Silicon Spraying Enhances Wheat Stem Resistance to Lodging under Light Stress

: In recent years, the decrease in solar radiation has led to insufﬁcient light, resulting in a shading effect on crops and a deterioration of stem quality, which seriously affects wheat yield. In this experiment, two different lodging-sensitive wheat varieties, SN16 (SN16) and SN23 (SN23), were selected as experimental materials, and two treatments were set up, with 50% shade (S1) and natural light as control (S0) from the jointing stage to the maturity stage. Two treatments, spraying 400 mg L − 1 (C1) silicon fertilizer and spraying water as control (C0), were set up at the jointing stage of wheat. The effects of spraying silicon fertilizer on the yield, morphological and mechanical characteristics of the stem, and lignin content of winter wheat under low-light stress were investigated. The results showed that spraying silicon fertilizer increased the lignin content of the stem and improved stem lodging resistance mainly by improving the degree of ligniﬁcation. An effective cultivation measure for wheat’s resistance to lodging can be provided by spraying silicon fertilizer when future low-light stress occurs.


Introduction
Wheat (Triticum aestivum L.) is a major food crop worldwide, with more than onethird of the population depending on wheat as its primary food source and the level of wheat production directly relates to countries' livelihood [1].Currently, frequent human activities cause severe atmospheric pollution, resulting in a decrease in effective solar radiation reaching the Earth's surface, which has become a limiting factor for agricultural development [2].Light is critical for crop growth, and insufficient light intensity affects crop yield and yield components [3,4].Reduced solar radiation leads to insufficient light, causing a shading effect on the population [5].Insufficient light changes the internal structure of the stems, which reduces stem filling and stem thickness, increases plant height, and reduces the mechanical strength of the stems, easily triggering lodging [6,7].Lodging is one of the main factors limiting wheat yield, quality, and harvesting, and studies have shown that the problem of reduced wheat yields due to failure persists in the Huanghuaihai region [8].At the same time, light is critical for crop yield formation, and the degree and period of shade affect yield to varying degrees.The yield of the crop decreases severely with increasing shade levels.Luo et al. [9] found that shade treatment at the nodulation stage significantly reduced the tiller spike formation rate of wheat, increased shade time, and severely reduced wheat yield.It was found that shade treatment during the pre-grazing period resulted in grain abortion and a significant reduction in the number of grains in the spike, and shade treatment during the mid-to late-grazing period reduced the rate of filling, decreased the transfer of material to the grains, and reduced grain weight [10,11].
Silicon is a macronutrient that is widely found in monocotyledonous and dicotyledonous plants.Although it is not considered an essential nutrient for plants, it plays a vital role in plant growth [12,13].Especially in monocotyledonous plants (such as wheat and rice), the absorption of Si even exceeds that of essential nutrients [14].Studies have shown that silicon increases crops' resistance to abiotic and biotic stresses such as low light, drought, salt, heavy metals, and pests [15], thereby increasing crop productivity.As these benefits to crop production have been recognized, the global use of silicon to improve soil or foliar spray is rising.
How silicon affects crop stem resistance has been preliminarily studied.The application of silicon can improve stem strength by increasing the thickness of secondary cell walls and the number of secondary cells.Lignin biosynthetic enzyme activity and lignin accumulation increased with increasing silicon application [16].Silicon can polymerize with lignin to form a more stable structure, significantly increasing the resistance of stems to stunting [17].For crop yield, silicon can improve the community structure by reducing the inclination angle of the plant leaf while increasing the chlorophyll content in the leaves, enhancing the photosynthetic capacity of the leaves, increasing the accumulation of dry matter in the stems and leaves, and facilitating the transfer of dry matter to the seeds, which increases the seed yield [18].Additionally, silicon promotes yield by increasing the number of spikes and grains, and grain weight in crops [19].
It can be seen from the above that silicon can improve crops' lodging resistance and yield.However, under low-light stress, it is unclear whether exogenous silicon can help wheat resist adversity and positively impact crops' lodging resistance and yield.Therefore, in this study, we selected two winter wheat varieties with significant differences in lodging resistance as materials and simulated low-light stress via artificial shading to clarify how the exogenous spraying of silicon fertilization affects (1) silicon accumulation in wheat stems, (2) wheat stalk lignin content, (3) the morphological characteristics and breaking resistance of wheat stems, and (4) wheat-yield formation under low-light conditions.The results may provide a theoretical basis and technical support for the regulation of wheatlodging-resistant cultivation under the background of the reduction in solar radiation caused by extreme climate change.

Site Description
This experiment was conducted in 2020-2021 at the experimental station of Shandong Agricultural University, Tai'an City, Shandong Province, China (36 • 17 N, 117 • 17 E, 128 m above sea level).The region has a temperate continental monsoon climate, with a solar radiation of 3131.33 MJ m −2 and a mean temperature and precipitation of 8.92 • C and 193.06 mm, respectively, during the wheat-growing season.The experimental site comprised brown loam soil, and the previous crop was maize (Zea mays L.), which was harvested and returned to the field with all the straw.Before the experiment, the tillage soil (0-20 cm) contained 12.71 g kg −1 of organic matter, 1.01 g kg −1 of total nitrogen, 85.2 mg kg −1 of alkaline nitrogen, 30.19 mg kg −1 of available phosphorus, and 90.33 mg kg −1 of available potassium with a pH of 7.92.

Field Experiments
The experiment was conducted in a split-plot design with three replications.The main plot had two wheat varieties (i.e., the lodging-sensitive wheat variety Shannong16 (SN16) and lodging-resistant wheat variety Shannong23 (SN23)), the sub-plot had light treatment (i.e., shading treatment (S1, shading rate 50%) and normal light treatment (S0)), and the sub-sub-plot was silicon treatment [i.e., spraying Na 2 SiO 3 •9H 2 O solution with silicon concentration of 400 mg L −1 (C1) and spraying NaCl solution with the same amount of Na + as control (C0)].The plot size was 3 × 3 m 2 .When the first stem internode of wheat was exposed to the ground about 1.5-2 cm, a shading shed was built, and the wheat was shaded with a black shading net with a transmittance of 50%.The roof was 1.8 m away from the ground to ensure normal ventilation of the wheat canopy.At the jointing stage, the wheat was sprayed with silicon for 3 days after 17:00 every day.In order to make silicon better attached to the leaves, the silicon solution was mixed with 0.5% (v/v) Tween-20 before spraying.The final spraying silicon solution was a Na 2 SiO 3 •9H 2 O solution with a concentration of 400 mg L −1 .In each plot, 1 L solution was sprayed uniformly with a spray pot at a height of 20 cm above the plant's highest point.

Sample Collection
Samples were taken every 7 days from the second internode of the wheat base extending about 2 cm from the ground.Thirty single stems of wheat with the same growth vigor were selected each time, and fifteen single stems were taken as fresh samples, which were quickly frozen and stored in liquid nitrogen and then stored in a refrigerator at −80 • C to determine total lignin content.Another 15 single stems were used as the second internode, and the leaves were used as dry samples.They were killed at 105 • C for 30 min in the oven and then dried at 50 • C until constant weight.They were used to determine stem plumpness, lignin monomer, and silicon.

Morphological Characteristics of Stems and Breaking Strength
The morphological characteristics of wheat stem were measured at the flowering stage (GS65), milk stage (GS75), and wax stage (GS85).In each treatment, 20 stems of wheat with the same growth vigor were selected, and the roots were removed.The length of each node, panicle length, plant height, and center of gravity height (the distance from the base of the stem to the horizontal balance fulcrum of the single stem of wheat) were measured with a steel ruler.The basal second internode sheath was removed with YYD-1 stem strength tester (Hangzhou Tuopu Instrument Co., Ltd., Hangzhou, China) to determine the stem-breaking resistance.After removing leaf sheath, the internodes were cut in half from the middle, and the inner and outer diameters of the stem were measured via vernier caliper to calculate the stem diameter and wall thickness.

Lignin Content
According to the method of Zheng et al. [20] and slightly modified, fresh samples were taken in the mortar, and an appropriate amount of liquid nitrogen was added to grind them into powder.Then, 0.1 g samples were taken in a 10 mL centrifuge tube, 8 mL 95% ethanol was added, extracted for 24 h, and centrifuged at 5000 rpm for 5 min to remove the supernatant.Next, 8 mL n-hexane/anhydrous ethanol = 2:1 solution was added to the sediment, extracted for 12 h, and centrifuged at 5000 r/min for 5 min.The supernatant was removed, and the sediment was dried for later use.Additionally, 2.5 mL 25% bromoacetyl glacial acetic acid mixed solution was added to the dry matter, shaken and mixed, bathed in a water bath for 30 min at 70 • C in a water bath pan, and quickly cooled down to cold water afterward.The 0.9 mL 2 M NaOH solution was added to terminate the reaction.Then, 0.1 mL 7.5 M hydroxylamine hydrochloride and 4 mL glacial acetic acid were added, mixed well, and centrifuged at 5000 r for 5 min.The 0.1 mL supernatant was diluted in 3.9 mL glacial acetic acid, and the absorbance of the solution at 280 nm was measured using a spectrophotometer.The absorbance at 280 nm per milliliter of solution in unit mass sample was used to represent the lignin content (OD 280 mL −1 g −1 FW).

Silicon Content
Chen et al.'s [21] method was slightly modified.The silicon content of the sample was determined via ICP-MS (Thermo Fisher Scientific, Waltham, MA, USA).A total of 0.5 g of dried sample was weighed in a microwave digestion tube, added with 5 mL of concentrated HNO 3 solution, digested in a microwave digestion furnace (KDNX-20, Shanghai Yidian Agronomy 2023, 13, 2565 4 of 12 Scientific Instrument Co., Ltd., Shanghai, China) for 120 min (until the sample was clarified), transferred to a 100 mL volumetric flask, diluted to a constant volume, filtered through a 0.22 µm filter membrane, and measured on the machine (with 50 µg L −1 scandium solution as an internal standard).

Yield and Yield Components
At maturity, 1 m 2 area of wheat with uniform growth was selected in each plot to count spike number, and then, 30 spikes were taken to count the grain number per spike, which were harvested and threshed after completion.The 1000-grain weight was investigated, and grain yield was measured at 14% moisture content.

Statistical Analysis
A two-way ANOVA was conducted using SPSS 17.0 Statistical Package (SPSS Inc., Chicago, IL, USA) on the wheat trait as the response variable and the 'light strees' and 'silicon' as fixed variables.Multiple comparisons of each indicator under different treatments were performed using the LSD method with a significant probability level of 0.05.

Effect of Silicon on Yield and Yield Components of Winter Wheat under Low-Light Stress
As shown in Table 1, under the same treatment, the number of spikes per acre of SN16 was higher than that of SN23, but the number of spikes and 1000-grain weight of SN16 were significantly lower than that of SN23, and the final yield of SN16 was lower than that of SN23.Shade treatments significantly reduced the yield of winter wheat and the yield components.Under low-light stress, the spike number, grain number per spike, 1000-grain weight, and the yield of SN16 were reduced by 32.94%, 18.8%, 2.44%, and 44.79%, respectively; SN23 decreased by 34.17%, 11.77%, 4.23%, and 43.37%, respectively, and exogenous spraying of silica, significantly increased the yield and yield component factors of wheat, with the spike number, grain number per spike, 1000-grain weight, and yield increasing by 9.18%, 4.44%, 2.2%, and 16.56%, respectively, in SN16; and SN23 increased by 4.30%, 5.65%, 2.02%, and 12.27%.

Effect of Silicon on the Silicon Content of Winter Wheat under Low-Light Stress
It can be seen from Figure 1 that the silicon content in wheat stems increased with the advancement of the fertility period, in which the silicon content in the stems and leaves of SN23, a variety with resistance to lodging, was significantly higher than the silicon content in SN16.The low-light treatment affected silica uptake in wheat, and the accumulation of silica in wheat stems and leaves was significantly reduced after shading.Compared with the S0 treatment, the silicon content in the stems of SN16 and SN23 was reduced by 19.59% and 16.84%, and the silicon content in the leaves was reduced by 14.14% and 24.51% under the S1 treatment.Under low-light stress, exogenous silicon spraying promoted silicon uptake in wheat, and silicon content in wheat increased significantly after silicon spraying.Compared with C0, C1 treatment SN16 and SN23 increased silicon content in stems by 16.25% and 22.68% and in leaves by 15.58% and 25.25%.
icon content in SN16.The low-light treatment affected silica uptake in wheat, and the accumulation of silica in wheat stems and leaves was significantly reduced after shading.Compared with the S0 treatment, the silicon content in the stems of SN16 and SN23 was reduced by 19.59% and 16.84%, and the silicon content in the leaves was reduced by 14.14% and 24.51% under the S1 treatment.Under low-light stress, exogenous silicon spraying promoted silicon uptake in wheat, and silicon content in wheat increased significantly after silicon spraying.Compared with C0, C1 treatment SN16 and SN23 increased silicon content in stems by 16.25% and 22.68% and in leaves by 15.58% and 25.25%.

Plant Height and Center of Gravity
As can be seen from Figure 2, there were significant differences in plant height among different varieties of wheat, in which SN16 plant height was 15.53% higher than that of SN23.The low-light stress led to an increase in plant height as well as the length of the basal second internode of winter wheat.Under S1 treatment, the plant height of SN16 and SN23 increased by 5.92% and 5.09%, respectively, compared with S0 treatment; the basal second internode increased by 20.45% and 16.11%, respectively.After exogenous silicon spraying, wheat plant height decreased, and the length of the basal second internode decreased.After exogenous silicon spraying, SN16 and SN23 plant heights decreased by 4.63% and 4.32%, respectively, and the length of the basal second internode decreased by 13.72% and 12.51%, respectively.As can be seen from Figure 2, there were significant differences in plant height among different varieties of wheat, in which SN16 plant height was 15.53% higher than that of SN23.The low-light stress led to an increase in plant height as well as the length of the basal second internode of winter wheat.Under S1 treatment, the plant height of SN16 and SN23 increased by 5.92% and 5.09%, respectively, compared with S0 treatment; the basal second internode increased by 20.45% and 16.11%, respectively.After exogenous silicon spraying, wheat plant height decreased, and the length of the basal second internode decreased.After exogenous silicon spraying, SN16 and SN23 plant heights decreased by 4.63% and 4.32%, respectively, and the length of the basal second internode decreased by 13.72% and 12.51%, respectively.2, the basal internode stem thickness of both winter wheat varieties decreased continuously with the advancement of the growth process, and there was a difference between the stem thicknesses of different varieties of wheat.The basal

Thickness and Wall Thickness of the Second Internode at the Base of the Stem
According to Table 2, the basal internode stem thickness of both winter wheat varieties decreased continuously with the advancement of the growth process, and there was a difference between the stem thicknesses of different varieties of wheat.The basal second internode stem thickness of SN23 was 12.15% higher than that of SN16 at the dough stage.Under low-light stress, the two varieties of winter wheat had stunted stems and reduced stem thickness, which decreased by 8.21% and 5.19% in SN16 and SN23 under the S1 treatment, respectively, compared with the S0 treatment.Wheat stem thickness increased after exogenous silicon spraying, and under shade stress, SN16 and SN23 stem thickness increased by 5.63% and 2.8% under C1 treatment, respectively.Table 3 shows that the wall thickness of the basal second internode of the two varieties of winter wheat gradually decreased with the advancement of fertility, and the thickness of the basal second internode of the lodging-sensitive variety SN16 was significantly lower than that of the lodging-resistant variety SN23.The low-light treatment significantly reduced the wall thickness of winter wheat, and the thickness of the stems of SN16 and SN23 decreased by 29.88% and 26.85%, respectively, under the low-light treatment.Exogenous silicon spraying increased the wall thickness of winter wheat, and the wall thickness of SN16 and SN23 increased by 13.92% and 20.32%, respectively, under the C1 treatment compared with the C0 treatment.

Filling of the Second Internode at the Base of the Stem
In Table 4, it can be seen that the filling degree of the two varieties of winter wheat behaved differently with the advancement of the fertility process: the filling degree of SN23 gradually decreased with the development of wheat fertility, while the filling degree of SN16 gradually decreased with the advancement of the fertility process under S0 treatment, and then increased and decreased under S1 treatment.The filling degree of SN16 stems was lower than that of SN23 stems.Low-light stress significantly reduced wheat stem fullness by 30.01%and 26.96% in SN16 and SN23, respectively, under S1 treatment compared with S0.Exogenous silicon sprays increased wheat basal second internode filling under low-light stress, with SN16 and SN23 stem filling increasing by 20.49% and 13.61%, respectively, under C1 treatment.

Breaking Strength of the Second Internode at the Base of the Stem
As can be seen from Figure 3, the effects of silicon on the breaking resistance of the two varieties of winter wheat under low-light stress were consistent.In order to advance with the fertility period, the breaking resistance of wheat stems was decreasing, which was manifested as GS65 > GS75 > GS85.The breaking resistance of the lodging-resistant variety SN23 was higher than that of the lodging-sensitive variety SN16, which was 51.52% higher than that of SN16 under low-light stress, and SN23 was 40.99% higher than that of SN16 under normal light conditions.Low-light stress significantly reduced the stem-breaking resistance of two winter wheats.Under S1 treatment, SN16 breaking resistance was reduced by 34.62%, 49.66%, and 62.19% at anthesis, milk, and dough stages, respectively, and SN23 was reduced by 30.28%, 49.34%, and 53.32%, respectively.Exogenous silicon spraying increased the wheat-breaking strength, which increased by 10.72%, 16.42%, and 17.12% at anthesis, milk, and dough stages, respectively, in SN16, and by 8.81%, 9.88%, and 20.01%, respectively, in SN23, under C1 treatment.

Effect of Silicon on Lignin Content in Winter Wheat under Low-Light Stress
As can be seen from Figure 4, the exogenous silicon sprays showed basically the Low-light stress significantly reduced the stem-breaking resistance of two winter wheats.Under S1 treatment, SN16 breaking resistance was reduced by 34.62%, 49.66%, and 62.19% at anthesis, milk, and dough stages, respectively, and SN23 was reduced by 30.28%, 49.34%, and 53.32%, respectively.Exogenous silicon spraying increased the wheat-breaking strength, which increased by 10.72%, 16.42%, and 17.12% at anthesis, milk, and dough stages, respectively, in SN16, and by 8.81%, 9.88%, and 20.01%, respectively, in SN23, under C1 treatment.

Effect of Silicon on Lignin Content in Winter Wheat under Low-Light Stress
As can be seen from Figure 4, the exogenous silicon sprays showed basically the same performance on the lignin content of the two varieties of winter wheat under low-light stress.The lignin content of the two varieties of winter wheat increased continuously with the advancement of fertility.The lignin content of different varieties of wheat differed significantly, and the lignin content of the lodging-resistant type winter wheat SN23 was higher than that of the lodging-sensitive type winter wheat SN16.Low-light stress significantly reduced the lignin content of stems, and spraying silicon could effectively increase the lignin content of wheat stems under low-light stress, and different varieties of winter wheat responded differently to silicon, in which the effect of silicon was more pronounced in SN23, with the lignin accumulation higher than that in SN16.The lignin accumulation of SN23 was higher than that of SN16, and the lignin content of SN23 was 8.35%, 13.41%, and 15.14% higher than that of SN16 in the anthesis, milk, and dough stages, respectively, from the comparison of the two winter wheat varieties with different resistance to lodging.Under low-light stress, the lignin content of SN16 and SN23 decreased by 16.1% and 14.94% at the anthesis stage, respectively.

Discussions
Low-light stresses plants with shade avoidance responses, resulting in greater allocation of carbohydrates in the plant to stems and leaves at the expense of allocating carbon sources to yield, decreasing spike number and 1000-grain weight [22].Shade treatment at the jointing stage was detrimental to the formation of spikes from lower tillers and significantly reduced the number of spikes in wheat [23].Shade treatment before anthesis significantly reduced the spike number of wheat [24].Shade treatment after anthesis with reduced dry matter accumulation as well as reduced translocation to the kernel significantly reduced the number of spikes and 1000-grain weight of wheat [25,26].This experiment showed (Table 1) that shade treatment significantly reduced the number of spikes and grains and 1000-grain weight of wheat and reduced wheat yield.Ji et al. [27] found that silicon application could increase the number of tillers in rice, which increased with the increase of silicon application.At the same time, silicon application improved the photosynthetic characteristics of crops, increased the number of spikes, and increased crop yield [28]. Berahim et al. [29] concluded that silicon application mainly affects 1000-grain weight and the number of spikes in rice and thus contributes to the increase in yield.Under low-light stress, we found that exogenous spraying of silicon significantly increased the adequate number of spikes, as well as increased translocation to the grain, increasing the number of spikes and 1000-grain weight and improving wheat yield (Table 1).
Wheat stem morphological characteristics, including plant height, stem thickness, wall thickness, and stem filling degree, are essential indicators for evaluating the re-

Discussions
Low-light stresses plants with shade avoidance responses, resulting in greater allocation of carbohydrates in the plant to stems and leaves at the expense of allocating carbon sources to yield, decreasing spike number and 1000-grain weight [22].Shade treatment at the jointing stage was detrimental to the formation of spikes from lower tillers and significantly reduced the number of spikes in wheat [23].Shade treatment before anthesis significantly reduced the spike number of wheat [24].Shade treatment after anthesis with reduced dry matter accumulation as well as reduced translocation to the kernel significantly reduced the number of spikes and 1000-grain weight of wheat [25,26].This experiment showed (Table 1) that shade treatment significantly reduced the number of spikes and grains and 1000-grain weight of wheat and reduced wheat yield.Ji et al. [27] found that silicon application could increase the number of tillers in rice, which increased with the increase of silicon application.At the same time, silicon application improved the photosynthetic characteristics of crops, increased the number of spikes, and increased crop yield [28]. Berahim et al. [29] concluded that silicon application mainly affects 1000-grain weight and the number of spikes in rice and thus contributes to the increase in yield.Under low-light stress, we found that exogenous spraying of silicon significantly increased the adequate number of spikes, as well as increased translocation to the grain, increasing the number of spikes and 1000-grain weight and improving wheat yield (Table 1).
Wheat stem morphological characteristics, including plant height, stem thickness, wall thickness, and stem filling degree, are essential indicators for evaluating the resistance of wheat stems to heading.The higher the plant height and center of gravity height, the poorer the stems' ability to resist lodging and the higher the risk of lodging [30].In contrast, Xue et al. [31] found a decreasing trend in plant height with increasing shade level in maize shade treatments, where shade led to a decrease in dry matter synthesis, which was harmful to stem morphogenesis.Under low-light stress, photosynthetic assimilation capacity was reduced, and the accumulation of carbohydrates by stems was reduced, resulting in thin and weak stems and reduced stem wall thickness [31].Hussain et al. [32] found that lowlight stress significantly reduced the stem filling degree of soybean, which was harmful to the morphological characteristics of the stems, significantly reduced the breaking strength of the stems, and increased the risk of lodging.Under shade stress, wheat basal internodes elongated, plant height and center of gravity height improved, and basal internode stem thickness, wall thickness, and filling degree decreased, reducing stem breaking strength and increasing the risk of lodging (Figures 2 and 3; Tables 2-4).Exogenous silicon sprays can effectively improve the morphological characteristics of crops, and Ma et al. [33] and Hong et al. [34] also found that silicon can reduce internode length, decrease plant height, increase stem sheath filling degree, and enhance stem breaking strength.Fallah [35] found that silicon could increase stem thickness and wall thickness and improve stem breaking strength.The results of this experimental study are consistent with the results of previous studies after the treatment of low-light stress, exogenous spray silicon reduced the length of wheat basal internodes and plant height, and spray silicon fertilizer can increase wheat stem thickness, wall thickness, stem filling degree, and improve stem breaking strength (Figures 2 and 3; Tables 2-4).
Lignin is an essential component of the cell wall, accounting for 30% of plant organic carbon, and plays a vital role in plant rigidity and resistance to lodging, and cross-linking with other carbohydrates enhances cell wall strength [36][37][38].Lignin biosynthesis was found to be significantly reduced by shade stress, and the effect on lignin synthesis became more severe with increasing shade [39,40].Under shading stress, the expression of PAL, 4CL, and CAD decreased, reducing lignin synthesis [41].Shade stress significantly reduces photosynthetic rate, decreases carbohydrate formation, and harms lignin synthesis in stems.Similarly, this study found that the lignin content of both varieties of winter wheat was significantly reduced under low-light stress and differed significantly between the two varieties of winter wheat, with SN23 having significantly higher lignin content than SN16 (Figure 4).Increasing planting density decreased lignin synthesis-related enzyme activities, which was unfavorable to lignin synthesis [42,43].Silicon can increase the expression of lignin synthesis genes and promote lignin synthesis [44,45].Meanwhile, silicon can enhance carbon uptake and fixation, promote lignin synthesis, and improve stem strength [46].This experiment is consistent with the results of previous studies (Figure 4) that exogenous silicon spraying can effectively promote the accumulation of lignin synthesis in wheat stems under low-light stress.
In recent years, the uncertainty of global climate change has posed a severe challenge to wheat production.There is frequent rainy weather in the critical period of wheat growth and development, which is a potential threat to stem development.It is an efficient, economical, and convenient method to improve stem quality and ensure wheat's stable yield by spraying silicon fertilizer to deal with the weather with insufficient light, such as rain and rain.However, in the future, genome, RNAseq transcriptome, proteome, and metabolome analysis should be carried out to understand the benefits of silicon on crop growth and development.

Conclusions
Spraying silicon promoted the silicon absorption of wheat and increased silicon accumulation in the stem, thereby significantly increasing stem diameter, wall thickness, and lignin content, thereby improving stem lodging resistance.Spraying silicon also significantly increased wheat spike number, grain number per spike, and 1000-grain weight to increase yield.The straightforward and cost-effective exogenous silicon spraying measures

Figure 1 .
Figure 1.Effects of silica fertilization on silica content in stems of wheat in different groups.Vertical bars above mean values indicate standard deviations (n = 3).The different lowercase letters indicate significant differences (p < 0.05) between treatments.ns and ** indicate no significant difference and significant differences at p < 0.01, respectively.

Figure 1 .
Figure 1.Effects of silica fertilization on silica content in stems of wheat in different groups.Vertical bars above mean values indicate standard deviations (n = 3).The different lowercase letters indicate significant differences (p < 0.05) between treatments.ns and ** indicate no significant difference and significant differences at p < 0.01, respectively.

3. 3 .
Effect of Silicon on the Resistance of Winter Wheat Stems to Lodging under Low-Light Stress 3.3.1.Plant Height and Center of Gravity

Agronomy 2023 , 12 Figure 2 .
Figure 2. Effects of silica on plant height and internode configuration of winter wheat under low-light stress.The first, second, third, fourth, and fifth internode of the stem from bottom to top and spike are shown in the figure as S1, S2, S3, S4, S5, and P, respectively.The black dot represents the height of the center of gravity.

Figure 2 .
Figure 2. Effects of silica on plant height and internode configuration of winter wheat under low-light stress.The first, second, third, fourth, and fifth internode of the stem from bottom to top and spike are shown in the figure as S1, S2, S3, S4, S5, and P, respectively.The black dot represents the height of the center of gravity.

Figure 3 .
Figure 3.Effect of silica on breaking strength of the second internode of winter wheat base under low-light stress.

Figure 3 .
Figure 3.Effect of silica on breaking strength of the second internode of winter wheat base under low-light stress.

Figure 4 .
Figure 4. Effect of silica on the second internode lignin content in the base of winter wheat under low-light stress.Vertical bars above mean values indicate standard deviations (n = 3).The different lowercase letters indicate significant differences (p < 0.05) between treatments.

Figure 4 .
Figure 4. Effect of silica on the second internode lignin content in the base of winter wheat under low-light stress.Vertical bars above mean values indicate standard deviations (n = 3).The different lowercase letters indicate significant differences (p < 0.05) between treatments.

Table 1 .
Effects of silica on yield and yield composition of winter wheat under low-light stress.

Grain Number per Spike 1000-Grain Weight (g) Grain Yield (kg•hm −2 )
Note: Values followed by different lowercase letters within columns are significantly different at the 0.05 probability level.

Table 2 .
Effect of silica on stem diameter of the second internode of winter wheat base under low-light stress.
Note: Values followed by different lowercase letters within columns are significantly different at the 0.05 probability level.

Table 3 .
Effect of silica on the wall thickness of the second internode at the base of winter wheat under low-light stress.
Note: Values followed by different lowercase letters within columns are significantly different at the 0.05 probability level.

Table 4 .
Effect of silica on basal second internode filling degree of winter wheat under low-light stress.
Note: Values followed by different lowercase letters within columns are significantly different at the 0.05 probability level.