Heterochronies, or changes in the timing of developmental processes, have fascinated biologists since the last century. Since plants develop by sequential maturation of their organs and segments, the mechanical semi-independence of the individual organs makes their development much less canalized than that of the more highly integrated animals, and allows more developmental variation. Heterochronies have been found to cause form changes of all plant parts and generations: from gametophyte development to the formation of vegetative parts of the sporophyte as well as its reproductive parts. Last year's symposium organized by Tucker and Grimes included reports of heterochonies in inflorescence development. In this symposium we will explore heterochronies in floral and female gametophyte development and evolution, connect changes in leaf form and function with their genetic regulation, and discuss developmental mechanisms and their effect on evolution.

Key words: Heterochrony in plants