Araceae

Alocasia macrorrhiza.

The Araceae (scientific name Araceae) are a family of herbaceous monocotyledonous plants comprising some 104 genera and more than 3000 species, easy to distinguish by their characteristic inflorescence. Araceae include the well-known rings (Anthurium), callas (Zantedeschia) and philodendrons (Philodendron). Nowadays, duckweeds (Lemna and similar), traditionally lemnaceae and here subfamily Lemnoideae, are also nested in the araceae. The non-lemnoidal Araceae are the aroid group, the traditional Araceae. The family is used by modern classification systems such as the APG III classification system (2009) and the APWeb (2001 onwards).

They are herbaceous monocotyledonous plants, sometimes arborescent or like lianas (except in Lemnoideae, where the vegetative body is reduced and globose to thaloid). Simple, entire or lobed leaves, sometimes fenestrated (with a perforated edge), often large. The flower is actually the inflorescence, the flowers are small, with no perianth or with 4-8 scaly parts. Inflorescences in spadix (spike with a fleshy axis, surrounded by a spathe, which is the one that is usually confused with the "petal" of the flower). Berry fruits.

This family is more diverse in the tropical areas of the New World, although they are also distributed throughout the Old World, in warm areas.

Description

Theoretical Introduction in Descriptive Terminology of Plants

Terrestrial to aquatic herbs, or vines with aerial, epiphytic, or floating aquatic roots, the latter many times very reduced with a more or less thaloid vegetative body. Stems often rhizomatous, or corms, or tuberous.

Wavy raphidian crystals of calcium oxalate present in specialized cells, and with associated chemicals that cause mouth and throat irritation if ingested. Cyanogenic compounds often present, and sometimes with alkaloids. Many times with laticifers, mucilage channels, or resin channels, and aqueous or milky latex.

The roots are often mycorrhizal, without root hairs.

Simple hairs, but often absent.

Alternate and spiral or distichous leaves, bifacial, sometimes basal, usually simple, the blade often well developed, sometimes strongly lobed, pinnate or palmately compound or fenestrated, usually entire, with parallel, penni-parallel venation, or reticulated, sheathing at the base. No stipules, but glandular hairs or small scales sometimes present at node within leaf sheath.

Indeterminate inflorescences, usually terminal, forming a spike of numerous small flowers packed inside a fleshy axis (a spadix), which may be sterile at the apex, usually bearing below a large leaf- or petal-like bract (a spathe). The inflorescence is reduced to 1-4 flowers in a small pocket in floating aquatic taxa (Lemnoideae).

Amorphophallus titanum is unique in having one of the most conspicuous inflorescences among angiosperms, while Wolffia (a Lemnoideae) is unique in having the smallest flowers.

Flowers small, bisexual to unisexual (plants usually monoecious), radial, without individual bracts, sessile, sometimes odorous. Normally the female flowers are arranged proximally and the male ones distally on the spadix.

Tepals usually 4-6 in 2 whorls (rarely 8) or absent, separated to basally conate, inconspicuous and often fleshy, valvate or imbricate. Absent hypanthus.

Stamens 4, 6 or 8 (rarely 1-12), filaments separated into conates, anthers sometimes poricidal (opening through pores), or longitudinally or transversely dehisced, separated into conades. In bisexual flowers, the stamens are antitepals (the pieces are arranged in the same radius as the tepals).

Varied pollen.

Carpels usually 3 (rarely 1-about 50), conate, ovary usually superior, usually as many locules as carpels, variegated placentation. 1 style and 1 stigma, pointed or capitate, short, or absent.

Ovules 1 to numerous per carpel, anatropous to orthotropic (usually anatropous and bitegmic).

No nectaries.

Fruit usually a berry (grouped in an infructescence), but occasionally utricle, drupe, or nut-like.

Seeds are oily (sometimes also starchy), endospermate (endosperm sometimes missing), with a sometimes fleshy seed coat.

Ecology

Cosmopolitan, but best represented in tropical and subtropical regions, very common in tropical forests and humid lands.

Araceae inflorescences are pollinated by many groups of insects, especially beetles, flies and bees. The inflorescence usually produces a strong odor and often heat as well. The gynoecium matures before the androecium, and when the flowers are unisexual, the female flowers mature before the male ones, facilitating cross-pollination.

In Arisaema, small (usually young) plants are male and larger (older) plants are female, thus facilitating cross-pollination.

Dispersal of green to brightly colored berries is presumably by birds or mammals. The utricles of Lemna and allies are dispersed by water.

Phylogeny

Theoretical Introduction in Philogenia

A few genera of very small floating aquatics, including Spirodela, Landoltia, Lemna, Wolffia, and Wolffiella, were once segregated into the family Lemnaceae (see Cronquist 1981, Dahlgren et al. 1985, den Hartog 1975, Landolt 1980, 1986, Landolt and Kandeler 1987), but are now seen as highly modified aroids (French et al. 1995, Mayo et al. 1995, Stockey et al. 1997, Tam et al. > 2004). In Lemna, Landoltia and Spirodela the spathe is represented by a membranous sheath, while it is completely absent in Wolffia and Wolfiella.

Although the rbcL sequences place the much larger floating aquatic aroid Pistia, in the Aroideae, it is not closely related to Lemna and so forth (French et al. 1995).

Araceae as defined here is considered monophyletic on the basis of morphology (Grayum 1990, Mayo et al. 1995 ) and cp DNA sequences (Chase et al. 1993, French et al. 1995). The family is probably sister to the rest of the Alismatales families (Chase et al. 1995b, Dahlgren and Rasmussen 1983, Dahlgren et al. 1985, Stevenson and Loconte 1995), which is why today it is placed in that order.

Araceae was divided into many subfamilies on the basis of variation in habit, leaf arrangement and morphology, inflorescence structure, flower morphology, pollen structure, anatomy, and chromosome number (Grayum 1990).). Phylogenetic relationships were also made within Araceae through sequences of rbcL (French et al. 1995), of trnL-F (Tam et al. 2004), and morphology (Mayo et al. 1998).

Gymnostachys, Orontium, Symplocarpus, and the like have condensed stems that are not exactly corms but thickened, and are sister to the rest of the family. Most other Araceae are united by their leaves with expanded lamina, a large internode in the inflorescence between the spathe and the next leaf below it, the formation of a continuation of the stem in the axil of the penultimate leaf below. the spathe, and more or less basal the placentation.

Monoecious taxa comprise a large clade, the Aroideae, with 74 genera (Zamioculcas, Dieffenbachia, Spathicarpa, Philodendron, Caladium, Syngonium, Aglaonema, Zantedeschia, Amorphophallus, Peltandra, Asarum, Arum, Arisaema, Alocasia, Colocasia, and Pistia, Mayo et al. 1998).

A second large clade, the Monsteroideae, is delimited at the base of an undifferentiated spathe (that is, without a tubular portion) that is readily deciduous or marcescent, with a distinct basal abscission zone. This group includes genera such as Monstera, Scindapsus, and Epipremnum. Spathiphyllum and allies may be related to these (French et al. 1995).

Pothos and relatives, and Anthurium, form the Pothoideae, these plants are characterized by fine leaf venation with secondary veins and tertials forming cross veins to the primaries (Mayo et al. 1998).

Taxonomy

Theoretical Introduction in Taxonomy

The family was recognized by the APG III (2009), the Linear APG III (LAPG III 2009) assigned it the family number 30. The family had already been recognized by the APG II (2003).

109 genera, 2,830 species.

The most represented genera are Anthurium (900 species), Philodendron (500 species), Arisaema (150 species), Homalomena (140 species), Amorphophallus (100 species), Schismatoglottis (100 species), Spathiphyllum (60 species), Monstera (50 species), Pothos (50 species), Xanthosoma (40 species), Dieffenbachia (40 species), and Syngonium (30 species).

For a complete list of genera see Annex:Genera of Araceae

Synonyms according to APWeb: Arisaraceae Rafinesque, Caladiaceae Salisbury, Callaceae Bartling, Pistiaceae C. Agardh

Economic importance

The starchy corms of Alocasia, Colocasia (Colocasia esculenta is taro) and Xanthosoma (the species Xanthosoma sagittifolium) are edible after appropriate treatment to remove irritating chemicals.

The Monstera berries are occasionally eaten.

Another taxon that is an important food source in the tropics ("rootstocks", leaves, seeds, or fruits) is for example, Amorphophallus.

Indians use some Araceae for medicines, fibers (from the roots), or poison for arrows.

The family contains numerous ornamentals, including Philodendron, Zantedeschia ("water lily", "cala"), Anthurium, Caladium ("elephant ear"), Colocasia, Dieffenbachia, Epipremnum, Monstera, Spathiphyllum, Syngonium, Aglaonema, Xanthosoma, Scindapsus, Spathicarpa, and Zamioculcas.