Plants living in the shade get much more light than previously believed

We’ve all seen houseplants tucked in corners far from windows or lush greenery growing under dense tree canopies. Yet, these plants manage to grow and thrive in shade without direct sunlight. How do they do it?

New research reveals that shaded plants capture more light than previously believed. Scientists from Utrecht University and Wageningen University & Research (WUR) found that these plants effectively use light beyond the visible spectrum.

Published in the journal Plant Cell & Environment, the findings could transform photosynthesis research and greenhouse horticulture practices.

“When you have a better understanding of how different colors of light affect photosynthesis and plant growth, you can help growers develop smart ways to supplement natural sunlight with colored light,” noted the researchers.

Shaded plants capture far-red light

Shaded plants benefit from light that filters through the leaves of plants above them. When sunlight hits the upper plant leaves, they absorb most of the light for photosynthesis but allow some light to pass through.

This unabsorbed light primarily consists of green and far-red wavelengths, which are less useful to the upper plants but become crucial for the plants below.

Far-red light, in particular, falls within the 700–750 nm range of the light spectrum. Unlike visible light, which plants predominantly use for photosynthesis, far-red light was previously thought to have little impact.

However, the study reveals that shaded plants have adapted to use far-red light effectively for photosynthesis, allowing them to survive and grow even in low-light environments. This ability is vital for plants in dense forests or closely planted crops, where direct sunlight is scarce.

Photosynthesis in shaded plants

“Until now, researchers have seldom considered the possibility that plants utilize far-red light for photosynthesis,” said WUR PhD candidate Tinko Jans.

Conventional experiments suggested that photosynthesis relied mainly on visible wavelengths (400–700 nm).

However, this study reveals that far-red light significantly boosts photosynthesis when combined with small amounts of visible light. The team developed a new method to measure and model this contribution.

Plants grow taller using far-red light

Far-red light also affects plant behavior, triggering a “shade avoidance response.” “Many plants react to a relative increase in far-red light by growing straight up, to win the competition for light,” Jans explained.

This response benefits horticulturists, allowing plants to grow closer together in limited spaces.

Recent advances in LED technology have enabled researchers to study far-red light more effectively.

“In earlier experiments, we showed that shade plants grow faster when supplemented with far-red light from LEDs,” noted Utrecht University environmental scientist Hugo de Boer, who initiated the study.

The findings highlight how controlled light environments can optimize plant growth.

Considering the full light spectrum

The scientists faced challenges in studying the role of far-red light in photosynthesis because existing models only considered visible light (400–700 nm) as the primary contributor to plant growth.

Far-red light was largely overlooked in traditional research and calculations.

“It turned out to be much more difficult to quantify the color effect on photosynthesis,” explained Hugo de Boer, as earlier models and measurement methods were not designed to account for the influence of far-red light.

To overcome this, the researchers adapted widely used photosynthesis models to include far-red light. They combined measurements of photosynthesis with data from the full spectrum of light reaching plant leaves.

This updated approach allowed them to accurately demonstrate how far-red light, when integrated with visible light, significantly enhances photosynthesis and supports plant growth.

This breakthrough highlights the importance of considering the full light spectrum in both research and agricultural practices.

Greenhouse crop cultivation

The research highlights a previously underestimated factor in plant growth: the role of far-red light in photosynthesis.

Far-red light was once thought to contribute little to photosynthesis. However, the study demonstrates that plants can effectively use this light, especially when combined with visible light, to enhance their growth.

The findings hold significant potential for greenhouse horticulture. By integrating far-red light into lighting strategies, growers can optimize plant growth even in shaded or crowded environments where sunlight is limited.

This approach could improve crop yields while reducing the energy and space required for cultivation.

Leveraging far-red light offers a smarter, more sustainable method of farming, allowing plants to thrive in conditions that were previously considered suboptimal. This advancement could transform modern agriculture, making it more efficient and environmentally friendly.

The study is published in the journal Plant Cell & Environment.

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