GEOL 107 Lecture Notes - Lecture 17: Lepidodendron, Trimerophytopsida, Marchantiophyta
25 Oct 2017
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Important: the discussion of land plants in cowen 2013, chapter 8 (first half, pp. 98-104) is much shorter than in previous editions of his book and omits several critical diagrams. These essential diagrams are attached as . pdf files: background. Molecular phylogeny shows land plants were probably derived from green algae (chlorophyta) Oldest green algae approximately 850 ma, fully marine (ancestors of terrestrial plants) Co2 is more easily extracted from air than water. Air is seldom at 100% humidity, so above-ground tissues will dry out (need to find a means of getting water from soil up into the photosynthesizing tissues) Reproduction and dispersal must use some method other than water transport. Terrestrial plant life is dominated by embryophytes (= bryophytes + vascular plants) Bryophytes (polyphyletic group comprising liverworts, hornworts and mosses, cowen et al. , 8. 3-8. 4) have thin-walled, water-conducting cells but lack xylem. Waxy cuticle on leaves cuts down on evaporation.
