Ch. 38
Angiosperm Reproduction and Biotechnology
Feb 12­2:05 PM
1
Essential Questions:
How do angiosperms reproduce?
What does the future hold for plant technology?
Feb 12­2:07 PM
2
Review of Reproductive structures:Alternation of generations
Gametophytes ­ reduced size
Sporophytes ­ dominant generation
Feb 12­2:10 PM
3
Structures of a flower review
Feb 12­2:16 PM
4
Sepals­ enclose floral bud, nonreproductive
Petals ­ attract pollinatiors, nonreproductive
Stamen ­ male part, consists of anther and filament
Anther ­ male part, holds pollen sacs (pollen)
filament ­ male part, holds up anther
Apr 3­8:40 AM
5
Carpel ­ female reproductive organ, contains ovary, style and stigma
Ovary ­ contains ovules where eggs are located
Style ­ stalk that holds stigma
Stigma ­ end of carpel, sticky surface to attach pollen
carpels can be single or fused
Apr 3­8:44 AM
6
Lily
anther with pollen
filament
style
stigma
Feb 12­2:19 PM
7
Lily
Complete flower ­ has all four basic organs
Incomplete ­ lack either sepals, petals, carpals or stamens Ex grass
Feb 12­2:22 PM
8
inflorescences (clusters of flowers)
lupine
sunflower
foxglove
Feb 12­2:23 PM
9
Male gametophytes develop in pollen grains
microsporangia = pollen sacs
­has diploid cells called microsporocytes
­ microsporocytes undergo meiosis to make male gametophytes (4 microspores)
­ microspore undergoes mitosis to produce generative cell and tube cell = pollen grain
Apr 1­8:54 AM
10
pollen grains
Apr 3­9:02 AM
11
Development of female gametophyte
female gametophyte = embryo sac
megasporocyte enlarges and undergoes meiosis to produce 4 megaspores
­only one survives; other disintegrate
­the megaspore grows (nucleus divides by mitosis 3x without cytokinesis = 1 large cell with 8 haploid nuclei
­partions put up and becomes embryo sac
so get: 3 cells near micropyle (1 egg cell & 2 synergids (flank egg cell to help attract pollen)
3 antipodal cells at opposite end­ unknown function
2 polar nuclei ­ share cytoplasm
Apr 3­9:02 AM
12
development of angiosperm
gametophytes
Apr 3­8:51 AM
13
Pollination
pollination ­ process that brings male and female gametophytes together
Apr 3­8:36 AM
14
Pollenation
Apr 1­9:26 AM
15
Modes of Pollenation
Abiotic pollenation by wind
Apr 1­9:28 AM
16
by water ­ Ex. coconuts
http://www.florida­palm­trees.com/coconut­palm­tree­pictures/
Apr 1­9:36 AM
17
By Animals:
1. Pollenation by bees ­ attracted by color of petals
Apr 1­9:30 AM
18
2. Pollenation by moths and butterflies ­ attracted by odor
Apr 1­9:31 AM
19
3. Pollenation by flies ­ reddish, fleshy flowers that smell like rotten meat
Apr 1­9:33 AM
20
4. Pollenation by birds ­ attracted by nectar, not smell
some petals fuse forming a bent tube
Apr 1­9:32 AM
21
5. Pollenation by bats ­ attracted by light colored, aromatic flowers
Apr 1­9:34 AM
22
Double fertilization
1. pollen grain germinates, pollen tube grows down style to ovary
2. pollen tube discharges two sperm into female gametophyte within ovule
3. One sperm fertilizes egg to form zygote, other sperm combines with two polar nuclei to form a triploid cell that develops into endosperm (food for zygote)
Each ovule then develops into a seed and ovary becomes a fruit enclosing the seed
Apr 1­9:43 AM
23
seed structure
Dicot
seed coat ­ protection­ made from integuments
radicle ­ embryonic root ­ first part of plant to emerge
monocots have:
scutellum (corn, wheat) ­ specialized cotyledon
coleorhiza ­ covering over young root
coleoptile ­ covers young shoot
monocot
Apr 3­9:25 AM
24
Seed dormancy
­condition of extremely low metabolism/no growth and development
­embryo and food supply enclosed in seed coat
To bring seed out of dormancy:
a. rainfall b. fire Ex. lodgepole pine
c. light Ex. lettuce
d. passing through digestive tract of animal (chemicals)
Apr 5­5:00 PM
25
seed germination
Imbibition = uptake of water due to low water potential
­causes seed to expand and rupture
Apr 3­9:33 AM
26
fruit = mature ovary
­protects seeds
­aids in seed dispersal by wind, animals or water
­no pollenation, usually no fruit development
Apr 5­4:54 PM
27
How do plants reproduce?
Apr 5­5:15 PM
28
Asexual reproduction (vegetative reproduction)
Aspen
root system
Kalanchoe
plantlets
Apr 3­9:34 AM
29
Advantages of asexual reproduction
1. dispersal (dandelions)
2. can clone self
3. more stable, less frail than seedlings
Apr 7­9:41 AM
30
Mechanisms to prevent self­fertilization
Why???
dioecious plants ­ can't self fertilize Why??
Mechanisms:
1. stamen and carpels mature at separate times
Apr 3­9:02 AM
31
bisexual flower­ has both stamen and carpels in same flower
unisexual flower ­ missing either stamen or carpals
monoecious ­ if stamen and carpels are on the same plant
Apr 3­8:53 AM
32
dioecious ­ stamen and carpels are on separate plants
Sagittaria
Apr 3­8:56 AM
33
Trillium
Monot or dicot??
bisexual or unisexual?
Feb 12­2:18 PM
34
2. stamen and carpels are structurally arranged so hard for insect to transfer pollen to stigma ­ ex primrose
http://search.live.com/images/results.aspx?q=primrose+image&p1=
OneRow&FORM=IGRE2#focal=
404463b21e2a2289a6a8f57443576d2b&furl=
http%3a%2f%2fohric.ucdavis.edu%2fphotos%2ffullsize%
2fPrimrose.jhtpg
Apr 3­9:12 AM
35
3. self incompatibility ­ the ability of a plant to reject its own pollen
­ biochemical block used
pollen from separate plant
half pollen will not germinate
no pollen will germinate
Apr 3­9:13 AM
36
Possible mechanism
1. pollen produces chemical signal
2. receptor bind to membrane's kinase
3. kinase triggers signal transduction pathway (STP)
4. STP activates one or more effector proteins
5. effectors block formation of pollen tube
Apr 3­9:17 AM
37
Vegetative propagation
Test tube cloning
use few parenchyma cells
callus
Apr 3­9:37 AM
38
cuttings­ shoots or stem Plant grafting ­ stock ­ plant that provides root system
scion ­ twig grafted onto the stock
ex. used with grapes, fruit trees
Apr 3­9:39 AM
39
DNA gun
Apr 3­9:36 AM
40
Protoplasts
­wall­less cells (treated with purified wall degrading enzymes isolated from some fungi)
­can fuse protoplasts from different species to make hybrids, then culture
Apr 3­9:42 AM
41
Genetically modified foods
Maize
Teosinte
Apr 3­9:44 AM
42
Types of plants that have genetically modified:
1. triticale ­ cross between wheat and rye
­nutritionally superior to rye and better bread flour
2. Golden rice ­ makes beta­carotene, helps eyesight
3. corn ­ large kernal size
4. Papaya ­ resistant to ring spot virus
Apr 5­5:18 PM
43
controversial aspect of GMO's
1. issues of human health
may transfer allergens
2. effects on nontargeted organisms
­Ex if pollen of GMO lands on another plant; would it harm the insects that eat those plants leaves?
3. introducing genes escaping from a transgenic crop into related weeds Ex. herbicide resistance ­ would it cause super weeds?
Apr 5­5:25 PM
44
What do you think about GMO's?
Apr 5­5:31 PM
45
Apr 6­9:20 AM
46