Download AP Notes Plant Reproduction 09

Plant reproduction
 Structures: http://www.cals.ncsu.edu/course/ent591k/nectar_guide.html
o Sepal: protects the floral bud, leaflike
o Petals: advertise for pollinators
o Stamen: male parts
 Anther:* sac with pollen grains (Meiosis occurs to produce pollen)
 Filament: stalk, holds up anther
o Carpel:* female parts
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Stigma: sticky, catches pollen grains
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Style: long tube, pollen tube grows (self-incompatibility acts)
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Ovary: has ovules, embryo sacs develop
 More about flowers
o All the organs present = complete flower; no = incomplete
o Both sexes on a flower = perfect flower; (imperfect flowers: both sexes on same plant = monocot; no = dicot)
Plant Sex
 Alternation of Generations
 Fertilization in Mosses (bryophytes) and Ferns (pteridophytes)
o Gametophyte makes egg and sperm  sperm swim to egg
 Fertilization in Gymnosperms
o Pollen and egg produced in cones  Generally wind pollinated
 Fertilization in Angiosperms
o Pollen development: cells develop within the anther
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Flower  stamen  anther  pollen sacs (sporangia)
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Spores: formed when cell undergo meiosis, forms 4 haploid cells
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Development: Meiosis  4 Microspore  4 pollen grains
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Pollen Grain: 3 parts
▫ Generative cell: divides when mature into 2 sperm
▫ Tube cell: creates tube that grows down style
▫ Pollen Wall: resistant outer layer, cause of allergies
o Embryo Sac Development
 Flower  Carpel  Ovary  Ovule (sporangia)
 Spores: central cell undergoes meiosis, forms 4 haploid cells – 3 degenerate, 1 survives
 Development: Meiosis  4 megaspores 1 megaspore  1 embryo sac
 Embryo Sac:* female gametophyte. surviving haploid spore, through
mitosis becomes multicellular
▫ 2 synergid cells – direct pollen tube formation
▫ 3 antipodal cells – no known function
▫ 2 polar nuclei in middle form endosperm
o Pollination: transfer pollen from anther to stigma
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Ways: wind, water, pollinators, self-pollination
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Cross pollination
▫ Use 2 different parents – increase diversity, good for evolution
▫ Barriers: chemical (self-incompatible), timing, structural
o Double Fertilization*http://www.emunix.emich.edu/~ghannan/systbot/doublefertanimation.html
 Pollen lands on stigma Tube cell: directs growth of pollen tube into ovary
 Generative cell: makes two sperm  Pollen tube enters ovary, piercing embryo sac and releasing sperm
 Two Sperm:
▫ Endosperm:* formed when one sperm fuses with 2 polar nuclei to create 3n cells, forms nutritive tissue
▫ One sperm merges with egg to become embryo
Embryology in Plants
 Embryo Development http://zygote.swarthmore.edu/phyto1.html
o First division makes basal cell and terminal cell
o Basal cell  suspensor for anchor and nutrient transfer
o Terminal cell  embryo
o Ball of cells  cotyledons
o Shoot and root apex form, also primary meristems