Life-history monographs of Japanese plants. 6: Convallaria keiskei Miq. (Convallariaceae)

Abstract

The life-history characteristics of Convallaria keiskei Miq. (Convallariaceae), an Asian lily of the valley, are described. This is a perennial species of temperate broad-leaved deciduous forests in the Japanese islands and adjacent Far East regions. Convallaria keiskei is a clonal plant and depends on two reproductive modes, sexual reproduction via seeds and clonal growth. New aerial shoots (sheath leaves) elongate and appear above ground in late April to May, and subsequent flowering takes place in late May to June On the forest floor, there are two distinct vegetative aerial shoots, shoots with a single leaf and those with two leaves, as well as two-leaved shoots that bear an inflorescence. As found in two other Convallaria species, Convallaria montana of North America and Convallaria majaris of Europe, flowers of C. keiskei have a mild fragrance, and nectar-glands are developed at the base of the corolla. The number of ovules per flower ranges from 3 to 17 with an average of 12. Convallaria keiskei is a typical insect-pollinated outbreeder and, in general, pollinators belong to the orders Coleoptera and Diptera. In addition, the observed self-incompatibility suggests that pollen from ramets of a genet have little importance in the reproduction of this species, and that sexual reproduction requires pollen from different genets. The fruits ripen in July to August, and are globose berries, approximately 6 mm in diameter, and red or reddish brown when matured. The number of seeds produced per fruit ranges from 1 to 14 (average 4), and the fruit-setting and seed-setting rates are 32% and 11%, respectively. Fruit sets are distinctly influenced by the numbers of neighboring compatible flowers.