Exposure to the cold triggers a process in plants known as vernalization, where the meristem - a region on the growing point of a plant where rapidly dividing cells differentiate into shoots, roots and flowers - is rendered competent to flower.
In a series of studies of Arabidopsis, a small mustard plant commonly used to study plant genetics, Amasino and his colleagues have found there are certain critical genes that repress flowering.
"The plants we've studied, primarily Arabidopsis, don't flower in the fall season because they possess a gene that blocks flowering," Amasino explains. "The meristem is where the repressor (gene) is expressed and is where it is shut off."
The key to initiating flowering, according to the Wisconsin group's studies, is the ability of plants to switch those flower-blocking genes off, so that they can bloom and complete their pre-ordained life cycles.
But how that gene was turned off was a mystery until Amasino and his group found that exposure to prolonged cold triggered a molecular process that effectively silenced the genes that repress flowering.
Another processes known as bud dormancy, which is similar to vernalization, occurs in many plants that grow in temperate climates. "Bud dormancy is not broken until the plant has 'counted' a sufficient number of days of cold to ensure that any subsequent warm weather actually indicates that spring has arrived," Amasino says.
The Wisconsin team led by Amasino has worked out much of the process of vernalization, and their hope is to add to knowledge of other cold-regulated processes such as the regulation of bud dormancy in trees. Bud dormancy may be similar to vernalization or, the Wisconsin scientists adds, it may be controlled by a completely different mechanism.
"But our study of vernalization may help us get our foot in the door," Amasino sa
Source:University of Wisconsin-Madison