Effects of TiO(2) nanoparticles on wheat (Triticum aestivum L.) seedlings cultivated under super-elevated and normal CO(2) conditions

Concerns over the potential risks of nanomaterials to ecosystem have been raised, as it is highly possible that nanomaterials could be released to the environment and result in adverse effects on living organisms. Carbon dioxide (CO(2)) is one of the main greenhouse gases. The level of CO(2) keeps increasing and subsequently causes a series of environmental problems, especially for agricultural crops. In the present study, we investigated the effects of TiO(2) NPs on wheat seedlings cultivated under super-elevated CO(2) conditions (5000 mg/L CO(2)) and under normal CO(2) conditions (400 mg/L CO(2)). Compared to the normal CO(2) condition, wheat grown under the elevated CO(2) condition showed increases of root biomass and large numbers of lateral roots. Under both CO(2) cultivation conditions, the abscisic acid (ABA) content in wheat seedlings increased with increasing concentrations of TiO(2) NPs. The indolepropioponic acid (IPA) and jasmonic acid (JA) content notably decreased in plants grown under super-elevated CO(2) conditions, while the JA content increased with increasing concentrations of TiO(2) NPs. Ti accumulation showed a dose-response manner in both wheat shoots and roots as TiO(2) NPs concentrations increased. Additionally, the presence of elevated CO(2) significantly promoted Ti accumulation and translocation in wheat treated with certain concentrations of TiO(2) NPs. This study will be of benefit to the understanding of the joint effects and physiological mechanism of high-CO(2) and nanoparticle to terrestrial plants.