Plant reproduction involves an alternation of generations between haploid and diploid phases. In seed plants like gymnosperms and angiosperms, the sporophyte phase is dominant. During reproduction, sporophyte plants produce male gametophytes (pollen grains) and female gametophytes (embryo sacs) through meiosis. Pollination transfers pollen grains which contain sperm for double fertilization - one sperm fuses with the egg to form a diploid zygote, and the other fuses with polar nuclei to form triploid endosperm which nourishes the developing embryo. Each fertilized ovule develops into a seed containing the next sporophyte generation.
Fungi are eukaryotic, spore bearing, achlorophyllous, heterotrophic organisms that generally reproduce sexually and asexually and whose filamentous, branched somatic structures are typically surrounded by cell walls containing chitin or cellulose or both with many organic molecules and exhibiting absorptive nutrition.Fungi frequently reproduce by the formation of spores. A spore is a survival or dispersal unit, consisting of one or a few cells, that is capable of germinating to produce a new hypha. Unlike plant seeds, fungal spores lack an embryo, but contain food reserves needed for germination. Many fungi produce more than one type of spore as part of their life cycles. Fungal spores may be formed via an asexual process involving only mitosis (mitospores), or via a sexual process involving meiosis (meiospores). Sexual and asexual reproduction may require different sets of conditions (e. g., nutrients, temperature, light, moisture).
Fungi are eukaryotic, spore bearing, achlorophyllous, heterotrophic organisms that generally reproduce sexually and asexually and whose filamentous, branched somatic structures are typically surrounded by cell walls containing chitin or cellulose or both with many organic molecules and exhibiting absorptive nutrition.Fungi frequently reproduce by the formation of spores. A spore is a survival or dispersal unit, consisting of one or a few cells, that is capable of germinating to produce a new hypha. Unlike plant seeds, fungal spores lack an embryo, but contain food reserves needed for germination. Many fungi produce more than one type of spore as part of their life cycles. Fungal spores may be formed via an asexual process involving only mitosis (mitospores), or via a sexual process involving meiosis (meiospores). Sexual and asexual reproduction may require different sets of conditions (e. g., nutrients, temperature, light, moisture).
it is useful for classroom teaching , remedial classes. it consist of important questions and answers according to the board point of view, students it is very helpful for your examination
Pollination, transfer of pollen grains from the stamens, the flower parts that produce them, to the ovule-bearing organs or to the ovules (seed precursors) themselves. In plants such as conifers and cycads, in which the ovules are exposed, the pollen is simply caught in a drop of fluid secreted by the ovule. In flowering plants, however, the ovules are contained within a hollow organ called the pistil, and the pollen is deposited on the pistil’s receptive surface, the stigma. There the pollen germinates and gives rise to a pollen tube, which grows down through the pistil toward one of the ovules in its base. In an act of double fertilization, one of the two sperm cells within the pollen tube fuses with the egg cell of the ovule, making possible the development of an embryo, and the other cell combines with the two subsidiary sexual nuclei of the ovule, which initiates formation of a reserve food tissue, the endosperm. The growing ovule then transforms itself into a seed.
Pollen pistil interaction
Types of Incompatibility in plants
Methods to overcome Incompatibility
Prepared by
Dr. T. Annie Sheron
Assistant Professor of Botany
DEPARTMENT OF BOTANY
KAKATIYA GOVERNMENT COLLEGE, HANAMKONDA
it is useful for classroom teaching , remedial classes. it consist of important questions and answers according to the board point of view, students it is very helpful for your examination
Pollination, transfer of pollen grains from the stamens, the flower parts that produce them, to the ovule-bearing organs or to the ovules (seed precursors) themselves. In plants such as conifers and cycads, in which the ovules are exposed, the pollen is simply caught in a drop of fluid secreted by the ovule. In flowering plants, however, the ovules are contained within a hollow organ called the pistil, and the pollen is deposited on the pistil’s receptive surface, the stigma. There the pollen germinates and gives rise to a pollen tube, which grows down through the pistil toward one of the ovules in its base. In an act of double fertilization, one of the two sperm cells within the pollen tube fuses with the egg cell of the ovule, making possible the development of an embryo, and the other cell combines with the two subsidiary sexual nuclei of the ovule, which initiates formation of a reserve food tissue, the endosperm. The growing ovule then transforms itself into a seed.
Pollen pistil interaction
Types of Incompatibility in plants
Methods to overcome Incompatibility
Prepared by
Dr. T. Annie Sheron
Assistant Professor of Botany
DEPARTMENT OF BOTANY
KAKATIYA GOVERNMENT COLLEGE, HANAMKONDA
Alternation of generation in archegoniatesSumit Sangwan
Altrenation of generations:
All plants undergo a life cycle that takes them through both haploid and diploid generations. The multicellular diploid plant structure is called the sporophyte, which produces spores through meiotic (asexual) division. The multicellular haploid plant structure is called the gametophyte, which is formed from the spore and give rise to the haploid gametes. The fluctuation between these diploid and haploid stages that occurs in plants is called the alternation of generations.
Bryophyte generations
Bryophytes are nonvascularized plants that are still dependent on a moist environment for survival (see Plant Classification, Bryophytes . Like all plants, the bryophyte life cycle goes through both haploid (gametophyte) and diploid (sporophyte) stages. The gametophyte comprises the main plant (the green moss or liverwort), while the diploid sporophyte is much smaller and is attached to the gametophyte. The haploid stage, in which a multicellular haploid gametophyte develops from a spore and produces haploid gametes, is the dominant stage in the bryophyte life cycle. The mature gametophyte produces both male and female gametes, which join to form a diploid zygote. The zygote develops into the diploid sporophyte, which extends from the gametophyte and produces haploid spores through meiosis. Once the spores germinate, they produce new gametophyte plants and the cycle continues.
Tracheophyte Generations
Tracheophytes are plants that contain vascular tissue; two of the major classes of tracheophytes are gymnosperms (conifers) and angiosperms (flowering plants). Tracheophytes, unlike bryophytes, have developed seeds that encase and protect their embryos. The dominant phase in the tracheophyte life cycle is the diploid (sporophyte) stage. The gametophytes are very small and cannot exist independent of the parent plant. The reproductive structures of the sporophyte (cones in gymnosperms and flowers in angiosperms), produce two different kinds of haploid spores: microspores (male) and megaspores (female). This phenomenon of sexually differentiated spores is called heterospory. These spores give rise to similarly sexually differentiated gametophytes, which in turn produce gametes. Fertilization occurs when a male and female gamete join to form a zygote. The resulting embryo, encased in a seed coating, will eventually become a new sporophyte.
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Chap. 4 plant reproduction final
1. Chapter 4.
Plant Reproduction
KEY CONCEPT
All plants alternate between two phases in their life
cycles.
AP Biology 2005-2006
2. Plant life cycles alternate between
producing spores and gametes.
A two-phase life cycle is called alternation of
generations.
haploid phase
diploid phase
alternates SPOROPHYTE
PHASE
between fertilization
the two GAMETOPHYTE
meiosis
PHASE
AP Biology
3. Animal vs. Plant life cycle
Animal Plant
multicellular multicellular
sporophyte
2n
2n
gametes spores
1n 2n
unicellular multicellular
gametes gametophyte
1n 1n
AP Biology
alternation of generations
6. Gametophytes of seed plants
Gymnosperm Angiosperm
male gametophyte male gametophyte
pollen in male cone pollen in anthers of
flower
female gametophyte female gametophyte
develops in female develops in ovaries
cone of flower
seed seed
naked in cone protected in ovary
ovary wall can
develop into fruit
AP Biology
7. The sporophyte is the dominant phase for
seed plants.
AP Biology
8. Gymnosperm life cycle
female
gametophyte
in cone
male
gametophyte
in pollen
sporophyte
in seed
AP Biology
9. Angiosperm life cycle
male
gametophyte
in pollen
female
gametophyte
in ovary
sporophyte
in seed
AP Biology
10. Reproduction in angiosperm
Sporophyte plant produces unique reproductive
structure = the flower
male gametophyte = pollen grain
develop within anthers of flower
female gametophyte = embryo sac
develop within ovaries of flower
pollination by wind or animals brings pollen grain to
female gametophyte
fertilization takes place within ovary
double fertilization = embryo & endosperm
seeds contain sporophyte embryo
development of seeds in ovary
ovary develops into fruit around the seed
AP Biology
14. Parts of flower
Male
stamens = male reproductive organs
stamens have stalks (filament) &
terminal anthers which carry pollen
sacs
pollen sacs produce pollen
pollen grain = gametophyte
sperm-producing structure
AP Biology
15. Parts of flower
Female
carpels = female reproductive organs
ovary at the base
slender neck = style
within the ovary are 1 or more ovules
within ovules are embryo sacs
female gametophyte = embryo sac
egg-producing structure
AP Biology
16. Fertilization in Angiosperms
When pollen grain lands on stigma it
begins to grow pollen tube.
Nucleus within pollen grain divides and
forms 2 sperm nuclei
Pollen tube contains tube nucleus and
2 sperm nuclei
Pollen tube grows into style and
eventually reaches ovary and enters
ovule
AP Biology
17. Fertilization in Angiosperms
Inside embryo sac, two fertilizations
occur
One sperm nuclei fuses with egg nucleus
to produce diploid zygote – grows into
plant embryo
Second sperm nucleus fuses with two
polar nuclei to form triploid (3N) cell –
food tissue known as endosperm.
AP Biology
19. Fertilization (recap)
Pollination
pollen released from anthers is carried by wind
or animals to land on stigma
pollen grain produces a pollen tube
pollen tube grows down style into ovary & discharges
2 sperm into the embryo sac
1 sperm fertilizes egg = zygote
zygote develops into embryo
ovule develops into a seed
ovary develops into a fruit containing
1 or more seeds
AP Biology
21. Self-pollination
Why?
Guarantees seeds (no need for mates or
pollinators)
May save resources if flowers are smaller
Maximizes transmission of own genes
Why not?
Inbreeding depression - short-term cost
Loss of genetic diversity - long-term cost
An evolutionary dead end? - very long-term
cost
AP Biology
22. Preventing self-pollination
Various mechanisms
stamens & carpels may mature at different times
arranged so that animal pollinator won’t transfer
pollen from anthers to stigma of same flower
biochemical self-incompatibility = block pollen
tube growth
AP Biology
23. Fertilization takes place within the
flower.
Male gametophytes, or pollen grains, are produced in
the anthers.
– male spores produced in
anthers by meiosis
– each spore divides by
mitosis to form two
haploid cells
– two cells form a
single pollen grain
pollen grain
AP Biology
24. One female gametophyte can form in each ovule of a
flower’s ovary.
four female spores produced in ovule by
meiosis
one spore develops into female
gametophyte
female gametophyte contains seven
cells
one cell has two nuclei, or polar nuclei
one cell will develop into an egg
AP Biology
25. Pollination occurs when a pollen grain lands
on a stigma.
pollen tube
sperm
stigma
– one cell from pollen grain forms pollen tube
– other cell forms two sperm that travel down tube
AP Biology
26. Flowering plants go through the process of
double fertilization.
female
gametophyte
egg
sperm
polar nuclei
ovule
AP Biology
27. Flowering plants go through the process of double
fertilization.
endosperm
– one sperm fertilizes
the egg seed coat
– other sperm unites
with polar nuclei,
forming endosperm
– endosperm provides
food supply for
embryo
embryo
AP Biology
28. Each ovule becomes a seed.
The surrounding ovary grows into a fruit.
AP Biology
29. Fertilization in flowering
plants
Double fertilization
2 sperm from pollen
1 sperm fertilizes
egg = diploid zygote
1 sperm fuses with
2 polar nuclei to
form 3n endosperm
endosperm = food
tissue in seed
coconut milk
grains
AP Biology
32. Fruit
Fruit is a mature ovary
seeds develop from ovules
wall of ovary thickens to form fruit
fruits protect dormant seeds &
aid in their dispersal
AP Biology
34. Seed dispersal
• Why disperse?
• sample more (better?) sites for
germination/growth
• avoid predation or disease
• avoid competition
AP Biology
35. Seed dispersal
Plants produce enormous numbers of seeds to
compensate for low survival rate
a lot of genetic variation for natural selection to screen
AP Biology 2005-2006
39. Dormancy
Metabolism falls
Number of organelles per cell falls
Dehydration – water content falls
Vacuoles in cells deflate
Food reserves become dense
crystalline bodies
AP Biology
40. Maintaining dormancy
Physical barriers
The seed coat (testa) is waxy =
waterproof and impermeable to oxygen
Physical state – dehydrated
Chemical inhibitors present e.g. salts,
mustard oils, organic acids, alkaloids
Growth promoters absent
AP Biology
41. Seed viability
Viability: When a seed is capable of
germinating after all the necessary
environmental conditions are met.
Average life span of a seed 10 to 15 years.
Some are very short-lived e.g. willow (< 1
week)
Some are very long-lived e.g. mimosa 221
years
Conditions are very important for longevity
Cold, dry, anaerobic conditions
These are the conditions which are
maintained in seed banks
AP Biology
42. Germination: The breaking of dormancy
The growth of the embryo and its penetration of the seed
coat
Break down of barriers
Abrasion of seed coat
(soil particles)
Decomposition of seed
coat (soil microbes, gut
enzymes)
Cracking of seed coat Change in physical
(fire) state - rehydration
Destruction and dilution
of inhibitors
Light, temperature, water
Production of growth
AP Biology promoters
43. Seeds begin to grow when
environmental conditions are favorable.
Seed dormancy is a state in which the
embryo has stopped growing.
– Dormancy may end
when conditions
are favorable.
– While dormant,
embryo can
withstand extreme
conditions.
AP Biology
45. Germination begins the growth of an embryo
into a seedling.
– water causes seed to swell and crack coat
– embryonic root, radicle, is first to emerge
– water activates enzymes that help send sugars to
embryo
AP Biology
46. Germination begins the growth of an
embryo into a seedling.
water causes seed to swell and crack coat
embryonic root, radicle, is first to emerge
water activates enzymes that help send
sugars to embryo
– embryonic shoot, plumule, emerges next
AP Biology
47. Germination begins the growth of an
embryo into a seedling.
water causes seed to swell and crack coat
embryonic root, radicle, is first to emerge
water activates enzymes that help send
sugars to embryo
embryonic shoot, plumule, emerges next
– leaves emerge last
AP Biology
49. Germination
STAGE EVENTS
PREGERMINATION (a) Rehydration – imbibition of water.
(b) RNA & protein synthesis stimulated.
(c) Increased metabolism – increased respiration.
(d) Hydrolysis (digestion) of food reserves by
enzymes.
(e) Changes in cell ultra structure.
(f) Induction of cell division & cell growth.
GERMINATION (a) Rupture of seed coat.
• Emergence of seedling, usually radicle first.
POST GERMINATION (a) Controlled growth of root and shoot axis.
(b) Controlled transport of materials from food stores
to growing axis.
(c) Senescence (aging) of food storage tissues.
AP Biology