Nanotubos de carbono de parede múltipla no crescimento in vitro de girassol ornamental

Abstract

Different nanomaterials are studied regarding their potential to affect plant development in a positive or negative way. Amongst them, carbon nanotubes are reported in literature to play the role of growth regulators or toxic agents for plants. This duality raises the need to learn more about the physiological effects from this interaction, in different species and with different forms of exposure. Especially in situations of abiotic stress, such as water deficit, given that forecasts point to changes in the distribution and availability of water for agriculture. Thus, this work aims to evaluate the toxicity of multi-walled carbon nanotubes in ornamental sunflower, in the germination process and in the initial plant development. The in vitro culture medium was supplemented with carboxylic acid functionalized multi-walled carbon nanotubes (CNT) and seeds were inoculated to develop for seven days. Initial germination was not affected by CNT, although there is a promotion of antioxidant system enzymes (SOD, CAT, APX and POX) up to 96 hours after inoculation. The seedlings produced showed greater growth and accumulation of fresh matter in the shoot and root system with exposure to CNT, indicating that these are promoters of initial development in ornamental sunflower. The nanomaterials were also tested under water deficit conditions induced in vitro, by adding PEG 6000 to the culture medium (10%). In this case, there was also no difference in seed germination, but the presence of NTC mitigated the negative effects of low water availability on shoot and root system growth. There was a modulation of the antioxidant enzymatic activity, with higher shoot activity of SOD and CAT, as well as APX in root system in the presence of CNT. Furthermore, the accumulation of osmotically active solutes was observed with the stress induced in vitro, mainly proline in the shoot and soluble sugars in the root system, after CNT exposure. In conclusion, it is possible to state that carboxylic acid-functionalized multi-walled carbon nanotubes positively affect the initial development of ornamental sunflower and still have the potential to mitigate abiotic stresses during seedling establishment.