In this research, scientists studied the genes CO and FT that were first isolated from the annual plant Arabidopsis. The genes in that plant are responsible for the day-length regulation of flowering. They discovered that the same genes had been conserved through millions of years of separate evolution and also performed similar functions in aspen trees.
To their surprise, however, the researchers found that the CO/FT combination also controlled the cessation of vegetative tree growth in the fall ?something that Arabidopsis plants, which die after a single growing season, do not need to do.
These processes, scientists say, reflect a critical tradeoff between tree growth and survival. Temperate trees have to stop growing and go dormant in the winter or they literally freeze to death.
"From an evolutionary perspective, it's easy to understand why forest trees don't flower and produce seed and pollen earlier," Strauss said. "When they are young, the trees that survive need to focus their energy on growth and height in order to compete for sunlight with other trees, and only later in their life do they divert energy to produce seed."
Strauss noted that for the same reasons, any releases of such early-flowering genes into wild populations are very unlikely to be of ecological concern, as trees bearing them would have a competitive disadvantage when growing with wild forest trees, and thus would not spread to any significant degree.
It also appears that the CO/FT genetic combination is critical to help trees adapt to local conditions, the researchers found. They studied aspen trees from different populations, and found that trees adapted to colder northern climates shut down growth earlier in the summer
Source:Oregon State University