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The potential of wild plants in Israel as sources of edible sprouts has not been investigated until now. Milk thistle (Silybum marianum L.) is native to the Mediterranean basin and is now widespread throughout the world; its young fleshy stems are traditionally eaten by the local Arab sector in Israel, and its sprouts are rich in antioxidants and have been used as a traditional medicine for diseases of the liver and biliary tract. The active extract of milk thistle, silymarin, is a mixture of flavonolignans and is a strong antioxidant that has been proved to promote liver cell regeneration, to reduce blood cholesterol and to help prevent cancer. The present objective was to investigate the potential of milk thistle as a source of edible sprouts rich in antioxidants. We found that seed germination within 3-4 days was high (96%, except for striated seeds). Exposure to light significantly reduced sprout growth and significantly increased the polyphenol content and antioxidative capacity. The polyphenol content was 30% higher in seeds originating from purple inflorescences than in those from white ones. We thus found milk thistle to be a good candidate source of healthy edible sprouts.

Plant regeneration and transformation in vitro is often improved by adding silver ion (Ag(+)) to the culture media as AgNO(3) or silver thiosulfate (STS). Ag(+) reacts with substances to form insoluble precipitates, while thiosulfate (S(2)O(3) (2-)) interferes with these reactions. We studied the implications of silver precipitation and S(2)O(3) (2-) in the medium for culture development by (1) examining formation of Ag(+) precipitates from AgNO(3) versus STS in agar gels and their possible dependence on agar type; (2) comparing Corymbia maculata culture responses to AgNO(3) and STS and determining which better suits control of culture development; (3) clarifying whether STS-dependent alterations in culture development are due to Ag(+) alone or also to a separate influence of S(2)O(3) (2-). Silver precipitates appeared in aqueous gels of four agar brands supplemented with AgNO(3), but not in Phytagel(™), which remained transparent. No precipitation was observed in gels with STS. Indole-3-butyric acid (IBA)-mediated adventitious root induction and shoot growth were higher in C. maculata shoot tips cultured on gels with STS versus AgNO(3) (6-25 μM Ag(+)). IBA-treated shoot tips exhibited enhanced adventitious root regeneration, accelerated root elongation, increased frequency of lateral root formation, and stimulated shoot growth mediated by 100-250 μM sodium thiosulfate (Na(2)S(2)O(3)) in medium without Ag(+). The potency of S(2)O(3) (2-) in facilitating culture development has never been recognized. It is inferred that superiority of STS in stimulating multiple responses of C. maculata culture results from sustained biological activity of Ag(+) through prevention of its precipitation, and from impact of S(2)O(3) (2-) on cell differentiation and growth.