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GYMNOSPERMS

GYMNOSPERMS

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GYMNOSPERMS

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  1. GYMNOSPERMS BY S.Sreedevi B.Amudha U.Kalaivani M.Kalaivani K.Deepa

  2. In Gymnosperms, seeds are exposed and not covered with pericarp. The trees are tall, pyramid like or conical in appearance. Gymnosperms occur in northern temperature zone.In India these plants occur in Himalayan regions. In Tamilnadu Pinus and Cycas which are gymnosperms occur in Ooty and Kodaikanal.

  3. Commonly more gymnosperms is classified into four distinct groups. CLASSIFICATION OF GYMNOSPERMS Cycadales Ginkgoales Coniferales Gnetales

  4. CYCADALES • The stem of the saprophyte is columnar. The compound leaves occur in cluster at the tip of the stem. The young leaves are coiled like a watch spring as in the fern which is called cycadales. • Example:Cycas

  5. GINKGOALES • The two kinds of branches occur in saprophyte of this group. They are long and short shoot. Broad leaves occur in cluster at the end of the short shoots. • Example:Ginkgo

  6. CONIFERALES • The two types of branches are seen in the saprophyte of coniferales. The scale leaves occur in the long shoots and needle like leaves occur in cluster on the dwarf shoots. • Example:Pinus

  7. GNETALES • The leaves of the Gnetales are either broad or narrow and they are arranged in opposite manner. The vessels are also occur in almost all the Gnetales. • Example:Gnetum.

  8. POLLINATION AND FERTILIZATION • The pollen grain are yellow colour. The floating pollen reach the ovule easily.The female cone remains closed till fertilization and is called pollination. The microspore germinates and reaches the archegonium and fertilization takes place. The fertilized egg becomes a zygote. Male cone Female cone

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