Download How do plants do it? Reproduction: from algae to flowering plants

How do plants do it?
Reproduction: from algae to
flowering plants
Plants come in all
shapes and sizes
Chara, Chlamydomonas, Pitcher
plant, Giant Sequoia
Plants and Biotechnology
Howard Univ. Summer Workshop
July 18, 2012
By Heven Sze & Dan Czerny
University of Maryland, College Park, MD
Fossil records indicate that higher plants evolved from algae
Why are seed plants the most successful land plants?
Seed Plants include
recent
65 m
1. Gymnosperms (naked seeds)
200 m
2. Angiosperms or flowering plants (contained seed)
450 m
Why?
Most advanced and dominant, because of their reproductive features.
•Embryo is protected and can survive harsh environment
600 m
Years
ago
•Fertilization does not depend on water.
Pollen and seeds are dispersed by wind or insect.
•Plants have developed vascular tissues, so they can survive on land
and reach great heights.
The fossil records of some protist and plant groups. The width of
the shaded space is an indicator of the number of species.
Image from Purves et al., Life: The Science of Biology, 4th Ed.
Algae is related to plants:
evidence?
Land plants evolved from an algal ancestor.
•
•
Biologists hypothesized that green
algae are closely related to plants.
Why?
b/c morphological traits,
a) chloroplast
b) cell wall.
The green algae include species
that are unicellular, colonial, or
multicellular.
Algae live in marine or freshwater
habitats.
Tiny alga:
Ostreococcus
lucimarinus.
Fig 30-15.
Water is essential for all
life processes
Green algae produce sperms and egg.
Sperms swim to the egg.
Egg (n)
FE
• Algae grow in marine
environments and in fresh
water.
Take up minerals and water
directly.
• Mosses need moist
environment and water for
fertilization.
Chara alga
How do they reproduce?
Moss developed organs to protect
egg and sperms from drying.
-Sperms swim to egg.
ION
Archegonium
Haploid (n)
Diploid (2n)
FERTILIZATION
MITO
SI
S
Egg (n)
Zygot
e (2n)
Eggs form in
archegonia
Developing
sporophyte
(2n)
Sper
m
swim
to egg
Mature
sporophyt
e (2n)
Sperm form in
antheridia
Developing
sporophyte
(2n)
Spores (n) are produced
in sporangia by meiosis,
dispersed by wind
Mature
gametophyte
(n)
Mature
gametophyte (n)
MEIOS IS
Diploid (2n)
Sperm (n)
Zygote (2n)
(retained on
parent)
Multicellular
adult (n)
M
MITO
SIS
O
EI
S
SI
R: unfertilized
L: fertilized
FIE promoter
1. Seed Germination
Major stages in the life of a flowering plant
1. Seed germination
4. Seed
formation
Reproductive
plant
Heterotrophs
Seedling
2. Development of
the plant body
3. Development of
the reproductive
organs (flower)
Vegetative Plant
Autotrophs
Alternation of
generation?
• 1. Surface to prevent drying out. [leaf cuticle]
• 2. Pores for gas exchange [stomata]
• 3. Support to give structure to plant body [cell
wall]
• 4. Plumbing system to distribute nutrients and
water. [vascular tissues]
• 5. Accomplish fertilization without an aqueous
environment. How?
• 6. Development of seed with dormant embryo.
Physcomitrella patens
Seed
Haploid (n)
Plants developed adaptations to
survive on dry land
Mosses: Gametophyte is large and long lived; sporophyte depends on gametophyte for
nutrition.
Spore
(n)
AT
Spores (n)
moss
Developing MIT
OSIS
gametophyte
RT
ILI
Z
Gametes are produced
in gametangia
2. Development of the
vegetative plant body.
3. Development of the reproductive organs:
a. formation of flowers
1. Sepal
2. Petal
Plants develop appropriate
structures to carry out
special functions.
Vegetative plant body is
made of 3 organs:
•leaf
•Stem
•root
3. Stamen:
male organ
4. Pistil: female
organ
•Sperms & eggs are wellprotected
•Separated by long distance
•How do they find one another?
Travel
•How does one travel and not get
dried out? Protection
What are these parts?
4. Reproduction
•
Pollination: transfer
of pollen grain to the
pistil
•
Fertilization:
fusion of the sperm
with the egg.
?
?
Insect or bird
pollinated flowers
are colored and
fragrant.
?
Inside Anther  Pollen Mother Cell –
> meiosis ->microspore  pollen
What is a pollen grain?
A protective cell containing 2 sperms
Pollination
Transfer of pollen grain to the pistil
How? Do sperms have flagella?
No, they cannot swim.
So how do they move?
• How can they survive long hot journeys?
• Successful pollination is landing on the
right pistil. [compatible vs incompatible]
David Twell’s Pollen website
http://www.le.ac.uk/biology/research/pollen/pollen.html
Answers
Successful fertilization depends on pollen
germination, tube growth & guidance
• Fly: pollen is carried by wind, gravity
carried by bees, insects,
or other flying organisms.
• Pollen wall is hard and thick.
Some pollen grains can survive a few
hours of heat and drought.
7 Fertilization:
pH/osmotic shock of tube to discharge
content
Taken from Johnson & Lord 2006
Growing pollen tube
Pollen tubes can sense signals from the female cells
& then orient the tube to targeting the ovule
Wild typeg
Pollen
chx 21/23 mutant
A mutant pollen is
completely clueless
Pollen tubes grow
into the stigma &
transmitting tract
Lu, Yongxian
Pollen tube growth: videos
• Ravi Palanivelu Lab:
• http://ag.arizona.edu/research/ravilab/lab
%20images&movies%20page.html
See video 1: semi-in vivo pollen tube growth towards an ovule
See video 2: tube is attracted to and enters an ovule
Video 4: When one pollen tube enters ovule, other tubes are repelled.
Video 15: in vitro pollen tube growth! Just like what you saw with tiger
lily and other lilies.
Lab. expt.
• Form: What is a flower?
What does each part do?
Get acquainted with all the flower parts
• Function:
In vitro pollen germination & tube growth
What nutrients are needed and why?
Determine % germination and tube lengths
of pollen in different test solutions.