Dr. Manishika Jain in this lesson explains Plant Kingdom – Gymnosperms ? ?
Seed Plants (Spermatophyta)
Ovule includes integument & nucellus (both are diploid & belong to sporophytic generation)
Adaptation to Land plants
• No external water supply ?
• Development of pollination
• Transform megasporangium to ovule (has 1 megaspore mother cell), fertilize egg in ovule & production of embryo
• Transformation of ovule into seed for dispersal
• Extensive root system
• Vascular system/tissues
• Cambium for secondary growth
• Bark for protection
Gymnosperms
Seeds exposed (naked) on megasporophyll as latter are not folded as pistils
900 species
Perennial & woody (tallest is Sequoia sempervirens & smallest is Zamia pygmia)
Pollen cones & seed cones
Pollination is direct/wind (anemophily)
? Male gametophyte – 2 male gametes & one is functional
Seed contains endosperm (for future growth of seedling)
? Xylem – no vessels (except some gnetophyte)
? Phloem – without companion cells & sieve tubes
? Sieve cells – no arranged end to end in rows
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