Ct. Philbrick et A. Novelo, OVULE NUMBER, SEED NUMBER AND SEED SIZE IN MEXICAN AND NORTH-AMERICAN, SPECIES OF PODOSTEMACEAE, Aquatic botany, 57(1-4), 1997, pp. 183-200
The purpose of this study is to present and analyze empirical data on
seed production and seed characteristics of Mexican and North American
species of Podostemaceae. Species of Marathrum, Oserya, Podostemum, T
risticha and Vanroyenella were studied. Podostemaceae flower annually
in abundance. Eight of the nine species examined produced seeds in abu
ndance. Podostemum ricciiforme (Liebmann) Royen seldom produces seed.
Significant differences occurred between annual and perennial species
in mean ovule and seed number. In Podostemaceae, the outer integument
of the seed plays a central role in the establishment of seeds on soli
d substrate. Significant differences between species were observed whe
n comparing overall seed width and length for dry versus wetted seed (
cf. percent contribution of the hydrated outer integument). In all spe
cies there was a significant positive correlation between integument s
ize and seed size. It remains to be shown whether the observed differe
nces in seed characteristics are ecologically significant, e.g. equate
with differences in microhabitat attachment, or reflect differential
selection for seed establishment. Clear patterns of relationships betw
een seed production and geographic distribution of species studied her
ein are lacking. Questions that remain to be addressed concerning seed
ecology are discussed. (C) 1997 Elsevier Science B.V.