The yields of some crops can be substantially boosted by covering them in a material that increases the amount of red light they receive. The simple technology could help to feed the world’s growing population, although more research is needed to see if it affects the flavour and nutrition of plants.
Red wavelengths of sunlight are known to be the biggest drivers of plant growth because they stimulate leaves to produce chlorophyll, which is needed for photosynthesis. This is why some farms have started shining red LED lights on crops to boost their yields. But these lights are costly to install, are energy-draining and don’t distribute light as evenly to plants as sunlight.
To address these issues, and at the University of New South Wales in Sydney, Australia, have developed a material called LLEAF that passively converts some of the green wavelengths in sunlight – which are less important for plant growth – to red ones.
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The material is a transparent plastic containing a fluorescent dye that absorbs green wavelengths of sunlight and re-emits them as red ones. It can be hung over existing greenhouses and creates a soft pink light inside. “It’s quite pretty,” says Soeriyadi.
In greenhouse trials, the researchers found that the material increased plant yields by an astonishing amount for various crops, including 37 per cent for pak choi. “People were very sceptical when we told them because the greenhouse industry is already so optimised that you’re normally only expecting single-digit increases with new technologies,” says Soeriyadi.
The material is now being tested in bigger, independent trials run by Western Sydney University and the New South Wales government’s Department of Primary Industries.
at Western Sydney University and his colleagues recently completed a trial of the material with lettuce. They installed it over a greenhouse so it covered a 200-square-metre plot of lettuces that was next to an identical plot of lettuces that wasn’t covered by the LLEAF material.
The yield of cos lettuce, also known as romaine, rose by 14 per cent when grown under the material, while those of butterhead lettuce increased by 27 per cent.
“I think the technology could be really important, especially as it’s inexpensive and can be applied to existing facilities,” says Tissue, who is now testing LLEAF on cucumbers and plans to trial it on several other crops over the next five years.
The Department of Primary Industries is currently trialing the material with blueberries, but the results aren’t available yet.
One important consideration is whether taking green light away from plants and giving them extra red light might harm them, says Tissue. He noticed that the lettuces grown under the material had an orange tinge, probably because the altered sunlight they received changed their composition of carotenoids and other pigments. “But we need to do further research to see if this changes the flavour or nutrition,” he says.
at CSIRO, Australia’s national science institute, says it is also unclear how well the technology would work for other types of crop like cereals. “But I think it’s worth exploring,” he says.
Soeriyadi and Falber are now developing a library of dyes to tailor their material to different crops. They hope that boosting crop productivity will help meet growing food demand, which is expected to increase by up to from 2010 to 2050.
By manipulating the light that plants receive, they believe it may even be possible to grow crops in parts of the world where they aren’t normally suited, if other variables like temperature and humidity are also controlled. For example, they recently completed a trial showing it was possible to increase the yield of a Dutch strawberry cultivar in Indonesia by covering it with a LLEAF material that converts red sunlight wavelengths to far red, mimicking the light of shorter days.
“We trick the plants into thinking they are feeling the same light profile as they have in the Netherlands,” says Soeriyadi.
If this technique works more widely, it could help reduce food miles by allowing countries to grow most crops themselves instead of importing them, says Soeriyadi. “We believe that LLEAF could be part of a more sustainable, productive and efficient future,” he says.
