Plant reproduction, development & growth- 5%
What is embryogeny ?
-Aka embryogenesis -A process that occurs after the fertilization of an ovule to produce a fully developed plant embryo -The zygote produced after fertilization must undergo various cellular divisions & differentiations to become a mature embryo
How does the microgametophyte develop
-During the maturation of pollen, the microspore divides mitotically to produce generative and vegetative nucleus. -When the pollen lands on the stigma (pollination), the pollen germinates and enters the stigma. -It then grows through the style. -The generative nucleus now undergoes mitotic division to produce 2 male gametes or sperms. -The pollen along with the pollen tube is known as a microgametophyte. -The pollen tube enters the ovule through a small pore and discharge the sperms into the embryo sac.
What is the 3rd step of germination
-First, the seed growth a root to access water underground. -Next the shoots, or growth above ground, begin to appear. The seed sends a shoot towards the surface where it will then grow leaves to harvest energy from the sun. The leaves continue to grow towards the light source.
What is primary growth ?
-Grows in length which allows roots to extend throughout the soil and shoots increase their exposure to light
What does an embryo sac generally contain ?
-One egg cell, -two synergids -3 antipodal cells -Diploid secondary nucleus
What is alternation of generations
-Plant life cycle alternate between sporophyte & gametophyte generations. -It's a reproductive cycle in which a sexual reproductive cycle interchanges or alternates with an asexual reproductive phase
What is the male plant reproductive system called ?
-Stamen -Contains a filament & an anther
What are gametophytes
-The gamete-producing (sexual) & usually haploid phase producing the zygote from which the sporophyte arises. -Dominant form in bryophytes
What is germination
-The process by which an organism grows from a seed or similar structure -Environmental conditions must trigger the plant to grow
What are the 5 major components of the end stage embryo ?
-The shoot apical meristem -hypocotyl -root meristem -root cap -Cotyledons
What is fertilization
-When ripe pollen from an anther of the same kind of flowers catches on the stigma -each pollen grain sends out a tiny threadlike tube. -The tube grows down through the style & pierces one of the ovules in the ovary
What is microsporogenesis ?
-each anther has 4 pollen sacs, which contain numerous pollen mother cells. -Each pollen mother cell undergoes meiosis to produce 4 haploid cells or microspores. -The microspores mature into pollen grains mainly by thickening their cell walls.
What is megasporogenesis?
-occurs in ovules which are present inside the ovary. -A single cell in each ovule differentiates into a megaspore mother cell, which undergoes meiosis to produce 4 haploid megaspores. -3 of these megaspores degenerate leaving one functional megaspore per ovule.
What are sporophytes
-the asexual & usually diploid phase, producing spores from which the gametophyte arises. -It is the dominant form in vascular plants
How does megagametogensis work ?
-the nucleus of a functional megaspore divides mitotically to produce 4 or more nuclei. -Megaspore nucleus undergoes 3 mitotic divisions to produce 8 nuclei. -3 of these nuclei more to one pole and produce a central egg and synergid cells situated on either side of the egg cell. -Another 3 nuclei migrate to the opposite pole to give rise to antipodal cells and the 2 nuclei remaining in the center (the polar nuclei), fuse to form a secondary nucleus. - The megaspore thus develops into a mature megagametophyte or embryo sac.
what is megagametogenesis?
-the production of a mature ovule with gamete -The development of an embryo sac from a megaspore
What is the function of the style ?
A tube on the top of the ovary that connects to the stigma
What is intermediate growth ?
Growth in plants occurs throughout the plants whole life due to meristems.
What is the function of the ovary ?
contains ovules (reproductive cells which will become fertilized by pollen)
What Is secondary growth ?
growth in thickness, caused by Lateral meristems: called vascular cambium and cork cambium.
What does plant embryogenesis result in ?
immature form of the plant, lacking most structures like leave, stems & reproductive structures
What is apical meristems ?
located at the tips of roots and shoots, provide additional cells that enable growth and length,
What are meristems ?
perpetually dividing embryonic tissue that allows for indeterminate growth
What is sporogenesis?
production of microspores and megaspores.
What is cork cambium ?
replaces the epidermis with a thicker, tougher periderm.
What is the function of the filament ?
stalk like structure attaches to base of flower and supports anther, which is the structure that produces pollen
What are lateral meristems?
vascular cambium and cork cambium
What is the 1st step of germination?
water imbibition (a special type of diffusion when water is absorbed by solids-colloids causing an enormous increase in volume) results in the rupture of seed coat.
Where are microspores produced ? (microsporogenesis)
In anthers
Where are megaspores produced ? (megasporogenesis).
Ovules
What is the female plant reproductive system called ?
Pistil or carpel Contains an ovary with ovules, a style & a stigma
What is the function of the anther ?
Produces pollen that consists of male reproductive cells. These cells fertilize ovules
What is the function of the stigma ?
Receives pollen during fertilization
What is an example of sporophytes?
The frond of a fern
What is gametogenesis ?
The production of male & female gametes in microspores & megaspores
What is microgametogenesis?
The production of male gametes or sperm
What is the flower
The reproductive unit of some plants (Angiosperms) parts of the flower- Petals, sepals, one or more carpals & stamens
What is an example of germination?
The sprouting of a seedling from a seed of an angiosperm or gymnosperm
What is the 2nd step of germination
The water activates special enzymes that begin the process of seed growth.
What is vascular cambium ?
adds layers of vascular tissue called secondary xylem (wood) and secondary phloem.
