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Botanical Buzz - How do plants know when it's spring?

Monday, September 22, 2014

In the spirit of the 2014 Science Cafe@Dubbo Regional Botanic Garden 9am-2pm Saturday 23rd August (running parallel with Dubbo Sustainable City Expo) this article will address the question “How do plants know when it’s spring?”.

Every September the Japanese Flowering Crabapples in Shoyoen, Dubbo Regional Botanic Garden announce the arrival of spring with an abundance of sweetly scented, light pink blossoms and crimson buds.

The timing of the eagerly awaited blossoms is crucial. If the blossoms come too early they may be damaged by frost. Furthermore, if the blossoms arrive before the pollinators are ready, there is a risk that not all of the flowers will be pollinated.

Like all plants, the crabapples have an internal biological clock called a circadian rhythm. The circadian rhythm is governed by the daily cycle of day and night (light and dark) as the Earth rotates every 24 hours. The term "circadian" comes from the Latin words for about (circa) a day (diem).

Advances in microbiology have led to the discovery that circadian rhythms are controlled by "clock genes" that trigger the production of “clock proteins”. The levels of these proteins rise and fall in rhythmic patterns in response to light stimuli.  These oscillating biochemical signals control various functions.

When the crabapple’s circadian clock detects the shorter days of autumn it initiates a biochemical signal that it is time to drop its leaves. When the clock senses the longer days of spring, it sends the signal that it is time to burst into blossom.

The biological clocks of plants influence a host of other behavioural responses including preparation for sunrise by raising leaves in readiness for photosynthesis to convert sunlight into food and the opening and closing of leaf pores.

Understanding the genetic mechanism of circadian rhythms will help scientists genetically modify agricultural crops to adapt to climate change.

Science Cafe is an Inspiring Australia initiative supported by the Australian Government as part of National Science Week.

                                                                                                                                     By Ian McAlister & Karen Hagan