Reproductive Biology and Uniform Culture of Portulaca in Hawaii

Abstract

Ten taxa of Portulaca that occur in Hawaii (P. lutea, P. molokiniensis, P. oleracea, P. pi/osa, P. sclerocarpa, P. villosa, two imperfectly known species, and two cultivars) were included in a study of reproductive biology and uniform cultivation. The response of plants under uniform conditions upholds the merger of the reputed Hawaiian endemic P. cyanosperma with P. pilosa. All Portulaca taxa in Hawaii are autogamous, and in most instances large numbers of seeds are set even when the flowers are totally undisturbed. Some taxa are facultatively cleistogamous, but even in chasmogamous forms the flowers are open for only about 3-9 hr. The cultivars were the only taxa observed to attract pollinators, but P. molokiniensis, which was not studied in nature, appears to have adaptations for biotic pollination. Most of the portulac as studied have capsular fruit that require about 13-17 days to mature, but in P. sclerocarpa the fruits are thick-walled and indehiscent and require about 28 days for maturation. The life cycle ranges from about 8 weeks in most cases to several months in P. molokiniensis. However, individuals of most taxa typically flower and fruit man y times during one growing season. Seeds were generally nondormant, but partial seed dormancy was encountered in P. molokiniensis.