Pandanus utilis

Within the family Pandanaceae, the genus Pandanus composes the largest genus. It is estimated that there are between 500 and 1,000 species within this genus; the Plants of the World Online database accepts 562 species. Pandanus utilis, otherwise known as the common screwpine, is one species in this genus. It was discovered by the French naturalist Jean Baptiste Bory de Saint-Vincent in 1801–02 and described in 1804. The origin of P. utilis has traditionally been thought to be Madagascar, but more recently the Mascarene Islands have been suggested as a possible place of origin. As with many Pandanus, the trunk has aerial prop roots. It is found in tropical areas, and has an upright trunk that is smooth with many horizontal spreading branches with annular leaf scars. Old leaf scars spiral around the branches and trunk, like a screw. The anatomy of Pandanaceae stems can be distinguished from other monocotyledons by the presence of a compound vascular bundle. This bi- or tripolar vascular bundle has two or three distinct conduction strands encased by a common bundle sheath. These roots not only anchor the tree but also keep it upright during times of heavy winds and rain in tropical regions. The prop roots can be diameter. P. utilis is dioecious, with the female and male reproducing structures occurring on different plants. Individual plants are either male, producing microspores, or female, producing megaspores. This plant being unisexual allows it to cross-fertilize with other individuals. The male plants produce fragrant creamy-white flowers in long spikes. These long spikes have 8–12 stamens inserted in a pseudo-umbel on slender columns long. The female plants produce fruit slightly resembling oversized pine cones, changing from green to yellow, orange, or reddish when ripe. The female structure has a 3–8 celled ovary crowned by a sessile stigma. This species is naturalised in several of the Mascarene islands, where it coexists with a number of other indigenous and endemic Pandanus species. It can usually be distinguished from these however, by the tip of the free portion of each drupe of its fruit-head, which usually does not have an areole. The tip is usually also cleft between the stigmas. The fruit-heads are very variable, but usually stand out by being up to 20 cm wide and containing 100–200 drupes. == Ecology ==

P. utilis grows well near the sea, being salt-tolerant. It is a strictly tropical tree that will not survive frost. It grows in full sun to partial shade but prefers at least 6 hours of direct sunlight. Seeds take two to three months to germinate. == Use and management==

Common screwpine has many uses. In coastal areas, it has been used for erosion control due to its numerous aerial roots. == Chemical Composition ==

Pandalisines A and B are two novel indolizidine alkaloids from this plant. == Pests and Diseases ==

Few diseases have been recorded on members of the Pandanaceae within Papua New Guinea or worldwide. With the exception of a single suspected virus disease causing yellow mottling on the leaves and an MLO disease causing decline in P. utilis in Florida all diseases recorded on Pandanus have been caused by fungal pathogens. No major pests are of much concern to this plant. ==Gallery==