He says that a drop in temperature slows down a plant's metabolism largely because the enzymes that drive these biochemical reactions don't work so well in the cold. Seasonal patterns not only affect seeds but the whole plant, says Associate Professor Brian Atwell from Macquarie University, who studies how plants grow in harsh environments. At this time, if environmental conditions are favourable - say there's enough water around - the seed can then germinate, again a process governed by plant hormones. Ooi says it's only when a seed has been exposed to low temperatures for long enough, a process known as cold stratification, that plant hormones trigger the end of dormancy. So, seeds lie dormant, metabolising at low levels, waiting for spring. They just haven't been in Australia long enough to adapt to local conditions. They're still adapted to the conditions in which they evolved," he says. "Garden species from the northern hemisphere evolved to survive these harsh conditions. If the seeds are from an introduced species that originated from a colder climate, they will be genetically programmed to survive winter, says Dr Mark Ooi, a plant ecologist who studies seed dormancy at the University of Wollongong. Let's start with seeds in the ground, perhaps tucked away in a corner of your vegie patch. It's part survival mechanism, part housekeeping exercise, all meant to help plants gear up for warmer days ahead. This period of dormancy, where plants are ticking over but not growing, comes with the falling temperatures and reduced day length that winter brings.īut this dormancy is much more than a period of suspending animation. As winter approaches, deciduous trees transfer nutrients from the leaves into the branches where they're deposited in the bark (Source: frankiefotografie/iStockPhoto)Įven though Australia doesn't experience the long, harsh winters of the northern hemisphere, your lawn might have stopped growing, leaves are falling off deciduous trees and some seeds are weeks or months away from germinating.
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