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Recent years has seen increasing interest in the genus Hypericum because it is the source of a variety of compounds and the biological activities of the genus are mainly derived from its hypericin content. The present study was conducted to determine whether this compound may be implicated as part of an inducible plant defense response in H. perforatum and H. pruinatum. Greenhouse-grown plants were inoculated with the plant pathogens Phytophthora capsici and Diploceras hypericinum. Hypericin levels of the Hypericum species increased significantly in response to inoculation with both pathogens. While up to now little effort has been made to determine whether hypericin is inducible by pathogen/herbivore attack or if it could play a role in plant defense, the present study indicates that hypericin is a component in inducible plant defense response of H. perforatum and H. pruinatum.

Aim of this study was to investigate the nature of dormancy in black henbane (Hyoscyamus niger) seeds which have low germination rate under normal laboratory conditions. To do this, before placing the seeds in Petri dishes, they were soaked in 5, 10 and 15 mg/L GA; 1, 2 and 3% H2SO4, 15 mg/L GA + 1% H2SO4, 0.01 M KNO~ solutions, tap water, 40, 50 and 60~ hot water for 30 min. The study was performed under both continuous illumination and darkness in growth chambers to evaluate the effect of light on germination rate. The results showed that H2SO4 and GA treatments were the most important factors affecting seed germination and their germination enhancing effects were more evident in darkness. The results also suggested that black henbane seeds exhibit double dormancy involving a hard seed coat and a partially dormant embryo and have a partial dark requirement to germinate. K, eywords: black henbane, dark requirement, double dormancy, CA, H2SO4

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ABSTRACT:In this research, leaf area prediction models were developed for some leaf-used medicinal plants namely Calamintha nepeta, Datura stromonium, Melissa officinalis, Mentha piperita, Nerium oleander, Origanum onites and Urtica dioica growing wild in Black Sea region of Turkey. Lamina width, length and leaf area were measured non-destructively to develop the models. The actual leaf areas of the plants were measured by PLACOM Digital Planimeter, and multiple regression analysis with Excel 7.0 computer package program was performed for the plants separately. The produced leaf area prediction models in the present study were formulized aswhere LA is leaf area, W is leaf width, L is leaf length and a, b 1 , b 2 , b 3 , b 4 , b 5 , b 6 , and b 7 are coefficients. R 2 values for medicinal plants tested varied with species from 0.82 in Origanum onites to 0.98 in Urtica dioica. All R² values and standard errors were found to be significant at the P < 0.001 level.