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Chapter 9 Flowers and Reproduction (Flower Structure (Design (Pollination,…

- - - - Receptacle - end of stalk where flowers are attached
        
        Petal - leaf-like pigmented appendage above the sepals that serves to attract pollinators with colors, shapes, and chemicals
        
        Stamen - part of flower that produces pollen
        
        Carpel - have a stigma for catching pollen, a style that elevates the stigma, and an ovary that produces megaspores
        
        Sepal - modified leaves that surround the other parts as they mature
  - - - Self-pollination barriers
        
        Compatibility barriers like chemical reactions between pollen and carpels that cause the plant to seal off pollen tubes from incompatible pollen
        
        Different maturation times on stamens and stigmas separate pollen release from pollen reception
      - Animal-pollinated flowers - fertilization is accomplished by animals moving pollen from one flower to the stigma of another flower
        
        Symmetry
        
        Actinomorphic - radially symmetrical flowers
        
        Zygomorphic - bilaterally symmetrical flowers, evolved with a pollinator to only allow a pollinator in at one orientation to place pollen on a specific area
        
        Chemical attractants
        
        Pigments
      - Wind-pollinated flowers
        
        Usually have no petals and reduced or absent sepals
        
        Large stigmas for massive release of pollen
    - - Imperfect flowers - missing one or both essential organs
        
        Monoecious - have staminate and carpellate flowers on the same plant
        
        Dioecious - have staminate and carpellate flowers on different plants
      - Perfect flowers - have both essential organs
    - - Inferior - flower parts grow around ovary such that it appears to be below everything else or in the receptacle (epigynous)
      - Superior - no fusion of parts to ovary and the ovary is obviously above the other parts (hypogynous)
      - Half-inferior - ovary partially buried (perigynous)
    - - Determinate - limited growth potential because flowers grow at apex
      - Indeterminate - no flower grows at apex, inflorescence axis can grow as long as it needs to be
- - - - Fertilization - the pollen grain grows a pollen tube into the microgametophyte until it reaches the synergids, where it releases the sperm cells; a sperm cell fuses its nucleus (karyogamy) with the nucleus of the egg, in angiospems the second sperm cell fuses nuclei with both polar nuclei, making triploid cells (double fertilization) #
        
        Triploid endosperm nuclei divide rapidly, produce a huge cell with hundreds or thousands of nuclei which develop cell walls and become their own cells, creating endosperm tissue to nourish the zygote
        
        Zygote grows into an embryo, one end of which divides into a ball of cells which is the embryo proper, while the other end stretches into a stalk-like suspensor which serves to push the embryo deep into the endosperm
        
        The end of the embryo farther from the suspensor develops one cotyledon in monocots and two in eudicots
        
        Embryo continues to develop into an elongate cylinder with and embryonic root (radicle), an embryonic stem (epicotyl), and a junction between the two (hypocotyl); then vascular tissue differentiates
        
        Mature embryo becomes dormant and partially dehydrates, a mature seed that still has significant endosperm is albuminous, sparse endosperm is exalbuminous, embryo can contain varying amounts of young leaves, integument grows into seed coat
        
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  - - - Microgametophyte (1n)
    - - Megagametophyte (1n)
        
        Zygote (2n)
        
        Embryo (2n)
- - - - Dry - not typically distributed by animal ingestion
        
        Indehiscent - do not break open to release seeds #
        
        Dehiscent - break open and release seeds
      - Fleshy - eaten during natural seed distribution process
    - - Simple - fruit develops from single ovary or ovaries of one flower
      - Aggregate - fruit developed from fusion of separate carpals of one gynoecium
      - Multiple - fruit developed from all of the fruits of an inflorescence fusing into one fruit