Armen Takhtajan was a russian plant taxonomist, presented a system of classification of Angiosperms for the first time in 1942 and its revised edition in 1954,1966,1969,1980.
He was the president of 12th International Botanical Congress held in Leningard 1975.
He developed a preliminary phylogenetic diagram of the orders of higher plants in a paper on Structural type of Gynoceium and Placentation.
He purposed his classification and Russian which was later on translated as Flowering plants -Origin and Dispersal by C jeffry which became very popular, and the last version was published in 1997.
It was an phylogenetic system based upon his 67 Phyletic principles.
He recognized 92 orders and 418 families.
According to him Angiosperms are of Monophyletic origin and evolved from some ancient group of gymnosperms.
Takhtajan divided the sub-classes into
1.Super-Order
2.Orders
3.Families
Sub Classes are large natural groups which are grouped on the basis of all known information.
Takhtajan divided the division Magnoliophyta also called as angiospermae into two classes-
1.Magnoliopsida(dicotyledons) 2.Liliopsida(monocotyledons)
He furthur divided class magnoliopsida into seven seven sub classes and twenty super ordewrs .But in revised classification eleven subclasses were there.
The Liliopsida is furthur divided into three sub classes and eight superorders . But in revised classification six sub-classes were there.
The order Magnoliales was considered as most primitive among flowerings plants and other angiosperms derived from magnoliales.
Among Monocots the orders Alistmales is considered to be more primtive.
The highly evolved order among dicots was Asterales and Arales among monocots.
Families are all homogenous unit, comprising closely related genera.
The system is based on 67 clear phyletic principles.
It considers Angiosperms are of Monophyletic origin.
The system is more phylogenetic compared to other systems.
Monocots are belived to originated from Dicots.
Angiosperms are considered as single division named Magnoliophyta divided into Liliopsida and Magnoliopsida.
The sub-class Magnoliales are considered as most basic group from which other sub-classes have originated.
The sub-class are not found on single character but all known information.
Order Alistmales considered to be more primitive among monocotyledons.
Despite Takhtajan tried to remove deficiencies of his system in 1947 some of the
defects were left such as: -
The main objection of the system is the derivation of monocot from Nymphaeles.
The system is highly phylogenetic but not helpful for identification and adoption in Herbaria as it provides classification only up to family level.
Although the system is based on all information available, but more weightage was given to cladistics.
Takhtajan suggested that smaller families are more natural. But according to Stevens this is incorrect. Monocots were placed after dicots but whereas in recent system of classification monocots placed between angiosperms eudicots.
The families Winteraceae and Canallaceae are two separate orders whereas multigene analysis have provided support in their relationship.
Dahlogram and Thone considers angiosperms to deserve a class rank.
Bubble diagram for his latest version of classification 1997 was not available.
Woody plants proceeds the Herbaceous plants.
Sparingly branched trees give rise to trees with numerous slender branches.
Evergreen trees proceeds the decidous trees.
Simple leaves proceed the compound leaves.
Pinnate venation proceed the palmate venation .Reticulate venation proceed the parallel venation.
Alternate leaf arrangement proceeds the opposite leaf arrangement.
Cymose infloroscence is primitive and racemose is derived one.
Apocarpy proceed Syncarpy.
Entomophilly proceed anemophilly .
Endospermic seeds are primiitive while non endospermic seeds are advanced.
The monocot embryo has evolved from dicot embryo.
QUESTION PRACTICE
Who used the word Magnoliopsida for Dicotyledons? (Assistant professor Exam)
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