Abstract <p>Agricultural production increasingly incorporates various chemical agents that stimulate and accelerate plant development. Consequently, the search for physiologically active compounds (PACs) and their optimal effective concentrations remains highly relevant. This study aimed to evaluate the effects of 6-hydroxy-2,2,4-trimethyl-1,2-tetrahydroquinoline, 6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline, and their derivatives on the growth of yellow rhododendron (<i>Rhododendron luteum</i> Sweet) and sugar beet (<i>Beta vulgaris</i> L.), to expand the scope of application for these compounds. The experiments took place in Voronezh oblast in 2018 and 2021. Researchers classified the tested PACs into two categories: tetrahydroquinolines—6-hydroxy-2,2,4-trimethyl-1,2-tetrahydroquinoline (PAC 1) and its derivative (PAC 3); and dihydroquinolines—6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline (PAC 2) and its derivatives (PAC 4 and PAC 5). Each compound was tested using yellow rhododendrons at concentrations of 0.01, 0.05, and 0.10%. Sugar beet seeds underwent treatment with 6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline at the same concentrations. For <i>Rh. luteum</i>, dihydroquinolines demonstrated greater effectiveness, while tetrahydroquinolines produced weaker results. Following seed treatment with PACs, <i>Rh. luteum</i> seedling height increased by 18.2–54.5%, and shoot height rose by 3.0–61.2% compared to the control, indicating a long-lasting stimulatory effect of the synthesized organic substances on plant growth. Across all tested concentrations of aqueous 6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline solutions, sugar beet plants exhibited improved growth parameters following pre-sowing treatment of nonpelleted seeds. Specifically, leaf blade length increased by 5.5–11.7%, leaf blade width by 6.5–16.3%, leaf count by 7.7–20.5%, petiole length by 14.8–20.3%, and plant survival by 7.5–11.5% compared to the control.</p>