Discovering the chemical nature of the flowering hormone (florigen, as it has been named) continues to be one of the most sought-after goals of plant scientists. The elusive florigen moves across grafts between photoinduced and uninduced plants, causing both to flower. It also moves between certain grafted long-day and short-day plants; when either is photoinduced, the other also flowers. But, as with all plant hormones, florigen is effective in extremely low concentrations and is therefore difficult to detect. A prevailing theory among plant physiologists is that florigen is actually a
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