| Chickpea is the oldest cultivated major legume crop in India and has a well-developed root system with a drought-tolerant primary root,as well as root nodules and a high nitrogen fixation capacity,making the root system critical to the growth and development of chickpea and the efficiency of the use of carbon-based nanomaterials.Carbon-based nanomaterials are used in a variety of applications and their release into the environment may lead to environmental pollution.The effects of different dimensions of carbon-based nanomaterials on chickpea seedlings are difficult to assess due to a lack of knowledge of the chickpea crop.In this study,the effects of three different dimensional carbon-based nanomaterials on chickpea seedling growth were investigated in this study.A total of 10 treatments were set up: control(CK),low amount of Carbon Quantum Dots(C0-25),medium amount of Carbon Quantum Dots(C0-50),high amount of Carbon Quantum Dots(C0-100),low amount of carbon nanotubes(C1-25),medium amount of carbon nanotubes(C1-50),high amount of carbon nanotubes(C1-100),low amount of Graphene Nanoplatelets(C2-25),medium amount of Graphene Nanoplatelets(C2-50),high amount Graphene Nanoplatelets(C2-100),low,medium and high amounts corresponding to the same amount of carbon(25,50,100 mg/L),grown hydroponically in a growth chamber with a light/dark photoperiod at 18±2°C for 14 days.Seedling growth and development,root viability,fluorescence parameters,nitrogen metabolism,nutrient and carbon metabolism related indicators and root tip metabolites were measured The study was carried out to further understand the growth mechanism of chickpea seedlings and their corresponding metabolic pathways,and to provide a theoretical basis for the regulation of growth and development of chickpea seedlings by three different dimensional carbon-based nanomaterials.The main findings of the study are as follows:(1)The growth of chickpea seedlings was inhibited by the three dimensional carbon-based nanomaterials.The growth(length,root dry weight and root fresh weight)of chickpea seedlings was inhibited to different degrees by Carbon Quantum Dots.The C0-25 and C0-100 treatment groups significantly inhibited chickpea root length by 27.49% and 51.23% compared to the pair CK treatment group.The C1-50 treatment group significantly reduced chickpea length,surface area,volume,root tip number and root fresh weight by 36.33%,20.99%,30.66%,4.99% and50.78%,respectively,compared to the CK group.The growth inhibition of chickpea seedlings was the strongest in the C2-50 treatment group,including root length,surface area,volume and root fresh weight,which decreased by 35.43%,32.65%,36.76% and 56.45% respectively compared to the CK treatment group.All three carbon-based nanomaterial additions promoted root tip number in chickpea seedlings,most significantly in the C0-50,C1-100 and C2-50 treatment groups,reaching 556.67 Tips,378.33 Tips and 441.33 Tips,respectively.the average diameter of the C0-100,C1-25 and C1-50 treatment groups compared to the CK treatment group increased to 0.56 nm,0.51 nm and 0.51 nm,which promoted the lateral development of the root system.(2)All three dimensions of carbon-based nanomaterials enhanced the growth characteristics of chickpea seedlings,among which the two-dimensional carbon-based nanomaterials had the most significant promotion effect.195.91%,119.84% and 190.89% of root vigour,active root absorption area and total absorption area were significantly enhanced in the C1-100 treatment group compared with the CK treatment group.195.91%,119.84% and 190.89% of root vigour,total root absorption area and total absorption area were significantly enhanced in the C0-50 treatment group compared with the CK treatment group.The root vigour,total root area and active root area were 122.66%,55.92% and 34.79% higher in the C0-50 treatment group than in the CK treatment.155.88%,133.44% and 73.77% higher in the C1-50 treatment group than in the CK treatment.At the leaf scale,the characteristics of leaf fluorescence parameters under different dimensional carbon-based nanomaterial treatments were analyzed at different periods based on fluorescence parameters.The results showed that Phi2 was 41.85%,61.59% and 70.79% higher than the CK treated group at 14 days for C0-25,C1-50 and C2-50.Phi NPQ was 30.38%,31.21%and 22.36% higher than the CK treated group at 7 days for C0-100,C1-25 and C2-1000.The three dimensional carbon-based nanomaterials showed a trend of Phi2 increasing and then decreasing,and Phi NO and Phi NPQ decreasing and then increasing with the growth of chickpea seedlings.(3)The addition of different dimensional carbon-based nanomaterials significantly affected the carbon and nitrogen metabolism of chickpea seedlings.77.28%,91.51% and 18.05% of soluble sugars,ammonium nitrogen and GOT were higher in the roots of C0-50 treated chickpea seedlings than in the CK treated group.Above ground GOT,ammonium N,soluble protein,soluble sugar were 116.77%,92.21%,31.13%,40.98%.ammonium N,soluble protein,soluble sugar,GOT in the roots of chickpea seedlings treated with C1-25 were 92.18%,2.63%,29.82%,59.45% higher than those of the CK treatment group.The above ground GOT,ammonium N,soluble protein and soluble sugar contents were 180.47%,91.83%,17.51% and 19.25% higher than those of the CK treated group.39.41%,43.68%,181.93% and 29.32% higher than those of the CK treated group for ammonium N,soluble sugar,GOT and GPT in the roots of chickpea seedlings treated with C2-50.Above ground soluble sugar,soluble protein,ammonium nitrogen,GOT and sucrose synthase were 15.83%,34.05%,65.49%,290.87% and 7.08% higher than those of the CK treated group.(4)Different dimensions of carbon-based nanomaterials significantly affected the nutrient uptake capacity of the plants.The highest accumulation of roots and total phosphorus and potassium were found in the C0-25 treated chickpea seedlings,where the roots were 33.99% and22.88% higher than the CK treated group,and the aboveground parts were 22.76% and 25.74%higher than the CK treated group,respectively,and the root total nitrogen content reached the maximum of 33.47% in the C0-50 treated group.in the C2-50 treated group,the chickpea root and aboveground The total nitrogen content in the roots and above ground parts of chickpea was significantly higher in the C2-50 treatment group than in the CK treatment group at 89.05% and81.55%,while in the C1-50 treatment group,the total nitrogen content in the roots and above ground parts was lower than in the CK treatment group at 14.99% and 27.01%.The appropriate amount of carbon-based nanomaterials can cause some promotion of chickpea in agricultural production.There was a highly significant and significant negative correlation between nitrate and ammonium nitrogen content in chickpea seedlings,a significant positive correlation between GOT and GPT activity in chickpea seedling roots and a significant positive correlation between NR and nitrate nitrogen content.There was a positive correlation between above ground dry weight and soluble protein content in chickpea seedlings.Improving morphological characteristics of chickpea seedlings and promoting the metabolic process of nutrients in chickpea seedlings provide the basis for late chickpea production.(5)A total of 27 differential metabolites were detected in the four comparison groups,including amino acid,sugar,fatty acid,alcohol,organic acid and polyol metabolites.The multi-walled carbon nanotube treatment resulted in a significant accumulation of amino acids such as asparagine,glutamate,glutamine,aspartate and homoserine in the root tips of seedlings.Graphene Nanoplatelets had some amino acids showing a decreasing trend,such as glutamine,aspartic acid,alanine and aspartic acid,but the decreasing fold was relatively small.Comparing Multi-Walled Carbon Nanotubes and Graphene Nanoplatelets differential metabolites are mainly enriched to the galactose metabolic pathway,and inositol involved in this metabolic pathway shows an increasing trend.Organic acids,citric acid and were accumulated in the root tips under the carbon quantum dot and multi-walled carbon nanotube treatments relative to the other treatment groups.Of these,citric and malic acids are also major metabolites of the tricarboxylic acid cycle,the carbon-based nanomaterials and Multi-Walled Carbon Nanotubes had a stronger tricarboxylic acid cycle compared to CK. |
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