Plant genetics: Fast flowering

Poplars are fast-growing trees of cool, temperate climates that find use in the manufacture of pulp, matches and packing cases. They are also widely grown for shelter and for ornamental purposes. Poplars are deciduous trees that flower in the spring soon after new leaves arise. Flowers develop from the axils of these leaves, and arise on short stems carrying a string of flowers (a catkin). They are either male or female depending on the individual tree. As in most plants, poplars do not flower immediately, but need to undergo a period of purely vegetative growth before they will produce floral shoots. This means they may flower only after eight or more seasons of growth, a major constraint to breeding programs. Because they are readily grown from cuttings, many poplar plantations are clones of just one individual, so one aim of breeding programs is to increase the diversity of forms available.