Carbon nanotubes affect early growth, flowering time and phytohormones in tomato

Authors: JORDAN, JULIETTE - Texas Tech University; OATES, ROBERT - Texas Tech University; SUBBIA, SEENIVASAN - Texas Tech University; Payton, Paxton; SINGH, KAMALESHWAR - Texas Tech University; SHAH, SMIT - Texas A&M University; GREEN, MICHAH - Texas A&M University; KLEIN, DAVID - Texas Tech University; CANAS-CARRELL, JACLYN - Texas Tech University

Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2020
Publication Date: 5/11/2020
Citation: Jordan, J., Oates, R., Subbia, S., Payton, P.R., Singh, K., Shah, S., Green, M., Klein, D., Canas-Carrell, J. 2020. Carbon nanotubes affect early growth, flowering time and phytohormones in tomato. Chemosphere. 256:127042. https://doi.org/10.1016/j.chemosphere.2020.127042.
DOI: https://doi.org/10.1016/j.chemosphere.2020.127042

Interpretive Summary: Carbon nanotubes (CNT) are synthesized carbon particles 1-100 nm in size. CNT applications are increasing in consumer products, including agriculture devices, making them an important contaminant to study in the field of plant nanotoxicology. Several studies have observed the uptake and effects of CNTs in plants but with varying results. This study evaluated CNT effects on phenotypic (growth, flowering, and fruiting time) and physiological (amino acid and phytohormone content) changes in tomato plants grown under controlled environment conditions in a greenhouse. Tomato is an ideal species for this study as previous studies have reported decreased root elongation, decreased germination time, increased fruiting, and increased expression of stress response genes following exposure to CNTs. For this study, ARS scientists and collaborators showed the CNT exposure altered early growth and flowering but had little effect on long-term phenology or physiology. Although the experiments were short-term and under controlled conditions, these results show that certain types of CNTs may impact growth of tomato differently than other types of CNTs and serve as a baseline for future studies to gain a better understanding of the fate and toxicity of CNTs in terrestrial ecosystems or under stressful environmental conditions.

Technical Abstract: Carbon nanotube (CNT) applications are increasing in consumer products, including agriculture devices, making them an important contaminant to study in the field of plant nanotoxicology. Several studies have observed the uptake and effects of CNTs in plants. However, in other studies differing results were observed on growth and physiology depending on the plant species and type of CNT. This study focused on the effects of CNTs on plant phenotype with growth, time to flowering, fruiting time as endpoints, and physiology, through amino acid and phytohormone content, in tomato after exposure to multiple types of CNTs. Plants grown in CNT-contaminated soil exhibited a delay in early growth and flowering (especially in treatments of 1 mg/kg multi-walled nanotubes (MWNTs), 10 mg/kg MWNTs, and 1 mg/kg MWNTs-COOH). However, CNTs did not affect plant growth or height later in the life cycle. No significant differences in abscisic acid (ABA) and citrulline content were observed between the treated and control plants. However, single-walled nanotube (SWNT) exposure significantly increased salicylic acid (SA) content in tomato. These results suggest that SWNTs may elicit a stress response in tomatoes. Results from this study offer more insight into how plants respond and acclimate to CNTs. These results will lead to a better understanding of CNT impact on plant phenotype and physiology.