Nature Commun. 6, 6450 (2015)

Credit: © SHAPENCOLOUR / ALAMY

The leaves of plants can take on many different shapes from simple flat vaguely oval disks seen in Arabidopsis to the complicated horn shaped traps of the carnivorous pitcher plants. Kenji Fukushima and colleagues have studied the purple pitcher plant, Sarracenia purpurea, and found that changes in the orientation of cell division in the developing leaf form the basis of the creation of their lethal ‘trumpets’.

The diversity of leaf structures is created by the interplay of the layers of cells lying on their adaxial and abaxial sides. These two surfaces are determined by the mutually exclusive expression of different sets of transcription factors, with cell division and growth being stimulated at the junction between these domains. If the layers grow at approximately the same rate simple flat leaves result but any disparity produces mechanical tensions that mould more exotic morphologies.

Fukishima et al. saw that the early development of the S. purpurea leaf looked no different to that of Arabidopsis but soon the abaxial region began to dominate restricting adaxial identity to a band on one side of the organ. In the distal part of the developing leaf this produced a hollow, but in the proximal region a ridge of adaxial tissue is maintained creating a tube. Using microscopy to inform mathematical modelling the researchers showed that although the cells forming the hollow divide longitudinally to the leaf axis, the division plane of the cells underlying the ridge is rotated through 90 degrees. This periclinal division is sufficient to create the different structures in the growing leaf and so the ornate architecture of the adult pitcher.