Red means go for plants
RUNNING a red light has taken on a whole new meaning during a study into plant growth at one of the world’s leading agriculture institutes.
A research program is under way at the Wageningen University and Research Centre at Wageningen, about 80km southeast of Amsterdam in The Netherlands, to determine the perfect “light recipe” for plants in greenhouse and vertical farm environments. And results show that red – and potentially far red with a mix of blue – are certainly the new, well, black when it comes to tomato production.
The QS World University Ranking last year named Wageningen – which has more than 12,000 students from more than 100 countries – the world’s best university for agriculture and environmental science.
Its professor of horticulture and plant physiology, Leo Marcelis, has been a plant scientist for 31 years and during his time at the university has worked in a range of different departments.
His research has focused on plant physiology in greenhouses and, more recently as the world attempts to become more energy efficient, the more-intensive vertical farms where plants are grown indoors without solar light.
Light is a major issue for greenhouse horticulture production throughout Europe with the amount of sunlight during winter insufficient when it comes to the growth and production of crops.
PROF Marcelis said while greenhouses offered a huge production level of up to 70kg of tomatoes per square metre, and were sustainable “in a number of aspects”, their reliance on assimilation lighting meant they consumed significant amounts of energy.
“A large part of the energy is used for lights, especially now we are heading towards the winter period (in Europe),” he said.
He said traditionally the greenhouses used high-pressure sodium lamps – “like lamps you see on the street” – but now more growers were converting to the more energy efficient LED lighting. Coloured lights in particular have been proven to stimulate plant development and growth resulting in the production of more energy efficient produce.
Prof Marcelis said the aim of the research at Wageningen was to determine which coloured LED lighting produced the most tomatoes with “taste, shelf life and all the nutritional values”.
As part of the experiment, plants are grown under different colours of light – red, blue, green – and are monitored for plant length, photosynthesis, plant temperature, stomatal opening and leaf angles.
After three to four weeks, the plants are harvested and divided into leaves and stems.
The number of leaves are counted, the leaf area is measured and weighed, so too the stems.
Prof Marcelis said red was proving the most efficient light from a production standpoint with blue and, to a lesser, extent green (“we don’t need that much but it has specific effects”) throwing up interesting results.
THE study has also found that plants are sensitive to the ratio between red and far red light “in particular at the end of the day” which Prof Marcelis said was not unsurprising as it “is what also happens in nature”.
He predicts a lot of work on the role of far red light to be carried out, with opportunities to increase production by at least five per cent.
Prof Marcelis said although the more light the plant was exposed to, the more flavour the fruit had, he was not in a position to determine which colour produced the best-tasting product.
“It is too early to say now because it seems that it also affects a whole level of anti-oxidants or in general secondary metabolites,” he said.
Prof Marcelis said in The Netherlands, red and blue were the most common lights used, with a mixture of 90 per cent red and 10 per cent blue the most common.
When it came to different tomato varieties he said some fared better under the red-blue and some under white lights proving a “huge genetic difference”.
“I would think in five years from now that you’d probably add a little bit of far red light and maybe a bit of green light,” he said.
Adding more than a splash of colour to the tomato source.
LIGHT EFFICIENCY: Coloured lights have been proven to stimulate plant development and growth, with red light proving to have a positive effect on the growth of tomatoes.