-NITIN PURI
Bell pepper (Capsicum spp.), part of the Solanaceae family, are nutritionally rich, offering capsaicin, carotenoids, vitamin C, and essential minerals. Carotenoids, responsible for fruit green pigmentation, act as antioxidants, protecting cells from oxidative damage and converting into provitamin A, which supports eye health and reduces cardiovascular disease and cancer risks. However, open-field cultivation faces challenges due to extreme climates and inefficient input delivery, making protected cultivation increasingly popular. Advances in breeding have improved disease resistance, yield, and fruit quality, yet long generation times hinder rapid cultivar development.
Advancements in agricultural technologies, particularly the use of LED grow lights, have revolutionized plant research and cultivation by providing precise control over light conditions. Unlike traditional lighting systems, LED grow lights allow researchers to manipulate light intensity, spectrum, and photoperiod, enabling a deeper understanding of plant responses to different wavelengths. This has been highly beneficial to growers, as optimizing light conditions can substantially decrease generation time and improve crop characteristics. By utilizing LED technology, we conducted experiments to assess the impact of specific wavelengths on capsicum growth and yield.
Far-red light is a crucial component of solar radiation that triggers a wide range of plant physiological and developmental responses. It plays a significant role in photomorphogenesis by influencing stem elongation, leaf expansion, and shade avoidance responses. As per results from our previous experiments, Red & Far-red light plays a critical role in regulating plant growth, flowering, and fruiting processes, particularly when supplemented alongside the PAR spectrum. Our findings from this experiment reveal some interesting insights about the role of FR radiation in bell pepper farming indicating improved photosynthesis, flowering, and fruit development. This in particular can help growers in maximising yield by using the supplemental Far- Red lighting.
In this experiment, we explored the effects of supplementing additional far-red (FR) light to achieve the different R:FR ratios in a full-spectrum LED grow lights and assessed the results on physiological parameters, while also assessing the duration of reproductive period and the output yield. The addition of far-red light to the full spectrum accelerated the reproductive phase by enhancing phytochrome response to far-red photons, thus promoting earlier flowering and better fruit production. Furthermore, the supplemental far-red light contributed to greater plant height compared to the chamber without far-red supplementation. These findings are expected to have significant implications for breeding and genetic research as well as for commercial farming, focused on optimizing the flowering cycle in bell peppers.
As urban farming continues to expand and the need for sustainable, high-efficiency agriculture grows, LED grow lights with UV capabilities are becoming crucial. These lighting solutions not only improve plant growth and yield but also support healthier, more resilient crops, paving the way for more sustainable agricultural practices in controlled environments.
Two distinct insulated growth chambers were set up, both maintained under identical environmental conditions, with air ventilators installed to ensure proper air exchange. Temperature and humidity levels were continuously monitored through sensors installed within the chambers. Temperature between 24-28°C and humidity between 70-75% were maintained in both the chambers.
Seedlings were initially prepared in common grow trays, utilizing cocopeat as the substrate, and were placed under controlled conditions with maintained temperature of 22-24°C and humidity of 70-75% in an insulated grow chamber with Fluortronix Grow Tubes (FLUPT22-LG) installed to support the germination phase. Once the seedlings developed a four-leaf structure, they were carefully transplanted into growing pots. Cocopeat served as the substrate for plant growth, while the fertigation process, which included both macronutrients and micronutrients, was employed to provide the necessary nutrients for plant development.
The seedlings were transplanted in pots and placed in chambers with a common drip irrigation system for both the chambers installed to provide consistent fertigation. Regular fertigation was administered to the plants within the chambers throughout the growth cycle. Each chamber contained six growing pots. Multi-spectrum Fluortronix LED grow lights 600W i.e. FLUPXE-SP6000R were used to power both the chambers, the Photosynthetic Photon Flux Density (PPFD) and photoperiod of the lights were controlled from Fluortronix online dashboard. Same PPFD levels were maintained in both the chambers throughout the cultivation period. The height of the plants was measured at various intervals, from the top of the pot to the longest part of the stem, using a measuring scale. The time of flowering and fruit set were recorded in both chambers.
In this experiment, both growth chambers were provided with photosynthetically active radiation (PAR) spectrum with full spectrum 5700K white, supplemented with 660NM deep red and 450NM deep blue light. Both the chambers were provided with light intensity (PPFD) of 320 µmol/m²/s, maintaining the photoperiod to 12hrs a day. Chamber A received only the PAR spectrum (400nm-700nm) maintaining a red-to-far-red (R:FR) ratio of 22.8 (High R:FR), while Chamber B was additionally supplemented with far-red (FR) light (400nm-750nm), maintaining a red-to-far-red (R:FR) ratio of 3.7 (Low R:FR). This controlled R:FR ratio was maintained to evaluate the effects of far-red light on plant development, particularly in relation to fruiting, flowering, and structural differences. At the conclusion of the experiment, the number of fruits, their weight, and the height difference of the plants were recorded to assess the impact of far-red light on the growth and development of pepper plants.
The results of the experiment indicate a significant difference in various growth and developmental aspects of bell pepper under both the light treatments. Several studies have reported enhanced yields, reduced flowering time and increased individual fruit fresh weights under PAR light supplemented with additional far-red (FR) light. In the present experiment, the chamber with FR supplementation (low R:FR) exhibited a greater number of flowers and enhanced fruit formation compared to other treatments. Notably, a significant difference in plant height was observed, which served as a visually distinguishable factor for both light supplementation conditions. The addition of FR light (low R:FR) resulted in a approx. 30% increase in height and approx. 20% increase in fruit formation compared to the chamber exposed solely to the photosynthetically active radiation (PAR) spectrum (high R:FR). Furthermore, the time to flowering was reduced in the FR-supplemented chamber ( Chamber-B) relative to other treatments, indicating a potential role of FR light in accelerating the flowering process.
| PARAMETERS | CHAMBER-A | CHAMBER-B |
|---|---|---|
| R:FR | 22.8 (High) | 3.8 (Low) |
| First Flower | 28DAT | 24DAT |
| First Fruit Set | 33DAT | 28DAT |
| Average Height | 38cm | 50cm |
| Average No. of Fruits | 29 | 35 |
| Average Weight per fruits | 75gm | S85gm |
Far-red radiation in plant grows light play a critical role in regulating plant growth, flowering, and fruiting processes, particularly when supplemented alongside the PAR spectrum. In Capsicum, FR supplementation resulted in a notable increase in both flower production and fruit set, highlighting its importance in optimizing horticultural lighting strategies. FR light influences phytochrome signalling pathways, which regulate the transition from vegetative to reproductive phases, thereby reducing the time to flowering. Additionally, its synergistic interaction with red light enhances the activation of flowering genes and promotes reproductive success. The findings from this experiment align with previous research, underscoring the necessity of incorporating FR light into controlled environment agriculture to enhance crop productivity and efficiency. We are conducting further experiments to investigate the effects of supplementation of high levels of Far-Red light on both their phenotypical and genotypical characteristics.
The supplementation of far-red (FR) light offers significant advantages for commercial growers in protected cultivation, particularly when integrated with LED grow light technology or natural sunlight. One of the primary benefits of FR supplementation is its ability to accelerate flowering and enhance fruit set, which directly improves yield and reduces production cycles. By carefully adjusting the red-to-far-red (R:FR) ratio using multi-spectrum LED grow lights or supplemental Far-Red lights, growers can improve phytochrome responses in plants, triggering early flowering and increased fruit formation. This is especially beneficial in greenhouse and vertical farming systems, where controlled lighting conditions can play a crucial role in optimizing crop productivity. As demonstrated in this experiment, bell pepper plants grown under FR-enriched light exhibited a significant increase in fruit production compared to those grown under standard photosynthetically active radiation (PAR) conditions. This ability to fine-tune light conditions allows commercial growers to achieve more harvest cycles per year, ensuring consistent supply and profitability.
In addition to yield enhancement, LED grow lights with far-red supplementation offer greater energy efficiency, cost-effectiveness, and long-term sustainability compared to traditional lighting methods. Unlike conventional lighting, modern LED systems provide customizable spectral outputs, allowing growers to tailor light conditions based on specific crop needs without unnecessary energy waste. The elongation effect of far-red light also contributes to improved canopy structure and light penetration, optimizing space utilization in high-density cultivation settings. Furthermore, far-red supplementation has been linked to improved plant health and stress tolerance, which is crucial in protected environments where climatic control is essential. By incorporating specific wavelength light into horticultural lighting strategies, commercial growers can enhance crop quality, maximize efficiency, and ensure year-round production, making protected cultivation more viable and profitable.
1. Cerdán, P. D., and Chory, J. (2003). Regulation of flowering time by light quality. Nature ` 423 (6942), 881–885. Doi: 10.1038/nature01636.
2. Cohen, O., Borovsky, Y., David-Schwartz, R., and Paran, I. (2012). CA JOINTLESS is a MADS-box gene involved in suppression of vegetative growth in all shoot meristems in pepper. J. Exp. Bot. 63 (13), 4947–4957. Doi: 10.1093/jxb/ers172.
3. Dongpil Kim Jung Eek Son (2022). Adding Far-Red to Red, Blue Supplemental Light-Emitting Diode Interlighting Improved Sweet Pepper Yield but Attenuated Carotenoid Content. Doi: 10.3389/fpls.2022.938199.
4. Dongpil Kim Taewon Moon Sungmin Kwon (2022) Supplemental inter-lighting with additional far-red to red and blue light increases the growth and yield of greenhouse sweet peppers (Capsicum annuum L.) in winter. Doi: 10.1007/s13580-022-00450-6.
5. Hayoung Choi, Seungki Back, Geon Woo Kim, Kyeongseok Lee, Jelli Venkatesh, Hyo Beom Lee, Jin-Kyung Kwon and Byoung-Cheorl Kang. Development of a speed breeding protocol with flowering gene investigation in pepper (Capsicum annuum). Doi: 10.3389/fpls.2023.1151765.
6. Halliday, K. J., Salter, M. G., Thingnaes, E., and Whitelam, G. C. (2003). Phytochrome control of flowering is temperature sensitive and correlates with expression of the floral integrator FT. Plant J. 33 (5), 875–885. Doi: 10.1046/j.1365313X.2003. 01674.
7. Jähne, F., Hahn, V., Würschum, T., and Leiser, W. L. (2020). Speed breeding short-day crops by LED-controlled light schemes. Theor. Appl. Genet. 133 (8), 2335–2342. Doi: 10.1007/s00122-020-03601-4.
8. L.F.M. Marcelis Remko Offringa (2024). Far-red light-enhanced apical dominance stimulates flower and fruit abortion in sweet pepper. Doi: 10.1093/plphys/kiae088.
9. Valverde, F., Mouradov, A., Soppe, W., Ravenscroft, D., Samach, A., and Coupland, G. (2004). Photoreceptor regulation of CONSTANS protein in photoperiodic flowering. Science 303 (5660), 1003–1006. Doi: 10.1126/science.1091761.
10. Watson, A., Ghosh, S., Williams, M. J., Cuddy, W. S., Simmonds, J., Rey, M.-D., et al. (2018). Speed breeding is a powerful tool to accelerate crop research and breeding. Nat. Plants 4, 23–29. Doi:10.1038/s41477-017-0083-8.
Read more about how different wavelength can affect the plant growth.