The origin and early evolution of plants on land

摘要: The origin and early diversification of land plants marks an interval unparalleled innovation in the history plant life. From a simple body consisting only few cells, (liverworts, hornworts, mosses vascular plants) evolved elaborate two- phase life cycle extraordinary array complex organs tissue systems. Specialized sexual (gametangia), stems with intricate fluid transport mechanism (vascular tissue), structural tissues (such as wood), epidermal structures for respiratory gas exchange (stomates), leaves roots various kinds, diverse spore-bearing (sporangia), seeds tree habit had all by end Devonian period. These other innovations led to initial assembly plant-dominated terres- trial ecosystems, great effect on global environment. Early ideas were based living groups, but since discovery exceptionally well-preserved fossil Rhynie Chert, research has focused almost exclusively record 1,2 . During 1970s, syntheses palaeobotanical stratigraphic data emphasized Late Silurian periods critical during which occurred , identified group fossils (rhyniophytes, such Cooksonia Rhynia) likely ancestral forms 2 They