Effects of Paclobutrazol and Mepiquat Chloride on the Physiological, Nutritional, and Morphological Behavior of Potted Icterina Sage under Greenhouse Conditions

Abstract

Plant growth regulators (PGRs) are commonly used in horticulture to improve crop quality, save water, and enhance plant resilience to stress. In this study, we examined the effects of two PGRs, paclobutrazol (PBZ) and mepiquat chloride (MC), on the growth and health of Salvia officinalis ‘Icterina’, a popular ornamental and aromatic plant. Parameters such as growth and development, water status, chlorophyll levels, nutrient content, photosynthetic performance, and gas exchange were evaluated. The study took place in a greenhouse with automatic watering and three plant groups: one treated with PBZ, another with MC, and a control group (untreated). Only one application of growth retardants was made, with 0.1 L per pot of a 100 mg/L solution of PBZ, and 0.1 L per pot of a 2.5 g/L solution of MC. The results showed that both PBZ and MC treatments reduced the plant’s water consumption, with PBZ being more effective in limiting leaf growth and promoting the accumulation of substances in the leaves. Both PGRs resulted in smaller plants, reducing the need for soil and potting materials. The MC treatment improved nutrient absorption, reducing the requirement for fertilizers. When subjected to environmental stress from March to June in the greenhouse, Salvia plants benefited from the application of both PGRs, as they helped maintain photosynthetic activity. These findings contribute to improving the sustainability of nursery practices by utilizing PGRs to conserve resources and mitigate the impact of stressful environmental conditions on sage plants.