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Gymnosperms (evolution of of the ovule (megaspores were retained inside of…
Gymnosperms
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produce seeds
Hetrosprous
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seeds typically contain megaphylls (generally large leaves with several/many veins can be modified to needles or scales
seeds are extreme forms of hetrospory and is considered a modified version of an ovule. It is a modified ovule consisting of megaporangium(produces mega spores )
also consist of 1/2 integuments
after fertilization,the integuments develop ito the seed coat
Types of gymnosperms
Coniferophyta
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pines
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after year one or two the pines start to produce leaves in bundles or fascicles . these fasicicles, wrapped at the base by a series of small scale like leaves which are actually short shoots in which the activity of the apical meristem is restricted
in the stem of the pine and other conifers secondary growth begins early and leads to the internal formation of substantial amount 2ndary xylem
the microsporangia and megasporangia of pines and most conifers are borne on different cones or strobili
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leaves are well suited for their growth condition where water may be scare :star:thick cuticle
:star:stomata are sunken beow the leaf surface
:star: the mesophyll or ground tissue consist of parenchyma which increases surface area
:star: one or two resin ducts
:star:one or two vascular bundles located side by side consisting of a xylem and phloem surrounded by transfusion
tissue
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