Nanotubo de carbono na germinação de Clitoria ternatea L.

Abstract

The Clitoria ternatea L. is an herbaceous vine, and its flowers are edible and medicinal. In Brazil, it is primarily used as a forage plant, but it has recently gained popularity in gastronomy due to the blue pigment (anthocyanin) found in its flowers, which can be used as a food dye, both in its natural form and as a tea. However, one of the main limitations to the expansion of its cultivation is the low seed germination rate and seedling vigor, due to the seeds having an impermeable seed coat that hinders water entry and impairs uniform germination. An important tool that aids in the characterization of seeds, as well as the early stage of plant development (seedlings), is image analysis techniques (Biospeckle and GroundEye), which allow for optimized analysis of morphological parameters of seeds and seedlings. Nanotechnology, using primarily multi-walled carbon nanotubes (MWCNTs), is a technology that emerges as an innovation in seed treatment in the agronomic field. Due to its cylindrical structure and nano-scale, it creates openings in the seed coat, facilitating water entry into the embryo and improving germination. The objective of the project was to evaluate the effect of multi-walled carbon nanotubes functionalized with carboxylic acid (MultiWalled Carbon Nanotubes - MWCNTs) on the germination and vigor of Clitoria ternatea seedlings. The seeds were treated with MWCNTs at different concentrations (0, 100, 200, 400, 800 mg L-1), aiming to understand the interaction of MWCNTs with the seeds and seedlings. In the first experiment, intact seeds were subjected to 24 hour imbibition at different concentrations of MWCNTs for evaluation in the germination test. In the second experiment, the seeds were mechanically scarified prior to imbibition in MWCNTs. In the third experiment, nanopriming (200 mg L-1 MWCNTs) and hydropriming (water) were performed on intact and scarified seeds. In the last experiment, both intact and scarified seeds were subjected to chronic exposure to MWCNTs (200 and 800 mg L-1) to assess whether there is toxicity of the product over a longer period of exposure. Germination (%), IVG, normal seedlings (%), fluid movement analysis in the embryo (Biospeckle), and seedling growth parameters through image analysis (GroundEye) were evaluated. MWCNTs (200 mg L-1) in the first and second experiments showed an improvement in seed germination and seedling development, and mechanical scarification proved to be a good method for improving dormancy overcoming and germination speed. In the third experiment, the nanopriming method associated with mechanical scarification achieved 74% germination, the same as that found in hydropriming. However, the seedling characteristics of nanopriming indicate an improvement in growth parameters, indicating an enhancement in seedling vigor. As for the evaluation of toxicity (chronic exposure), it can be affirmed that even at the highest dose (800 mg L-1), there are no harmful effects on the germination and vigor of Clitoria ternatea seedlings. Therefore, the use of MWCNTs can be a valuable tool to improve the cultivation of Clitoria ternatea and explore its gastronomic and medicinal potential.