Angiosperms are the flowering plants also known as Magnoliophyta. The botanical term "Angiosperm" meaning ‘bottle or vessel’ is derived from the ancient Greek. These are the most diverse group of land plants. Angiosperms are seed-producing plants and the distinguished features of angiosperms over gymnosperms are angiosperms bear flowers, endosperm within the seeds and the production of fruits that contain the seed. According to the botanists the flowering plants diversified and widespread 120 million years ago. The classification of the flowering plants also has a long history. In the past, classification systems were typically produced by an individual botanist or by a small group resulting large number of systems. Different systems and their updates were generally favored in different countries. Bentham and Hooker’s system was popular in the Britain and the Engler’s system was famous in the Europe etc. These systems were introduced before the availability of genetic evidences and angiosperms were classified using their morphology and biochemistry. After the 1980’s genetic evidences were available and phylogenetic methods came into the classification procedures. In the late 1990s, an informal group of researchers from major institutions worldwide came together and they established the Angiosperm Phylogeny Group (APG). The objective was to provide a widely accepted and more stable point of reference for angiosperm classification. APG I was published in 1998 as their first attempt in Annals of the Missouri Botanical Garden. The initial 1998 paper by the APG made angiosperms the first large group of organisms to be systematically re-classified primarily on the basis of genetic characteristics. The group emphasized the need for a classification system for angiosperms at the level of families, orders and above. The existed systems are rejected is because they are not phylogenetically classified. The outline of a phylogenetic tree of all flowering plants became established and several well supported major clades involving many families of flowering plants were identified. The new knowledge of phylogeny revealed relationships in conflict with the then widely used modern classifications. The principles of APG system are retaining the Linnean system of orders and families, Use of monophyletic groups (Consist of all descendants of a common ancestor), taking a broad approach to defining the limits of groups such as orders and families and use of term ‘clades’ above or parallel to the level of orders and families. A major outcome of the classification is the disappearance of the traditional division of the flowering plants into two groups, which are monocots and dicots. Even though there are several controversies about APG the botanists worldwide are influenced by the concept and are currently practice the system.

1. Angiosperm
Phylogeny Group I
(APG I)
PABASARA GUNAWARDANE

2. Angiosperms
•The botanical term "Angiosperm", from the Ancient
Greek
•The flowering plants
•Also known as Magnoliophyta
•The most diverse group of land plants
•Seed-producing plants
•Flowers, endosperm within the seeds, and the
production of fruits that contain the seed are the
distinguished features

3. Flowering plants
diversified and
widespread
120
million
yearsago

4. History of Angiosperm
Classification
•Artificial System: On the basis of one or few
characters of plants
•Natural system: A large number of
morphological characters were taken into
consideration, in the natural systems of
classification
•Phylogenetic system: Based on evolutionary
sequence as well as genetic relationships among
different groups of plants

5. Angiosperm Classification
•In the past, classification systems were typically
produced by an individual botanist or by a small
group
•The result was a large number of systems
• Different systems and their updates were
generally favored in different countries

6. Bentham & Hooker System

7. Engler System
Adolf Engler (1844–1930)

8. Takhtajan System
Armen Takhtajan

9. Cronquist System
Arthur Cronquist

10. •Before the availability of genetic evidences, angiosperms
were classified using their morphology and
biochemistry
•After the 1980’s genetic evidences were available
and phylogenetic methods came into action

11. Angiosperm Phylogeny Group
•In the late 1990s, an informal group of researchers
from major institutions worldwide came together
•Established APG
•Objective was to provide a widely accepted and
more stable point of reference for angiosperm
classification
•APG I was published in 1998 as their first attempt
in Annals of the Missouri Botanical Garden

13. Angiosperm Phylogeny Group
•The initial 1998 paper by the APG made angiosperms the
first large group of organisms to be systematically re-
classified primarily on the basis of genetic characteristics
•Emphasized the need for a classification system for
angiosperms at the level of families, orders and above
• Existed systems are rejected is because they are
not phylogenetic

14. Angiosperm Phylogeny Group
•The group published 462 families of angiosperms
grouped into 40 monophyletic orders
Monophyletic: Consists of an ancestral species and
all its descendants

15. •The outline of a phylogenetic tree of all flowering plants
became established
•Several well supported major clades* involving many
families of flowering plants were identified
•the new knowledge of phylogeny revealed relationships in
conflict with the then widely used modern classifications
• It became clear that none of the previous classifications
accurately reflected phylogenetic relationships of
flowering plants
* A clade is a group of organisms that consists of a common ancestor and all its lineal descendants

16. Principles of the APG system
•The Linnean system of orders and families should
be retained
•Groups should be monophyletic (Consist
of all descendants of a common ancestor)
•A broad approach is taken to defining the limits of
groups such as orders and families
•Above or parallel to the level of orders and
families, the term clades is used more freely

17. Features of APG
•Formal, scientific names are not used above the level of
order, named clades being used instead
•A substantial number of taxa whose classification had
traditionally been uncertain are given places
•Alternative classifications are provided for some groups
•A major outcome of the classification is the
disappearance of the traditional division of the flowering
plants into two groups, monocots and dicots (The monocots are
recognized as a clade, but the dicots are not)

19. Why Dicots became Eudicots??
• The angiospermous plants were divided into two distinct
classes: the monocotyledons or Monocotyledoneae, and
the dicotyledons or Dicotyledoneae
• The two cotyledons descriptive of the traditional
classification ‘dicots’ also occur in the Coniferales,
Cycadales, and Gnetales (Judd and Olmstead 2004) and is
now thought as an ancestral feature of the flowering
plants and not distinct to any group within.

20. • The genetic approach is more modern, precise and
objective
• The system is a group-work
• Use of monophyletic groups (i.e. groups which consist of
all descendants of a common ancestor) provides a
descriptive link between the groups
• A substantial number of taxa whose classification had
traditionally been uncertain are given places
Advantages of APG

21. • Named clades being used instead of Formal, scientific
names above the level of order. thus, eudicots and
monocots are not given a formal rank
• Taxa which were uncertain to rank were ranked but 25
families are still remain uncertain position
• Alternative classifications are provided for some groups
(e.g. the Fumariaceae can either be treated as a separate
family or as part of Papaveraceae)
• What came first and what came after is not clearly
determined
Disadvantages of APG

22. • APG II (2003) and APG III (2009) has been introduced
and updated APG I
Updating APG

23. • A significant number of major herbaria, including Kew,
are changing the order of their collections in
accordance with APG
• The influential World Checklist of Selected Plant
Families (also from Kew) is being updated to the APG
III system
• In the USA, a recent photographic survey of the plants
of the USA and Canada is organized according to the
APG II system.
• In the UK, the latest edition of the standard flora of the
British Isles is based on the APG III system
Influence of APG

24. • The Angiosperm Phylogeny Group (1998) An ordinal classification for the family of flowering plants
Annals of the Missouri Botanical Garden Vol. 85, No. 4 (1998), pp. 531-553
• Angiosperm Phylogeny Group II (2003), An update of the Angiosperm Phylogeny Group classification for
the orders and families of flowering plants: APG II (PDF), Botanical Journal of the Linnean Society 141:
399–436
• Ben G. Bareja (2012) Monocots, Dicots and Eudicots Distinguished. Available at:
http://www.cropsreview.com/monocots.html (Accessed 22 September 2015)
• Michal Yakir (2013) Which Phylogenic systematics should be used. Available at: http://www.michal-
yakir.de/cronquist-apg-1.html (Accessed 22 September 2015)
• Ho Dinh Hai (2012) APG Systems of Plant Classification. Available at:
http://www.edibleplantsinvietnam.com/apg-systems-of-plant-classification.html (Accessed 22
September 2015)
References