naked ovule develops into seed. The endosperm is haploid and develop before fertilization. • The life cycle shows alternation of generation. The sporophytic phase is dominant and gametophytic phase is highly reduced.
The photograph of some of the gymnosperms is given in Figure . Sporne ( ) classified gymnosperms into classes, orders and families. The classes include i) Cycadospsida ii) Coniferopsida iii) Gnetopsida. Figure .
: Gymnosperms a) Taxus b) Ginkgo . . Comparison of Gymnosperm with Angiosperms Gymnosperms resemble with angiosperms in the following features • Presence of well organised plant body which is differentiated into roots, stem and leaves. • Presence of cambium in gymnosperms as in dicotyledons.
• Flowers in Gnetum resemble the male flower of the angiosperm. The zygote represent the first cell of sporophyte. • Presence of integument around the ovule. • Both plant groups produce seeds.
• Pollen tube helps in the transfer of male nucleus in both. • Presence of eustele. The difference between Gymnosperms and Angiosperms were given in Table . .
Table . : Difference between Gymnosperms and Angiosperms S.No Gymnosperms Angiosperms . Vessels are absent [except Gnetales] Vessels are present . Phloem lacks companion cells Companion cells are present .
Ovules are naked Ovules are enclosed within the ovary . Wind pollination only Insects, wind, water, animals etc., act as pollinating agents . Double fertilization is absent Double fertilization is present . Endosperm is haploid Endosperm is triploid .
Fruit formation is absent Fruit formation is present . Flowers absent Flowers present . . Economic importance of Gymnosperms Table .
: Economic importance of Gymnosperms S.No Plants Products uses . Cycas circinalis, Cycas revoluta Sago Starch used as food . Pinus gerardiana Roasted seed Used as a food . Abies balsamea Resin (Canada balsam) Used as mounting medium in permanent slide preparation .
Pinus insularis, Pinus roxburghii Rosin and Turpentine Paper sizing and varnishes . Araucaria (Monkey's puzzle) , Picea and Phyllocladus Tannins Bark yield tannins and is used in Leather industries . Taxus brevifolia Taxol Drug used for cancer treatment . Ephedra gerardiana Ephedrine For the treatment