Introduction

The escalating pressures of abiotic stress, driven by global climate change and water scarcity, necessitate a fundamental shift toward climate-resilient agricultural systems. Protected cultivation has emerged as a critical strategy to mitigate these environmental constraints. Within this domain, spectral-shading technology represents a sophisticated agrotechnical advance, integrating physical crop protection with the selective filtration of solar radiation to manipulate the field microclimate and plant physiological responses. Spectral-shading nets modulate key environmental parameters, including irradiance, temperature, wind speed, and vapor pressure deficit. This modification can significantly reduce water consumption by diminishing evaporation and transpiration, while concurrently protecting crops from radiative damage, hail, and birds1,2,3,4,5. For instance, studies report that shade nets can reduce damaging radiation by 15–39%, lower canopy temperature by 1.3–7.6%, and decrease water use by up to 40%, collectively enhancing crop productivity and value2,3,4.

The agricultural efficacy of spectral shading is fundamentally rooted in a deep understanding of plant photobiology, where plants perceive light intensity, quality, direction, and duration via specialized photoreceptors that activate distinct morphophysiological pathways; notably, the spectral composition of the transmitted light acts as a potent physiological signal6. The roles of specific wavelengths are clear: red light (600–700 nm) is critical for photosynthesis and biomass accumulation as it is sensed by phytochrome photoreceptors, while blue light (400–500 nm), beyond photosynthesis, plays a more significant regulatory role in photomorphogenesis, governing stomatal conductance, chloroplast development, and photoprotective mechanisms6,7. Consequently, the strategic filtering of specific spectral bands allows for targeted manipulation of plant architecture, metabolic efficiency, and stress tolerance. This principle is highly relevant for high-value ornamental crops such as Polianthes tuberosa L., which thrives in warm conditions (16–30 °C) but is highly sensitive to excessive radiation and temperature fluctuations that compromise flowering, a process largely governed by light intensity8,9,10,11. While photoselective shade cloths have demonstrated measurable impacts on microclimate and various physiological traits—including PAR, water use efficiency, and yield12,13,14,15—these responses are species-specific and thus non-generalizable, even though prior research on Polianthes confirms that shading, coupled with temperature management, influences flower color and development16,17. Critically, while these studies establish Polianthes’s responsiveness to light quantity and stress mitigation, the specific application of photoselective nets—which manipulate light spectrum in addition to intensity—remains completely uninvestigated for this species. Given this crop’s commercial value and documented physiological sensitivities, there is a compelling need to examine how deliberate light spectrum modulation influences its performance.

Therefore, this study aims to address this gap by evaluating Polianthes under blue, green, and white photoselective nets against a full-sunlight control. We will rigorously assess integrated nutrient uptake, key morphological traits, and biochemical parameters to determine how spectral filtering influences stress response, growth, and ultimate floral yield. The findings are expected to provide actionable strategies for enhancing the climate resilience and resource-use efficiency of high-value ornamental production.

Materials and methods

The study was carried out at the research farm of the Ornamental Plants Research Center (OPRC) in Mahallat, Markazi Province, Iran, situated at 33 °88′ N latitude, 50 °48′ E longitude, and an altitude of 1714 m above sea level.

The net house was constructed in a north–south orientation, with 200 m2 area for each shade color, and with a height of 3 m.

The experimental design was a randomized complete blocks design with three replications. The treatments consisted of three different colors of green, blue and white shading and cultivation without shading as control. All shade nets (Rahpouyan Company, Iran) provided a nominal 50% reduction in light intensity but possessed distinct spectral transmittance properties in the PAR range.

Bulbs (3–4 cm in diameter) of Polianthes tuberosa L. cv. ‘Pearl’ were planted on June 1. Each experimental plot measured 1 m × 8 m and contained four rows, with bulbs planted at 20 cm intra-row spacing (total 160 bulbs per plot). Data were collected exclusively from plants in the two central rows to avoid edge effects; the mean value from ten representative plants per plot was used for analysis.

The experimental field was prepared by standard plowing and leveling. A drip irrigation system was installed, and plants were watered daily according to evapotranspirative demand. Fertilization done based on experimental soil analysis and local recommendations: all fertilizers except ammonium nitrate were applied in two equal splits at planting and one month later. Ammonium nitrate was applied in three splits (at planting, 30, and 60 days after planting). The complete fertilizer regimen per hectare was: potassium sulfate (360 kg), ammonium nitrate (500 kg), triple superphosphate (200 kg), magnesium sulfate (100 kg), copper sulfate (40 kg), boric acid (20 kg), iron sulfate (30 kg), and manganese sulfate (20 kg). Soil and irrigation water characteristics are provided in Tables 1 and 2.

Table 1 Physico-chemical analysis of soil sample from the experimental site.
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Table 2 Chemical analysis of water sample from the experimental site.
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Photosynthetically active radiation (PAR, μmol m−2 s−1) was monitored at 9:00 AM and 2:00 PM weekly throughout the 16 weeks growing season (Fig. 1A). General climatic data (temperature, relative humidity) for the experimental period are summarized (Fig. 1B).

Fig. 1
Fig. 1The alternative text for this image may have been generated using AI.
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Changes in photosynthetically active radiation (PAR) (A), relative humidity and temperatures at two times, 9 am and 2 pm during 120 days (B).

The collection and use of plant material complied with all relevant institutional and national guidelines. Formal permission for the study was granted by the Ornamental Plants Research Center (OPRC), Horticultural Sciences Research Institute (HSRI), Agricultural Research, Education and Extension Organization (AREEO), Mahallat.

Leaf, stem and flower traits

During the experiment, morphological characteristics were determined, including plant height, plant fresh and dry mass, number of flowers per plant, leaf length and width, flower and stem diameter, spike and sub spike length, flower number, leaf area, flower fresh and dry mass. The percentage of plant or flower dry masses were calculated by multiplying the dry mass by 100 and dividing the result by the fresh mass.

Nutrient analysis (NPK)

Leaf tissue samples (1 g) were analyzed for the primary macronutrients nitrogen (N), phosphorus (P), and potassium (K). Following drying at 70 °C for 24 h, samples were homogenized using an electric grinder. Total nitrogen concentration was determined via the Kjeldahl method18. For P and K analysis, a leaf extract was first prepared using a dry ashing procedure. Phosphorus concentration in the digest was then quantified spectrophotometrically using the phosphovanadate-molybdate yellow method19. Potassium concentration was measured by flame photometry (Jenway PFP7).

Peroxidase (POD) enzyme activity

The activity of POD was measured by Chance andMaehly20 method. Briefly, a crude enzyme extract was prepared by homogenizing 0.5 g of fresh leaf tissue in 10 mL of ice-cold 0.5 M phosphate buffer (pH 7.0). For preparation 225 mM of H2O2 buffer, 450 µL of hydrogen peroxide (H2O2) was added to 20 mL of phosphate buffer (extraction buffer). Then, for preparation 45 mM guaiacol buffer, 112 µL of guaiacol was added to 20 mL of phosphate buffer (pH = 7). The assay was initiated by adding 10 µL of crude enzyme extract to a reaction mixture containing 495 µL of the guaiacol substrate solution and 495 µL of the H2O2 solution, prepared on ice. The increase in absorbance at 470 nm due to the formation of tetraguaiacol was recorded for one min using a UV/VIS spectrophotometer (PG Instruments T80 +). A control reaction, in which the enzyme extract was replaced with 10 µL of phosphate buffer, was run concurrently. Enzyme activity was calculated using the initial linear rate of absorbance change and the extinction coefficient for tetraguaiacol (26.6 mM⁻1 cm⁻1 at 470 nm). Specific activity was expressed as units per gram fresh weight per minute (U g⁻1 FW min⁻1), where one unit (U) is defined as the amount of enzyme required to produce 1 μmol of tetraguaiacol per minute under the assay conditions.

Amount of leaf photosynthetic pigments

Chlorophyll a, chlorophyll b, total chlorophyll (TChl), and carotenoid concentrations were determined in fresh leaf tissue using the spectrophotometric method of Lichtenthaler21. Briefly, one gram of fresh leaf material was homogenized in 80% (v/v) aqueous acetone. Following centrifugation, the absorbance of the supernatant was measured at 663.2 nm, 646.8 nm, and 470 nm.

Pigment concentrations were calculated using the following formula 13and are expressed as milligrams per gram of fresh weight (mg g⁻1 FW):

$${\text{Chlorophyll}}\;{\text{a:}}\;{12}.{25}\;\left( {{\text{A}}_{{{663}.{2}}} } \right){-}2.{79 }({\text{A}}_{{{646}.{8}}} )$$
$${\text{Chlorophyll}}\;{\text{b:}}\;{21}.{21}\left( {{\text{A}}_{{{646}.{8}}} } \right){-}{5}.{1}\;({\text{A}}_{{{663}.{2}}} )$$
$${\text{Total}}\;{\text{chlorophyll:}}\;{\text{Chlorophyll}}\;{\text{ b + Chlorophylla}}$$
$${\text{Total}}\;{\text{carotenoids:}}\;\left( {{1}000 \times {\text{A}}_{{{47}0}} } \right){-}\left( {{1}.{82} \times {\text{Chl a}}} \right){-}\left( {{85}.0{2} \times {\text{Chl}}\;{\text{b}}} \right)/{198}$$

Proline content

Proline content was determined following the method of Bates et al.22with slight modifications. Dry leaf samples (0.5 g) were extracted with 13 mL of 3% sulfosalicylic acid and filtered after 42 h. One mL of the filtrate was mixed with 1 mL of ninhydrin and 1 mL of glacial acetic acid, then heated at 133 °C for 1 h. After rapid cooling in ice water, 2 mL of toluene was added and mixed. Following 42 h of refrigeration, the upper red layer was collected, and absorbance was measured at 520 nm using a spectrophotometer.

Statistical data analysis

Data analysis was done using SAS 9.1 series software and mean comparison of data was done through Duncan’s multiple range test at the statistical probability level of 5%. Furthermore, principal component analysis (PCA) was conducted in R (version 4.3.2). Bivariate Pearson correlation coefficients were calculated and visualized as a correlation plot using the corrplot package in R.

Results

Growth traits

The application of colored shade nets resulted in a modest increase in stem diameter in Polianthes plants relative to the control under full sunlight. However, statistical analysis confirmed that these differences in stem diameter, as well as those observed for spike length, were not significant across the treatments (Table 3).

Table 3 Effect of colored shading nets on morphological traits of Polianthes.
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In this study, the use of green, blue, and white shade nets led to increases in sub-spike axis length by 47.42%, 28.24%, and 30.22%compared to the control, respectively (p ≤ 0.001), with no statistically significant difference observed between the blue and white net treatments. According to the data presented in Table 3, while a slight reduction in flower number was observed in plants cultivated under various colored shade nets, there was a statistically significant increase in flower diameter compared to those grown under open-field conditions. Plants grown under the green shade net exhibited a significantly higher, with a pronounced increase of 20.8%. In contrast, those under the white shade net showed a more modest increase of 9.7%.

As shown in Table 3, leaf morphology and plant biomass were influenced by the spectral shading treatments. Leaves grown under the green shade net exhibited reductions in length, width, and area compared to the control, with leaf area and width decreasing by approximately 19.1% and 19.5%, respectively. In contrast, plants under the blue shade net showed increased leaf dimensions, with leaf length and area greater than the control by 24.7% and 29.4%, respectively.

Regarding biomass, the green shade treatment resulted in the lowest fresh and dry masses for both vegetative and floral tissues. The white shade treatment produced fresh masses that were 10.3% (plant) and 9.7% (flower) higher than the control. In contrast, maximal dry mass for all plant components was attained under full-sunlight conditions. Notably, the dry mass percentage of both the whole plant and the floral spike remained statistically invariant across all spectral treatments and the control (Table 3).

Uptake of nutrients

Leaf N, P, and K concentrations in Polianthes plants were higher under all shade net treatments compared to the full-sunlight control. No statistically significant differences in nutrient content were found among the different shade colors (green, blue, white).

As detailed in Table 4, the magnitude of increase in K concentration relative to the control varied by treatment. Plants grown under green shade nets demonstrated the highest percentage increase in K content (39.70%) relative to the control, followed by those under blue shade nets with a 36.18% increase, and the lowest potassium accumulation (30.65%) was found in plants cultivated under white shade nets (Table 4).

Table 4 Leaf macronutrient uptake of Polianthes.
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Peroxidase (POD) enzyme activity

The effect of shading color on leaf peroxidase activity in Polianthes flower was statistically significant (p ≤ 0.01). As shown in Fig. 2A, POD activity was highest under the white shade net, exhibiting an 80% increase relative to the full-sunlight control. The green shade net induced a moderate increase of 60%, while the blue shade net resulted in a marked decrease of 40% in enzyme activity.

Fig. 2
Fig. 2The alternative text for this image may have been generated using AI.
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Effect of colored shading nets on peroxidase (POD) enzyme activity (A) and proline content (B) in Polianthes leaf.

Proline content

The results revealed a statistically significant difference (p ≤ 0.01) between plants grown under shade nets and those exposed to direct sunlight (control). However, no significant differences were observed among the various colored shade nets. Notably, the highest proline accumulation was recorded in plants grown under full sunlight without shading. Furthermore, proline content showed a significant decrease under blue (51.74%), green (44.35%), and white (43.04%) shade nets, as presented in Fig. 2B.

Photosynthetic pigments

The application of colored shade treatments led to a marked enhancement in the concentration of photosynthetic pigments and carotenoids relative to exposure under full sunlight (Fig. 3A–D). However, this stimulatory effect was comparatively less pronounced under the blue shade treatment than under the other colored shade conditions. Covering with white, green, and blue nets resulted in increases in chlorophyll a by 80.25%, 63.04%, and 22.41%, respectively (Fig. 3A). Chlorophyll b levels also increased by 51.26%, 38.91%, and 11.45% under white, green, and blue shade nets, respectively (Fig. 3B).

Fig. 3
Fig. 3The alternative text for this image may have been generated using AI.
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Effect of shade nets on chlorophyll a (A), chlorophyll b (B), total chlorophyll (C), and total carotenoids (D) of Polianthes.

Multivariate analysis

Principle components analysis (PCA) was performed to determine the dispersion of types of shading and measured traits. The variances explained by the first two components were 72.9 and 16.9%, respectively for types of shading. The PC1 and PC2 showed the strongest positive correlations with green shading and also the strongest negative correlations with white shading. The PC1 and 2 was strongly and positively correlated with leaf width, sub-spike axis length, spike fresh mass, leaf length, Chl a and flower number, but PC2 also showed positive correlation with flower diameter and negative correlation with leaf area and plant fresh mass (Fig. 4).

Fig. 4
Fig. 4The alternative text for this image may have been generated using AI.
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The dispersion of Polianthes based on physical and chemical properties of leaf and flower according to the first and the second principal components (PC1/PC2).

Correlation analysis revealed that sub-spike axis length was strongly and positively associated with several key traits, including flower diameter (0.96), leaf length (0.77), potassium and nitrogen content (0.95), carotenoid concentration (0.93), and total chlorophyll content (0.76).

Morever, proline had strong positive correlations with spike length (0.9), sub-spike axis length (0.98), plant dry matter percent (0.9), spike dry matter (0.78) and spike dry matter percent (0.96) but there was no relation with plant fresh mass. POD had also strong correlation with Chla (0.86), b (0.87), total chlorophyll (0.86), carotenoids (0.62), and week negative correlation with proline (0.14). POD showed a positive correlation with N and K, but a negative correlation with P. Additionally, nitrogen exhibited a strong positive correlation with chlorophyll and carotenoid content, while phosphorus was also strongly correlated with carotenoids (Fig. 5).

Fig. 5
Fig. 5The alternative text for this image may have been generated using AI.
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Correlation plots of physical and chemical properties of leaf and flower. Abbreviations: TCar: Total carotenoid, TChl: Total chlorophyll, Chl a: Chlorophyll a, POD: Peroxidase, P: Phosphorus, N: nitrogen, K: Potassium, SDMP: Percentage of spike dry mass, SDM: Spike dry mass, SFM: Spike fresh mass, PDMP: Percentage of plant dry mass, PDM: Plant dry mass, PFM: Plant fresh mass, LA: leaf area, LW: leaf wide, LL: Leaf length, FD: Flower diameter, FN: Number of flowers per plant, SSAL: Sub spike length, SL: Spike length, SD: stem diameter.

Discussion

This study demonstrates that photo-selective shade nets are a potent tool for directing the physiology and morphology of Polianthes tuberosa L. cv. ‘Pearl’. Our findings reveal that the observed responses are not merely due to a reduction in light intensity, but are the result of specific spectral signaling that reprograms growth, resource allocation, and stress acclimation pathways.

A primary morphological effect was the reduction in floral spike length under all shade nets compared to full sunlight. Although spike length did not differ significantly among the treatments, plants under the white shade net exhibited the shortest mean length. This aligns with a classic, albeit moderated, shade-avoidance response, widely documented in species from Arabidopsis to crops, where a lowered red to far-red (R:FR) ratio inactivates phytochrome photoreceptors, leading to suppressed stem elongation via changes in gibberellin and auxin signaling23. The reduction in height was coupled with a concurrent increase in stem diameter. This suggests a compensatory morphological strategy where resources are reallocated from vertical growth to radial strengthening, thereby enhancing spike sturdiness, a trait of paramount importance for the post-harvest handling and vase life of cut flowers.

The strong positive correlations between spike length and both photosynthetic pigment content (total chlorophyll, r = 0.76; carotenoids, r = 0.93) and flower number (r = 0.99) reveal an integrated physiological strategy. It appears that the development of a longer, multi-flowered spike in Polianthes is energetically underpinned by a robust, high-capacity photosynthetic apparatus. This integrated source-sink relationship suggests that while spectral shading modulates architecture, it does so without severely disrupting the fundamental link between photosynthesis and reproductive investment, explaining the preserved ornamental value.

In present study, leaf traits responded differentially to light quality. Leaf expansion was significantly suppressed under green nets but strongly promoted under blue nets. This result provides a clear, physiological validation of cryptochrome-mediated photomorphogenesis. Blue light perceived by cryptochromes activates transcriptional networks, including the upregulation of cell wall loosening enzymes and cell cycle genes, which collectively drive cell expansion24.The shade avoidance response, mediated by phytochrome photoreceptors perceiving low red to far-red (R:FR) ratios, involves the precise transcriptional regulation of auxin biosynthesis. Specifically, phytochrome signaling coordinately suppresses the SUR2 gene while enhancing the expression of the TAA1 gene, thereby elevating the pool of indole-3-acetic acid (IAA) to promote cell elongation and stem growth25.

This finding by Kalaitzoglou et al.26 aligns with the established photobiological principle that a higher proportion of blue light can suppress overall vegetative growth by modifying plant architecture, often resulting in more compact plants with reduced total light interception. Blue shade nets have been found to reduce stem length and flower size of lisianthus27and ornamental sunflower28.

The resulting larger canopy likely improved light interception, contributing to the positive growth trends. In contrast, the suppression under green nets may relate to the lower relative quantum efficiency of photosynthesis in this waveband, leading to reduced carbohydrate availability for growth despite the otherwise favorable microclimate29.

Our data demonstrate a consistent hierarchy of light intensity beneath the photoselective nets, with white nets transmitting the highest photosynthetic photon flux density (PPFD), followed by blue and then green nets, a pattern maintained across morning and midday measurements (Fig. 1). The relative humidity (RH) and temperature were shown in Fig. 1. According to this Fig, the highest RH was seen in 10th July (day 15). The lowest minimum and maximum temperatures were recorded the days between 106 and 120. This gradient in irradiance directly shapes the growth environment. Critically, the superior light transmission of white nets—and by extrapolation, red nets referenced in the literature—creates a microclimate rich in PAR. This condition is fundamentally linked to enhanced photosynthetic capacity and resource allocation, manifesting in the well-documented increases in biomass, leaf area, and harvest index compared to open-field cultivation30. Our results align with studies reporting improved architectural traits, such as branch elongation and flower mass, under similar spectral manipulations12. Collectively, this evidence underscores that nets which optimize PAR availability, notably white and red, are particularly effective in promoting the integrated physiological processes that drive superior plant development and yield. Green shade nets, while reducing overall light intensity, do not significantly alter light quality. This feature enhances their photosynthetic efficiency compared to direct sunlight and blue shade nets, largely due to their superior ability to penetrate the plant canopy and support deeper light distribution within the vegetative structure31.

A key agronomic finding was the significant increase in macro-nutrient content, particularly potassium (up to 40% under green nets), under shaded conditions. We propose this is not a direct spectral effect on ion transporters, but an indirect benefit of an optimized root zone environment.

Previous research has shown that the color of shade nets impacts nutrient uptake in plants by modifying the spectral quality and intensity of light, which in turn influences photosynthetic performance, stomatal behavior, and root functionality32,33.The better absorption of nutrients in plants grown in colored shading may be due to good root growth, which is the result of suitable growth conditions provided by the shading, which has led to more root growth and thus increased the absorption of nutrients by the plant13.Blue-green light promotes auxin synthesis and stomatal opening, increasing carbon fixation and root exudation for nutrient absorption32,33.

Similar findings were reported in Chinese cabbage, where colored shading improved the uptake of N, P, and K., however, the increase in P absorption was not statistically significant34.

Additionally, Xu et al.35found that changes in the light spectrum and increased light intensity increase the nutrient uptake and crop productivity in Arabidopsis. Higher PAR under colored nets increases carbohydrate availability, fueling root growth and ion transporters32. The strong correlation between leaf nitrogen and photosynthetic pigments further underscores the central role of nutrient status, particularly N, in building and maintaining the photosynthetic machinery.

The antioxidant system exhibited a pronounced spectral sensitivity. Peroxidase activity was most stimulated under white nets and significantly suppressed under blue nets. We interpret this not as a sign of severe stress, but as a spectrum-specific induction of a protective, acclimatory response—a state of oxidative eustress. The diffused light quality under white nets may generate a mild, stimulatory redox signal that proactively upregulates enzymatic scavenging pathways, a phenomenon linked to photoreceptor-mediated gene expression36.

This pattern of increased antioxidant capacity under specific spectral filters aligns with observations in lettuce and pepper under white and yellow nets29,37 but contrasts with violets, where green nets were most effective14. These contrasting results among different plant species highlight that the effects of colored shade nets are highly species-specific. Additionally, plant antioxidant responses are highly influenced by light quality, with different spectral compositions eliciting distinct physiological adaptations. The coordinated accumulation of the osmoprotectant proline further indicates an integrated, multi-faceted strategy for cellular protection under the altered light environment. The simultaneous increase in POD activity and proline accumulation under coloured shading nets suggests not only enhanced antioxidant metabolism but also activation of molecular pathways that regulate ROS homeostasis and photoprotection. Photo-selective nets alter both irradiance and spectral composition, especially reducing high-energy blue/UV photons and modifying red: far-red ratios. These changes influence the activity of photoreceptors such as phytochromes (PHYs) and cryptochromes (CRYs), which in turn regulate transcription factors including HY5, PIFs, and bZIP proteins, leading to downstream modulation of stress-responsive genes. Reduced excitation pressure at PSII decreases electron-leak–driven ROS formation, while gene families encoding antioxidant enzymes such as POD, SOD, CAT, APX and GR are commonly up-regulated under moderated light conditions38.

At the metabolic level, stress-induced proline accumulation is coordinately regulated: biosynthesis via the P5CS pathway is transcriptionally upregulated by cues including a reduced redox potential, ABA signaling, and ROS, while catabolism is suppressed through the down-regulation of proline dehydrogenase (ProDH)39. Proline functions as a dual-purpose protectant, serving as both an osmoprotectant and molecular chaperone. It stabilizes thylakoid membranes, scavenges hydroxyl radicals, and supports NADP⁺ regeneration to facilitate photochemical quenching. Concurrently, elevated POD activity—driven by Ascorbate-Peroxidase-like and Class III peroxidase genes—accelerates H₂O₂ detoxification. This reduces lipid peroxidation and preserves Photosystem II (PSII) integrity. Together, this multi-layered antioxidant defense explains the reduced H₂O₂/MDA levels and improved chlorophyll fluorescence (Fv/Fm, ΦPSII) observed under shading treatments in various horticultural crops40,41.

Shading decreases photoinhibition-related repair load on D1 protein (encoded by psbA) by lowering ROS-driven degradation rates, allowing more efficient PSII turnover and enhancing photosynthetic efficiency. Changes in spectral quality also influence secondary-metabolite pathways, up-regulating phenylpropanoid genes (PAL, CHS, F3H) and enhancing non-enzymatic antioxidant pools—including phenolics, flavonoids and carotenoids—which collectively contribute to photoprotection42. When these biochemical defenses interact with attenuated ROS production under moderated light, the resulting oxidative-stress balance explains the superior physiological performance observed under coloured shading nets. Together, the enzymatic, metabolic and gene-regulatory evidence strongly supports the interpretation that coloured nets do not merely reduce light intensity but orchestrate a coordinated photobiological and redox-regulatory response. This orchestration encompasses photoreceptor-mediated transcriptional shifts, heightened expression of antioxidative enzymes, activation of proline biosynthesis genes, and structural stabilization of PSII under lessened oxidative pressure. In the context of this specific investigation, colored shade treatments elicited a marked enhancement in the accumulation of photosynthetic pigments and carotenoids when juxtaposed with plants exposed to full sunlight. This observation suggests that environments characterized by moderated light irradiance can actively stimulate pigment biosynthesis. The most pronounced biochemical alteration was the substantial elevation (> 70%) in chlorophyll and carotenoid content under white nets compared to the unshaded control group. This outcome is characteristic of superior photosynthetic acclimation. White nets supply a dual benefit: a reduced photon flux density coupled with spectrally balanced, diffused light. This specific milieu minimizes photodamage and decreases the energetic expenditure required for photoinhibition repair at Photosystem II, thereby enabling the sustained net synthesis and accumulation of light- harvesting pigments29. Spectral composition is a decisive modulator of pigment accumulation patterns. Similar trends have been documented across other plant taxa, where reduced light intensity has favored increased chlorophyll and carotenoid content in various horticultural crops14,43,44. Furthermore, the concurrent increase observed in both pigment levels and nitrogen content (Fig. 5) emphasizes the inextricable role of N in chloroplast morphogenesis and the assembly of the light-harvesting complex.

Conclusion

This study demonstrates that Polianthes tuberosa exhibits distinct and spectrum-specific morpho-physiological acclimation responses when cultivated under photoselective shade nets. Our findings confirm that manipulating light quality is a potent tool for directing growth patterns, resource allocation, and biochemical composition in this valuable ornamental species. The green spectrum fine-tunes architecture for floral robustness and nutrient accumulation, while the blue spectrum activates a photomorphogenic program that maximizes light capture and antioxidant defense. In contrast, full sunlight triggers a stress-acclimation phenotype focused on vertical growth and osmoprotection. This study deciphers the spectrum-specific trade-offs that govern growth and quality in Polianthes tuberosa. We demonstrate that photoselective nets are precise physiological tools, not mere shade providers. Critically, our work reveals a direct, market-relevant trade-off: colored nets enhance flower quality and resource-use efficiency, whereas full sun maximizes stem length. This provides a clear physiological blueprint for tailoring cultivation to specific market demands. By linking spectral signaling to defined morpho-physiological and biochemical outcomes, we advance photoselective shading from an agronomic practice to a targeted strategy for sustainable, quality-driven ornamental production. Further research focusing specifically on nutrient assimilation under different shade net colors would provide more definitive conclusions.