Keywords: Minitubers, hydroponics, Solanum tuberosum, growth inhibitors.
Three growth inhibitors (cycocel, uniconazole and paclobutrazol) applied at different concentrations were assessed to determine their ability to produce compact potato (Solanum tuberosum L.) plants with reduced leaf area, but without reduced tuber yield, in an experiment conducted in hydroponic greenhouse conditions. The treatments were: paclobutrazol (50, 100, 150, 200 and 250 mg.L-1), uniconazole (2.5, 5, 10, 20 and 40 mg.L-1), cycocel (200, 400, 800, 1,600 and 2,400 mg.L-1) and a control without regulators, with 10 pots as the experimental unit. A randomized complete block design with 16 treatments and four replications was used. Uniconazole and paclobutrazol were more effective in reducing growth, leaf area and leaf area index compared with cycocel. Uniconazole at concentrations >5 mg.L-1 reduced plant height (23 and 46 %), tuber biomass and total plant biomass compared with the control. Paclobutrazol applications at 100, 200 and 250 mg.L-1 reduced plant height (50 to 64 %), tuber biomass (44 to 69 %) and total plant biomass (45 to 67 %); at 150 mg.L-1, it reduced plant height (42 %) without affecting tuber biomass (47.0 g). Uniconazole at 20 mg.L-1 and paclobutrazol at 150 mg.L-1 produced stunted potato plants and reduced their leaf area index from 13.9 in plants without inhibitors (the control) to 10.93 and 9.34, respectively, without affecting the number of tubers per plant, tuber biomass or harvest index.