9/22/2021 Angiosperms and Gymnosperms: Introduction, Examples, Classification- FlexiPrep
FlexiPrep 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
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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.
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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.
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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.
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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.
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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
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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.
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