Angiosperms and Gymnosperms: Introduction, Examples, Classification (For CBSE, ICSE, IAS, NET, NRA 2022)

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Introduction

  • Gymnosperms can be defined a group of plants that produce seeds not enclosed within the ovary or fruit.
  • They are known as “Naked seeds” due to the word “Gymnosperm” coming from the Greek words “gymnos” (naked) and “sperma” (seed) .
  • They belong to kingdom ‘Plantae’ and sub-kingdom ‘Embryophyte.’
  • In gymnosperms the ovules are not enclosed within the ovary wall.
  • The stems can be branched or unbranched.
  • Examples are Cycas, Picea, Abies, Juniperus, Cedrus, Thuja, etc.

Classification of Gymnosperms

Classification of Gymnosperms

Cycadophyte

  • Means individual plants are either all male or female.
  • Cycads are seed bearing and found in the tropics and subtropics.
  • They usually have pinnate leaves.
  • Their unfertilized seeds are open to the air to be directly fertilized by pollination.
  • The trunks vary from only a few centimeters to several meters tall.
Cycas Rumphii with Old and New Male Strobili

Ginkgophyte

  • A genus of highly unusual non-flowering plants.
  • A plant division of non-flowering trees originating over 250 million years ago.
  • The Ginkgo trees are large with fan-like leaves.
  • Acts as a remedy for disorders like Alzheimer՚s.
  • These trees are further resistant to pollution.
  • These are resilient against diseases and insect infestations.
  • Fossils attributable to the genus Ginkgo first appeared in the Early Jurassic.
Classification of Gymnosperms: Ginkgophyte

Geophyte

  • These consist of tropical plants, trees, and shrubs.
  • Consists of some 70 species across the three relict genera.
  • They also have flowery leaves with a soft coating.
  • The coating reflect an ancestral connection of gymnosperms with that of angiosperms.
  • Geophytes possess vessel elements in their xylem.
Classification of Gymnosperms: Geophyte

Coniferophyte

  • These are gymnosperms, cone-bearing seed plants.
  • Also known as the Pinophyte and conifers.
  • These are evergreen and hence during the winters do not shed their leaves.
  • Male and female cones form needle-like structure.
  • Examples include Cedars, Giant sequoia, pines, redwood Douglas firs, cypresses, firs, junipers, etc.

Gymnosperms Life Cycle

Gymnosperms Life Cycle

Male Cones

  • Presence of microsporophyll՚s that contain microsporangia.
  • Haploid microspores are produced Microsporangia.
  • While some of the microspores develop into male gametes (pollen grains) , the rest degenerate.

Female Cones

  • They consist of ovules containing megasporangium.
  • Female cones are bigger than male cones and are located higher up in the tree.
  • Haploid megaspores and a megaspore mother cell are produced.

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