Chapter 38 Flashcards
Three basic reproductive structures of plants
Flower
Seed
Fruit
Flower
Produces gametes; develops seeds and fruit
Seed
Consists of embryo and nutrient stores
Fruit
Develops from flower and contains seeds
What is sexual reproduction based on
Meiosis and fertilization
Meiosis
nuclear division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells.
Fertilization
fusion of haploid gametes that produces diploid zygote
Alternation of generations
Land plants have a life cycle with two distinct multicellular forms: one diploid (sporophyte) & one haploid (gametophyte)
Mosses
non-flowering plants which produce spores and have stems and leaves, but don’t have true roots.
Gametophyte
Haploid stage of life cycle
In bryophytes, such as mosses and liverworts, the gametophyte is the dominant life phase and the sporophyte is dependent on it
Sporophyte
Diploid multicellular stage of life cycle
In angiosperms and gymnosperms the sporophyte is dominant.
Asexual reproduction
does not involve fertilization & results in genetically identical copies of parent (clones)
- Advantage- very efficient (based on Mitosis)
- Disadvantage- genetically similar populations more likely to succumb to diseases
Rhizomes
horizontal stems from which shoots & roots emerge (nodes separate from parent plant)
Corms
underground modified stems
Plantlets
from meristematic tissue located along margins of leaves (drop off to form new plant)
Apomixis
when seeds form without fertilization (result in seeds genetically identical to parent)
What is flowering stimulated by
External cues
Internal cues
External cues
length of day/night or arrival of seasonal rains
Internal cues
related to nutritional needs
Basic organs of reproductive structures that are modified leaves
- Sepals
- Petals
- Stamens
- Carpels
All attached to receptable
Sepals
Reproductive structure
leaf-like structures, usually green & photosynthetic
- Arranged in circle (whorl) attached to receptacle & enclose flower bud as it develops/grows
Calyx
entire group of sepals in flower
Petals
arranged in whorl, often brightly colored to advertise flower to pollinators
Nectary
Gland contained in base of petals that produces nectar that is harvested by animals
Corolla
Entire group of petals in flower
Stamens
reproductive structures that produce male gametophytes (pollen grains) by meiosis, which in turn produce sperm by mitosis
Consists of filament and anthers
Filament
Part of stamen
a stalk-like structure that attaches to the base of the flower and supports the anther
Anther
Structure in stamen that produces pollen
Carpel
Produces female gametophytes (by meiosis) which in turn produces eggs by mitosis
Contains 3 parts
Stigma
Style
Ovary
Stigma
Part of carpel
Moist tip that receives pollen
Style
Part of carpel
Slender stalk that connects the stigma and the ovary
Ovary
Base of carpel
Houses the ovules where female gametophytes are produces
Perfect flowers
Contains both stamens and carpels
Monoecious plants
Have separate stamen and carpel producing flowers on same individual in different locations of plant
Dioecious plants
Have either stamen or carpel producing imperfect flowers on different plants
Megasporangia
Structure in ovule that contains megasporocyte
megasporocyte
Divides by meiosis producing 4 cells; 3 degenerate; surviving megaspore divides by mitosis to produce haploid egg and polar bodies (embryo sac)
Formation of female gametophyte
- Megasporocyte undergoes meiosis creating 4 cells
- Three cells degenerate
- Surviving megaspore cell divides by mitosis.
- Female gametophyte (embryo sac) is created
Female gametophyte (embryo sac)
produces the female gametes and is developed in ovule
3 cells at the bottom are egg cells
2 in the middle are polar and create the endosperm
What happens in anther
microsporangia cells (microsporocytes)undergo meiosis, producing 4 microspores
Pollen grain (male gametophytes)
Result of each of the 4 microspores dividing mitotically
Haploid, immature male gametophyte with two nuclei
When are male gametophytes considered mature
When generative cell produces two sperm cells via mitosis
Formation of male gametophyte
- Microsporocyte divides by meiosis
- Resulting microspores divide by mitosis
- Mature pollen grains form
Generative cell
In pollen grain and divides mitotically into two sperm cells that pass through pollen tube to enter the embryo sac of the flower
Pollination
Transfer of pollen from anther to stigma
Fertilization
Sperm and egg unite to form diploid zygote
Mutualism of pollination
Pollinators benefit by receiving food by feeding on the flower; plants benefit because of outcrossing
Outcrossing
Mating of different individuals
How the fertilization in angiosperms occur
- Germination
- Pollen tube cells undergo mitosis and starts to grow into style while the generative cell divides into two sperm cells
- Pollen tube grows into microphyle and enters the female gametophyte
- Double fertilization occurs
One sperm fertilizes the egg to form zygote
The second sperm combines with those 2 polar bodies to form large 3n cell (endosperm)
How are fruits developed
From the ovary
Embryogenesis
Process by which single-celled zygote becomes multicellular embryo
Seed dormancy
Hibernation for seeds
- Adaptation that prevents seeds from germinating on parent plant
- Ensures they will not germinate till environment is ideal
How seed dormancy is broken
- Seed coat being scarified or broken
- Exposure to proper environmental conditions
Simple fruit
Develops from single flower with one carpel or fused carpels
Aggregate fruit
Develops from single flower with many separate carpels
Multiple fruit
Develops from many flowers with many carpels
Germination
Resumption of growth of male gametophyte
Maturation of seed
Embryo and endosperm develops inside ovule and becomes surrounded by covering - seed coat
Ovary around ovule develop into fruit
Function of fruit
Seed protection and seed dispersal
Seed germination
- Seed take up water, consume oxygen and synthesize proteins
- Water uptake stops, seed begins to manufacture new mRNAs and proteins needed to support growth and mitochondria begin to multiply
- Water uptake resumes as growth begins and cells enlarge as embryo bursts from seed coat
Role of endosperm
nourishes embryos as they develop.