Angiosperms and Gymnosperms: Introduction, Examples, Classification

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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

Classification of Gymnosperms

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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.

Cycas Rumphii with Old and New Male Strobili

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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

Classification of Gymnosperms: Ginkgophyte

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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

Classification of Gymnosperms: Geophyte

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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

Gymnosperms Life Cycle

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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.