This study aimed to provide new information about phyto-toxicology of nano-TiO2 on plant systems. To contribute to the evaluation of the potential harmful effects of the nanoparticles on monocots and dicots we considered their effects on seed germination and root elongation applying a concentration range from 0.2 to 4.0% in the plants Zea mays L. and Vicia narbonensis L. Moreover, we achieved a genotoxicity study at cytological level in root meristems by means of traditional cytogenetic approach, to evidence possible alterations in mitotic activity, chromosomal aberrations, and micronuclei release. From these analyses it comes out that nano- TiO2 particles, after short-term exposure and under our experimental conditions, delayed germination progression for the first 24 h in both materials. Root elongation was affected only after treatment with the higher nano-TiO2 concentration. Further significant effects were detected showing mitotic index reduction and concentration-dependent increase in the aberration emergence that evidenced a nano-TiO2- induced genotoxic effect for both species

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Carotenoids are terpenoid pigments which are accumulated in the chloroplasts of leaves and in the chromoplasts of many flowers and fruits. Phytoene desaturase (Pds), the second dedicated enzyme in carotenoid biosynthesis, is encoded in tomato by a single copy gene. A 2 kb fragment from the tomato Pds gene, comprising 1.5 kb from the promoter and 0.5 kb from the 5' non-translated region, is able to drive developmentally regulated expression of the GUS reporter gene in transgenic tomato and tobacco plants. In tomato, high levels of Pds/GUS expression are found in organs and at stages of development where chromoplasts are formed: petals, anthers and ripening fruits. Tobacco petals and fruits, which do not contain chromoplasts, show instead low levels of Pds/GUS expression. Transgenic tobacco seedlings were subjected to treatment with a range of inhibitors of carotenoid and chlorophyll biosynthesis. The results indicate that, in green tissues, carotenoid and chlorophyll levels are tightly co-regulated and that a chemically induced arrest in pigment biosynthesis results in activation of the Pds promoter. The promoter is also induced in etiolated seedlings, which contain much lower carotenoid levels than light-grown seedlings. These data suggest that in green tissues Pds gene transcription may respond to end-product regulation.