Uptake of CeO2 nanoparticles and its effect on growth of Medicago arborea In vitro plantlets.

The present study analyzes some effects of nano-CeO2 particles on the growth of in vitro plantlets of Medicago arborea when the nanoceria was added to the culture medium. Various concentrations of nano-CeO2 and bulk ceric oxide particles in suspension form were introduced to the agar culture medium to compare the effects of nanoceria versus ceric oxide bulk material. Germination rate and shoot dry weight were not affected by the addition of ceric oxide to the culture media. Furthermore, no effects were observed on chlorophyll content (single-photon avalanche diode (SPAD) measurements) due to the presence of either nano- or micro-CeO2 in the culture medium. When low concentrations of nanoceria were added to the medium, the number of trifoliate leaves and the root length increased but the root dry weight decreased. Also the values of maximum photochemical efficiency of PSII (F(v)/F m) showed a significant decrease. Dark-adapted minimum fluorescence (F 0) significantly increased in the presence of 200 mg L(-1) nanoceria and 400 mg L(-1) bulk material. Root tissues were more sensitive to nanoceria than were the shoots at lower concentrations of nanoceria. A stress effect was observed on M. arborea plantlets due to cerium uptake.

Involvement of peroxidase activity in developing somatic embryos of Medicago arborea L. Identification of an isozyme peroxidase as biochemical marker of somatic embryogenesis.

The legume Medicago arborea L. is very interesting as regards the regeneration of marginal arid soils. The problem is that it does not have a good germinative yield. It was therefore decided to regenerate via somatic embryogenesis and find a marker of embryogenic potential. In this study, peroxidase activity was evaluated in non-embryogenic and embryogenic calli from M. arborea L. A decrease in soluble peroxidase activity is observed in its embryonic calli at the time at which the somatic embryos begin to appear. This activity is always lower in embryonic calli than in non-embryonic ones (unlike what happens in the case of wall-bound peroxidases). These results suggest that peroxidases can be considered to be enzymes involved in somatic embryogenesis in M. arborea. In addition, isozyme analyses were carried out on protein extracts using polyacrylamide gel electrophoresis. The band called P5 was detected only in embryogenic cultures at very early stages of development. This band was digested with trypsin and analyzed using linear ion trap (LTQ) mass spectrometer. In P5 isoform a peroxidase-L-ascorbate peroxidase was identified. It can be used as a marker that allows the identification of embryological potential.