Do plant seeds have brains?

Botanical orthodoxy holds that plant germination is a purely mechanistic process, driven entirely by external stimuli. The plant seed itself has no say in the matter.

Research published in the Proceedings of the National Academy of Sciences (PNAS), however, is set to radically change that idea.

Scientists from the University of Birmingham have discovered that the plants themselves determine when to germinate, effectively making a decision through the interaction of two groups of cells that constitute an analogue of a brain.

The scientists, led by George Bassel of the university’s School of Biosciences, discovered two types of cell operating in concert in the embryos of a plant called Arabidopsis, or thale cress. One group of cells promotes seed dormancy, while the other drives germination.

Bassel’s team discovered tat the two groups collectively function as a decision-making centre by moving hormones from one to the other.

Using a genetically modified variety of the thale cress that amplified chemical signaling, the researchers found that the two exchange hormones between the two cell groups effectively led to a decision of when to trigger germination.

The interaction between the cells permitted greater control of the timing of germination, ensuring that the process didn’t start too early – when cold conditions might kill the young plant – or too late, when higher levels of competition might starve it.

“Our work reveals a crucial separation between the components within a plant decision-making centre,” explains Bassel.

“In the human brain, this separation is thought to introduce a time delay, smoothing out noisy signals from the environment and increasing the accuracy with which we make decisions. The separation of these parts in the seed ‘brain’ also appears to be central to how it functions.”

Co-author Iain Johnston likens the decision-making process to deciding whether or not to go to the cinema.

“The separation of circuit elements allows a wider palette of responses to environmental stimuli,” he says.

“It’s like the difference between reading one critic’s review of a film four times over, or amalgamating four different critics’ views before deciding to go to the cinema.”