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Ch10: Flowers and Reproduction, Concepts, Fertilization, Stamens, Carpels,…

- - - - sporophyte phase/generation: trees, shrubs, herbs
      - sporophytes are always diploid, have organs with cells capable of undergoing meiosis, resulting in haploid spores
        
        gametes can fuse with other gametes (syngamy/fertilization) thereby producing a diploid zygote. plant cells cannot undergo syngamy, instead each spore undergoes mitosis and grows into a new haploid plant called a gametophyte
        
        during sexual reproduction when a sporophyte reproduces it does not produce a new diploid plant like itself but rather a haploid plant
        
        oogamous plants: sperm are reproduced by one type of individual and eggs by another. male: microgametophytes, female: megagametophytes
        
        mocrogametophytes grow from microspores, and megagametophytes from megaspores. Two types of spores: heterospory
  - - - flower stalk: pedicel. End of axis where other flower parts are attached: receptacle
      - four types of floral appendages: sepals, petals, stamens, carpels, most flowers have all four making them complete flowers
      - flowers that lack 1-2 of these appendages are incomplete flowers
    - - modified leaves that surround/enclose other flower parts when they mature (thickest, waxiest parts)
      - protect the bud from nectar robbing insects and birds, protect from fungal spores, keeping the humidity high inside the bud
    - - leaflike, contain pigments other than chlorophyll
      - important in attracting the correct pollinators
      - petal arrangement, color, shape allow pollinators to recognize others. If nectar or pollen are rewarded then the pollinator is likely to go to other flowers with the same arrangement, enhancing cross pollination
      - many flowers have pigments that absorb ultraviolet light as well as UV light, creating patterns only insects can see
  - - - after a pollen grain lands on a stigma, it germinates by producing a pollen tube, absorbs nutrients from the stigma and grows downwards through the style towards the ovary
        
        the pollen tube is protected and nourished by the style tissue
        
        as it grows downwards it carries the sperm cells to the ovule
    - - within the ovule the surviving megaspore develops into a megagametophyte
      - one type of development: nucleus undergoes three mitotic divisions producing 8 haploid nuclei in a single cell (embryo sac)
      - walls form, seven cells: central cell, two polar nuclei, three antipodal cells, and an egg apparatus (two synergids and an egg)
      - also a full fledged plant
  - - - supsensor: stalk-like structure that pushes the embryo deep into the endosperm, crushed by later growth
      - globular stage: cells arranged as a small sphere at first
      - two primordia at end of embryo form into two cotyledons in basal angiosperms and eudicots
        
        give the embryo a heart shape (young) this is the heart stage
        
        in monocots only one cotyledon primordium grows out
        
        dicot is an abbreviation of dicotyledon
        
        a mature seed with abundant endosperm is albuminous seed, if endosperm is sparse its exalbuminous
        
        the amount of embryo growth before dormancy sets in is very variable
        
        seed coat (testa): integuments that surround the nucellus expand and mature into seed coat
  - - - stigma and style usually wither away along with sepals, petals, and stamens
      - 3 distinct layers during growth: exocarp (outer layer), mesocarp (middle layer), endocarp (innermost layer)
      - the entire fruit wall whether the fruit has all 3 layers or some or one, is the pericarp
- - - - exposed pollen does not live long
      - all pollination is effected by younger flowers if the style/stigma become mature and there's no living pollen left
  - - - in another system critical proteins are deposited on the outer surface of the developing pollen grain by the anthers tapetum, possible blocking of germination of the pollen grain
  - - - stamens/carpels: essential organs, sexual reproduction is dramatically effected if either of these organs are missing (produce two important spores)
      - sepals and petals are nonessential organs
      - stamens are involved in sperm production, carpels involved in egg production (a species must have both types of organs, missing one makes it an imperfect flower)
      - a species that has individuals that produce only carpellate flowers and others that produce only staminate flowers: dioecious species
        
        both staminate flowers and carpellate flowers on the same plant: monoecious species
        
        dioecy is adaptation to ensure cross pollination, no indv. can fertilize itself
  - - - half-inferior (perigynous) partially buried ovaries
- - - - terminal flower typically opens first, then the lower ones open successively
- - - - if the separate carpels of one gynoecium fuse during development: aggregate fruit (raspberries)
      - if all the individual fruits of an inflorescence fuse into one fruit: multiple fruit (figs)
  - - - for the most part fleshy fruits are indehiscent
      - fruits or seeds carried by wind must be light, they often have wings (maples) or parachutes (dandelions) to keep them in the air as long as possible
      - dry fruits typically have hooks or stickers, are sticky or tacky, to adhere to animal fur or feathers to be carried