BIO 200 Lecture Notes - Lecture 2: Microspore, Spore, Gametophyte
28 Nov 2017
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C is for conifers - they might be giants (??) Protected by two layers of tissue - integument and mega sporangium (fuel source) Hard seed coat - adaptation for dispersal of embryo. Internal food source - allows for dormancy - delay between dispersal and sprouting - allows embryo to choose when to develop. Seed plants are heterosporous - produces two different (m and f) sporangia and found in different parts of the plant. Pollen bearing cones - strobilus cones - microspore mother cells inside male sporangia - go thru meiosis to develop microspores - and again thru mitosis become pollen grains (pollen grain - male gametophyte) Pollen dispersed - individual cells (male gametes) fertilize egg. Female gametophyte is enclosed in protective tissue and is dependent on the sporophyte for nutrition. A system with two distinct types of spores evolved somewhat later. Plants of this type are said to be heterosporous (figure 27. 18b).
