Angiosperm Reproduction Review: Plants are characterized by an alternation of generations. – haploid (n) - gametophyte... reproduce sperm and eggs via mitosis. Fertilization results in a diploid zygote (grows into a sporophyte) – diploid (2n) - sporophyte... reproduces spores via meiosis producing the gametophytes

Seed formation after fertilization Pollen from another plant meets the stigma and germinates developing into a pollen tube digesting its way toward the ovule (consisting of an egg and 2 polar nuclei) once in the vicinity of the ovule 2 sperm are released for double fertilization – 1 sperm fuses with the egg (2n) – 1 sperm fuses with the 2 polar nuclei (3n) to form the endosperm a nutritive tissue of the seed after fertilization the ovule forms a seed and the ovary (structure containing the ovule) grows into a fruit

most plants exhibit self-incompatibility recognizing pollen from themselves and ensuring that fertilization occurs only with genetically different plants

Structure of the mature seed the embryonic tissue forms a cotyledon (heart shaped structure) and the embryo elongates – epicotyl contains 2 miniature leaves – radicle forms the embryonic root – the hypocotyl becomes the stem between the roots and forming leaves the seed coat forms once the cotyledon is fully developed from the integument layer of the ovule and hardens as the structure dehydrates – the structure is now in a dormant state awaiting germination – monocots - seeds with 1 part (corn) – dicots - seeds seeds with 2 parts (legumes) – ripened fruits signal the completed development of the seed

Seed to seedling (dicot) imbibition - process of germination – uptake of water by the seed due to low water potential – causes the seed to expand and rupture (like plasmolysis in a cell) – metabolism of the endospore begins as the nutrients are transferred to growing portions of the embryo Growth radicle (root) is first to emerge the hypocotyl extends to break the soil surface and expose the epicotyl (first leaves) to the sunlight

Asexual reproduction - produces clones via mitosis – accomplished through adventitious roots – asexual production of seeds (apomixes) – fragmentation - separation of parts that grow into whole plants...