Cm. Kampny et al., QUANTITATIVE COMPARISON OF FLORAL DEVELOPMENT IN VERONICA-CHAMAEDRYS AND VERONICASTRUM-VIRGINICUM (SCROPHULARIACEAE), American journal of botany, 80(4), 1993, pp. 449-460
Development in Veronica and Veronicastrum was studied to elucidate the
growth patterns responsible for differences between their mature flow
ers. Nineteen floral dimensions were measured on buds from initiation
to anthesis, and representative stages were recorded with the scanning
electron microscope. Bivariate plots indicate the heterochronic chang
es responsible for the derived flower form of Veronica. The growth pat
terns of the gynoecium and androecium were little changed. The calyx o
f Veronica showed slower size increase at the early stages, but contin
ued to grow after that of Veronicastrum had stopped. The most striking
change occurred in the corolla lobes of Veronica, where growth was re
tarded until the beginning of style formation, but afterward was accel
erated relative to that of Veronicastrum. The corolla tube of Veronica
remained short due to a later onset of growth and slower enlargement
later in development. Multigroup principal components analysis (M-PCA)
was used to summarize the measurements. The distribution of points al
ong M-PC 1 describes size increase during floral development. Along M-
PC 2 the trajectories of the two taxa diverge after the beginning of s
tyle growth, while along M-PC 3 they differ from the earliest stages o
n, corroborating differences observed with the scanning electron micro
scope. M-PCA can thus be used to portray differences in patterns of fl
oral development, facilitating simultaneous quantitative comparisons o
f two or more taxa.