Determination and Differentiation of Leaf and Petal Primordia in Impatiens balsamina

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Abstract
The development of primordia as leaves, petals, or as organs intermediate between leaves and petals can be regulated by photoperiod in Impatiens. In intermediate organs only some parts of the organ differentiated as petal, and then only in some cell layers. Allometric measurements of primordium shape suggested that intermediate organs may begin development as petals, and that their intermediate character at maturity resulted from a switch of some parts of the organs from petal to leaf development when the primordia were between 0.5 and 1 mm long. In reverted apices made to re-flower, primordia were not completely determined as leaves until they were about 750 μm long. Determination typically occurred first at the tips and last at the bases of these primordia. The determination of primordia as leaves or petals in Impatiens is discussed in relation to primordium determination in other species. It is suggested that the lack of commitment to flower may result in relatively late primordium determination in Impatiens.