Basal Angiosperms

The basal angiosperms are a broad group of the most primitive flowering plants. They do not belong to either the monocots or eudicots but were for a long time lumped together with the eudicots into a well-known group called the dicots. The basal angiosperms are mostly woody plants that produce seeds and flowers.

There is roughly 9000 basal angiosperm species currently existing on Earth that can separated into two categories: the ANITA basal angiosperms and the Magnoliids. The majority of species belong to the Magnoliids with only a couple of hundred of the most primitive species being ANITA basal angiosperms.

Characteristics of basal angiosperms

The traits of the basal angiosperms to not tend to fit very well into the characteristic categories used to distinguish between monocots and eudicots. Often basal angiosperms will have what appears to be both monocot and dicot characteristics. For a long time the basal angiosperms and eudicots were clumped together as dicots due to both groups having two embryonic leaves. They also tend to have net-like vein patterns in their leaves as eudicots do, but their pollen only ever has one pore or groove – the same as monocots – and not three as seen in eudicots.

Basal angiosperms have a number of characteristics that show their primitive evolution. They lack any real differentiation between their petal and their sepals and have very little fusion within their floral parts such as petals, stamens and carpels. They tend to have multiple, flattened stamens and multiple carpels, and their fruits are typically single-chambered and dry. Basal angiosperms also have a less advanced vascular system than other angiosperms.

Distribution of Basal angiosperms

Basal angiosperm flowerBasal angiosperms are found all around the world, with a few exceptions in extreme climates such as Antarctica and the Saharan desert. They enjoy most of their success in tropical and warm-temperate rainforests.

A number of the ANITA basal angiosperms are confined within Australia, Asia and Oceania; a fact that supports the idea that the basal angiosperms originated in Australia. In comparison, Magnoliid species tend to have much more variable distributions.

Diversity and taxonomy

All up the basal angiosperms make up less than 3% of all plant species. The estimated diversity of the basal angiosperms is around 9000 species and the vast majority of those species belong to the Magnoliids. There is a total of 10 orders of basal angiosperms – three belonging to the ANITA basal angiosperms and the remaining seven making up the Magnoliids.

Magnoliids

The Magnoliids are a large group of related basal angiosperms including roughly 9000 species. They include trees, shrubs, herb and vines, and are most common in tropical and warm temperate regions. Commonly known Magnoliids include black pepper, avocado, cactus, nutmeg, pawpaw and of course the Magnolias. They are aromatic plants that include a number of orders such as Magnoliales, Laurales, Piperales, Canellales and Caryophyllales.

The order Magnoliales are commonly trees are shrubs that produce scented, simple flowers and have dry aggregate fruits. This order includes nutmeg, pawpaw, Magnolias, the tulip tree and custard apple to name a few. The Laurales is the most diverse order of Magnoliids and includes aromatic trees or shrubs such as cinnamon and the laurels. Piperales is an order of shrubs, vines, herbs and epiphytes that includes the peppers.

ANITA basal angiosperms

The ANITA basal angiosperms include three orders of plants that include only a few hundred species. Each order is not necessarily closely related to the other two but they are known to be evolutionarily distinct from the remaining basal angiosperms that belong to the Magnoliids. The order Amborellales has only a single species, Amborella trichopoda, an evergreen shrub that is found only in New Caledonia in the South Pacific.

The remaining two orders from the ANITA basal angiosperms are the Austrobaileyales and the Nymphaeales. The order Nymphaeales includes a number of aquatic herbs including the water lilies and is the second oldest lineage of basal angiosperms after the order Amborellales. Species of Nymphaeales have a much wider distribution than any other ANITA basal angiosperm and is distributed through most places on Earth apart from in deserts and the polar regions of Antarctica and the Arctic. The order Austrobaileyales includes a number of shrubs and vines that are found in parts of Asia, eastern North America, a small spot in northern Australia and in the Caribbean.


Interesting fact

  • An Amazonian water lily has large, floating leaves that are buoyant enough for people to float on.

Last edited: 21 May 2015

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