Belfast Telegraph

Monday 21 April 2014

Plants clue to jet lag effects

A new study into how plants adjust to having less sunlight in winter could lead to a better understanding of the impact of shift work and jet lag on people, according to scientists.

Researchers looking at the daily rhythms in plants have discovered a complex process that allows the plants' genes to respond to the times of dawn and dusk each day, and the length of daylight in between.

This system enables the plant to reset its internal clock every day in response to seasonal changes in daylight, helping it to control the timing of crucial activities, such as flowering and making frost-resistant buds.

The findings could shed light on how other living things, including humans, respond when our daily rhythms are interrupted, perhaps by travel or unsociable working hours.

Daily activity cycles, known as circadian rhythms, are found in most living things and they influence the many biological functions that happen throughout the day. In people, these include sleepiness, body temperature, blood pressure, and physical strength.

Researchers at the University of Edinburgh used experimental data and mathematical models to show how much the plants' rhythms accounted for sunrise and sunset, as well as day length.

Professor Andrew Millar, who led the study, said: "Light input is absolutely crucial to understanding how the rhythms of most organisms work in daily life.

"We found how the genes that drive the plant clock respond to the light/dark cycle. Our particular piece of work looks at many genes at once and we were tracking separately several different light responses.

"Several different parts of the clockwork are controlled by light. It's not like a wristwatch where you have a single adjusting screw which changes the time and does it in just one way. The biological clock is adjusted in plants in several different ways.

"We were asking why that was necessary and what's the effect in the end. The answer to that is that it allows the plant clock to adjust automatically to the length of the day.

"Plants use their clocks to measure that day length and then to start these developmental processes that change them to make flowers, or to stop making frost-sensitive leaves and make frost-resistant buds instead."

Professor Millar, of the university's school of biological sciences, said it made evolutionary sense for plants, particularly in places where sunlight levels vary widely throughout the year, to have adapted a finely-tuned process helping them to distinguish between long and short days.

"In very broad terms, if you have a long day, you can stretch out your daytime activities to cover a longer duration of time and you have to compress the night time activity into the short night, and vice versa," he said.

"Our results give us valuable information on how plants - and people - respond to changing lengths of day. It could give a new way to understand how to cope when our daily rhythms of light and dark are interrupted."

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