01:119:101 Lecture Notes - Lecture 14: Microsporangia, Archegonium, Tracheid
25 Feb 2016
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Document Summary
Plant diversity: evolved from group called charophytes (green algae); closest relative of land plants. What was it about ancient charophytes that lent itself to evolution: characteristics of charophytes enabled move to land, many species live in shallow water around edges of ponds and lakes. Durable polymer layer prevents zygotes from drying out. Similar to what is found in plant spores: land plants share traits with only charophytes, rings of cellulose- synthesizing proteins. Synthesize cellulose microfibrils of cell wall: structure of flagellated sperm. Formation of structure called pragmoplast: phragmoplast. Assemble themselves and form between daughter nuclei during cell division. Gives rise to cell walls of new daughter cells: derived traits of plants. Key traits which are found in plants but not in charophytes. Summarized in 29. 3: alternation of generations, alternate between two multicellular stages, gametophyte haploid organism produces haploid gametes. Mitosis: sporophyte produces by fusion of gametes. Produceshaploid spores by meiosis: multicellular dependent embryos.
