Low efficiency of embryo maturation, germination and conversion to plantlets is a major problem in many species including Persian walnut. We studied the effects of abscisic acid (ABA) and sucrose, on the maturation and germination of Persian walnut (Juglans regia) somatic embryos. Individual globular somatic embryos were grown on a maturation medium supplemented with different combinations of ABA and sucrose for ca. 1 month, until shoot meristems and radicles had developed. White and opaque embryos in late cotyledonary stage were subjected to desiccation after the culture period on maturation media. The number of germinated somatic embryos was influenced by the concentrations of ABA in the maturation medium. The best treatment for germination, in which both shoot and root were developed contained 2 mg l -1 ABA and resulted in 41% conversion of embryos into plantlets. Regeneration was reduced at higher levels of ABA. While ABA always reduced the rate of secondary embryogenesis, treatments containing 4.0% sucrose significantly increased the number of secondary embryos. On the other hand, sucrose had little influence on maturation. Normal and abnormal embryos were verified anatomically.

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A somatic embryogenesis (SE) protocol was established for the regeneration of Lilium ledebourii (Baker) Boiss. whole plants using new vegetative bulblet microscales and transverse thin cell layers (tTCLs) of young bulblet roots as the explant sources. Bulblets were induced from bulb scale explants cultured for at least 3 months in the dark on Murashige and Skoog (MS) medium containing 3% sucrose, 0.8% agar, and different concentrations of a-naphthaleneacetic acid (NAA), 6-benzyladenine (BA), and thidiazuron. Embryo-like structures were obtained from tTCL explants of 3-month-old bulblets (excised from bulb scale explants) following culture on solid MS medium containing 3% sucrose and various concentrations of NAA and BA for 3 months in the dark. Both the explant source and the type of plant growth regulators affected the differentiation of somatic embryos. The highest percentage (65.55%) of embryogenesis was obtained from bulblet microscale tTCLs cultured on solid MS medium containing 0.54 lM NAA and 0.44 lM BA. Plants with normal shoots and roots were obtained following a 3-month culture of embryos on growth regulatorfree MS medium at 25 ± 1°C under a 16/8-h light/dark photoperiod (light intensity 40 lmol m -2 s -1 , cool-white fluorescent light). The plants were successfully acclimatized in the growth chamber.

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The mechanism of growth amelioration in salt-stressed pennyroyal (Mentha pulegium L.) was investigated by exogenous application of penconazole (PEN). Seven weeks after sowing, seedlings were treated with increasing NaCl concentrations (0, 25, 50, and 75 mM) with or without PEN (15 mg l −1) and were harvested randomly at different times. Results showed that some growth parameters and the relative water content (RWC) decreased under salt stress, while lipid peroxidation, H 2 O 2 content, activities of superoxide dismutase (