Single-Walled Carbon Nanotubes Modify Leaf Micromorphology, Chloroplast Ultrastructure and Photosynthetic Activity of Pea Plants

Abstract

Single-walled carbon nanotubes (SWCNTs) emerge as promising novel carbon-based nanoparticles for use in biomedicine, pharmacology and precision agriculture. They were shown to penetrate cell walls and membranes and to physically interact and exchange electrons with photosynthetic complexes in vitro. Here, for the first time, we studied the concentration-dependent effect of foliar application of copolymer-grafted SWCNTs on the structural and functional characteristics of intact pea plants. The lowest used concentration of 10 mg L−1 did not cause any harmful effects on the studied leaf characteristics, while abundant epicuticular wax generation on both leaf surfaces was observed after 300 mg L−1 treatment. Swelling of both the granal and the stromal regions of thylakoid membranes was detected after application of 100 mg L−1 and was most pronounced after 300 mg L−1. Higher SWCNT doses lead to impaired photosynthesis in terms of lower proton motive force generation, slower generation of non-photochemical quenching and reduced zeaxanthin content; however, the photosystem II function was largely preserved. Our results clearly indicate that SWCNTs affect the photosynthetic apparatus in a concentration-dependent manner. Low doses (10 mg L−1) of SWCNTs appear to be a safe suitable object for future development of nanocarriers for substances that are beneficial for plant growth.

Polymer-Modified Single-Walled Carbon Nanotubes Affect Photosystem II Photochemistry, Intersystem Electron Transport Carriers and Photosystem I End Acceptors in Pea Plants

“…It should be noted that in these experiments SWCNT were either applied on a leaf surface with compromised epidermis or infiltrated into the leaves, thus omitting the barrier properties of cuticular waxes. The results of our recent work, however, suggest penetration of SWCNT into chloroplasts upon non-invasive foliar application of polymer-grafted SWCNT [ 12 ] which was also applied in this work.…”

“…The retarded fluorescence rise in the J-I and I-P phases might be due to downregulation of electron transport through Cyt b 6 f known to be a subject of ‘photosynthetic control’ by thylakoid lumen acidity [ 28 ]. Our recent study demonstrates that the proton motive force in SWCNT 300 treated plants was slightly lower than in control plants [ 12 ] indicating that the slower increase of Chl fluorescence in the J-P phase is not due to Cyt b 6 f control. It is still to be cleared out if SWCNT are capable of pulling electrons at the PSI or Cyt b 6 f level or the observed phenomenon represents indirect effect of the SWCNT treatment.…”

“…Since SWCNT can be viewed as a novel and unexplored abiotic stress factor, it cannot be ruled out that the lower V red and ΔMR slow in SWCNT 300 reflects activation of CEF. Our recent work illustrates that foliar application of SWCNT alters CO 2 assimilation [ 12 ], which might lead to over-reduction of the photosynthetic electron transport chain and activation of CEF as a safety valve.…”

“…In addition to augmentation of photosynthesis, the action of SWCNT in intact plants was related to increased expression of antioxidant enzymes [ 10 ] which was found to alleviate the drought stress effects [ 11 ]. Our recent findings demonstrated that high doses of polymer-grafted SWCNT exert negative effects on the rate and efficiency of photosynthesis, when applied via foliar spraying [ 12 ]. We hypothesized that SWCNT interact with the components of electron transport chain.…”

Multi-walled carbon nanotubes wrapped with polyvinylpyrrolidone can control the leaf yellowing of Alstroemeria cut flowers

“…In addition, the increase in total chlorophyll content observed at low doses of MWCNTs/PVP (Table 4 ) may result from the increased photosynthetic activity 57 , 58 . Velikova et al 59 observed that SWCNTs could alter pea plants' leaf micromorphology and chloroplast ultrastructure, thereby affecting their photosynthetic activity.…”