FLOWERS ON DEMAND
Newly Discovered Hormone Controls When Plants Bloom
(July 31, 2007)
A group of researchers led by Professor Shimamoto Ko of Nara Institute of Science and Technology (NAIST) has identified the hormone that makes rice plants flower, while a group from the Max Planck Institute in Germany has identified the equivalent hormone in the arabidopsis plant. The teams confirmed that the two proteins, called Hd3a and FT, respectively, are produced in the plants' leaves and then transported to the tip of the stem. The theory that flower buds are formed by florigen (flowering hormone) produced in the leaves through stimulation from sunlight was first put forward in 1937. It has taken 70 years for scientists to track down the hormone.
What Is Florigen?
Plants time their flowering according to the length of the day. It is their leaves that sense how long a day is, while the flowers are actually made by the meristem at the tip of the stem. Some scientists postulated, therefore, that flowering hormone was produced in the leaves and then transported to the tip of the stem through the stem's sieve tubes.
It was previously thought that florigen was responsible for causing flowers to open, but researchers have learned that this is done by a separate hormone and that florigen is responsible for triggering the formation of buds. Countless plant hormones have been identified over the past few decades, but until recently florigen had proved elusive.
A World First
Professor Shimamoto and his NAIST team used rice plants for their research. By combining the rice plant’s Hd3a gene with a fluorescent material called GFP, they were able to observe the route by which the flowering hormone is transported. Introducing the gene to the rice plants caused them to flower early.
It is thought that these results could be used to control when plants flower. The main scientific significance of the work, though, is that the researchers have identified a hormone that had eluded plant biologists around the world for over 70 years.
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