Impact of Zinc oxide nanoparticles on eggplant (S. melongena): studies on growth and the accumulation of nanoparticles

Abstract

The increasing use of nanoparticles and their occurrence in the environment has made it imperative to elucidate their impact on the environment. Although several studies have advanced the authors' understanding of nanoparticle-plant interactions, their knowledge of the exposure of plants to nanoparticles and their effects on edible crop plants remain meager and is often paradoxical. The aim of this study was to increase their knowledge on the effect of zinc oxide (ZnO) nanoparticles on eggplant seed germination and seedling growth. ZnO nanoparticles had a negative effect on the growth of eggplant in plant tissue-culture conditions, as the growth of seedlings decreased with the increase in the concentration of ZnO nanoparticles. In contrast, ZnO nanoparticles enhanced eggplant growth under greenhouse conditions. The accumulation of ZnO nanoparticles in various parts of eggplant was observed through scanning electron microscopy of both plant tissue-culture and greenhouse-raised eggplant seedlings. To the best of their knowledge, this is the first study to report on ZnO nanoparticle accumulation in eggplant and its effect on seed germination and seedling growth.

Fig. 1

Germination percentage variations of eggplant exposed to ZnO nanoparticles in (a) MS medium and (b) soil medium. Concentration of ZnO nanoparticles (a) A‐0, B‐5, C‐10, D‐15, and E‐20mg/L, (b) Concentration of ZnO nanoparticles in A‐0, B‐5, C‐10, D‐15, E‐20, and F‐100mg/Kg; error bars represent standard error. Different letters represent significant differences among treatments (p <0.05)

Fig. 2

Eggplant seedlings with variations in root traits. Concentration of ZnO nanoparticles: Control – 0, A‐5, B‐10, C‐15, and D‐20 mg/l

Fig. 3

View of seedlings of eggplant in different concentrations of ZnO nanoparticles. Concentration of ZnO nanoparticles: Control – 0, A‐5, B‐10, C‐15, and D‐20 mg/l

Fig. 4

Effect of ZnO nanoparticles on (a) Number of lateral roots, (b) Root length, (c) Root mass, (d) Leaf length; concentration of ZnO nanoparticles: Control – 0, A‐5, B‐10, C‐15, and D‐20 mg/l; error bars represent standard error. Different letters represent significant differences among treatments (p <0.05)

Fig. 5

Effect of ZnO nanoparticles on (a) Shoot length, (b) Root length, (c) Plant mass, (d) Root mass; concentration of ZnO nanoparticles: control – 0, A‐5, B‐10, C‐15, D‐20, and E‐100 mg/kg; error bars represent standard error. Different letters represent significant differences among treatments (p <0.05)

Fig. 6

Effect of ZnO nanoparticles on (a) Number of leaves, (b) Leaf length, (c) Leaf width; concentration of ZnO nanoparticles: control – 0, A‐5, B‐10, C‐15, D‐20, and E‐100 mg/kg; error bars represent standard error. Different letters represent significant differences among treatments (p <0.05)

Fig. 7

SEM micrographs of control eggplant without ZnO nanoparticles (a) In vitro stem, (b) In vitro root, (c) In vitro leaf

Fig. 8

Energy dispersive spectroscopy of control eggplant

Fig. 9

SEM of in vitro cultured eggplant (a) Stem, (b) Root with ZnO nanoparticles accumulation

Fig. 10

Energy dispersive spectroscopy of observed ZnO nanoparticles of in vitro cultured eggplant

Fig. 11

SEM micrographs of eggplant with ZnO nanoparticles accumulation (a) Stem, (b) Leaf of potted plan

Fig. 12

SEM micrographs of eggplant with ZnO nanoparticles accumulation in (c), (d), and (e) flower of a potted plant with different magnifications

Fig. 13

Energy dispersive spectroscopy of observed ZnO nanoparticles in eggplant of potted plant flower