The Effects of Different Solid Content Carbon Nanotubes and Silver Quantum Dots on Potential Toxicity to Plants through Direct Effects on Carbon and Light Reactions of Photosynthesis

Abstract

We examined the effects of two types of carbon nanotubes (CNTs) and one type of silver quantum dot (Ag-QD) on potential plant toxicity through effects on plant gas exchange across four different experiments. First, Arabidopsis thaliana seeds were directly grown in growth medium containing 75% solid content CNTs at concentrations of 24.93µg/ml and 53.55 µg/ml in petri dishes. Second, A. thaliana seeds were directly grown in growth medium containing 95% solid content CNTs at concentrations of 4μg/ml; or third, 18 nm Ag-QDs at a concentration of 4μg/ ml. Fourth, we grew A. thaliana in soil for 6 weeks and added the 95% solid content CNT suspension at increasing concentrations of 10, 30, 90, 150, 190, 250 μg/ ml each week. The 75% solid content CNT, and the CNTRENE® C100LM material production waste produced for disposal, had no negative effects on growth or gas exchange. We found that gas exchange in petri dish grown A. thaliana was greatly negatively affected by the Ag-QD, and relatively marginally negatively affected by the 95% solid content CNT. There were significant reductions in photosynthesis rates and related light and carbon fixation reactions in both the Ag-QD and 95% solid content CNT A. thaliana grown in petri dishes. We found that gas exchange in soil grown A. thaliana was unaffected by 95% solid content CNTs, even at very high concentrations. These findings have implications for understanding toxicity of engineered nanoparticles on plant and animal health, public awareness, and environmental remediation.