Flowering height and postfloral elongation of flower stalks in 13 species of angiosperms

Abstract

All species studied, except Lilium columbianum, flowered at or above the height of the surrounding vegetation, and the difference in height was significant. For L. columbianum and Fritillaria lanceolata we showed experimentally that they set significantly more fruit when their flowers bloomed at or above the surrounding vegetation than below it, probably because they were more visible or it was easier for pollinators to get to them. In 12 of the 13 species studied the flower stalk elongated after flowering so that the fruit capsule was above the surrounding vegetation. We showed experimentally that in F. lanceolata elongation of the flower stalk occurred intrinsically and was not brought on by extrinsic factors, such as competition for light by the surrounding vegetation. Raising the seed capsule, which opens first at the top in all species, above the surrounding vegetation probably aids in the distribution of seeds. In several species, flowering stalks that bear fruit become woody and remain standing, thus keeping the capsule exposed to the wind for some time. Postfloral elongation of the flower stalk appears related to season; early flowering species elongated the most. Key words: flowering height, fruiting height, pollination, flowering season, seed dispersal.