Summary
An aquatic multicellular green alga was probably the ancestor of all land plants, but these became less dependent on external water for reproduction as their conducting tissue, cuticle, stomata and seeds evolved. Their photosynthetic pigments (chlorophyll and carotenoids), their chief storage product of starch and their cellulose-rich cell walls all provide evidence for this origin. Plants have a life cycle with an alternation of generations in which haploid gametophytes alternate with diploid sporophytes. Spores resulting asexually from meiosis in sporophytes grow into gametophytes, which produce male and female cells for sexual reproduction.
The oldest fossils of land plants date from the Silurian period, somewhat over 400 million years ago.
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- Publisher: Cambridge University PressPrint publication year: 2018