Engage with researchers to make the most of lighting advances, growers urged

Research is revealing the surprising extent to which crop growth can be manipulated by light of different wavelengths and times, to the benefit of quality and yield.

Image: University of Essex
Image: University of Essex

But growers should engage with this process to guide it towards commercially desirable outcomes, according to a leading researcher in the field.

University of Essex molecular biology lecturer Dr Matt Jones catalogues the many different directions this is taking in a new paper published this month in Horticulture Research which analyses the mechanisms underlying effects detailed across some 180 individual pieces of research on crops and lighting.

 "Now LEDs are more viable, it’s important to take what we do in the lab and apply it on a commercial scale," Jones told Horticulture Week. "There is a big gap between what we know and what can be usefully applied."

He explained: "It’s hard to generalise. What’s increasingly apparent is that plants’ responses to light are very different from each other, and so the light recipe has to be tweaked in each case. Even different subspecies of the model plants being studied have different numbers of photo-receptors – we have to double-check each crop."

And across the corpus of recent academic literature on the subject, "There’s a lot on controlling vegetative growth versus flowering, but little in fruit quality," he said. "What people aren’t looking at is the effect of different light quality at different times, for example blue light at night."

Meanwhile, he added: "A lot of the research is proprietary [to manufacturers], and there is a lack of transparency on how well they are tested. They may have a general light recipe which is not necessarily as useable."

Lighting can even improve crops post-harvest, he noted. "How easy is that in practice? It depends on the practicalities of the crop, which might go straight into crates after picking."

In general, he said: "We need dialogue, as we are not always sure what growers want."

Applications for lighting to improve crops

  • Supplemental LED lighting can induce colour break in winter-grown peppers;
  • Light irradiation of peppers can also induce colour break after harvesting;
  • Extending day length can increase yield in peppers, though not in related crops such as tomatoes;
  • Blue LEDs at the end of day can improve tomato quality, though not yield;
  • Red-light night breaks delay flowering and decrease plant height in tomato, while also improving fresh weight;
  • Altering the ratio of blue and red light used to irradiate lamb’s lettuce can improve yield and also leaves’ sugar and phenol content;
  • supplemental lighting can reduce senescence of outer leaves of crops such as lettuce, so enhancing yield.

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