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Flowers & Reproduction (flower structure & cross-pollination…

- - - - zygote 1 sperm & 1 eggs brought together form a new diploid cell
    - - sporophytes are always diploid & have organs w/ cells capable of meiosis
        
        meiosis results in haploid spores
        
        spores cannot undergo syngamy/fertilization, but each undergo mitosis & grow into an entire new haploid plant(gametophyte)
        
        sporophytes reproduce a haploid plant that does not resemble the diploid sporophyte it came from
        
        haploid gametophyte: tiny mass of cells w/o roots,stems, leaves, or vascular tissues, yet it is an entire plant
        
        gametes formed from haploid plants undergo mitosis
        
        1 more item...
    - - megagametes nonswimming large eggs
        
        megagametophytes female plant
        
        produce megaspores
      - microgametes swimming small sperm cells
        
        microgametophytes male plant
        
        produce microspores
      - having both spore types is known as heterospory
      - alternation of generations 2 generations sporophytes & gametophytes
        
        heteromorphic generations gametophytes do not resemble sporophytes at all
        
        complex life cycle with at least 3 distant plants (1 sporophyte, 2 gametophytes)
  - - - never wood, no secondary growth
        
        pedicel flower stalk; at the very end of the axis
        
        receptacle where the other flower parts are attached
        
        4 types of floral appendages: sepals, petals, stamens, & carpels
        
        complete flowers have all 4 appendages
        
        incomplete flowers lacking one or more of the appendages
    - - modified leaves that surround & enclose the other flower parts as they mature
        
        typically the thickest, toughest, & waxiest of the flower parts
        
        protects flower bud from bacterial & fungal spores, maintains a high humidity inside the bud, & deterring insect feeding
        
        also protects the nectar from being stolen
        
        sepal can become colorful (petaloid) & help attract pollinators
        
        calyx all sepals together
    - - perianth sepals & petals together
        
        petal contain pigment other than chlorophyll, have fewer to no fibers, & tend to be thinner & more delicately constructed than leaves
        
        important in attracting the correct pollinators
        
        petal produce volatile fragrances, & insects & bats follow the aroma to the flower
    - - aqndroecium collectively known
        
        2 parts
        
        filament the stalk
        
        anther where pollen is produced
        
        composed of diploid cells
        
        microspore mother cells/ microsporocytes continue to enlarge & then undergo meiosis, each producing 4 microspores
        
        tapetum a layer in neighboring anther cells
        
        1 more item...
        
        4 long columns of tissue become distinct as some cells enlarge & prepare for meiosis
    - - located at the highest level on the receptacle
        
        3 main parts
        
        stigma catches pollen grains
        
        style elevates the stigma to a useful position
        
        ovary where megaspores are produced
        
        located inside are placentae
        
        ovules regions of tissue that bear small structures
        
        has a short stalk called, funiculus that carries water & nutrients from the placenta to the ovules by a small vascular bundle
        
        nucellus central mass of parenchyma
        
        many carpal are usually fused together to form a single compound structure: pistil
  - - - producing a large vegetative cell & a small lens-shaped generative cell
        
        generative cell divides & forms 2 sperm cells
        
        microgametophyte: consists of the vegetative cell & 2 sperm cells
        
        pollen tube absorbs nutrients from the stigma & grows downward through the style toward the ovary
    - - embryo sac multinucleated megagametophyte
        
        large 8 nucleated megaspore becomes a megagametophyte w/ 7 cells
        
        central cell the 7 cells are one large central cell
        
        with 2 polar nuclei, 3 small antipodal cells & an egg apparatus consisting of 2 synergids & an egg
  - - - in angiosperms, the 2nd sperm nucleus released from pollen tube migrates from the synergid into the central cell
        
        it undergoes karyogamy w/ both polar nuclei
        
        esta. a large endosperm nucleus triploid, containinf 3 full sets of genes
  - - - cotyledons give the embryo a heart shape (heart stage)
        
        (torpedo stage) embryo is an elongated cylinder: short axis is established
        
        consisting of radicle (embryonic root)
        
        consisting of epicotyl (embryonic stem)
        
        consisting of hypocotyl (the root/shoot junction)
        
        albuminous seed mature seed in which endosperm is abundant
        
        exalbuminous endosperm is sparse/absent at maturity
        
        seed coat/testa integuments that surround the nucellus expand & mature
  - - - 3 distinct growth layers
        
        exocarp outer layer; skin or peel
        
        mesocarp middle layer; flesh
        
        endocarp innermost layer; may be tough like the stones/pit of a cherry or may be thin
      - pericarp entire fruit wall (any # of layers)
- - - - in many species, anthers release pollen while stigma tissues are immature & unreceptive
        
        when the stigma & style become mature, there may be no living pollen left in the flower
  - - - if either organ is missing, the sexual reproduction is dramatically affected
        
        imperfect flowers both essential organs missing; also it is an incomplete flower
        
        perfect flower a flower with both essential organs, even if it is lacking sepal, petals or both
        
        nonessential organs sepals & petals do not produce spores
    - - dioecious the species of dioecy
        
        dioecious species life cycle has 4 plant types
        
        (1) microgametophytes
        
        (2) megagametophytes
        
        (3) staminate sporophytes
        
        (4) carpellate sporophytes
      - extreme adaptation that ensures cross-pollination
    - - monoecious species of monoecy
        
        if fertilization occurs, the carpels develop into large fruits, & only healthy & robust plants can afford to do this
  - - - coevolution a flower becoming adapted for visitation by a particular insect & the insect for efficient exploitation of the flower
    - - zygomorphic bilaterally symmetrical
    - - animals try to eat plants, lay eggs in them, or do other harmful things
      - plants defend themselves with poisons, spines, & sclereid barriers
      - mutations that make a plant more recognizable/more convenient to its pollinators helping both the plant & animal
  - - - after pollen is released to the wind, the chance of any particular pollen grain landing on a compatible stigma is small, so huge #s of grains must be produced
    - - each flower is tiny
        
        entire plant has a large total stigma surface area
  - - - burying the ovaries deep within the flower provides further protection
    - - epigynous sepals, petals, stamens appendages
      - superior ovary/hypogynous parts ovary located above the sepals, petals, & stamens
        
        half-inferior intermediate, partially buried ovaries w/ perigynous flower parts
- - - - height from the ground
        
        distance from an open
        
        uncluttered flight path for pollinators
  - - - determinate inflorescences
        
        only a limited potential for growth bc the inflorescences apex is converted to a flower, ending its possibilities for continued growth
      - indeterminate inflorescences
        
        the outermost flowers open first, & new flowers are being initiated at the apex
- - - - ex: pecans, walnuts, brazil nuts, & coconuts
        
        they offer maximum protection but are heavy & expensive metabolically
      - protected seed must be able to break out to make germination possible; more fragile fruits are better for this
      - if animals are to disperse seeds the seed & embryo must be protected from consumption
  - - - each fruit develops from one carpel containing a single ovule
        
        during maturation the seed fills the fruit & fuses w/ the fruit wall
        
        both fruit & the single seed are fused in a single structure
        
        fruit/seed falls & germinates close to the parent sporophyte
        
        fruits are indehiscent, & during germination the embryo absorbs water, swells, & bursts the weak fruit
        
        the fruits are caryopses
  - - - dry & inedible but do not fuse to the seeds
        
        at maturity, 2 halves of the fruit twist & break open along the 2 specialized lines of weakness