Brassinolide at the widest spacing of 45 cm × 60 cm, with 83.99 and 91.21 q/ha in the first and second seasons, respectively, and a pooled yield of 87.60 q/ha, primarily due to reduced plant density and absence of hormonal stimulation. The study concludes that integrating Brassinolide application at 12 ppm with a closer spacing of 45 cm × 30 cm can significantly enhance lettuce productivity under similar hot and humid agro-climatic conditions.