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Plants become less competitive in the deep shade

In a new study from the John Innes Centre, experts have discovered how plants cope with life in the deep shade of a dense forest, where light and other resources are very limited.  Typically, even the threat of shade causes plants to elongate in an attempt to outgrow each other. 

“Shade-avoiding plants can detect the presence of neighboring vegetation and evoke escape responses before canopy cover limits photosynthesis,” explained the researchers. “Rapid stem elongation facilitates light foraging and enables plants to overtop competitors.”

In the deep shade, however, neighboring plants become less competitive and more cooperative. 

“Plants can detect the proximity and density of neighboring vegetation using phytochrome photoreceptors,” wrote the study authors. 

“In shade-sensitive species, canopy cover drives stem elongation, facilitating light foraging. In deep shade, where resources are severely limited, excessive elongation growth can be detrimental to plant survival.”

The researchers set out to investigate how plants prevent elongated growth under deep shade conditions. The study revealed that when plants detect deep shade, this changes the expression of genes in certain parts of their circadian clocks. As a result, stem elongation is suppressed.

“The majority of plant shade avoidance research focuses on early neighbor detection and moderate shading. This work reveals new insights into how plants adapt to very deep shade, where resources are severely limited,” said Professor Kerry Franklin of the University of Bristol.

According to the researchers, their work identifies a previously unknown role for the circadian clock in regulating plant development, and the findings have implications for both natural plant populations and crops.

“The biological clock of plants is a key regulator of their development and fitness,” said Professor Antony Dodd. “This work sheds new light on a new role for circadian rhythms in adapting plants to competition with other plants in their environments.”

The study is published in the journal Proceedings of the National Academy of Sciences.

By Chrissy Sexton, Staff Writer

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