Influence of nutrition and water stress in Hyptis suaveolens

Hyptis suaveolens (L.) Poit. is a medicinal plant that produces essential oil with high therapeutic potential, but its essential oil production is still low and it may vary according to growing conditions. The objective was to evaluate the effect of water stress and fertilization on the production of biomass and essential oil of H. suaveolens (L.) Poit. In factorial experiment (3 × 3), with eight replicates, H. suaveolens were grown in three substrates: natural soil (NS) without fertilization, NS + NPK, and NS + Poultry manure (PM), at three levels of pot capacity (PC) (field capacity for soil in pots): 100, 50, and 25% PC. At 30 days after planting, the variables were evaluated: shoots and root dry matter, root/shoots ratio, plant height, stem diameter, relative water content in the plant, chlorophylls, protein, proline, carbohydrates, content of nutrients: N, P, K, and Na+ in plant tissue, oil yield and translocation factor. Cultivation in NS + PM improved plant growth at the water availability levels of 100 and 50% PC, except root dry matter, whose best result was obtained in NS + NPK. The contents of all biochemical variables increased due to organic fertilization, proline and carbohydrates, when plants were grown in soil under water regime of 25% PC. The substrates NS + NPK and NS + PM increased the contents of N, P, and K. The Na+ contents were high and accumulated in the roots of plants grown with poultry manure, regardless of the studied water conditions. The best oil yield was promoted by PM fertilization. Hyptis suaveolens developed under good conditions of water and fertilization. Under water and salt stress conditions there was reduction of growth, osmotic adjustment and Na+ storage in the root. Oil production was favored by fertilization, but it is still low compared with the literature.