Image: Young seedlings bending towards light. credits: www.science.org.
Have you ever noticed how plants always seem to bend towards the sunlight, no matter where it comes from? This fascinating behavior, known as phototropism, has intrigued scientists and gardeners alike for centuries. But how do plants “know” where the light is and adjust their growth accordingly?
To understand this, let’s go back to a bit of school physics! You may recall that light bends or refracts when it passes from one medium to another, such as from air into water, because of differences in their refractive indices. This basic principle is now at the heart of a groundbreaking discovery made by Christian Fankhauser group at the University of Lausanne(http://cigreport.genomyx.ch/let-there-be-light-shade-avoidance-response-in-plants/).
The Role of Air Channels in Light Sensing
In a recent study, scientists from UNIL found that plants rely on intercellular air channels within their stems to sense the direction of light! Here’s how it works:
When light hits one side of a plant stem, that side receives the most direct sunlight. However, air spaces between the cells in the stem scatter the light, reducing the amount that reaches the opposite side. This happens because air, water, and plant cells all have different refractive indices. These air channels make it easier for the plant to create a light gradient across the stem, with one side being well-lit and the other remaining relatively dark.
This difference in light intensity across the stem tells the plant which way to bend—toward the brighter side. By sensing and responding to this light gradient, plants can direct their growth toward the sunlight, optimizing photosynthesis.
A Simple Yet Brilliant Mechanism
This discovery showcases how plants use simple yet effective mechanisms to interact with their environment. The idea that air channels inside plant stems play a crucial role in directing light perception adds a new layer to our understanding of plant biology. It also reminds us how even the most familiar processes, like phototropism, can still surprise us with their underlying complexity.
Science often takes us on unexpected journeys, and this discovery is another example of how plants continue to inspire and amaze us.
Let’s continue to marvel at the wonders of nature and the simplicity behind the complexity of life!
References
1. Ganesh M. Nawkar et al. , Air channels create a directional light signal to regulate hypocotyl phototropism.Science382,935-940(2023).DOI:10.1126/science.adh9384