Lecture 3- Flowering Plants Flashcards
(24 cards)
The invention of the _____ gives rise to angiosperms
flower
Flowering plants
-division anthophyta
+250,000 species
Reproductive organs in flowers
both male and female: bisexual or cosexual
Vascular plants, therefore sporophyte dominant
Heterosporous
Microgametophyte= pollen
Megagametophyte= 8 nuclei
Triploid (3n) endosperm
-Bagged lunch for embryo in seed is new tissue called endosperm
-Endosperm: triploid, three chromosome sets
Structure of a flower
4 whorls
1) Sepal: base of flower
2) Petals: attract pollinators
3) Stamen: consists of the anther and filament. produces microspores
filament- stalk that anther sits on
anther- has two sporangium, where meiosis and pollen is
4) Carpel: consists of stigma, style, and ovary
stigma:tip of carpel that receives pollen
style: connects stigma to ovary
ovary: contains one or more ovules
-develops into fruit
Androecium
all male structures of flower
gynoecium
all female structures of flower
Pollination
when pollen lands on stigma
Fertilization
when pollen grows down the style and fertilizes ovule
Monocot
- one cotyledon
- parallel veins
- scattered vascular tissue
- fibrous roots, no main root
- pollen grain with one opening
- organs in multiples of 3
Eudicot
- two cotyledon
- vascular tissue ring like
- net like veins
- one main root called tap root
- pollen grain opening with 3 holes
- organs in multiples of 4-5
pollination
Definition: The arrival of pollen on the stigma (flowering plants) or on receptive female cone (conifers)
Only occurs in seed plants
Types of pollination
insects, birds, bats, wind
Reward for pollinator
nectar pollen
Advertisement for plant
- showy flower
- odour
Pollination syndrome
- set of floral traits associated with specific pollinator groups
- convergent evolution
Bee syndrome
- various shapes: specialized or nah
- any colour but red
- odour: specialized or none
Bat/moth syndrome
- tubular in shape, open at night
- white and yellow
- sweet odour at night
- large quantity nectar
Bird syndrome
- tubular in shape
- red and yellow
- no odur
- weak nectar
Wind syndrome
- not attractive or specialized
- no colour
- no odour
- no nectar
- large quantities pollen
Deceit pollination
- plants gives no reward to pollinator
- seen in orchids
- bees come in, mess around, gets pollen on its self, goes to other plants and fertilizes
Angiosperm Life cycle
In the megasporangium of each ovule, the megasporocyte divides by meiosis, producing four megaspores. One survives and gives rise to a female gametophyte.
(In conifers: the megaspores divides many times to get a megagametophyte that’s thousands cells big). In flowering plants, megaspore divides 3 times to make 8 cells.
Female gametophyte is 8 nuclei and 7 cells big because female gametophyte has middle cell called central cell that has 2 of the nuclei in it called POLAR NUCLEI
That central cell is a NOVEL feature in plants. Unique to flowering plants, is going to be fertilized
POLAR NUCLEI MAKE UP THE CENTRAL CELL
On the anther, each microsporangium contains microsporocytes that divide by meiosis, producing 4 microspores that develop into pollen grains. Pollen grain of flowering plant is different from that of a conifer in that it has 2 active sperm cells
-2 active sperm cells, conifers have 1
- Pollen growns down style to meet ovule
One sperm fertilizes egg nucleus and becomes zygote, other sperm fertilizes central cell and becomes brand new tissue called endosperm.
Endosperm: triploid because it has 2 haploid chromosome sets from mom, 1 chromosome set from dad
2 genetically identical to egg, 1 genetically identical to sperm that fertilized egg
Double fertilization
Angiosperms have double fertilization One sperm fertilizes the egg Embryo (2n= diploid) One sperm fertilizes the two polar nuclei of the central cell Endosperm (3n= triploid) Sperm have no cell wall, simply nuclei
Ovaries
become fruit
Ovules
become seeds
fruit
has atlas one seed
-protective covering
