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چکیده
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Water defcit stress is one of the most signifcant environmental abiotic factors infuencing plant growth and metabolism globally. Recently, encouraging outcomes for the use of nanomaterials in agriculture have been shown to reduce the adverse efects of drought stress on plants. The present study aimed to investigate the impact of various carbon nanomaterials (CNMs) on the physiological, morphological, and biochemical characteristics of bell pepper plants subjected to water defcit stress conditions. The study was carried out as a factorial experiment using a completely randomized design (CRD) in three replications with a combination of three factors. The frst factor considered was irrigation intensity with three levels [(50%, 75%, and 100% (control) of the feld capacity (FC)] moisture. The second factor was the use of carbon nanomaterials [(fullerene C60, multi-walled carbon nanotubes (MWNTs) and graphene nanoplatelets (GNPs)] at various concentrations [(control (0), 100, 200, and 1000 mg/L)]. The study confrmed the foliar uptake of CNMs using the Scanning Electron Microscopy (SEM) technique. The efects of the CNMs were observed in a dose-dependent manner, with both stimulatory and toxicity efects being observed. The results revealed that exposure to MWNTs (1000 mg/L) under well-watered irrigation, and GNPs treatment (1000 mg/L) under severe drought stress (50% FC) signifcantly (P<0.01) improved fruit production and fruit dry weight by 76.2 and 73.2% as compared to the control, respectively. Also, a signifcant decrease (65.9%) in leaf relative water content was obtained in plants subjected to soil moisture of 50% FC over the control. Treatment with GNPs at 1000 mg/L under 50% FC increased electrolyte leakage index (83.6%) compared to control. Foliar applied MWNTs enhanced the leaf gas exchange, photosynthesis rate, and chlorophyll a and b concentrations, though decreased the oxidative shock in leaves which was demonstrated by the diminished electrolyte leakage index and upgrade in relative water content and antioxidant capacity compared to the control. Plants exposed to fullerene C60 at 100 and 1000 mg/L under soil moisture of 100 and 75% FC signifcantly increased total favonoids and phenols content by 63.1 and 90.9%, respectively, as compared to the control. A signifcant increase (184.3%) in antioxidant activity (FRAP) was observed in plants exposed to 200 mg/L MWCNTs under irrigation of 75% FC relative to the control. The outcomes proposed that CNMs could diferentially improve the plant and fruit characteristics of bell pepper under dry conditions, however, the levels of changes varied among CNMs concentrations. Therefore, both stimulatory and toxicity efects of employed CNMs were observed in a dose-dependent manner. The study concludes that the use of appropriate (type/dose) CNMs through foliar application is a practical tool for controlling the water shortage stress in bell pepper. These fndings will provide the basis for more research on CNMs-plant interactions, and with help to ensure their safe and sustainable use within the agricultural chains.
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