Here’s why leaves turn red in autumn

November 14th, 2007 - 2:52 am ICT by admin  
The researchers found that the quality of soil plays as significant a role in dictating the array of fall colours.

Emily M. Habinck, a graduate student at the university, found that trees produced more red pigments known as anthocyanins in places where the soil was relatively low in nitrogen and other essential elements.

In a previous study, plant physiologist William Hoch of Montana State University, Bozeman had shown that genetically blocking anthocyanin production in red-leafed plants caused their leaves to become unusually vulnerable to fall sunlight, and thus sent less nutrients to the plant roots for winter storage.

Based on his finding, Hoch hypothesised that for trees living in nutrient-poor soil, it made sense to produce more anthocyanins, which protect the leaves longer, so that as much nutrient as possible could be recovered from leaves before winter sets in.

According to Habinck, it is the process of recovering of nutrients from leaves that turns leaves from green to yellow, orange and sometimes anthocyanin-red.

The trees studied by Habinck, says the researcher, appeared to be acting in accordance with Hoch’s hypothesis.

“It makes sense that anthocyanin production would have a function, because it requires energy expenditure,” said Habinck.

The researchers say that anthocyanins are a sort of investment made by stressed trees in situations where they stand to gain from the extra recovery of nutrients from leaves.

“The rainbow of colour we see in the fall is not just for our personal human enjoyment — rather, it is the trees going on about their lives and trying to survive,” said Habinck’s advisor, Martha C. Eppes, a soil scientist and assistant professor of Earth sciences at the University of North Carolina at Charlotte.

The researchers believe that the soil-leaf connection could not be discovered long ago partly because Hoch’s hypothesis was needed to put it into perspective. They say that it also might be that many plant researchers were missing the forest for the trees.

“I think that most of the work has been done by biologists looking at production of anthocyanins in trees themselves,” said Eppes, adding that they had not stepped back and looked at patterns of tree colour.

Eppes, who will present the research at the Geological Society of America Annual Meeting in Denver on 29 October, wants to follow up Habinck’s study with a wider analysis of satellite data showing tree colour, which can be compared to geological maps of the types of soils over large portions of land. (ANI)

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