Question

Short note on distribution of gymnosperm.

Answer 1

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The name gymnosperm derived from the Greek word, ‘gymnospermos’ (‘gymnos’ – naked, ‘sperma’ – seed) meaning naked seeds; ovules are naked and freely exposed to pollination, and the fertilized seeds are not enclosed by carpels. The ovules are embedded in a leaf–like structure (homologous to a leaf), or on a scale or megasporophyll (homologous to a shoot) or on the apex of a (dwarf) shoot. Gymnosperms are also characterised by various other characters such as absence of companion cells, presence of orthotropous, unitegmic three-layered ovules, anemophilous pollination, absence of double fertilization, formation of endosperm before fertilization, presence of polyembryony and manoxylic wood.

Gymnosperms are currently placed in five distinct and widely divergent orders namely Cycadales, Ginkgoales, Taxales, Coniferales and Gnetales. Hooker (1888) reported 42 taxa (40 species and 2 varieties) belonging to 16 genera under three orders namely Gnetaceae, Coniferae (with 6 tribes viz. Cupressineae, Taxidieae, Taxeae, Podocarpeae, Araucarieae and Abietineae) and Cycadaceae from then British India, of which only 33 species and 2 varieties were from the present political boundaries of India.

According to Maarten & al. (2011) there are 1026 species in 84 genera in the world in almost all continents, except Antartica. Singh & Srivastava (2013) reported 146 species and 8 varieties (indigenous/introduced) of gymnosperms in 46 genera belonging to 12 families from India.

In addition to their ornamental value, the Gymnosperms are of much use to the human beings as they provide valuable timbers, wood pulp, soft wood, resins, edibles and medicines.

LIST OF FAMILIES AND GENERA OF GYMNOSPERMS IN INDIA

Sl. No.

Family

Genera

1.

Araucariaceae

Agathis Salisb.

Araucaria Juss.

2.

Cupressaceae

Callitris Vent.

Calocedrus Kurz

Chamaecyparis Spach

Cupressus L.

Fitzyroya Lindl.

Juniperus L.

Taiwania Hayata

Tetraclinis Mast.

Thuja L.

Thujopsis Siebold & Zucc. ex Lindl.

Platycladus Spach

Widdringtonia Endl.

3.

Cycadaceae

Cycas L.

4.

Ephedraceae

Ephedra L.

5.

Ginkgoaceae

Ginkgo L.

6.

Gnetaceae

Gnetum L.

7.

Pinaceae

Abies Mill.

Cedrus Trew

Larix Mill.

Picea A. Diet.

Pinus L.

Pseudotsuga Carriere

Tsuga Corr.

8.

Podocarpaceae

1.                     Afrocarpus (Buchholz & N.E. Gray)

2.                    Nageia Gaertn.

3.                     Podocarpus L’ Herit ex Pers.

9.

Taxaceae

1.                     Amentotaxus Pilger

2.                    Cephalotaxus Sieb. & Zucc. ex Endl.

3.                     Taxus L.

10.

Taxodiaceae

1.                     Cryptomeria D. Don

2.                    Cunninghamia R. Br. ex Rich. & A. Rich.

3.                     Metasequoia Hu & W.C. Cheng

4.                    Sequoiadendron J. Buchholz

5.                    Sequoia Endl.

6.                    Taxodium Rich.

11.

Welwitschiaceae

1.                     Welwitschia Hook.f.

12.

Zamiaceae

1.                     Bowenia Hook.

2.                    Dioon Lindl.

3.                     Encephalartos Lehm.

4.                    Lepidozamia Regel

5.                    Microcycas A. DC.

6.                    Macrozamia Miq.

7.                     Stangeria T. Moore

8.                    Zamia L.

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