Download The weird and wonderful ways plants reproduce

The weird and wonderful
ways plants reproduce
A Plant’s Life Cycle
Seed production
Seed germination
Juvenile
vegetative growth
Flower formation
Mature
vegetative growth
The result is offspring with genetic diversity that can
adapt to new or changing environments.
A Plant’s Life Cycle
Plantlets
form
rather than
seeds
Apomixis
Seed production
Seed germination
Juvenile
vegetative growth
Flower formation
Cleistogamy
Precocious
germination
Mature
vegetative growth
Modified
stems
Clonal
maintenance of
juvenile form
Plantlets on
leaves and
roots
The result is offspring with reduced genetic diversity (clonal) or
adaptations that allow colonization of specialized niches.
A Plant’s Life Cycle
Precocious
germination
Seed production
Seed germination
Juvenile
vegetative growth
Flower formation
Mature
vegetative growth
Precocious germination
Seeds complete development and
are dry when shed from the plant
and in many cases dormant.
Precocious germination
Premature germination
Generally undesirable
Genetic mutation in
response to ABA
Tomato
Zinnia
Precocious germination
Precocious germination is the
normal type of seed and seedling
development in species from
over 25 genera.
Most grows along the edge of
waterways, in swamps or wet
forests.
In mangrove (Rhizophora
mangle), the seed germinates
while still on the plant.
Precocious germination
A Plant’s Life Cycle
Precocious
germination
Seed production
Seed germination
Juvenile
vegetative growth
Flower formation
Mature
vegetative growth
Clonal
maintenance of
juvenile form
Juvenile form
Bamboo is an example of a
monocarpic plant with
delayed maturation.
It spreads by rhizomes
until it flowers, sets seeds
and dies.
Juvenile form
Juvenility
Phase of development where
the plant can not flower even
when the environment is
inductive for flowering.
Mature
Juvenile
Hedera helix (English ivy)
Juvenile form
Foliar dimorphism
Pseudopanax
Pinus
A Plant’s Life Cycle
Precocious
germination
Seed production
Seed germination
Juvenile
vegetative growth
Flower formation
Mature
vegetative growth
Plantlets on
leaves, and
roots
Clonal
maintenance of
juvenile form
Adventitious plantlet formation
Terminology
Apogamy – without gametes
Vegetative apomixis
Vivipary – also used for
precocious germination
Gemmae
Plantlets on leaves
Gemmae are clonal plant
fragments produced on
the leaf margin or in
specialized cups of
several bryophytes like
mosses and liverworts.
Gemmae cups on the leaves of the liverwort (Marchantia)
Plantlets on leaves
Mother-of-thousands (Bryophyllum daigremontianum)
Plantlets on leaves
Bryophyllum delagoense
Bryophyllum
crenatodaigremontianum
Plantlets on leaves
Piggy-back plant (Tolmiea menziesii)
Plantlets on leaves
This is most likely due to
the over production of
cytokinin in portions of
the leaf.
Piggy-back begonia (Begonia hispida cucullifera)
Plantlets on leaves
Hen and chickens fern (Asplenium bulbiferum )
Plantlets on leaves
Button fern (Tectaria cicutaria )
Plantlets on leaves
Walking fern (Camptosorus rhizophyllus )
Plantlets on leaves
Walking fern (Camptosorus rhizophyllus )
Plantlets on leaves
Walking fern (Camptosorus rhizophyllus )
Plantlets on leaves
Leaf cuttings
Plantlets on leaves
Micropropagation
Plantlets on roots
Root suckers
Paw paw (Asimina triloba)
Plantlets on roots
Root cuttings
Sassafras
A Plant’s Life Cycle
Precocious
germination
Seed production
Seed germination
Juvenile
vegetative growth
Flower formation
Mature
vegetative growth
Modified
stems
Plantlets on
leaves, and
roots
Clonal
maintenance of
juvenile form
Modified stems
Stolons
Runners
Aspen (Populus tremuloides)
populations can have over 1000
clonal offspring (ramets) from a
single dominant mother plant
(genet) covering over 30 acres.
Modified stems
Geophytic structures
Bulbs
Corms
Tubers
Rhizomes
Modified stems
Dropper – a new bulb that
forms at the end of a stolon.
Agnes Robertson. 1906. The ‘Droppers’ of Tulipa
and Erythronium. Annals of Botany20:429-440.
Modified stems
Dropper – a new bulb that
forms at the end of a stolon.
Agnes Robertson. 1906. The ‘Droppers’ of Tulipa
and Erythronium. Annals of Botany20:429-440.
Modified stems
Dropper – a new bulb that
forms at the end of a stolon.
Trout lily (Erythronium)
Modified stems
Trout lilies are colonizing
plants.
They produce many single and
a few double-leaved plants.
Only double leaved plants
flower.
A flowering plant can have
over 100 ovules, but a capsule
rarely has 8 seeds.
Trout lily (Erythronium)
Modified stems
The Minnesota trout lily (E.
propullans) appears to only
reproduce by droppers.
Trout lily (Erythronium)
It is endangered and restricted
to two counties in Minnesota.
Modified stems
Geophytes - Lilium
Arial bulbils
Bulb scale cutting
Modified stems
European bittercress (Dentaria bulbifera)
Modified stems
Small aerial tubers produced on the stem or leaves are often
called tubercles.
Hardy begonia
(Begonia evansiana)
String-of-hearts
(Ceropegia woodii)
Devil’s tongue
Amorphophallus bulbifera
Modified stems
All plants are clones reproduced by tubercles.
Hardy begonia (Begonia evansiana)
Modified stems
Cultivated forms of air potato are edible, while wild forms
can be invasive and poisonous.
Air potato (Dioscorea bulbifera )
A Plant’s Life Cycle
Precocious
germination
Seed production
Seed germination
Juvenile
vegetative growth
Flower formation
Cleistogamy
Mature
vegetative growth
Modified
stems
Plantlets on
leaves, and
roots
Clonal
maintenance of
juvenile form
Cleistogamy
Chasmogamous
flowers open prior
to pollination and
may be self or
cross pollinated.
Cleistogamous
flowers do not
open and are selfpollinated.
Cleistogamy is found in over 200 (mostly herbaceous) species.
The reproductive effort invested in the cleistogamous
flowers is smaller than in the chasmogamous ones.
Cleistogamy
Arial chasmogamous
flowers.
Subterranean
cleistogamous
flowers.
Flower
Fruit
Violet (Viola odorata)
Flower
Fruit
Seeds
A Plant’s Life Cycle
Precocious
germination
Apomixis
Seed production
Seed germination
Juvenile
vegetative growth
Flower formation
Cleistogamy
Mature
vegetative growth
Modified
stems
Plantlets on
leaves, and
roots
Clonal
maintenance of
juvenile form
Apomixis
Apomixis is the production of an
embryo that bypasses the usual
process of meiosis and fertilization.
The genotype of the embryo and
resulting plant will be the same as
the seed parent.
This is clonal seed production!
Apomixis
Apomixis occurs in over
300 species from at least
35 plant families.
It is most common in the
Asteraceae, Graminaceae,
Rosaceae, and Rutaceae.
Goat’s beard (Tragopogon)
Apomixis
Only a few economically important
food crops exhibit apomixis.
These include Citrus, Mango
(Mangifera), and Mangosteen
(Garcinia).
Several grass species and
cultivars are apomicts including
Kentucky blue grass.
Orange (Citrus)
Apomixis
Types of apomixis include:
1.
Diplospory
2. Apospory
3. Adventive embryony
Apple (Malus)
Apomixis
Sexual development
Megaspore
Mother Cell
Nucellus
Meiosis
Egg Sac
Apomixis
Diplospory
Normal
Meiosis
Diplospory = Diplo
(two) and spory
(spore).
Egg Sac
Megaspore
Mother Cell
Nucellus
1n
Megaspore mother
cell does not finish
or initiate meiosis.
Egg sac organizes
normally but cells
are diploid.
Diplospory
2n
Apomixis
Diplospory
Normal
Meiosis
Embryo initiates
development without
being fertilized.
Egg Sac
Megaspore
Mother Cell
Nucellus
1n
Diplospory
2n
Endosperm also
develops either with
or without
fertilization from
the polar nuclei.
Apomixis
Diplospory
In some cases (Poa), fertilization is
required for endosperm formation.
The egg does not get fertilized
because it is already growing.
Common in grasses and Asteraceae.
Eastern gamagrass
(Tripsacum dactyloides)
Apomixis
Adventive embryony
Normal
Megaspore
Mother Cell
Nucellus
Adventive
embryony
Meiosis
Egg Sac
The megaspore mother
cell undergoes normal
meiosis and forms a
normal sexual embryo
sac.
These cells are
fertilized by male
sperm cells as in
normal embryogenesis.
Apomixis
Adventive embryony
Normal
Megaspore
Mother Cell
Nucellus
Adventive
embryony
Meiosis
Egg Sac
However, cells in the
nucellus begin
forming multiple
embryos in the
micropylar region of
the ovule.
Apomixis
Adventive embryony
Nucellus
Adventive
embryos
Julius von Sachs – Lectures on the
physiology of plants, 1887.
Apomixis
Adventive embryony
Apomixis
Adventive embryony
These asexual embryos do not
produce their own embryo sac
but grow into the embryo sac of
the sexual embryo.
Endosperm must be fertilized.
Common in tropical fruit trees
like citrus and mango.
Apomixis
Adventive embryony
Multiple seedlings (polyembryony)
from a single seed in Citrus.
One of the seedlings will be
sexual and the others will be
clones.
Apomixis
Somatic embryogenesis
A Plant’s Life Cycle
Plantlets form
rather than
seeds
Precocious
germination
Apomixis
Seed production
Seed germination
Juvenile
vegetative growth
Flower formation
Cleistogamy
Mature
vegetative growth
Modified
stems
Plantlets on
leaves, and
roots
Clonal
maintenance of
juvenile form
Plantlets in place of seeds
Wild onion
Allium vineale
Plantlets in place of seeds
Plantlets in place of seeds
Alpine bistort (Polygonum viviparum)
Plantlets in place of seeds
Meadow grass (Poa bulbosa)
Plantlets in place of seeds
Spiderplant (Chlorophytum comosum)
Plantlets in place of seeds
Walking iris
Neomarica caerulea
Plantlets in place of seeds
Century plant (Agave americana)
These agave plants
are monocarpic.
They take decades to
flower, then the
mother plant dies.
Plantlets in place of seeds
Century plant (Agave americana)
A Plant’s Life Cycle
Plantlets form
rather than
seeds
Precocious
germination
Apomixis
Seed production
Seed germination
Juvenile
vegetative growth
Flower formation
Cleistogamy
Mature
vegetative growth
Modified
stems
Plantlets on
leaves, and
roots
Clonal
maintenance of
juvenile form
The weird and wonderful
ways plants reproduce