Increasing gland number and red pigments in St. John’s wort in vitro

Abstract

In order to develop a protocol for increasing the gland number and red pigments of Hypericum perforatum, this study was carried out to evaluate the effect of hydrolyzed casein (0.0 and 500 mg l^-1), mannitol (0.0, 5 and10 g l^-1) and sucrose (20 and 30 g l^-1) on the synthesis of these pigments and glands on the produced leaves. Leaf discs of in vitro plantlets, were prepared and cultured on MS medium with 0.5 mg l^-1 BAP to induce the shoot. All the cultures were incubated in the dark at 25 ± 2°C for 1 month. In all of the treatments, callus and shoot induction were observed. Percentage of calli and leaves containing red pigments, number of glands and percentage of leaves containing gland were noted as indicating the presence of hypericin and pseudohypericin pigments. Percentage of calli and leaves containing red pigments were significantly influenced by different concentrations of the hydrolyzed casein, mannitol and sucrose. The highest percentage of calli containing red pigments was observed in the culture medium which had 500 or 0.0 mg l^-1 hydrolyzed casein and 20 g l^-1 sucrose, without mannitol. Glands were observed on all the produced leaves. Number of glands and percentage of leaves containing gland were significantly influenced by the different concentrations of mannitol and sucrose and their interaction. The highest number of gland and percentage of leaves containing gland was achieved when explants were cultured in medium that included 30 g l^-1 sucrose with 5 or 10 g l^-1 mannitol and in medium containing 20 g l^-1 sucrose, with 5 g l^-1 mannitol. Morphological changes induced by carbon source and hydrolyzed casein were observed and described in detail. The obtained results will be applied in experimental botany and in the technology of H. perforatum cultivation for pharmaceutical applications.

Key words: Hydrolyzed casein, hypericin, Hypericum perforatum, mannitol, pseudohypericin, sucrose.