Fig. 3

Effects of CNTs during the life cycle of plants. A Schematic representation of the effects of CNTs at various stages of plant growth. B The effect of single-walled carbon nanotubes (SWCNTs), quantum dots (QDs), and SWCNT-QD conjugates on the phenotype of 2-month-old tomato plants grown on a medium supplemented with 0.5 µg/mL QDs, 50 µg/mL SWCNTs, or 50 µg/mL SWCNT-QDs, or without nanoparticles as a control [144]. C Morphological observations of red spinach and lettuce exposed to multi-walled carbon nanotubes (MWCNTs) at concentrations of 0, 20, 200, 1000, and 2000 mg/L in hydroponic culture for 15 days [146]. D Image showing the effects of natural MWCNTs, synthetic MWCNTs, amorphous carbon, and a control group on Eysenhardtia polystachya growth [141]. E Effect of synthetic MWCNTs on the growth of Lupinus elegans [142]. F Effect of water supplied CNTs (50 and 200 µg/mL) on the number of flowers on tomato plants [53]. G Effect of CNTs on the nodule development of plants grown in soil treated with activated carbon (AC), MWCNTs, SWCNTs, and graphene oxide (GO) at low (50 µg/mL) or high (500 µg/mL) concentration for 14 days post-inoculation (dpi), respectively. Nodules on the roots are shown by red triangles. Scale bar = 10 mm [147]