Many thanks, Gurcharan ji. Nice to get this bare minimum knowledge about the Gymnosperms. The listing of family / genera is a great help. Looking forward to watch exciting uploads. Lots of thanks in advance to Dr. R. C. Srivastava ji for volunteering to coordinate the fortnight.
Regards. Dinesh On Thu, Nov 28, 2013 at 12:43 PM, Gurcharan Singh <[email protected]>wrote: > Dear members > With an expert from BSI Dr. R. C. Srivastava kindly agreeing to coordinate > Gymnosperms Fortnight should be a very useful one. > Gymnosperms constitute an interesting group of plants, usually shrubs > or trees which produce seeds but don't have fruits like flowering plants as > ovules (developing seeds) are naked and not enclosed in an ovary. Here are > some details from my book: > > "Gymnosperms comprise a small group of seed plants characterized by naked > seeds (gymno- naked, sperms- seeds) and absence of vessels (except > Gnetopsids), endosperm formation independent of fertilization and commonly > resulting in halploid endosperm (absence of double fertilization), absence > of sieve tubes and companion cells. Group is represented by nearly 15 > families, 80 genera and nearly 820 species, mostly consisting of evergreen > trees and shrubs, distributed worlwide and forming extensive forests in > North America, Europe and Asia. They represent some of the largest > (Sequoiadendrod giganteum of California), tallest (Sequoia sempervirens of > California and Oregon) and longest living (Pinus aristata) organisms in the > world. > Gymnosperms are woody trees or shrubs, herbaceous plants being absent from > the group. The plants have well-developed tap root system, sometimes with > symbiotic nitrogen fixing cyanobacterium (coralloid roots of Cycas) or > mycorrhizae (Pinus). Vascular cylinder has xylem with tracheids with > bordered pits and phloem with sieve cells. Leaves lack lateral veins > (except in Ginkgo with dichotomous veins and Gnetum) , but are compensated > by transfusion tissue. Sporangia are heterosporous, microsporangia and > megasporangia borne on microsporophylls and megasporophylls, respectively; > latter often arranged in distinct cones. Each microsporangium produces > numerous microspores arranged in tetrads, since each microspore mother cell > undergoes meiosis to produce four haploid microspores. Microspore nucleus > undergoes repeated divisions to form male gametophyte, which develops wall > to become a pollen grain. The megasporangium, known as ovule, on the other > hand, develops a single megaspore mother cell, surrounded by nucellus and > integument, with an opening known as micropyle, at the end of integument. > Of the four haploid megaspores resulting after meiosis, three degenerate, > and only one megaspore is functional. Latter, after repeated nuclear > divisions and wall formations produces a female gametophyte with several > archegonia, consisting of an enlarged egg cell and two or four neck cells. > Pollen grains of gymnosperms are carried by wind, land on micropyle and > adhere to sticky fluid released by the female gametophyte. The pollen > germinates to produce a pollen tube, that grows through nucellus and > releases two sperms. One fuses with the egg to form zygote after > fertilization. Latter develops into an embryo within matured ovule known as > seed." > > The paper by Dr. R. C. Srivastava: "Diversity and economic importance of > living gymnosperms in India" National Academy Science > Letters<http://www.cabi.org/ISC/Default.aspx?site=144&page=4066&LoadModule=CABISEARCHRESULTS&query=do:%22National+Academy+Science+Letters%22> > 2006 Vol. 29 No. 3/4 pp. 75-84 gives following in the Preface: > > "It reports the occurrence of 101 species, 4 varieties and 1 forma > belonging to 33 genera in the present political boundaries of the country. > Out of these, 7 taxa are endemic to India: *Amentotaxus assamica, Cycas > beddomei* [*C. circinalis*], *C. circinalis* var.*orixensis, Gnetum > montanum* var. *megalocarpum, G. contractum, G. latifolium* var. > *macrocarpus* and *Pinus wallichiana* var. *parva"* > > *The Following Genera are recorded in our database* > *Cycadaceae* > > Cycas<https://sites.google.com/site/efloraofindia/species/a---l/cl/cycadaceae/cycas> > > *Zamiaceae* > Dioon<https://sites.google.com/site/efloraofindia/species/m---z/z/zamiaceae/dioon> > Zamia<https://sites.google.com/site/efloraofindia/species/m---z/z/zamiaceae/zamia> > > Ginkgoaceae > Ginkgo<https://sites.google.com/site/efloraofindia/species/a---l/g/ginkgoaceae/ginkgo> > > *Pinaceae* > Abies<https://sites.google.com/site/efloraofindia/species/m---z/p/pinaceae/abies> > > Cedrus<https://sites.google.com/site/efloraofindia/species/m---z/p/pinaceae/cedrus> > > Picea<https://sites.google.com/site/efloraofindia/species/m---z/p/pinaceae/picea> > > Pinus<https://sites.google.com/site/efloraofindia/species/m---z/p/pinaceae/pinus> > > > *Cupressaceae* > Cryptomeria<https://sites.google.com/site/efloraofindia/species/a---l/cl/cupressaceae/cryptomeria> > > Cupressus<https://sites.google.com/site/efloraofindia/species/a---l/cl/cupressaceae/cupressus> > > Juniperus<https://sites.google.com/site/efloraofindia/species/a---l/cl/cupressaceae/juniperus> > > Platycladus<https://sites.google.com/site/efloraofindia/species/a---l/cl/cupressaceae/platycladus> > > Sequoiadendron<https://sites.google.com/site/efloraofindia/species/a---l/cl/cupressaceae/sequoiadendron> > > Thuja<https://sites.google.com/site/efloraofindia/species/a---l/cl/cupressaceae/thuja> > > Taxodiaceae > Cunninghamia<https://sites.google.com/site/efloraofindia/species/m---z/t/taxodiaceae/cunninghamia> > > Taxodium<https://sites.google.com/site/efloraofindia/species/m---z/t/taxodiaceae/taxodium> > (These need to be shifted to Cupressaceae, or some from Cupressaceae > shifted here if family is to be recognised). Recent treatments merge > Taxodiaceae with Cupressaceae. > > Podocarpaceae > Podocarpus<https://sites.google.com/site/efloraofindia/species/m---z/po/podocarpaceae/podocarpus> > > Araucariaceae > Agathis<https://sites.google.com/site/efloraofindia/species/a---l/ar/araucariaceae/agathis> > > Araucaria<https://sites.google.com/site/efloraofindia/species/a---l/ar/araucariaceae/araucaria> > > Taxaceae > Taxus<https://sites.google.com/site/efloraofindia/species/m---z/t/taxaceae/taxus> > > Ephedraceae > Ephedra<https://sites.google.com/site/efloraofindia/species/a---l/e/ephedraceae/ephedra> > > Gnetaceae > > Gnetum<https://sites.google.com/site/efloraofindia/species/a---l/g/gnetaceae/gnetum-montanum> > > > I am sure more taxa would be added after the completion of this episode. > > Dr. Gurcharan Singh > Retired Associate Professor > SGTB Khalsa College, University of Delhi, Delhi-110007 > Res: 932 Anand Kunj, Vikas Puri, New Delhi-110018. > Phone: 011-25518297 Mob: 9810359089 > http://www.gurcharanfamily.com/ > http://people.du.ac.in/~singhg45/ > > -- > You received this message because you are subscribed to the Google Groups > "efloraofindia" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/indiantreepix. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "efloraofindia" group. 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