During the recent COVID-19 pandemic, Quebecers became aware of the need to increase their food autonomy and grow more fruits and vegetables locally, especially in winter. In connection with this observation, plant biology professor Tagnon Missihoun from UQTR launched a project aimed at studying the effect of additional infrared light on greenhouse production of red pepper. The excellent results obtained by the researcher and his team, in terms of yield and fruit quality, offer promising new avenues to greenhouse producers in the province.
“For our experiment, we illuminated pepper plants with supplemental light in the infrared spectrum. Thanks to this treatment, the plants produced up to 74% more fruit, in terms of kilograms harvested. The individual weight of fresh peppers also increased by up to 25%. The quality of the fruit has also improved with a 3 to 6% higher sugar content. Peppers also contained up to 58% more phenolic compounds, which have antioxidant and health benefits,” reports Tagnon Missihoun.
These remarkable results were obtained on two different experimental sites: a commercial greenhouse located in Montérégie, as well as a culture chamber housed in a laboratory in the Pierre-Boucher pavilion at UQTR.
“It was Serres Lefort, today called Gen V, which welcomed us to their facilities in Sainte-Clotilde for the part of our work taking place in a real agricultural production context. Gen V freed up space for us where we were able to follow the growth of around 200 red pepper plants of the Margrethe variety under different infrared lighting, from October 2022 to March 2023,” explains Professor Missihoun.
LED lamps to control light parameters
The red pepper plants grown in Gen V were divided into three groups, to provide them with different amounts of “far-red” light, a type of radiation in the infrared range. Some plants, designated as a “control group”, received a proportion of 5% far red in their lighting, a level comparable to that present in sunlight. The other two groups were administered 10% and 15% far red, respectively.
“To vary the infrared levels, we could not use the artificial lighting in place at Gen V. The latter, like most commercial greenhouses, uses high-pressure sodium vapor lamps which do not allow us to modify the amount of infrared and only offer a negligible amount of this type of light. We therefore had to install light-emitting diode, or LED, lamps in our portion of the greenhouse, which provide lighting similar to that of the sun and whose infrared level can be modulated. These lamps were provided to us by Sollum Technologies, a Quebec company which partnered with our project and supported us with the installation and management of the LEDs, both in the greenhouse and in our growth chamber, at UQTR. , points out Tagnon Missihoun.
The light-emitting diode (LED) lights used by the research team provided a precise level of infrared lighting for the pepper plants.
While a portion of the scientific work was taking place at Gen V – during a cold season – Professor Missihoun started the same type of experimentation on a smaller scale, in a culture chamber at UQTR. A space has been specially designed to build three closed sections offering different infrared lighting (5%, 10% and 15%) and each being able to accommodate around twenty pepper plants.
“Once our work was completed in the commercial greenhouse, we continued our research in our growth chamber. We grew pepper plants on different occasions under our three lights, to ensure the validity and reproductivity of our observations. Working in the laboratory also allowed us to better control certain parameters such as the quality of light, humidity or temperature. Our experiments on infrared light and pepper plants are still underway in the culture chamber, which is used by members of the Plant Biology Research Group at UQTR, of which I am a part,” underlines Tagnon. Missihoun.
Results leading to the improvement of production methods
Throughout the experiment, both in the greenhouse and in the growth chamber, data was collected on the photosynthesis process of pepper plants. Agronomic monitoring was also carried out regularly to measure the size of the plants, count the fruits harvested and weigh them. Samples of peppers were then analyzed in the laboratory to determine their chemical composition.
Pepper plants grown in the laboratory at UQTR.
“The results obtained in the greenhouse and in the growth chamber were relatively similar. Basically, photosynthesis of pepper plants did not change too much in the 10% and 15% IR groups, compared to the 5% control group. But what has changed is the height of the plants. The greater the infrared input, the taller the plants were. As for fruit yield, it was higher in peppers lit with 10% far-red light, compared to those receiving 5% or 15% of this light. This result shows that a rate of 10% is already sufficient to obtain more kilograms of fruit. As for the increase in the individual weight of peppers and the content of sugar and phenolic compounds, it was reflected as much in the groups at 10% as at 15% of far red,” notes Professor Missihoun.
Throughout the work, the researcher also noted that the gains obtained could vary, depending on when the far red supplement was added to the lighting of the pepper plants. Additionally, the data obtained showed that supplementing far-red light increased the maturation time of pepper plants by 5 to 9 days. The higher the infrared level, the more it delayed the fruit harvest.
“If the ripening time extends, the producer will have to light the pepper plants longer, which can result in additional costs,” notes Professor Missihoun. But at the same time, lighting with LED lamps is less energy intensive and allows you to achieve an increased yield of fruits. It is therefore necessary to consider all of these aspects to choose the best rate of infrared light which will both optimize performance and minimize costs. »
Using LED lights as a lighting Source in a greenhouse also presents another challenge. This type of lighting emits little heat, compared to the high-pressure sodium vapor lamps traditionally used by producers. “By replacing the current lighting in greenhouses with LED lamps, there will be a lack of heat to fill during the winter period. We therefore need to address this difficulty, which we are currently doing in our research,” added Professor Missihoun, who works in the Department of Chemistry, Biochemistry and Physics at UQTR.
Teamwork, in exchange with the community
To carry out his scientific project, Tagnon Missihoun surrounded himself with collaborators. Student Georges Yannick Fangue Yapseu and student Awa Marina Mouliom Ntapnze, both doctoral students in cellular and molecular biology at UQTR, are actively participating in the research work.
Doctoral student Awa Marina Mouliom Ntapnze (foreground) and doctoral student Georges Yannick Fangue Yapseu are working on the analysis of data obtained during the experimentation of different infrared lighting on pepper plants.
“Professor Vincent Maire of the Department of Environmental Sciences at UQTR and Professor Martine Dorais of the Department of Phytology of the Faculty of Agricultural and Food Sciences of Laval University have also joined forces with the project, mentions Tagnon Missihoun. We also obtained a grant from the Innov’Action program of the Quebec Ministry of Agriculture, Fisheries and Food, MAPAQ. We also work in collaboration with the Greenhouse Producers of Quebec and the Agtech Zone, which is interested in innovative agricultural technologies. »
In August 2023, Professor Missihoun participated in a meeting of Quebec greenhouse producers, in order to provide them with his scientific results on the effects of infrared lighting. He is also preparing a report on his research work for MAPAQ. “In collaboration with the Agtech Zone, we also plan to organize other knowledge transfer activities to greenhouse producers. Our discussions with them allow us not only to inform them about our progress, but also to receive their comments and stay on the lookout for new developments in the field of greenhouse cultivation,” he says.
