CLASSIFICATION SYSTEM OF TAKHTAJAN BY K.DIWAKAR

CLASSIFICATION SYSTEM OF TAKHTAJAN BY K.DIWAKAR

• 1.
  SEMINOR BY K.DIWAKAR 1ST YEARMSC BOTANY RAYALASEEMA UNIVERSITY KURNOOL,ANDHRA PRADESH
• 2.
   ARMEN TAKHTAJANWAS BORN IN 1910  WAS DIED IN 2009  Armen Takhtajan who is the head of the department of higher plants at the komarov botanical institute in Leningrad,Russia, presented a system of classification,which was first published in a very preliminary form in 1942 ARMEN TAKHTAJAN
• 3.
   TAKHTAJAN wasinspired by Hailier’s attempt to create a synthetic evolutionary classification of flowering plants based on Darwinian philosophy and his approach is very much similar to that of Cronquist
• 4.
   Takhtajan’s systemof classification is basically of Bessey-Hallier tradition which considerd all evidences from different fields including morphological,anatomical,embryological,cytol ogical,palynological,paleobotanical,chemical and ultrastructural evidences while classifying Angiosperms
• 5.
   Takhtajan dividedthe Magnoliophyta(Angiosperms) into two classes-Magnoliopsida(Dicotyledons) and Liliopsida(Monocotyledonds),of which Magnoliopsida is considered primitive and Liliopsida to have been derived from Magnoliales under Magnoloiopsida .  The two classes have been further divided in to 10 subclasses, 7 under the Magnoliopsida and 3 under Liliopsida(1980),which are as follows
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  Class: Magnoliopsida (Dicots) Class: Liliopsida (Monocots) ManolidaeAlismatidae Ranunculidae Liliidae Hamamelididae Arecidae Caryophyllidae Dilleniidae Rosidae Asteridae
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   However accordingto Takhtajan’s system of classification,1997,the two classes have been divided into 15 sub classes, 11 under the Magnoliopsida and 5 under Liliopsida, which are as follows:
• 9.
   Among thesub classes,Takhtajan considered Magnoliidae to be the most primitive,forming basal group from which all other subclasses have been derived.  Among the Magnoliopsida,he considered the Asteridae the most advanced.  The three subclasses under Liliopsida(Aalismatadae,Liliidae and Arecidae) are considered to the primitive than the other sub classes of Magnoliopsida,and have been derived from Magnoliiodae.  Among Anigiosperms,the Winteraceae family is most primitive and Poaceae the most advanced
• 10.
  Takhtajan’s system isbased on 67 phyletic principles.some of the important criteria used by him to evaluate the relative degree of advancement of flowering planta are as follows:  Woody plants are primitive than herbaceous plants  Deciduous woody plants are considered evolved from ever green plants  Xylem fiber evolved from tracheids to libriform fibers,through fiber tracheids  Trilacunar or penta lacunar nodes are primitive to unilacunar nodes
• 11.
   Alternate leafarrangement is primitive while parallel venation is most advanced  Stomata with subsidary cells are primitive than those lacking subsidary cells  Cymose inflorescence is primitive than racemose  Flowes with an indefinite or variable number of floral parts are primitive  Pollen with unsculptured exine is primitive to sculptured pollen  Apocarpous gynoecium is primitive
• 12.
   Bitegmic ovulesare primitive than unitegmic ovules,while anatropous ovule is most primitive  8-nucleated polygonum type female gametophyte is most primitive  Mesogamic and Chalazogamic conditions have evolved from Porogamic conditions  Among fruits many seeded follicle is most primitive
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   The Dicots(Magnoliopsida)hasbeen disscussed prior to Monocots(Liliopsida)  The familes are small homogenous units made up of closely related genera  The Dicots begin with Magnoliales,which is highly satisfactory as Magnoiliales are universally considered to be the most primitive living Angiosperms
• 14.
   Among Monocots,the Alismatales, which are considered to be the most primitive living Monocots,have been placed at the starting point,which is satisfactory  Engler and Prantl’s division of Dicots into two traditinal groups- Archichlamydae and Metachlamydae,has been abolished in this system  Problems such as monophyly are polyphyly, interrelationhips of Dicots and Monocots, primitive position of Magnoliales, the secondary nature of anemophilous families with reduced unisexual flowers, etc.have been satisfactorily settled.
• 15.
   The mainobjection to Takhtajan’s system is his derivation of Monocotyledons from the stocks of ancestral to the Nymphaeales  The extremely narrowly defined taxa in this system has resulted in the unwarranted splitting of related groups