It’s all about the soil temperature

By changing their sensitivity to plant hormones, dormant seeds detect and respond to changes in soil temperatures say researchers who believe their work may have important implications for food security.

A team from the University of Warwick’s School of Life Sciences looked at gene expression over the dormancy cycle of Arabidopsis seeds in field soils to see how it might be affected by the seasons. Using a strain whose seedlings emerge in late summer and early autumn, combined with modern molecular biology and traditional seed ecology, they found gene sets related to dormancy and germination are highly sensitive to seasonal changes in soil temperatures.

“Our research sheds new light on how genetics and the environment interact in the dormancy cycling process,” said Dr Steve Footitt. “By looking at seeds over an annual cycle we now have a clearer idea of how seeds sense and react to changes in the environment throughout the seasons so they know the best time to emerge into plants.”

A balance between the hormones abscisic acid (ABA) and gibberellic acid (GA) is thought to be central to controlling dormancy and germination. One set of genes is regulated by ABA – which is linked to dormancy – and another set linked to GA, which act to increase germination potential.

As the soil warms up, seeds become less sensitive to ABA and more sensitive to GA, which spurs them toward germination. Once dormancy begins to recede, increased sensitivity to light, nitrates and the differences between day and night temperatures play a greater role in signalling that this is the right time to germinate.

“Many will have seen how the amount of weeds in their garden differs with the weather from year to year,” said Footitt. “Understanding how this happens will help us to predict the impact future climate change will have on our native flora and the weeds that compete with the crops we rely on for food.”

This work – published in Proceedings of National Academy of Sciences – was funded by DEFRA, and Footit and his colleague Professor Bill Finch-Savage have won a BBSRC grant to investigate further how climate has an impact on dormancy cycling, and how genetics and environment interact in the dormancy cycling process.

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