plant life cycle / more details on reproduction !

• Perfect flowers


  Flowers that have both male and female parts
• Imperfect/Incomplete flowers


  • Staminate flowers - only contain an androecium
  • Carpellate flowers - only have a gynoecium

  
• Stamen


  • Pollen producing part of a flower, with a slender filament supporting the anther
  • Anther - where pollen is produced
  • Filament - holds the anther up

  
• Pistil/Carpel


  • Stigma - sticky surface at the top that traps and holds the pollen
  • Style - a tube-like structure holding up the stigma
  • Ovary - connected to the style where the ovules are contained
• Petals


  • Modified leaves surrounding the plant that attract pollinators
• Sepals


  • The green petal-like parts at the base of the flower

  
• Microsporangium


  Microspore mother cell divides by meiosis to give rise to four microspores, each of which will ultimately form a pollen grain
• Female gametophyte: the embryo sac


  • Formed from 3 mitotic divisions of the megaspore, forming an eight-nuclei ovule sac
  • Covered by a layer called "integument" which contains an opening called "micropyle" that the pollen tube enters

  
• Asexual reproduction


  • New plant will reach maturity faster
  • Less investment than making a flower and attracting pollinators
  • In stable condition, genetically identical plants will do as well as parent plant
• Disadvantages of asexual reproduction

  No increase in genetic diversity
• Natural asexual reproduction


  • Growth from buds on stem surface
  • Adventitious roots or runners
  • Small buds on leaves that form independent plants
  • Propagation through cuttings
• Artificial asexual reproduction


  • Grafting - produces plants combining favorable stem characteristics with favorable root characteristics
  • Layering - A part of the stem is buried to form a new plant
  • Micropropagation - producing a large number of plants from a single plant in a short time under sterile laboratory conditions
• Length of Plant life cycles

  • ANNUALS - plant species that complete their life cycle in one season
  • BIENNIALS - complete life cycle in two seasons

  First season - vegetative phase

  Second season - completes its reproductive phase

  • PERENNIALS - complete life cycle in two years or more
  • MONOCARPIC PLANTS - flower only once in their lifetime
  • POLYCARPIC PLANTS - form flowers many times during their lifetime
• Aging and death in plants


  • Factors that determine survival include susceptibility to disease, changing environmental conditions, drought, cold, and competition for nutrients
  • They continue to grow despite the presence of dead tissue
  • Leaf fall is triggered by factors like decrease in photosynthetic efficiency due to shading or oxidative damage
• Pine can live for 4500 years

  
• Pollination


  • Biotic agents: insects, bats, birds, and other animals
  • Abiotic agents: wind and water
• Types of pollination


  • Self-pollination- pollen from the anther is deposited on the stigma of the same flower, or another flower of the same plant
  • Cross-pollination - transfer of pollen from the anther of one flower to the stigma of another flower on a different individual of the same species
• Preventing self-pollination


  • Pollen and ovary mature at different times
  • Physical features on the flower
  • Male and female flowers on different parts of the plant
  • Dioecious - male and female flowers are born on different plants (individual plants)
• POLLINATION BY DECEPTION

  Certain orchids use food deception or sexual deception to attract pollinators (e.g. bee orchid)
• Pollination in angiosperms


  1. Transfer of pollen from anther to stigma

  2. Pollen grain produces a pollen tube which grows and discharges sperm near the embryo sac, resulting in egg fertilization

  3. Zygote gives rise to an embryo, and ovule develops into a seed

  4. Ovary develops into a fruit containing one or more seeds
• Double fertilization


  In angiospersm, one sperm fertilizes the egg to form the 2n zygote, and the other sperm fertilizes the central cell to form the 3n endosperm
• From ovule to seed


  1. After double fertilization, each ovule develops into a seed, and the ovary develops into a fruit enclosing the seed(s)

  2. As the embryo develops, the seed stockpiles proteins, oils, and starch
• From ovary to fruit


  As the seeds are developing from ovules, the ovary of the flower develops into a fruit, which protects the enclosed seeds and aids in their dispersal

  • During fruit developments, the ovary wall becomes the pericarp, the thickened wall of the fruit
  • As the ovary grows, the other parts of the flower wither and are shed
• Gymnosperms


  • Seed-producing plants that include conifers, cycads, ginkgo, and gnetophytes
  • Have male and female reproductive organs
• Angiosperms


  • Plants that have flowers and produce seeds enclosed within a carpel
  • Include herbaceous plants, shrubs, grasses, and most trees
  • Divided into monocots and dicots, based on their seed structure
• Monocot seed


  • Surrounded by protective seed coat
  • Aleurone layer - lies under the seed coat - functions as a digestive organ
  • Mostly consists of starchy endosperm - forms separately from the embryo
  • Coleorhiza protects the radicle
  • Scutellum is a large cotyledon

  
• Dicot seed


  • Have two cotyledons
  • Cotyledons can function as leaves or food storage in place of the endosperm
  • Have radicle, plumule, and suspensor
  • Suspensor - a filament of cells developed from the basal cell

  
• Dormancy


  A state of suspended development, when germination takes place
• Breaking dormancy


  1. Embryo emits gibberellin hormone - diffuses through the seed

  2. In monocots, hormone triggers production of digestive enzymes by aleurone

  3. In dicots, digestive enzymes are produced by cotyledons

  4. Enzymes break down stored food in endosperm or cotyledons
• Zones of root growth

  • Zone of division - apical meristem. growing tip of embryonic, differentiating tissue
  • Zone of elongation - responsible for most lengthwise growth
  • Zone of maturation - tissue differentiation begins
• Primary meristems


  • Give rise to differentiated tissues like phloem and xylem
  • Some remain undifferentiated and form cambium and pericycle
• Leaf growth and fall

  1. LEAF GROWTH - Each leaf originates on the side of the meristem, growing upward as it enlarges and differentiates

  2. LEAF FALL - leaves ages and die

  • As xylem ages, it becomes clogged and turns to heartwood

  3. Abscission - is the process by which plants shed parts, an adaptation that permits loss of leaves
• Types of fruits


  • Simple fruit - developed from one ovary
  • Aggregate fruits - derived from multiple ovaries of a single flower
  • Multiple fruits - develop from a cluster of flowers
  • Accessory fruits - do not develop from an ovary, develop from different part of the flower
• Seed and fruit dispersal

  • Seeds in fruits need to be dispersed far from mother plant to find favorable and less competitive conditions
  • Seed dormancy allows plants to disperse their progeny through time
• a pollen grain becomes mature male gametophyte when ?

  its nucleus divides and forms two sperms
• Female cone


  upper branches where they can fertilize by pollen blown on wind from male cones
• Male cone


  grow on lower branches
• structures in a monocot seed will be discarded once they have served their function, leaving only the

  Radicle, Nesocotyle (future stem), Shoot apex
• If a pollen grain germinates, a pollen tube grows down the 


  style toward the ovary
• ANGIOSPERM

  • The female gametophyte exists in an enclosed structure - the ovule
  • Double fertilization
  • Male and female structures are part of the flower