Family Pandanaceae

Pandanaceae R. Br.

Habit and leaf form. Trees, shrubs, and lianas. Rhizomatous. Self supporting (usually with prop roots at the base of the stem), or epiphytic, or climbing; when climbing, root climbers. Stem growth conspicuously sympodial (appearing dichtomous). Pachycaul. Helophytic, or mesophytic (often maritime). Leaves medium-sized to very large; alternate; spiral (appearing so, through torsion of the stem), or tristichous (usually, in fact), or four-ranked (rarely); leathery; imbricate; sessile; sheathing. Leaf sheaths with free margins. Leaves simple. Lamina entire; usually linear, or lanceolate; parallel-veined; without cross-venules. Leaves eligulate. Vernation plicate.

General anatomy. Plants without silica bodies. Accumulated starch exclusively ‘pteridophyte type’.

Leaf anatomy. Stomata present; tetracytic.

The mesophyll containing mucilage cells (with raphides); containing calcium oxalate crystals. The mesophyll crystals raphides, or druses (?), or solitary-prismatic. Minor leaf veins without phloem transfer cells (Pandanus). Vessels present; end-walls scalariform.

Stem anatomy. Secondary thickening absent (with compound vascular bundles). Xylem with vessels. Vessel end-walls scalariform. Sieve-tube plastids P-type; type II.

Root anatomy. Root xylem with vessels; vessel end-walls scalariform.

Reproductive type, pollination. Unisexual flowers present. Plants dioecious, or polygamodioecious. Female flowers with staminodes (often), or without staminodes. Pollination anemophilous, entomophilous, ornithophilous, and cheiropterophilous (mostly by wind).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles, in racemes, and in heads (often crowded into dense panicles). Inflorescences terminal; spatheate. Flowers minute, or small.

Perianth of ‘tepals’ (?—Sararanga), or absent (Freycinetia and Pandanus); 3–4 (Sararanga); when present, joined (cupuliform); 1 whorled; in Sararanga, more or less sepaloid (?).

Androecium of male-fertile flowers 10–100 (?—‘many’, the situation in Freycinetia and Pandanus complicated by the fact that homologies are so unclear that it is not possible with any certainty to distinguish ‘flowers’ from aggregates of flowers). Androecial members branched (ostensibly), or unbranched (?); free of the perianth; variously coherent (often with stemonophores), or free of one another (and then no trace of flower structure discernable). Stamens 10–100 (‘many’ — regardless of what constitutes a single flower); filantherous, or with sessile anthers. Anthers basifixed; dehiscing via longitudinal slits; appendaged (via apical prolongation of the connective), or unappendaged. Tapetum amoeboid. Pollen grains aperturate; 1 aperturate; sulcate, or ulcerate; 2-celled.

Gynoecium (1–)80 carpelled. The pistil 1 celled (when monomerous), or 2–100 celled (to ‘many’, when syncarpous). Gynoecium monomerous (rarely), or apocarpous to syncarpous; of one carpel (rarely), or eu-apocarpous to eu-syncarpous (syncarpous in Sararanga and Freycinetia, carpels free or connate in Pandanus); superior. Carpel (when apocarpous or unilocular) 1–5 ovuled. Placentation when apocarpous or one-carpelled marginal, or basal. Ovary when syncarpous 1 locular (in Freycinetia), or 2–100 locular (i.e. to ‘many’). Placentation when bi- multilocular axile (Freycinitia), or basal. Ovules when plurilocular 1–5 per locule (carpels uniovulate in Pandanoideae, several-ovuled in Freycinetioideae); anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle (Freycinetia), or not contributing to the micropyle. Embryo-sac development Polygonum-type, or Allium-type. Antipodal cells formed; 3 (Freycinetia), or 64–200 (Pandanus, where the antipodals are supplemented by migration of nuclei from elsewhere); proliferating, or not proliferating. Hypostase present. Endosperm formation nuclear.

Fruit fleshy to non-fleshy; more or less an aggregate, or not an aggregate. The fruiting carpels (when apocarpous) coalescing into a secondary syncarp, or not coalescing. The fruiting carpel indehiscent; drupaceous (12–80 in Sararanga). Fruit when syncarpous, indehiscent; when syncarpous, a berry. Gynoecia of adjoining flowers generally combining to form a multiple fruit. The multiple fruits coalescing (to varying extents, in Pandanus), or not coalescing. Fruit 1 seeded. Seeds endospermic. Endosperm oily, or not oily. Seeds minute. Seeds with starch. Embryo well differentiated (small). Cotyledons 1. Embryo straight. Testa without phytomelan.

Seedling. Hypocotyl internode present (long). Seedling collar not conspicuous. Cotyledon hyperphyll compact; non-assimilatory. Coleoptile absent. Seedling cataphylls absent. First leaf dorsiventral. Primary root ephemeral.

Physiology, biochemistry. Not cyanogenic. Alkaloids absent (3 species). Proanthocyanidins absent. Flavonols absent. Ellagic acid absent. Saponins/sapogenins absent. Anatomy non-C4 type (Freycinetia, Pandanus).

Geography, cytology. Temperate (warm, a few), or temperate to sub-tropical. Southwest tropical Africa, Madagascar, India to Thailand, Malaysia and Australia. X = 30 (with aneuploidy).

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Pandaniflorae; Pandanales. APG 3 core angiosperms; Superorder Lilianae; non-commelinid Monocot; Order Pandanales.

Species 700. Genera 3; Freycinetia, Pandanus, Sararanga.

Economic uses, etc. Pandanus leaves are used for thatch, matting, clothing and containers, and the immature fleshy perianths of some species are edible.

Illustrations.
• Technical details: Pandanus, Freycinetia.
• Pandanus candelabrum (Thonner).