Flower on order

Genetic engineering can soon make plants bloom on cue and change the shape of a plant as required

Published: Monday 15 September 1997

 Instant bloom: George Couplan genetic tinkering can produce plants that can be made to bloom as and when required. Doused with the correct chemical trigger, they spring into bloom within days. George Coupland and his colleagues at the John Innes Centre, Norwich, say that if plants could be persuaded to flower as and when required, farmers would be able to control the time of the harvest of their crops and flower growers could produce a continuous supply of blooms ( New Scientist , Vol 155, No 2090).

Coupland's cooperative weeds are an offshoot of a growing body of knowledge about the process of flowering. In the past few years, researchers have pieced together a map of the genes that link flowering to environmental signals. They have identified a genetic switch that determines whether a bud turns into a flower or a normal shoot. They have even begun to understand how plants choose where flowers will appear on the shoot. The fruits of this research -- from trees that bloom when they are just a few centimetres high to embryonic plants that begin the flowering process within the seed -- show that a change in the right genes can dramatically alter when and how plants bloom.

Geneticists have identified four main groups of flowering genes. The first pushes the plant towards blooming during the long summer days. The second delays flowering when the days are short. Another relays information about the temperature and tips the balance towards producing blooms when the weather warms up in spring. A final group responds to the plant's internal state and presses the flowering button more insistently as plants grow older and bigger. This allows factors such as rainfall, soil quality and disease, which affect a plant's growth rate to influence flowering. Under natural conditions, it may bloom any time from around three weeks to nearly a year after germination. But as Coupland's research shows, a sufficiently strong push on a single pathway can change the decision-making circuits, creating plants that flower on demand.

Coupland's group used a gene that promotes flowering when the days are long, encouraging plant genes to flower in summer. Up to a point, the more daylight hours there are when the plant is growing, the quicker it will come into bloom. Plants carrying only mutant copies of the gene, however, lose this response. Length of day has no effect on how quickly they flower. In Canada, where the short summer means that the oilseed rape crop does not always have time to ripen, forcing plants to flower a couple of weeks early might make all the difference.

Genetic flower arrangement could also be just around the corner. If one could turn all the lateral shoots into lateral flowers, one could have a rose which not only flowers at the apex of each branch, but also flowers in all the axils. A less colourful but more practical application would be crops tailored to produce more fruits or seeds or to make these more accessible for harvesting.

The process of genetically arranging flowers could also be used to change the shape of a plant. Normally, growth occurs only at the shoot tip and at the bud at the base of each leaf. Each growing point can form either a flower or a shoot, but not both. so manipulating the position of flowers can alter a plant's shape.

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