Effects of Far-red (FR) Enriched Spectrum and End of Day FR on Tomato Seedling in a Controlled Environment

February 15, 2019

FAR-RED Treatment Effects on Tomato Seedlings: What You Need to Know.

Light is vital during the entire plant growth cycle. Not only as an energy source, but also as an important signal to regulate physiological responses and the way plants grow. Inadequate light to crops at the seedling stage can lead to extended production cycles and increase rates of seedling mortality. Plant morphology is extremely important in controlled environment agriculture. Not only is it crucial to produce a plant which looks appealing to a customer but having plants in the right shape/size simplifies production procedures such as grafting, harvesting, packaging, and transportation. Heliospectra’s Plant Lab and Light experts have over a decade of experience researching how individual colors of light, or spectra of light, influence various growth and flowering responses. By combining this extensive knowledge and programmable LED lighting solutions to guide plant growth and development, we help empower growers to maximize their growth potential. In order to study the growth response of tomato in a seedling stage, Heliospectra’s Plant Lab and light experts investigated the effects a far-red enriched spectrum can have on seedling production of tomatoes. The research below, will familiarize commercial tomato growers; especially those using controlled environments, with how to control stem height and thickness in tomato seedlings. Far-red light (often abbreviated FR), can be defined as light with wavelengths ranging from 700 to 800 nanometers (nm). As humans, we can barely see far-red light because it is at the edge of our eye’s visual sensitivity. Although we cannot see Far-red, it has a major effect on plants and the morphology of plants, mainly extension growth and flowering.

The purpose was to investigate the effect of far-red (FR) enriched spectrum and end-of-day FR on a tomato seedling in a controlled environment. Investigating benefits such as providing a more uniform stock material, allowing easier matching of rootstock and scions for grafting by using specific light wavelengths or colors.

The effects of Far-red (FR) enriched spectrum and end of day FR on Tomato seedling in a controlled environment.

The research was carried out in Heliospectra’s in-house Plant Lab on seedlings of tomato rootstock cultivar; Kaiser and Emperador. The seedlings were germinated under the Heliospectra light bar, then moved into grow chambers for experimental light treatment and cultivated under the fully adjustable spectrum LED grow light ELIXIA. In order to gain more insight into how far-red effects tomato seedlings, three different LED lighting strategies were used using Heliospectra’s light control system helioCORETM and its scheduling module;
  1. a spectrum containing only red, blue and white LEDs
  2. a FR- enriched spectrum
  3. a third light treatment adding FR only as a 30-minute end-of-day (EOD) treatment.
With a total photosynthetic photon flux density (PPFD) of 200 mol photons/m2/s across all lighting regimes. Plant morphology was monitored, such as color, stem height, and diameter. Further, electricity consumption was measured for each lighting strategy, and recorded in kilowatts per hour (kWh). The initial plant height was measured at the start of the light treatments and then recorded throughout the experiment. At the end of the experiment, after 15-18 days of treatment, the stem diameter was measured. The experiment was repeated three times.

Tomato Seedling's response to Far-Red.

Tomato seedlings grown with FR were taller and had larger leaves compared to seedlings grown without far-red which were shorter with a darker leaf color. Tomato seedlings which had been exposed to the EOD FR treatment showed the greatest difference. They were taller, almost 15% taller than plants grown under no far red (Kaiser 14,7%, Emperador 14,9%), and had larger leaves than plants grown under a FR-enriched spectrum. The FR-enriched spectrum still showed a significant increase in height of 11,6% (Kaiser) and 12,4% (Emperador). The FR in the light treatments also had an impact on the stem diameter. Seedlings grown under far red showed a 3,3% (Kaiser) and 3,5% (Emperador) thicker stem than seedlings grown without FR. Further the seedlings treated with EOD FR had a thicker and taller stem than those grown with a FR enriched spectrum, resulting in an increase of 3,6% (Kaiser) and 3,8% (Emperador) in diameter compared to crops grown without far-red. Far red light treatment on plants  


Light is a powerful tool in order to influence crop morphology, biomass and overall quality. The results from this test indicates that differences in growth performance should be expected as an outcome of applying different light strategies. If a grower’s goal is to achieve extensive growth of a tomato seedling, then far-red can be utilized to reach that goal. If the goal is to produce more compact seedlings, far-red should be excluded. Furthermore, by adding FR only at the end of the day, growers can reduce energy consumption using smart LED lighting systems to achieve energy efficiency and non-chemical control of plant morphology. By deploying Heliospectra’s helioCORE control software’s Scheduling module, growers can use different lighting strategies to influence the growth of a tomato seedling, like an EOD treatment. Providing intelligent LED lighting solutions, a potential advantage over traditional non-flexible HPS or HID lighting applications. Growers with the goal to graft tomatoes should consider incorporating far–red treatments into their lighting strategies, as the ability to obtain thicker stems could benefit the process significant. This research was presented by Heliospectra’s Plant and Light Solution Expert Ida Fällström as a research poster at the National Conference of the Canadian Society for Horticultural Science on October 4th, 2018 in Niagara Falls,Ontario. Download the poster here Heliospectra’s team share a relentless focus to help growers and cultivation teams improve crop quality, accelerate harvest cycles, increase yields and control consistency. Heliospectra’s Technical Services team stands ready to assist you in developing lighting strategies based on your crop type and business goals. Ready to discuss your own lighting strategy? Get in touch