1 Introduction

Maize is one of the staple cereal crops with high global production (Parihar et al. 2019). It is cultivated in over 100 countries worldwide due to its wide adaption to various ecological regions (Shi et al. 2016). With the increasing world population, the global cereal demand is projected to double from 2000 to 2050, of which more than 40% is contributed by maize production (Li et al. 2023). However, the current maize supply meets only 66% of the expected global demand (Ray et al. 2013).

The decrease in global radiation, also known as global dimming, has been reported to impact crop production (Wang et al. 2015; Gu et al. 2017; Shao et al. 2021). Thus, understanding the effect of light on maize production is of great importance for the global food supply. Maize is a typical C4 plant and high photo-synthetically efficient food crop. Thus, optimum sunlight conditions enhance the maize high-yielding potential (Bellasio and Griffiths 2014). Nonetheless, climate change has induced adverse environmental conditions such as reduced solar radiation, which reduces maize yields (Bellasio and Griffiths 2014; Shi et al. 2018). Generally, plants adversely suffer from dynamic light environments characterized by frequent alternation between high and low light intensities. These dynamic light environments are mostly caused by cloud cover, shading from own upper leaves, and leaf cover from neighboring plants. The shading limits the range of light available for photosynthesis within the canopy, leading to yield changes (Kaiser et al. 2015; Slattery et al. 2018).

Moreover, climate change and environmental pollution reduce solar radiation, which seriously reduces maize yields when coupled with cloudy and rainy weather during the maize flowering stage (Ma et al. 2011; Xu et al. 2014). Various shading experiments have been performed to investigate the influence of the decreased global radiation on crop production and quality (Mo et al. 2015; Shao et al. 2021). For example, a previous study revealed that light affects carbohydrate biosynthesis and crop distribution (Slewinski and Braun 2010). In maize leaves, adverse light stress alters the antioxidant enzyme activities and the chlorophyll fluorescence (Zhang et al. 2015). The lower light intensity or artificial shading also affects maize growth, decreasing nitrogen accumulation, dry matter, grain yield, and quality (Gao et al. 2020). The low light also increases the intercellular carbon dioxide concentration and ROS content (Fu et al. 2023). Therefore, understanding maize coping mechanisms under LL stress is urgently needed to enhance maize production in light-restricted environments.

Nanobiotechnology improves crop production by promoting nutrient bioavailability, refining nutrient use efficiency, and reducing environmental and pathogen-related stresses (Li et al. 2021b; Chen et al. 2023; Sun et al. 2023; Yao et al. 2023). For example, nano fertilizers are quickly and efficiently translocated between plant parts due to their tiny sizes, which boosts nutrient utilization (Babu et al. 2022). In addition, silicon is beneficial for crop growth and defense against adverse environments (Mo et al. 2017; Li et al. 2018; Deng et al. 2023; Li et al. 2023). Compared to traditional silicon fertilizers, silica nanoparticles offer several advantages, such as a relatively high surface area to volume ratio, unique thermal and electrical properties, and increased permeability in plant cells. As a result, the silica nanoparticles fertilizers easily penetrate the leaf and are rapidly absorbed onto the leaf surface (Cui et al. 2020; Jeelani et al. 2020; Babu et al. 2022). According to Rastogi et al. (2019), silicon nanoparticles benefit the plant physiological features, as they easily enter the plant system and affect its metabolic activities. Additionally, silica nanoparticles reduce oxidative damage in various crops (Albalawi et al. 2022). For instance, the SiO2 NPs reduced the malondialdehyde (MDA) content and increased the activity of antioxidant enzymes in drought-stressed roses (Hajizadeh et al. 2022). Besides, applying silica nanoparticles promotes seedling growth and development, characterized by increased seedling height, improved root growth-related indicators, and enhanced plant photosynthesis (Lin et al. 2004). The SiO2 NPs stress-reducing agent also reduced chromium-aided oxidative damage and improved the antioxidant defense system (Ulhassan et al. 2023). Therefore, silicon nanoparticles mitigate the adverse environmental effects on crops by regulating photosynthesis, antioxidant response, and growth parameters.

Herein, we hypothesized that the silicon nanoparticles would improve the accumulation and distribution of biomass and regulate the antioxidant defense system, photosynthetic pigments, and nitrogen mentalism in maize plants under low light stress. The study aimed to investigate the SiO2 NPs effects on the changes in morphological and physiological characteristics of maize seedlings under low light conditions. The findings from this study will provide insights into the tolerance mechanisms of plants under light deficit conditions treated with silicon nanoparticles, unraveling new research perspectives on LL stress under climate change scenarios.

2 Materials and Methods

2.1 Experimental Design

A hydroponic experiment was set up at the South China Agricultural University, Guangzhou, Guangdong Province, China, with two maize varieties, Yuebaitiannuo10 and Yuebaitiannuo12, these two maize varieties are popular in local maize production region. The maize seeds were provided by the Crops Research Institute, Guangdong Academy of Agricultural Sciences. The seeds were surface sterilized with 2.5% sodium hypochlorite solution for 10 min, and then placed in the seed-germination box for 48 h. The uniformly germinated seeds were transplanted in plastic pots (length × width × height = 63 cm×38 cm×15 cm) with total 48 seedlings for each treatment, arranged in a completely randomized design. The pots were maintained on the floating foam board with a density of 2 cm×2 cm at room temperature. During the experimental period, the average temperature and average humidity were 24.5 °C and 81.3%, respectively. The SiO2 NPs were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., China. SiO2 NPs were 99% pure, with a particle size of 20 nm.

2.2 Experimental Treatments

The treatments in this study comprised the application of SiO2 NPs and shading (light treatment) to Yuebaitiannuo10 and Yuebaitiannuo12. The SiO2 NPs treatments comprised the foliar application of 0 mg L− 1 (Si0), 150 mg L− 1 (Si1), and 300 mg L− 1 (Si2) of SiO2 NPs. Before application, 150 mg and 300 mg of SiO2 NPs were suspended in 1 L of distilled water to create 150 mg L− 1 (Si1), and 300 mg L− 1 (Si2) treatments, respectively. The foliar application of SiO2 NPs was conducted thrice at about 17 days after germination (three-leaf stage), 20 days after germination, and 23 days after germination. Each time, 18 ml of solution was sprayed on the plant in each plastic pot, ensuring all the leaves were uniformly covered with a layer of small droplets. After the spraying treatments at 17 days after germination, the shading treatment was immediately applied and maintained till harvesting. The shading treatments were achieved using enclosures covered with black polypropylene netting, reducing light intensity to 33.2 attenuation. The shading effect was induced by one layer of black netting level equivalent to a 67% reduction of full natural light (as measured by a Luxmeter, model ZDS-10, China). During the experimental period, the average temperature and humidity were maintained at 24.5 °C and 81.3%, respectively.

2.3 Sampling and Measurements

The plant samples were harvested 30 days post-germination, and the growth parameters, photosynthesis pigments, antioxidant response, and nitrogen metabolism parameters were assessed. In addition, biochemical analysis was performed on plant samples taken three days post-treatment. Specifically, the stem, leaf, and root were separated and flash-frozen in liquid nitrogen for 5 min and then stored at -80 °C, awaiting the analysis of the physiological parameters.

2.3.1 Determination of Biomass and Growth Traits

The maize plant height, leaf sheath length, leaf area, and fresh and dry weights were determined with three biological and three technical replicates. The fresh weight was determined immediately after harvest. Subsequently, the fresh samples were dried for three days at 60 °C to a constant weight to obtain the dry weight (Yang et al. 2022). The leaf area was measured as described by Hong et al. (2022). The shoot dry weight to plant height ratio and the root to shoot ratio were also calculated as described by Awan et al. (2014).

2.3.2 Determination of the Photosynthesis Pigments

The chlorophyll pigment was extracted from 0.1 g of fresh leaf samples using 7.5 mL of 95% ethanol for 24 h. Next, the samples were centrifuged at 5000 rpm for 5 min. In addition, the carotenoid and chlorophyll contents in the supernatant were determined by measuring the absorbance at 665, 649, and 470 nm (Li et al. 2021b; Gui et al. 2022).

2.3.3 Determination of the Antioxidant Enzyme Activities

The antioxidant enzyme activity was measured as described by Li et al. (2021b). The superoxide dismutase (SOD) activity was assessed using the nitro-blue tetrazolium method by measuring the absorbance at 560 nm and was expressed as U g− 1 FW. The peroxidase (POD) activity was assessed by measuring the absorbance at 470 nm and was expressed as U g− 1 FW. The catalase (CAT) activity was measured at 240 nm and was expressed as µmol min− 1 g− 1 FW.

2.3.4 Determination of the MDA, Proline, Hydrogen Peroxide (H2O2), the Ascorbic Acid (ASA) Content

The MDA content was quantified as using thiobarbituric acid. Specifically, the MDA content was estimated by measuring the absorbance at 532, 600, and 450 nm and was expressed as µmol g− 1 FW. The proline content was determined according to Mo et al. (2019) and was expressed as µg g− 1 FW. The H2O2 concentration was measured according to Mostofa et al. (2020) and was expressed as µg kg− 1 FW. For ASA, the fresh samples were extracted using 10% trichloroacetic acid. Subsequently, the ASA content was quantified as outlined by Rizwan et al. (2017) and expressed as µg g− 1 FW.

2.3.5 Determination of the Protein Content and Nitrate Reductase (NR) Activity

The protein content was assayed, according to Bradford (1976). The absorbance was measured at 595 nm, and the protein concentration was expressed as mg g− 1 FW. The NR activity in maize seedlings was measured following the method outlined by Li et al. (2016) and Li et al. (2021a). The NR activity was expressed as µg h− 1 g− 1 FW.

2.4 Statistical Analyses

Statistix 8.0 (Analytical Software, Tallahassee, FL, USA) was used for all statistical analyses. Comparisons between treatments were performed by analysis of variance (ANOVA), and the means were separated using the least significant difference (LSD) test at P < 0.05 level of significance. Correlations between variables were analyzed using the Pearson correlation coefficient.

3 Results

3.1 Maize Growth and Biomass

The shading treatment significantly reduced the plant height, leaf sheath length, leaf area, and aboveground dry weight/plant height (Table 1). On the contrary, it significantly increased the root-to-shoot ratio (P < 0.05). At the same time, the variety of interaction with light significantly affected the leaf sheath length, leaf area, and root-to-shoot ratio (P < 0.05). Compared to the LL-Si0, the LL-Si1 significantly increased the aboveground dry weight/plant height by 35.38% (Table 2). Light treatment significantly reduced the plant dry biomass (P < 0.05). Silica nanoparticles application slightly enhanced the leaf dry weight, aboveground dry weight, and total dry weight, with the highest dry weight detected at the Si1 treatment, irrespective of the maize variety and light treatment (Table 2). Besides, light treatment significantly reduced the plant fresh biomass (P < 0.05) (Table 3).

Table 1 Effects of silica nanoparticles on the maize seedling growth parameters under low light
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Table 2 Effects of silica nanoparticles on the dry weight of maize seedlings under low light
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Table 3 Effects of silica nanoparticles on the fresh weight of maize seedlings under low light
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3.2 Photosynthesis Pigments in Maize Leaves

Silica nanoparticle treatment significantly affected the photosynthesis pigments. At the same time, light significantly influenced the photosynthesis pigments except for the carotenoid content. Compared to the Si0 treatment, the Si1 treatment significantly reduced the photosynthesis pigments in Yuebaitiannuo10 under NL. On the contrary, the Si2 treatment significantly increased the photosynthesis pigments in Yuebaitiannuo10 under NL. Notably, Si1 and Si2 treatments significantly reduced the chlorophyll a, b, and the total chlorophyll contents in Yuebaitiannuo10 under LL compared to Si0. In addition, Si1 treatment significantly increased the chlorophyll a/b ratio in Yuebaitiannuo10 compared to Si0 under LL. However, there were no significant changes in the photosynthesis pigments in Yuebaitiannuo12 under NL. Nonetheless, the Si2 treatment significantly increased the photosynthesis pigments in Yuebaitiannuo12 under LL compared to the Si0 treatment (Fig. 1).

Fig. 1
figure 1

Effects of silica nanoparticles on the photosynthesis pigments in the leaf of maize seedlings under low light. Vertical bars with different lowercase letters above are significantly different at P < 0.05 by LSD tests. Capped bars represent standard error (SE). V: variety, L: light treatment, S: silica nanoparticles treatment. NL: normal light, LL: low light. Si0: applied silicon dioxide nanoparticles at a dose of 0 mg L− 1, Si1: applied silicon dioxide nanoparticles at a dose of 150 mg L− 1, Si2: applied silicon dioxide nanoparticles at a dose of 300 mg L− 1. * and ** represent a significant difference at P < 0.05 and P < 0.01, respectively; ns represents a non-significant difference

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3.3 Antioxidant Enzyme Activities in Maize Plants

Light and SiO2 NPs treatment and their interactions significantly impacted the SOD activity in the root, stem, and leaves. Compared to the Si0 treatment, the Si2 treatment significantly increased the SOD activity in the roots and leaves of Yuebaitiannuo10 under NL. On the contrary, it decreased the SOD activity in Yuebaitiannuo10 stem under LL. In addition, the Si2 treatment significantly increased the SOD activity in the Yuebaitiannuo12 roots under NL. At the same time, Si1 and Si2 treatments significantly increased the SOD activity in the Yuebaitiannuo12 leaves under LL (Fig. 2).

Fig. 2
figure 2

Effects of silica nanoparticles on the SOD activity in the (a) root, (b) stem, and (c) leaf of maize seedlings under low light stress. Vertical bars with different lower-case letters above indicate significant difference at P < 0.05. Capped bars represent standard error (SE). V: variety, L: light treatment, S: silica nanoparticles treatment. NL: normal light, LL: low light. Si0: applied silicon dioxide nanoparticles at a dose of 0 mg L− 1, Si1: applied silicon dioxide nanoparticles at a dose of 150 mg L− 1, Si2: applied silicon dioxide nanoparticles at a dose of 300 mg L− 1. * and ** represent a significant difference at P < 0.05 and P < 0.01, respectively; ns represents a non-significant difference

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Silica nanoparticles and the interactions of light and silica nanoparticles significantly impacted the POD activity in the root, stem, and leaves. Compared to the Si0 treatment, Si1 and Si2 treatments significantly increased the POD activity in the root but decreased the POD activity in the Yuebaitiannuo10 stem under NL. Interestingly, the Si2 treatment significantly increased the POD activity in the Yuebaitiannuo10 leaves under NL compared to the Si0 treatment. Under LL treatment, the Si1 treatment significantly increased the POD activity in the stem but decreased the POD activity in leaves of Yuebaitiannuo10 compared to the Si0 treatment. At the same time, the Si2 treatment significantly decreased the POD activity in the Yuebaitiannuo10 roots and stems under LL compared to the Si0 treatment. In Yuebaitiannuo12, Si1 and Si2 treatments increased the POD activity under NL, whilst the Si2 treatment significantly increased the POD activity in the stem and leaves under LL compared to Si0 treatment (Fig. 3). Furthermore, the light treatment significantly influenced the CAT activity in the root and leaf. On the contrary, no significant differences existed among the silica nanoparticle treatments in both cultivars and under the different light treatments (Fig. 4).

Fig. 3
figure 3

Effects of silica nanoparticles on the POD activity in the (a) root, (b) stem, and (c) leaf of maize seedlings under low light stress. Vertical bars with different lower-case letters indicate significant difference at P < 0.05. Capped bars represent standard error (SE). V: variety, L: light treatment, S: silica nanoparticles treatment. NL: normal light, LL: low light. Si0: applied silicon dioxide nanoparticles at a dose of 0 mg L− 1, Si1: applied silicon dioxide nanoparticles at a dose of 150 mg L− 1, Si2: applied silicon dioxide nanoparticles at a dose of 300 mg L− 1. * and ** represent a significant difference at P < 0.05 and P < 0.01, respectively; ns represents a non-significant difference

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Fig. 4
figure 4

Effects of silica nanoparticles on the CAT activity in (a) root, (b) stem, and (c) leaf of maize seedlings under low light. Vertical bars with different lowercase letters indicate significant difference at P < 0.05. Capped bars represent standard error (SE). V: variety, L: light treatment, S: silica nanoparticles treatment. NL: normal light, LL: low light. Si0: applied silicon dioxide nanoparticles at a dose of 0 mg L− 1, Si1: applied silicon dioxide nanoparticles at a dose of 150 mg L− 1, Si2: applied silicon dioxide nanoparticles at a dose of 300 mg L− 1. * and ** represent a significant difference at P < 0.05 and P < 0.01, respectively; ns represents a non-significant difference

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3.4 MDA, Proline, H2O2, and ASA Contents in Maize Plants

SiO2NPs significantly affected the MDA content in maize plants. In Yuebaitiannuo10, Si1 and Si2 treatment induced higher MDA contents in the leaves under NL and LL and in the stem compared to Si0 treatment under LL. On the contrary, Si1 and Si2 treatments reduced the MDA content in the root under LL in Yuebaitiannuo10 compared to Si0 treatment. In Yuebaitiannuo12, the Si1 and Si2 treatments significantly reduced the MDA content in the stem whilst the Si1 treatment significantly reduced the MDA content in the leaf compared to the Si0 treatment (Fig. 5).

Moreover, the SiO2 NPs significantly affected the proline content in the roots and leaf. In contrast, light treatment significantly affected the proline content in the stem and leaves. Compared to the Si0 treatment, Si1 and Si2 treatments significantly increased the proline content in the Yuebaitiannuo10 stems and leaves. In contrast, the Si2 treatment significantly reduced the proline content in the Yuebaitiannuo10 root under NL. Under LL, the Si1 and Si2 treatments significantly decreased the proline content in Yuebaitiannuo10 roots, while the Si1 treatment significantly increased the proline content in the stem compared to the Si0 treatment. In Yuebaitiannuo12, the Si2 treatment significantly reduced the proline content in the root compared to the Si0 treatment under NL. However, the Si1 treatment significantly reduced the root, stem, and leaf proline content. In contrast, the Si2 treatment significantly increased the proline content in the root and leaf in Yuebaitiannuo12 under LL (Fig. 6).

Fig. 5
figure 5

Effects of silica nanoparticles on the MDA content in (a) root, (b) stem, and (c) leaf of maize seedlings under low light. Vertical bars with different lowercase letters indicate significant difference at P < 0.05. Capped bars represent standard error (SE). V: variety, L: light treatment, S: silica nanoparticles treatment. NL: normal light, LL: low light. Si0: applied silicon dioxide nanoparticles at a dose of 0 mg L− 1, Si1: applied silicon dioxide nanoparticles at a dose of 150 mg L− 1, Si2: applied silicon dioxide nanoparticles at a dose of 300 mg L− 1. * and ** represent a significant difference at P < 0.05 and P < 0.01, respectively; ns represents a non-significant difference.

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Fig. 6
figure 6

Effects of silica nanoparticles on the proline content in the (a) root, (b) stem, and (c) leaf of maize seedlings under low light. Vertical bars with different lowercase letters indicate significant difference at P < 0.05. Capped bars represent standard error (SE). V: variety, L: light treatment, S: silica nanoparticles treatment. NL: normal light, LL: low light. Si0: applied silicon dioxide nanoparticles at a dose of 0 mg L− 1, Si1: applied silicon dioxide nanoparticles at a dose of 150 mg L− 1, Si2: applied silicon dioxide nanoparticles at a dose of 300 mg L− 1. * and ** represent a significant difference at P < 0.05 and P < 0.01, respectively; ns represents a non-significant difference.

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Furthermore, the Si1 and Si2 treatments significantly decreased the H2O2 content in the root, while the Si2 treatment increased the H2O2 content in the leaves in Yuebaitiannuo10 under NL. In addition, the Si1 treatment significantly increased the H2O2 content in the Yuebaitiannuo10 roots under LL compared to the Si0 treatment. On the contrary, the Si1 treatment significantly reduced the H2O2 content in the Yuebaitiannuo12 stem compared to the Si0 treatment under LL (Fig. 7).

Fig. 7
figure 7

Effects of silica nanoparticles on H2O2 content in the (a) root, (b) stem, and (c) leaf of maize seedlings under low light. Vertical bars with different lowercase letters indicate significant difference at P < 0.05. Capped bars represent standard error (SE). V: variety, L: light treatment, S: silica nanoparticles treatment. NL: normal light, LL: low light. Si0: applied silicon dioxide nanoparticles at a dose of 0 mg L− 1, Si1: applied silicon dioxide nanoparticles at a dose of 150 mg L− 1, Si2: applied silicon dioxide nanoparticles at a dose of 300 mg L− 1. * and ** represent a significant difference at P < 0.05 and P < 0.01, respectively; ns represents a non-significant difference.

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Light treatment also greatly affected the ASA content. At the same time, the SiO2 NPs significantly affected the ASA content in the maize roots (P < 0.05). Compared to the Si0 treatment, the Si1 treatment significantly reduced the ASA content in the Yuebaitiannuo10 roots and stems under NL. In contrast, the Si2 treatment significantly increased the ASA content in the Yuebaitiannuo10 roots compared to Si0 under NL. Similarly, the Si1 treatment significantly increased the ASA content in the Yuebaitiannuo12 stem compared to Si0 under LL (Fig. 8).

Fig. 8
figure 8

Effects of silica nanoparticles on the ASA content in the (a) root, (b) stem, and (c) leaf of maize seedlings under low light. Vertical bars with different lowercase letters indicate significant difference at P < 0.05. Capped bars represent standard error (SE). V: variety, L: light treatment, S: silica nanoparticles treatment. NL: normal light, LL: low light. Si0: applied silicon dioxide nanoparticles at a dose of 0 mg L− 1, Si1: applied silicon dioxide nanoparticles at a dose of 150 mg L− 1, Si2: applied silicon dioxide nanoparticles at a dose of 300 mg L− 1. * and ** represent a significant difference at P < 0.05 and P < 0.01, respectively; ns represents a non-significant difference.

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3.5 Protein Content and NR Activity in Maize Plants

SiO2NPs significantly affected the protein content in maize plants and light treatment in the stem and leaves (P < 0.05). In Yuebaitiannuo10 under NL, the Si2 treatment significantly increased the protein content in the roots compared to the Si1 treatment. At the same time, the Si1 and Si2 treatments significantly increased the protein content in the stem. In contrast, Si1 treatment significantly decreased the protein content in the leaves. Under LL, the Si2 treatment significantly increased the protein content in the Yuebaitiannuo10 stem compared to the Si1 treatment.

In Yuebaitiannuo12 under NL, the Si1 treatment considerably decreased the protein content in the roots, and the Si2 treatment significantly increased the protein content in the leaves compared to the Si0 treatment. However, contrasting findings were recorded when the Si1 treatment was compared to the Si0 treatment, with the protein content in the root, stem, and leaf dramatically reduced by 14.21%, 26.23%, and 10.23%, respectively (Fig. 9).

Fig. 9
figure 9

Effects of silica nanoparticles on the protein content in (a) root, (b) stem, and (c) leaf of maize seedlings under low light. Vertical bars with different lowercase letters indicate significant difference at P < 0.05. Capped bars represent standard error (SE). V: variety, L: light treatment, S: silica nanoparticles treatment. NL: normal light, LL: low light. Si0: applied silicon dioxide nanoparticles at a dose of 0 mg L− 1, Si1: applied silicon dioxide nanoparticles at a dose of 150 mg L− 1, Si2: applied silicon dioxide nanoparticles at a dose of 300 mg L− 1. * and ** represent a significant difference at P < 0.05 and P < 0.01, respectively; ns represents a non-significant difference

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Light treatment also significantly affected the NR activity in the maize plant and the SiO2 NPs in the roots and stems (P < 0.05). Compared to the Si0 treatment, the Si2 and Si1 treatments significantly increased the NR activity in the Yuebaitiannuo10 roots and stems under NL, respectively. However, the Si1 treatment significantly reduced the NR activity in the Yuebaitiannuo10 roots and stems compared to the Si0 treatment under LL. Compared to the Si0 treatment, the Si1 treatment significantly increased the NR activity in the stem. In contrast, the Si2 treatment significantly increased the NR activity in the roots and leaves of Yuebaitiannuo12 under NL treatment. Compared to the Si0 treatment, the Si1 and Si2 treatments enhanced the Yuebaitiannuo12 NR activity under LL (Fig. 10).

Fig. 10
figure 10

Effects of silica nanoparticles on the NR activity in the (a) root, (b) stem, and (c) leaf of maize seedlings under low light. Vertical bars with different lowercase letters indicate significant difference at P < 0.05. Capped bars represent standard error (SE). V: variety, L: light treatment, S: silica nanoparticles treatment. NL: normal light, LL: low light. Si0: applied silicon dioxide nanoparticles at a dose of 0 mg L− 1, Si1: applied silicon dioxide nanoparticles at a dose of 150 mg L− 1, Si2: applied silicon dioxide nanoparticles at a dose of 300 mg L− 1. * and ** represent a significant difference at P < 0.05 and P < 0.01, respectively; ns represents a non-significant difference

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3.6 Correlation Analysis

The maize plant growth and biomass were significantly correlated with the SOD activity and ASA content in the root, SOD activity and MDA content in the stem, and the leaf NR activity (P < 0.05) (Fig. 11).

Fig. 11
figure 11

Correlation analysis between the maize seedling early growth, photosynthetic and anti-oxidant defense parameters. A01, root fresh weight; A02, stem fresh weight; A03, leaf fresh weight; A04, aboveground fresh weight; A05, total fresh weight; A06, root dry weight; A07, stem dry weight; A08, leaf dry weight; A09, aboveground dry weight; A10, total dry weight; A11, plant height; A12, leaf sheath length; A13, leaf area; A14, root to shoot ratio; A15, dry weight/plant height; A16, the Chl a content; A17, the Chl b content; A18, carotenoid content; A19, total chlorophyll content; A20, the Chl a/b ratio; A21, SOD activity in root; A22, SOD activity in stem; A23, SOD activity in leaf; A24, POD activity in root; A25, POD activity in stem; A26, POD activity in leaf; A27, CAT activity in root; A28, CAT activity in stem; A29, CAT activity in leaf; A30, MDA content in root; A31, MDA content in stem; A32, MDA content in leaf; A33, ASA content in root; A34, ASA content in stem; A35, ASA content in leaf; A36, H2O2 content in root; A37, H2O2 content in stem; A38, H2O2 content in leaf; A39, protein content in root; A40, protein content in stem; A41, protein content in leaf; A42, proline content in root; A43, proline content in stem; A44, proline content in leaf; A45, NR activity in root; A46, NR activity in stem; A47, NR activity in leaf

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Fig. 12
figure 12

Conceptual scheme depicting the effect of silica nanoparticles on the growth of maize under low light

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4 Discussion

Nanoparticles (NPs) are characterized by large surface charge and area, improving plant nutrient uptake efficiency as foliar fertilizers (Babu et al. 2022). Silicon element is an important plant nutrient which increases crop yields, especially under abiotic and biotic stress conditions (Epstein 2009; Keeping and Reynolds 2009; Farooq and Dietz 2015). However, plants do not uptake and use silicon fertilizers directly due to their low solubility and bioavailability (Raven 2003). On the contrary, SiO2 NPs are rapidly taken up in plant leaves (Cui et al. 2020; Babu et al. 2022), which influences the plant metabolic activities and mitigates the negative stress effects on many plant species (Rastogi et al. 2019). Similarly, in the present study, the total aboveground dry weight and total dry weight of both maize cultivars were increased after applying SiO2 NPs under NL conditions. Interestingly, Si1 application had greater effects, significantly increasing the total aboveground dry weight and total dry weight. Under LL, the total aboveground dry weight and total dry weight in Yuebaitiannuo12 increased, with Si1 treatment, which could be related to the increased metabolism of maize seedlings after the application of SiO2 consistent with previous studies. Therefore, genotypes effect in response to the application of SiO2 NPs under different conditions should not be ignored.

Light is an important abiotic factor affecting plant growth by controlling the biosynthesis and distribution of carbohydrates in crops (Raza et al. 2019). Maize is one of the most important cereal crops in the world. Although it is well adapted to various environments (Elisa et al. 2022), it is still very sensitive to light, as a typical C4 plant (Yuan et al. 2012; Bellasio and Griffiths 2014). Previous studies revealed that a lower light intensity or artificial shading severely affects crop growth (Yuan et al. 2012; Gao et al. 2020). However, in recent years, numerous studies have revealed the positive effects of nanomaterials on plant growth and development under low light stress (Tripathi et al. 2017; Rastogi et al. 2019; Aguirre-Becerra et al. 2022). Therefore, the present study aimed to investigate the effect of spraying SiO2 NPs on the metabolism of maize seedlings under low light stress. In this study, the SiO2 NPs increased the seedling dry weight, which altered the maize phonotype. In addition, the physiological parameters were different under the different varieties and light treatments after applying the SiO2 NPs treatments.

Plants accumulate substances through photosynthesis, with chlorophyll playing an important role in photosynthesis (Agnihotri and Seth 2016), and the chlorophyll content reflects the plant’s potential to utilize light energy to synthesize the photosynthetic compounds (Najeeb et al. 2016). Generally, insufficient light alters the leaf chlorophyll synthesis, adversely affecting crop growth (Bellasio and Griffiths 2014; Zhong et al. 2014; Gao et al. 2017). For example, shading leads to whole plant stunting, reducing aboveground and root biomass (Amos and Walters 2006; Yang et al. 2021). In this study, chlorophyll content was significantly reduced by 9.14% in Yuebaitiannuo10 under LL-Si0 treatment compared to NL-Si0. Additionally, the chlorophyll b content in Yuebaitiannuo10 was significantly reduced by 19.64% under LL-Si2 compared to NL-Si2. Moreover, the total chlorophyll content in Yuebaitiannuo10 was significantly reduced by 26.47% with LL-Si2 compared to NL-Si2.

Previous studies have also shown that the application of SiO2 NPs has a positive response to plant growth and development (Albalawi et al. 2022; Al-Mokadem et al. 2023). Herein, the low light treatment significantly reduced the dry and fresh biomass of maize seedlings. However, the total dry weight was increased after applying SiO2 NPs. For example, under LL-Si1, the total dry weight of Yuebaitiannuo12 was increased by 16.70% compared to under LL-Si0, which might be related to the application of SiO2 NPs alleviating the unfavorable effects of low light stress.

ROS produced under stress conditions is mainly the result of enhanced photorespiration (Blokhina et al. 2003). Generally, light environment changes affect plant stress-induced ROS levels (Xia et al. 2015; Yuan et al. 2022; Fu et al. 2023). ROS is a strong oxidant which causes oxidative damage to important molecules such as lipids and proteins (Schieber and Chandel 2014). The oxygen radicals plant cells accumulate under stress induce lipid peroxidation by oxidizing unsaturated fatty acids, leading to membrane damage and electrolyte leakage (Siddiqui et al. 2020; Altaf et al. 2023). Based on this, the up-regulation of the activity of antioxidant defense enzymes is one of the biomarkers of the plant’s ability to withstand environmental stress (Dvorak et al. 2020). SOD, CAT, and POD are major antioxidant enzymes associated with the scavenging of ROS (Ali et al. 2021). They scavenge the superoxide anion (O2−) produced by H2O2, alleviating the adverse effects of lipid peroxidation in tissue membranes and retarding plant senescence (Bhattacharjee 2005; Li et al. 2019). Previous studies have shown that shading stress reduces leaf growth and adversely affects the leaf physiological functions (Choudhury et al. 2017), manifested as increased MDA content in the leaves (Ren et al. 2016; Gao et al. 2017; Guo et al. 2021). On the other hand, SiO2 NPs enter the plant and affect the metabolic activities, which positively impacts the crop (Rastogi et al. 2019). For example, several studies have shown that SiO2 NPs reduce ROS-related membrane deterioration features (lipid peroxidation and methoxy) by inducing the activity of specific antioxidant enzymes, which improves the antioxidant status of seedlings and subsequently increases plant tolerance to abiotic stresses (Sharma et al. 2012; Siddiqui and Al-Whaibi 2014). As an end product of membrane lipid peroxidation, MDA inhibits cytoprotective enzyme activity, reducing the activity of antioxidant enzymes (Jedrzejuk et al. 2018). In this study, LL-Si2 increased the Yuebaitiannuo10 MDA content in the stems by 37.04%, while SOD activity was significantly reduced by 90.34% compared to NL-Si2 in Yuebaitiannuo10. Similar results were observed in Yuebaitiannuo12, where SOD activity was significantly reduced by 37.42%. In addition, the CAT activities of stems and leaves of Yuebaitiannuo10 were significantly reduced by 10.32% and 66.27%, respectively. However, the POD activities of stems of Yuebaitiannuo10 and Yuebaitiannuo12 were significantly increased by 48.96% and 11.29%, respectively, with LL-Si1 compared to NL-Si1.

Proline inhibits lipid peroxidation and scavenges ROS, inducing stress tolerance and preventing electrolyte leakage (Kaur and Asthir 2015). In this study, the proline content in Yuebaitiannuo12 was significantly increased in roots, stems, and leaves by 460.78%, 179.62%, and 265.41%, respectively, under in LL-Si2 compared to NL-Si2, which potentially further offset the negative effects of ROS on maize seedlings, given SiO2 NPs play a key regulatory role in plant growth and maintaining membrane integrity (Ahanger et al. 2015). Proline inhibits lipid peroxidation and scavenges the ROS, which induces stress tolerance while preventing electrolyte leakage (Kaur and Asthir 2015). Mo et al. (2015) revealed that shading rice plants at the tasseling stage produces higher proline content. Additionally, the leaf proline accumulation was increased under salt stress with SiO2 NPs (Sharf-Eldin et al. 2023). In this study, spraying SiO2 NPs under LL stress significantly increased the proline content of stems of maize seedlings of both varieties. Notably, under LL-Si1 and LL-Si2 the proline content in Yuebaitiannuo10 was significantly increased by 31.82% and 6.87%, respectively, compared to LL-Si0. On the contrary, LL-Si2 significantly increased the proline content by 7.14%. This may be related to the fact that SiO2 NPs improve stress tolerance, resulting in greater scavenging capacity in treated plants (Behboudi et al. 2018; Ghorbanpour et al. 2020).

Nitrogen metabolism is an important substrate for energy metabolism. In plants, the photosynthetic capacity is closely related to the leaf nitrogen status, such as the leaf nitrogen content and nitrogen assimilatory enzyme activity (Ahmad et al. 2022). Therefore, nitrogen metabolism is an important physiological process that affects plant metabolism, growth and development. NR is an essential enzyme in nitrogen metabolism (Hu et al. 2021). According to Wang et al. (2020), shading interferes with the leaf nitrogen metabolism, leading to reduced grain yield. In addition, a previous study revealed that shading reduces the leaf-soluble protein content and NR activity, especially under severe shading treatments (Wang et al. 2020). However, in this study, the leaf NR activity was significantly elevated under low light, up to 31.70% in Yuebaitiannuo12 under LL-Si1 compared to NL-Si1.

Overall, SiO2 NPs regulate the antioxidant response, nitrogen metabolism, and photosynthesis parameters under LL stress resulting in biomass accumulation and strong maize seedlings. However, the different maize genotypes response to the application SiO2 NPs and light treatments are different, and the mechanism of underlying the mechanism of SiO2 NPs alleviate effect on low light stress is needed to be clarify in further molecular investigations.

5 Conclusion

The low light (LL) stress significantly decreases the biomass of maize seedlings in different varieties. However, applied the silica nanoparticles (SiO2 NPs) with 150 mg L− 1 (Si1) increasing the biomass and promoting the highest aboveground dry weight/plant height. Besides, the maize seedling growth parameters are highly related to the superoxide dismutase (SOD) activity and the ascorbic acid (ASA) content in the root, SOD activity and the malondialdehyde (MDA) content in the stem, and nitrate reductase (NR) activity in the leaf. Overall, SiO2 NPs influence the early growth stage of maize by regulating the antioxidant defense and metabolism of maize plants.