الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
A series of experiments were carried out successively during the years 2017 to 2020. The response of regenerated shoots to elicitation was tested to identify the more convenient treatment for secondary metabolites production under the present investigation. The obtained result revealed that, benzyladenine (BA) at 1.0 mg/l combined with 0.1 mg/l indole acetic acid (IAA) gained maximum shoot numbers, leaf numbers, fresh and dry weights/explant. It is clear that phenylalanine, emodin and yeast extract led to an increment in shoot fresh and dry weight/explant. The reverse was true for jasmonic acid (JA) and salicylic acid (SA) after 28 days from elicitation. The different stimulators led to an increase in hypericin percentage against the control. JA followed by SA were the most effective on hypericin production while, yeast extract negligibly affected hypericin accumulation. Treatments with precursors decreased total phenolic content while low concentrations slightly increased total flavonoid content against the control. Meantime, antioxidant activity gradually increased significantly with increasing their concentrations. Treatments with elicitors stimulated total phenolic and flavonoid contents and enhanced antioxidant activity. Hypericum perforatum regenerated shoots showed different responses in peroxidase (POD) activity when subjected to precursors and elicitors after 28 days from elicitation. Apart from phenylalanine 150 mg/l, other concentrations did not give any stimulatory effect on POD activity. Meantime, different concentrations significantly decrease phenylalanine ammonia lyase (PAL) activity and total soluble protein against the control after 28 days. A significant increase was achieved in PAL activity and total protein with emodin 20 mg/l while gave the same effect on POD activity as the control after 28 days. Yeast extract did not give any stimulatory effect on POD activity while a high concentration (75 mg/l) recorded a significant increment in PAL activity and protein content. It is obvious that all concentrations of JA and SA have a positive effect on POD and PAL activity as well protein content against the control. It is clear that polyphenol oxidase (PPO) activity run parallel to that detected in POD activity. Moreover, the activity of PPO was higher than POD activity. Based on the results, JA 400 µM/l was the most efficient one for secondary metabolites stimulation after 21 days from elicitation, under the present investigation. As well JA at a high concentration (400 µM/l) stimulated the expression of the genes melanin-related (mela 8) and protein kinase (PKS), both are hypericin synthesis regulators.