BSC 2011 Lecture Notes - Lecture 4: Spindle Apparatus, Phragmoplast, Oogamy
6 Jul 2016
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Monophyletic group of green plants; consists of coleochaetophytes and charophytes and land plants) Chlorophytes and streptophytes have a different microtubule structure present at end stage mitosis (telophase) before cytokinesis. Chorophytes have a phycoplast- microtubule array that organizes cell division. Phycoplast is an arrangement of transverse fibers parallel to plane of new cell wall formation. Streptophytes and other green algae have phragmoplast instead: microtubules arranged parallel to mitotic spindle; daughter nuclei start further apart, phragmoplast separates daughter nuclei and grows into a cell wall that separates cell into two daughter cells. Oogamy: chlorophytes use isogamy (gametes of similar morphology produced; not characteristically male or female gametes, streptophytes use oogamy involving production of distinct male and female gametes- sperm and egg, streptophytes retain their eggs in parental organism. Apical growth: streptophytes have primary growth at the apical meristem. Plasmodesmata: channels that join cytoplasm of adjacent cells; allow cells to communicate by exchanging materials in cytoplasm. Parenchyma: primary tissue type in streptophytes.
