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Flowers and Reproduction (Sexual Reproduction (involves flowers for…

- - - - portions of a plant separate from middle portion and start to function as individuals
    - - many individuals could be connected to one single individual
- - - - sex organs produce haploid cells
        
        either eggs or sperm via meiosis
        
        come together to form zygote, which becomes a diploid individual
        
        gametes fusing with other gametes= syngamy/fertilization
      - sporophyte generation/phase
        
        trees, shrubs, and herbs
        
        sporophytes are always diploid with organs capable of undergoing meiosis
        
        spores formed via meiosis which are haploid
        
        spores do not undergo syngamy
        
        they undergo mitosis and grow into a entire new haploid plant called gametophyte
        
        form gametes via mitosis and they then undergo syngamy to form new zygote that becomes a new diploid sporophyte
        
        gameteophytes formed from spores
        
        two types spores= heterospory
        
        male: microgametophytes formed from microspores
        
        female: megagametophytes formed from megaspoores
      - two generations-sporophyte and gametophyte- is a alternation of generations
    - - flower stalk= pedicel
        
        very end of axis where flower parts attached is the receptacle
      - four types of floral appendages
        
        sepals
        
        modified leaves that surround and enclose flower and protect flower part during development
        
        petals
        
        make up corolla. petals+sepals= perianth. petals are a leaf like structure with pigments other then chlorophyll. important in attracting pollinators
        
        stamens
        
        known as androecium, and produce the pollen. have two parts, the filament (stalk) and anther (where pollen is produced)
        
        carpels
        
        constitute the gynoecium. has three main parts: 1. stigma that catches pollen 2. style that elevates the stigma to a useful position 3. an ovary where megaspores are produced. the ovary contains placentae that have regions of ovules. Ovule has a central mass of parenchyma called nucellus which is surrounded by two sheets of integuments with a small hole, the micropyle. each ovule develops four megaspores via meiosis, but three are reabsorbed
        
        a plant with all four= a complete plant
        
        incomplete plant lacks 1 or 2 of the appendages
    - - microgametophyte
        
        developed from microspores
        
        microspore nucleus divides mitotically to produce a vegetative cell and a small lens shaped generative cell which divides into two sperm cells (microgametes). this constitutes the gametophyte
        
        gains nutrients from sporophyte
      - megagametophyte
        
        surviving megaspore within ovule develops into the megagametophyte
        
        nucleus undergoes 3 mitotic divisions to form embryo sac
        
        gains nutrients from sporophyte
  - - - forms diploid zygote
        
        inherits mitochondria and a nucleus from egg, and a nucleus and plastids from sperm
  - - - cells at one end of suspensor divide mitotically and form embryo
      - cells at other end initiates two primordia that grow into two cotyledons
        
        give embryo a heart shape forming heart stage
        
        number of cotyledons have depends on type of species
        
        used to store nutrients
        
        torpedo stage is where embryo elongates into a cylinder
        
        short axis is established consisting of radicle, epiicotyl, and hypocotyl
        
        vascular tissue differentiates in embryo
        
        seed with lots of endosperm= albuminous seed
        
        endosperm sparse= exalbuminous seed
  - - - three distinct layers formed
        
        exocarp- skin or peel
        
        mesocarp- flesh
        
        endocarp- tough like stones or a pit
        
        entire fruit wall= pericarp
- - - - pollination of a carpel by pollen of a different individual
      - allows genetic diversity among plants
    - - no genetic diversity because it is like asexual reproduction
    - - self fertilization prevented if anthers and stigma mature at different times
        
        pollen from anthers released while style is still immature
        
        exposed pollen only lives briefly due to damage to DNA or desiccation
        
        stigma and style mature but there is no living pollen left
    - - self pollination inhibited via compatibility barriers
        
        barriers are chemical reactions that prevent pollen growth between pollen and carpels
        
        certain proteins from genes used in blocking pollination
    - - incomplete flowers either lack sepals and petals, or they lack stamens and carpels
        
        essential organs, and if either is absent then it can affect sexual reproduction
        
        flowers lacking either or both essential organs= imperfect flower
        
        flower has both= perfect flower
        
        sepals and petals= nonessential organs
      - Dioecious
        
        plants species that produce individuals with staminate flowers and others that produce only carpellate flowers
        
        life cycle consists of four types of plants: 1. microgametophytes 2. megagametophytes 3. staminate sporophytes 4. carpellate sprophytes
        
        adaptation that ensure cross pollination due to plant only producing one kind of spore
        
        separate genders
      - Monoecious
        
        condition of having staminate flowers on the same plant as carpellate flowers
    - - pigments, fragrances, and sugar rich secretions used or atrraction
        
        use of an animal to to transfer pollen from flower to flower increases chances of pollen reaching stigma
        
        coevolution occurs as plants evolves to attract insects and insects evolving for efficient exploitation of the flower
    - - attracting pollinators is unnecessary
        
        sepals are reduced or absent, and ovaries need no special protection so flowers may be tiny
        
        huge amounts of pollen are released to increase the chances of reaching a stigma
        
        lots of small flowers to increase stigma surface area
    - - must be well protected from pollinators
- - - - two basic arrangements
        
        determinate
        
        inderterminate
- - - - dry is fruit not typically eaten by natural seed distributing animals
        
        dehiscent fruits break open and release seeds
      - fleshy fruits are those that are eaten during the natural seed distribution process
        
        indehiscent fruits do not open and release seeds
    - - fruit that are indehiscent
      - fruit and seed fused into one single structure
    - - carried by water means they must be heavier, larger, and buoyant, resist rot and mildew
        
        fruits carried by animals use hooks or stickers, or or be sticky and glue themselves to animals