Phytoremediation applications in natural condition and in mesocosm: The uptake of cadmium by Lemna minuta Kunth, a non-native species in Italian watercourses.

Metal pollution in water and soil is an environmental and public health issue. Cadmium (Cd) is included in the list of priority hazardous substances in the European Water Framework Directive. Phytoremediation system is a cost-effective, plant-based approach that takes advantage of the ability of plants to concentrate elements and compounds from the environment and to metabolize various molecules in their tissues. We studied the presence and the importance of an invasive species, such as Lemna minuta, in the environment and the effects of Cd pollution on this species. Growth, removal, and tolerance were evaluated for different Cd concentrations and different times of plant exposure. Overall, the results show that L. minuta has a good capacity of growth, metal bioconcentration, and tolerance up to 3 days of exposure at 0.5 and 1.5 mg L-1 of Cd. In particular, L. minuta was able to accumulate Cd up to 3771 mg kg-1 on dry mass basis. We can conclude that L. minuta possesses a great capability of Cd absorption and accumulation, thus supporting a potential use of this species in designing a metal bioremediation system in phytoremediation field.

High frequency of plant regeneration in sunflower from cotyledons via somatic embryogenesis.

A plant regeneration methodvia somatic embryogenesis of severalHelianthus annuus L. genotypes was developed. Starting from cotyledonary explants high frequency embryo induction was obtained following several subcultures on defined media. An appropriate cotyledon developmental stage was identified. Etiolated explants and darkness treatment were necessary to obtain somatic embryos in all tested genotypes. After 20-25 days on somatic induction medium containing an auxin:cytokinin ratio of 1:1, the germination of embryos was induced by a reduction of the hormonal ratio (1:2). Shoots were excised from callus and transferred onto a medium containing various vitamins. The range of embryogenesis frequency was 33-72%, depending on the genotype. High frequency of rooting (49-82%) was obtained using a medium supplemented with 0.5 mg/L of ancymidol and by a reduction of photoperiod. A large percentage of somatic embryos developed into normal regenerated plants producing viable seeds.