Write merits and demerits of Takhtajan system of classification.
Answers
The following points highlight the five eminent plant taxonomists. The taxonomists are: 1. John Hutchinson 2. Armen Takhtajan 3. Arthur Cronquist 4. Rolf M.T. Dahlgren 5. Robert Thome.
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Principles of Hutchinson’s System of Classification:
Hutchinson’s plant classification was mainly based on the following principles :
(i) Evolution has generally been consistent, and it is both downwards and upwards and does not necessarily involve all organs at the same time.
(ii) The dicots are primitive to the monocots, and the shrubs and trees in any one genus or family are more primitive than herbs. At the same time in any one genus or family, the shrubs and trees are older in comparison with climbers.
(iii) Perennials are older than biennials and annuals.
(iv) The aquatic flowering plants are considered to have been derived from terrestrial ancestors.
(v) Spiral arrangement of vegetative and floral leaves is primitive to cyclic arrangement.
(vi) Simple leaves are more primitive than compound leaves.
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Armen Takhtajan’s System of Classification:
Takhtajan’s system of classification is basically of Bessey-Hallier tradition which considered all evidences from different fields including morphological, anatomical, embryological, cytological, palynological, paleobotanical, chemical and ultrastructural evidences while classifying Angiosperms.
He considered Angiosperms to be monophyletic in origin and that they arose from some ancient group of Gymnosperms. The Monocotyledons are, considered to have been derived from primitive Dicotyledons.
Takhtajan divided the Magnoliophyta (Angiosperms) into two Classes – Magnoliopsida (Dicotyledons) and Liliopsida (Monocotyledons), of which Magnoliopsida is considered primitive and Liliopsida to have been derived from Magnoliales under Magnoliop