EEB337 20121030.docx

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University of Toronto St. George
Ecology & Evolutionary Biology

EEB337 20121030 Poales: - Order that includes grass-like families - Monophyletic group within the monocots, based on DNA sequence data - Multiple origins of wind pollination - Sedges and rushes form a well supported clade within the order - Juncaceae - Cyperaceae - Poaceae Key to families: - 1. Perianth members in 3s, stiff, greenish or brownish; stamens 6 or 3; fruit a 1 to many- seeded capsule; leaves usually wiry and round in t.s.  Junacaceae (Rushes) - 1. Perianth apparently absent; stamens 3; fruit with a single seed; flowers aggregated in short, scaly clusters (spikelets)….2 - 2. Leaves in 3 ranks; leaf sheaths tubular (not split); stems often 3-sided in t.s. and solid between nodes; each flower of spikelet subtended by single bract (Glume)  Cyperaceae (sedges) Rushes: Junacaceae - “graminoid” habit - Small family (6 genera, 400 species) - Mostly rhizomatous herbs of temperate habitats - Flowers usually bisexual, wind-pollinated, often in highly branched clusters - Perianth consisting of 6 tepals - Placentation various - Fruit a loculicidal capsule - Small enough to capture pollen grains  with stigmatic hair - 3 lobbed ovary - Inflorescences apparently lateral, with one erect bract appearing to be a continuation of the stem…  Juncus effuses – note bract standing on top - Inflorescence terminal, subtended by two or more spreading bracts or leaves Sedges: Cyperaceae - “Graminoid” habit - Large family (122 genera, 4500 species)  more than 10 times species than Juncaceae - Mostly rhizomatous herbs of temperate habitats - Leaves often three-ranked, stem solid, triangular in section  This family is more abundant in higher elevations - C3 and C4 photosynthesis, leaf anatomy present  C4: Photosynthesis that uses 4 carbon molecules in carbon fixation  It’s done in an architectural way. The process is made very efficiently by means of architecture of anatomy of the leaf cells  Net result is that C4 photosynthesis is specially efficient in elevated temperatures and in reduced water availability - Flowers unisexual or bisexual, usually wind-pollinated, in 1- to many-flowered spikes or spikelets - Perianth absent, or reduced to bristles, hairs, or scales - Placentation basal, the ovule arising from the floral apex - Fruit an achene, the single seed within not joined to the ovary wall - Genus Rhynchospora colorata - Genus Eriophorum gracile  In this genus the perianth bristle elongated after fertilization and aid
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