The effects of fullerene on photosynthetic apparatus, chloroplast‐encoded gene expression, and nitrogen assimilation in Zea mays under cobalt stress

Abstract

Carbon nanostructures, such as the water‐soluble fullerene (FLN) derivatives, are considered perspective agents for agriculture. FLN can be a novel nano‐agent modulating plant response against stress conditions. However, the mechanism underlying the impacts of FLN on plants in agroecosystems remains unclear. Zea mays was exposed to exogenous C60‐FLN applications (FLN1: 100; FLN2: 250; and FLN3: 500 mg L−1) with/without cobalt stress (Co, 300 μM) for 3 days (d). In the maize chloroplasts, Co stress disrupted the photosynthetic efficiency and the expression of genes related to the photosystems (psaA and psbA). FLNs effectively improved the efficiency and photochemical reaction of photosystems. Co stress induced the accumulation of reactive oxygen species (ROS) as confirmed by ROS‐specific fluorescence in guard cells. Co stress increased only chloroplastic superoxide dismutase (SOD) and peroxidase (POX). Stress triggered oxidative damages in maize chloroplasts, measured as an increase in TBARS content. In Co‐stressed seedlings exposed to FLN1 and FLN2 exposures, the hydrogen peroxide (H2O2) was scavenged through the nonenzymes/enzymes‐related to the AsA‐GSH cycle by preserving ascorbate (AsA) conversion, as well as GSH/GSSG and glutathione (GSH) redox state. Also, the alleviation effect of FLN3 against stress could be attributed to increased glutathione S‐transferase (GST) activity and AsA regeneration. FLN applications reversed the inhibitory effects of Co stress on nitrogen assimilation. In maize chloroplasts, FLN increased the activities of nitrate reductase (NR), glutamate dehydrogenase (GDH), nitrite reductase (NiR), and glutamine synthetase (GS), which provided conversion of inorganic nitrogen (N) into organic N. The ammonium (NH4+) toxicity was removed via GS and GDH but not glutamate synthase (GOGAT). The increased NAD‐GDH (deaminating) and NADH‐GDH (aminating) activities indicated that GDH was needed more for NH4+ detoxification. Therefore, FLN exposure to Co‐stressed maize plants might play a role in N metabolism regarding the partitioning of N assimilates. Exogenous FLN conceivably removed Co toxicity by improving the expressions of genes related to reaction center proteins of photosystems, increasing the level of enzymes related to the defense system, and improving the N assimilation in maize chloroplasts.

Graphene–Cu Nanocomposites Induce Tolerance against Fusarium oxysporum, Increase Antioxidant Activity, and Decrease Stress in Tomato Plants

“…Anthocyanins can prevent lipid peroxidation and act on ROS in the vacuole by increasing their content in response to various stress conditions [ 74 ]. Ozfidan-Konakci et al [ 75 ] reported that in cobalt-stressed Zea mays seedlings exposed to concentrations of 100 and 250 mg L −1 of fullerene, hydrogen peroxide (H 2 O 2 ) was eliminated through enzymes and non-enzymes related to the AsA-GSH cycle, which preserved ascorbate (AsA) conversion, as well as the redox status of GSH/GSSG and glutathione. Studies have shown that CNMs, such as single-walled carbon nanotubes (SWCNTs), can increase the total flavonoid content in plants subjected to biotic stress, as well as in in vitro crops [ 76 , 77 ].…”

Carbon Nanomaterials as Regulators of Stress Resistance in Plants

“…At cobalt stress, the modulatory effect of water-soluble fullerene derivatives on corn seedlings was realized through the removal of hydrogen peroxide from tissues by non-enzymatic/enzymatic systems associated with the ascorbate-glutathione cycle, by preserving the conversion of ascorbate, the ratio of glutathione/glutathione disulfide, as well as the redox state of glutathione. Fullerenes significantly reduced the inhibitory effect of cobalt on nitrogen assimilation, also increased the activity of enzymes in corn chloroplasts, such as nitrate reductase, glutamate dehydrogenase, nitrite reductase, and glutamine synthetase 88 .…”

Unveiling the Effects of Carbon-Based Nanomaterials on Crop Growth: From Benefits to Detriments

“…39 The increased activity of SOD, POD, and CAT can be considered as an excitatory effect, and this stimulation can enhance the protective mechanisms of plant and thus promote it to adapt to the adverse external environment (e.g., highly saline soils and drought). 40,41 This was regarded as one of the important applications of CNMs to assist in food production. 42 In the regulation of growth hormones in cereal crops, CNTs and FLEs had negative effects on phytohormone secretion, while GPEs had the opposite effect.…”