BIO 101 Lecture Notes - Lecture 22: Non-Vascular Plant, Pollen Tube, Plant Reproduction
25 Jan 2017
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Document Summary
Most plants exhibit three characteristics traits: photosynthesis, multicellular embryos, alternation of generations. Each of these traits occurs in some other kinds of organisms, but only plants combine all three. Plants are distinguished from other photosynthetic organisms by their characteristic embryos. A plant embryo is attached to and dependent on its parent. The embryo grows and develops as it receives nutrients from tissues of the parent plant. Such multicellular, dependent embryos are not found among photosynthetic protists. Plant reproduction is characterized by a type of life cycle called alternation of generations. Plants have alternating multicellular haploid and diploid generations: a diploid sporophyte plant produces haploid spores through meiosis, the spores divide by mitosis and develop into haploid gametophyte plants. Gametophytes produce male and female haploid gametes (sperm and eggs) by mitosis. Gametes of opposite sex fuse to form diploid zygotes, which divide by mitosis and develop into diploid sporophytes. Green algae called charophytes are the ancestors of plants.
