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Annonaceae

life science Maturity 5-7 Next article →

The Annonaceae are a massive family of flowering plants. They include trees, shrubs, and occasionally lianas, which are woody climbing vines. Many people know them as the custard apple or soursop family. This group is the largest family within the order Magnoliales. Scientists have identified about 2,400 known species across 108 different genera.

Annona muricata Blanco1.196
Annona muricata Blanco1.196

Most of these plants thrive in tropical environments. About 900 species are found in the Neotropics. Another 450 species live in the Afrotropics. The remaining species are located in the Indomalayan region.

These plants possess very specific physical characteristics. Their bark, leaves, and flowers are often aromatic, meaning they have a strong scent. The stems and leaves usually grow in an alternate or two-ranked pattern. This means they do not grow directly opposite one another on the stem. The bark is often fibrous, and the internal pith can be septate or diaphragmed. This refers to how the internal structure is divided by thin partitions.

Uvaria ovata II
Uvaria ovata II

The flowers are typically trimerous, which means they have parts in multiples of three. They usually have six petals arranged in two unequal layers. Some species may have as many as fifteen petals.

Inside the flower, the reproductive parts follow a complex arrangement. The stamens, which produce pollen, are often numerous, ranging from ten to twenty or even more. These stamens are arranged spirally and can form a ball or a flat-topped mass. They have short, stout filaments and linear or oblong anthers. The female parts, known as pistils, can be single or fused together. Each pistil contains one or more ovules. The seeds produced from these plants are often oily and possess a fleshy, brightly colored cover. They also contain ruminate endosperm, which is nutritive tissue surrounding the embryo.

Researchers use various methods to organize this family into groups. They use morphological evidence, which is the study of physical shapes, and molecular evidence from DNA. Based on the Angiosperm Phylogeny Group II system, the Annonaceae are most closely related to the Eupomatiaceae family. Modern classification recognizes four distinct subfamilies: Anaxagoreoideae, Ambavioideae, Annonoideae, and Malmeoideae. The subfamily Anaxagorea is considered a sister clade to the rest of the family. This means it branched off early in the family's history. The largest groups are Annonoideae and Malmeoideae, which contain most of the known species.

History shows that this plant family is incredibly ancient. The oldest fossil evidence is from the genus Futabanthus. This fossil was discovered in Japan and dates back to the Late Cretaceous period. This places the minimum age of the family's most recent common ancestor at approximately 89 million years ago. Scientists believe the family's wide tropical distribution happened after the Gondwanan supercontinent broke apart. They suggest the plants spread through geodispersal during the Eocene or through more recent long-distance dispersal events.

Many species in this family provide food for humans. Genera like Annona, Asimina, and Rollinia produce edible fruits. Common examples include the custard apple, cherimoya, and soursop. The American pawpaw, or Asimina triloba, is found in the Eastern United States.

Asimina triloba red fern farm
Asimina triloba red fern farm

Some species have historical uses in flavoring. For example, the petals of the sacred earflower were used to flavor chocolate before cinnamon became common. Today, people still use these dried petals to flavor coffee and other drinks.

Ylang-Eden
Ylang-Eden

While many parts are useful, some can be dangerous to health. The fruits, seeds, and leaves contain compounds called acetogenins. These are natural neurotoxins, meaning they can affect the nervous system. Research suggests that these compounds are linked to a neurodegenerative disease called a tauopathy. This is a condition where tau protein builds up in the brain. In places like Guadeloupe, consumption of soursop has been associated with atypical Parkinsonism. This is thought to be caused by the annonacin found in the seeds and leaves.

Annona muricata Blanco1.196
Annona muricata Blanco1.196
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File:Annona muricata Blanco1.196.png
Annona muricata Blanco1.196.png
File:Uvaria ovata II.JPG
Uvaria ovata II.JPG
File:Asimina triloba red fern farm.jpg
Asimina triloba red fern farm.jpg
File:Ylang-Eden.jpg
Ylang-Eden.jpg
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