Influence of light spectrum and photoperiod on yield and quality parameters of chilli (Capsicum Annuum L.) under indoor vertical farming

Introduction

Chilli (Capsicum annuum L.) is one of the most important vegetable and spice crops belonging to the family Solanaceae. It is widely cultivated in tropical and subtropical regions and is valued for its characteristic pungency, colour, flavour and nutritional properties. Chilli fruits are consumed both as fresh vegetables and in processed forms such as dried chilli, chilli powder, sauces and various food products. The crop is an important source of vitamins, minerals, antioxidants and bioactive compounds, particularly capsaicinoids, carotenoids, vitamin C and phenolic compounds. The productivity and quality of chilli are influenced by genotype, environmental conditions, nutrient availability, temperature, light intensity, light spectrum and photoperiod. Under controlled cultivation systems such as indoor vertical farming, manipulation of environmental factors, particularly artificial lighting, provides an opportunity to regulate plant growth, flowering, fruit development and yield. Therefore, understanding the response of chilli to different light spectra and photoperiods is important for developing efficient production strategies under controlled environments. Average fruit weight is an important yield-attributing trait that reflects the extent of fruit development and contributes directly to the total yield of chilli plants. It is influenced by genetic characteristics of the variety as well as environmental factors such as light, temperature, water availability and nutrient supply. Adequate light availability promotes photosynthetic activity and assimilate production, which supports the development and accumulation of dry matter in fruits. The spectral composition of artificial light can also influence plant morphology, flowering, fruit set and assimilate partitioning, thereby affecting individual fruit weight. In indoor vertical farming, the use of red and blue LED combinations provides an opportunity to manipulate light quality according to crop requirements. Differences in average fruit weight among varieties and light treatments can therefore indicate the effectiveness of particular light environments in supporting fruit development. Evaluation of average fruit weight is consequently essential for assessing the influence of LED spectrum and photoperiod on the productivity and marketable quality of chilli. (Abbas et al., 2025) [1] Yield per plant is a major indicator of crop productivity and represents the combined effect of several yield components, including number of fruits per plant, fruit size and individual fruit weight. In chilli, yield is influenced by genetic potential, flowering behaviour, fruit set, nutrient availability and environmental conditions throughout the growing period. Light is particularly important because it provides the energy required for photosynthesis and regulates several developmental processes associated with flowering and fruit production. Red and blue wavelengths are strongly involved in photosynthetic activity, plant architecture, flowering and biomass accumulation, while photoperiod influences the duration of light exposure available for photosynthesis and plant development. Under indoor vertical farming, controlled manipulation of light spectrum and photoperiod can improve the efficiency of light use and potentially enhance fruit production. Therefore, yield per plant is an important parameter for determining the suitability of specific LED light combinations and photoperiods for improving chilli productivity under controlled growing conditions. (Appolloni et al., 2021) [2] Chlorophyll content is an important physiological parameter associated with the photosynthetic capacity and overall functional status of plants. Chlorophyll pigments, mainly chlorophyll a and chlorophyll b, absorb light energy required for photosynthesis and play a fundamental role in the conversion of light energy into chemical energy. The concentration of chlorophyll can be influenced by genotype, nutritional status, environmental conditions and the quality and intensity of light received by plants. Red and blue wavelengths are particularly important in regulating chlorophyll formation and photosynthetic processes, making them significant components of LED lighting systems used in controlled-environment agriculture. Higher chlorophyll content may support greater photosynthetic activity and carbohydrate production, which can contribute to improved vegetative growth and reproductive performance. Measurement of chlorophyll content under different LED spectra and photoperiods therefore provides useful information on the physiological response of chilli plants to artificial lighting and helps in understanding the relationship between light environment, photosynthetic potential and crop productivity. (Jimenez-Viveros et al., 2023) [3] Ascorbic acid, commonly known as vitamin C, is an important nutritional and antioxidant compound present in chilli fruits and contrib-utes significantly to their dietary value. It plays important roles in human nutrition, including antioxidant protection and support of normal physiological functions. The concentration of ascorbic acid in chilli fruits is influenced by genotype, fruit maturity, environmental conditions, temperature, nutrient availability and light exposure. Light is particularly important in regulating the synthesis and accumulation of several primary and secondary metabolites involved in fruit quality. Changes in light spectrum and photoperiod can alter photosynthetic activity and carbon assimilation, potentially influencing the accumulation of vitamin C and other antioxidant compounds in developing fruits. Under indoor vertical farming, controlled LED lighting provides an opportunity to manipulate the light environment and evaluate its effect on nutritional quality. Therefore, estimation of ascorbic acid content is an important quality parameter for determining how different LED light spectra and photoperiods influence the nutritional value of chilli fruit. (Kabir, 2020) [4]

Materials and Methods

The present investigation entitled "Influence of Light Spectrum and Photoperiod on Yield and Quality Parameters of Chilli (Capsicum annuum L.) under Indoor Vertical Farming" was conducted during the year 2025-2026 at Urban Kisaan Private Limited, Gundlapochampally, Hyderabad, Telangana, India. The experiment was carried out under a controlled indoor cultivation system to evaluate the influence of different light spectrum and photoperiods on the growth and flowering performance of chilli. Two chilli varieties, namely Thai chilli and Bullet chilli were subjected to varying combinations of red and blue LED light treatments under 14-hour and 16hour photoperiods. The materials employed and the experimental procedures adopted for conducting the study are described in the following sections

Experimental design

The experiment was laid out in a Factorial Completely Randomized Design (FCRD) with ten treatments and 3 replications. Each treatment consisted of 30 plants established in pots arranged across vertical layers. One plant pot were randomly selected and tagged for recording observations. Planting was carried out during the last week of August 2025. Throughout the study period, uniform cultural practices were followed across all treatments. In each treatment, ten uniformly healthy plants were randomly selected for recording observations in each replication. The mean value for each parameter was calculated based on data recorded from selected plants.

Results and discussion

The results of the analysis of variance indicated that the treatment effects were highly significant, demonstrating considerable variation among the treatment combinations for the character under study. Among all the treatments, T 6 recorded the highest mean value (1.80 g), followed closely by T 7 (1.74 g). Since the difference between these two treatments was lower than the critical difference (CD = 0.32), they were found to be statistically at par and significantly superior to the remaining treatments. T 4 (1.08 g), T 8 (1.06 g), T 1 (1.05 g) and T 2 (1.05 g) formed the next superior group and were statistically comparable with one another. T 9 recorded a moderate mean value (0.90 g), whereas T 3 (0.73 g) exhibited relatively lower performance compared to the superior treatments. The minimum mean value was observed in T 5 (0.26 g), which was statistically at par with T 10 (0.30 g), indicating non-significant variation between these two treatments. Overall, the significant differences observed among the treatments clearly revealed the influence of the treatment combinations on the experimental parameter. The coefficient of variation (18.85%) further indicated satisfactory precision and reliability of the experimental findings. Similar results were observed by (Zhao et al., 2025) [5] in tomatoes.

The analysis of variance revealed that the treatment effects were significant (F = 5.11, p < 0.01), indicating the existence of considerable variation among the treatment combinations for the parameter under study. Among the ten treatments evaluated, T 6 recorded the highest mean value (3.07 g), followed by T 7 (2.30 g). However, the difference between these two treatments was non-significant, as the mean difference was lower than the critical difference value (CD = 1.00), indicating that both treatments were statistically at par. T 1 (1.95 g) also showed comparatively better performance and remaine0d statistically comparable with T 7 , T 2 , T 8 , and T 9 . T 2 (1.55 g), T 8 (1.33 g), T 9 (1.22 g) and T 3 (1.07 g) exhibited moderate performance and did not differ significantly from one another. T 4 (0.88 g), T 5 (0.71 g), and T 10 (0.70 g) recorded comparatively lower mean values and were statistically at par due to differences smaller than the critical difference value. The lowest mean value was observed in T 10 (0.70 g). Overall, the significant treatment effect indicated that the treatment combinations exerted a measurable influence on the experimental trait. The coefficient of variation (39.49%) suggested relatively higher experimental variability, although the treatment differences remained statistically significant. Similar results were observed by (Appolloni et al., 2022) [6] in tomatoes.

Chlorophyll content

The analysis of variance revealed that the treatment effects were highly significant (F = 6.37, p < 0.01), indicating the existence of considerable variation among the treatment combinations for the character under investigation. Among the ten treatments, T 2 recorded the highest mean value (37.70) and was found to be significantly superior to all other treatments, as the differences exceeded the critical difference value (CD = 7.16). T 4 (29.37) recorded the next highest mean value and remained statistically at par with T 1 (25.91), T 3 (24.47), and T 8 (23.73), since the differences among them were less than the CD value. T 1 also showed comparable performance with T 3 and T 8 . T 7 (21.11), T 5 (19.58), T 9 (19.56), T 10 (18.72), and T 6 (17.84) recorded comparatively lower mean values and were statistically at par with one another. The lowest mean value was observed in T 6 (17.84), which did not differ significantly from T 10 , T 9 , T 5 , and T 7 . Overall, the significant treatment effect indicated that the treatment combinations had a marked influence on the parameter studied. The coefficient of variation (17.538%) suggested acceptable precision and reliability of the experimental data. Similar results are observed by (Mori et al., 2026) [7] in egg plant.

The analysis of variance revealed that the treatment effects were highly significant (F = 30.48, p < 0.01), indicating substantial variation among the treatment combinations for the character under study. Among the ten treatments evaluated, T 1 recorded the highest mean value (119.53 mg), followed by T 2 (114.9 mg), T 3 (110.55 mg), and T 4 (109.92 mg). Since the differences among these treatments were less than the critical difference value (CD = 11.36), they were found to be statistically at par with each other. T 5 (104.44 mg) and T 9 (104.65 mg) also exhibited comparable performance and remained statistically similar to T 3 and T 4 . T 10 recorded a mean value of (102.91 mg) and was statistically at par with T 5 and T 9 . In contrast, T 6 (79.70 mg), T 7 (66.13 mg), and T 8 (59.17 mg) recorded significantly lower mean values than the superior treatments. Among these, T 8 registered the lowest mean value and was statistically at par with T 7 , whereas T 6 was significantly superior to T 7 and T 8 . Overall, the treatment combinations differed significantly in their influence on the experimental parameter, with T 1 producing the highest response, although it remained statistically comparable with T 2 , T 3 , and T 4 . The relatively low coefficient of variation (6.81%) indicated high experimental precision and reliability of the observed results. Similar results were observed by (Wittmann et al., 2025) [8] in chilli.

Conclusion

The present investigation demonstrated that LED light spectrum and photoperiod significantly influenced the yield and quality parameters of chilli grown under indoor vertical farming conditions. Among the treatments, the 1R:2B spectrum with a 14-hour photoperiod (T 1 , T 6 ) recorded the highest average fruit weight and yield per plant, with Bullet chilli (T 6 ) showing the maximum values of 1.80 g and 3.07 g, respectively. The 1R:2B spectrum with a 16-hour photoperiod (T 2 /T 7 ) resulted in the highest chlorophyll content, particularly in Thai chilli (T 2 ), which recorded 37.70. For ascorbic acid, Thai chilli (C 1 ) recorded the highest value of 119.53 mg under T 1 , while the highest treatment mean (107.29 mg) was observed under 2R:1B + 16 hours (T 4 /T 9 ). Overall, Bullet chilli exhibited superior performance for yield-related traits, whereas Thai chilli recorded higher chlorophyll and ascorbic acid content. The findings indicate that optimizing red and blue LED light spectra with suitable photoperiods can effectively improve the productivity and quality of chilli under indoor vertical farming systems.

References

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9. How to cite this article: Priya TS, Shanmukhi C, Rao AM, Chakraborty M. Influence of light spectrum and photoperiod on yield and quality parameters of chilli (Capsicum Annuum L.) under indoor vertical farming. International Journal of Research in Agronomy. 2026;9(10):250-258. doi: https://www.doi.org/10.335
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