Impact of shading on selected developmental, physiological and chemical parameters of southern sweet-grass (Hierochloë australis (schrad.) roem. et schult.)

Abstract

Southern sweet-grass is a tuft grass growing in coniferous and mixed forests of Eastern Europe. Its leaves, collected only from the wild, has been used for the aromatization of alcohol and tobacco products. Due to extensive collection of raw material, the species is threatened with extinction. Thus, introduction into cultivation gives the chance for its survival in natural habitat. The aim of the study was to assess in ex situ conditions the influence of shading on southern sweet-grass development and accumulation of biologically active compounds. The objects of the study were two-year-old plants, grown under 0% (full sunlight), 35% and 50% shading, provided by shading nets. The highest number of fertile shoots was obtained at 35% shading, however the highest mass of seeds per plant as well as the highest 1,000-seed weight was observed at 50% shading. The leaves were harvested twice, i.e., in June (1st cut) and in September (2nd cut, regrowth). The highest cumulative weight of leaves (from two cuts) was obtained at 35% shade (33.63 g plant-1 DM). In both cuts the content of coumarin (detected by HPLC-DAD), responsible for the industrial quality of raw material, was distinctly higher in the leaves of plants grown at 50% and 35% shading compared to those from full sunlight. Such relation was also observed concerning the content of chlorophyll a and b. The obtained results show that shade should be provided in southern sweet-grass cultivation to obtain high and good quality yield of leaves.