Day 5 Plant Reproduction

Label the plant life cycle diagram

Sporophytes: ploidy, what they produce and how

• 2n

• produce spores (n) via meiosis

What do the spores grow into and by what process

they grow into gametophytes via mitosis

Gametophytes: ploidy, what they produce and by what process

• n

• produce gametes (n) via mitosis

What do the gametes create and by what process

create a zygote via fusion/fertilization

What does the zygote grow into and by what process

grows into sporophyte via mitosis

Example of gametophyte dominant

moss

Example of sporophyte dominant

flowering plant

Sexual reproduction in angiosperm reproduction

sporophyte-dominated alternation of generations with gametes and fertilization

Asexual reproduction in angiosperm reproduction

clonal copies of parent plant created by mitotically driven growth

Asexual reproduction in plants

• many different mechanisms

• many plants use it

Angiosperm reproduction vis sexual mode

• sexual reproduction in plants requires flowers

• flowers host gametophytes in angiosperm life cycle

• flowers often use nectar to attract animals to carry pollen

Label the flower structures/parts

What is the stamen

male part/structures of the flower

What does the stamen consist of and their roles

1. anthers - produce pollen

2. filaments - elevate/hold up anther

What is the carpel

the female part/structures of a plant

What does the carpel consist of and their role

1. stigma - receives pollen

2. style - elevates/holds up the stigma

3. ovary - contains ovules

Facts of the carpel in flowers

1. defining feature of angiosperm

2. not found in any other plant

Type of sexes/sex combos in flowers

1. bisexual

2. unisexual

What does it mean when a flower is bisexual

they are perfect because they have both stamen and carpel

What does it mean when a flower is unisexual

the flower has only stamen or only carpel

Types of plants with unisexual flowers

1. monoecious - male and female flowers on same plant

2. dioecious - male and female flowers on different plants

Label angiosperm life cycle

How is pollen developed

1. (2n) microsporocytes for (n) micropores via meiosis

2. microspores grow into pollen - 2 cell male gametophytes via mitosis

(tube cell and generative cell)

What are the 2 male gametophytes produced when microspores grow into pollen

1. tube cell

2. generative cell

Draw/label pollen development

What is the cell wall of pollen grains made out of

sporopollenin

Role/benefits of sporopollenin

1. prevents desiccation

2. almost indestructible by microorganisms

3. insoluble in most solvents

4. leaves great pollen fossils

How female gametophytes formed

1. (2n) megasporocytes form (n) megaspores via meiosis

2. megaspores grow into a 7-cell female gametophyte via mitosis

(includes egg and central wall with 2 nuclei)

What are the 7-cell female gametophyte that megaspores grow into

1. egg

2. central wall with 2 nuclei

Purpose of the pollen tube

grows down into the style towards the female gametophyte

What is pollen competition

as pollen tubes grow through the style, they compete with each other

• only the fastest (most fit) will fertilize eggs

What is pollen competition an example of

a form of male-male competition

What is self-incompatibility

reactions to reduce inbreeding

How do flowers reduce inbreeding

1. pistil can arrest growth of pollen tubes of likely close relatives

How does the pistil arrest pollen tube growth

1. S gene has many different alleles within a population, so sharing same S allele suggests kinship

2. pollen tube (n) carries one allele and pistil (2n) carries two

3. if pollen tube chares an S allele with the pistil, then pollen tube growth is arrested

Steps of fertilization in flowers

1. the two sperm nuclei are released into the female gametophyte

2. one sperm fertilizes the egg to form a (2n) zygote

3. the other sperm “fertilizes” the central cell and forms an (3n) endosperm

What is double fertilization

the second sperm nuclei fertilize the central wall: fusing with polar nuclei to form (3n) endosperm

Benefits of endosperm

triploid endosperm may increase nutritive stores

Steps of fruit development

1. the ovules develop into the seeds (one per zygote)

2. the ovary becomes the fruit

3. the remaining flower parts die back

Whats a monocotyledon

type of angiosperm and is characterized by haing a single seed leaf, or cotyledon

Examples of monocotyledons

1. true grasses

2. orchids

3. corn seed

Whats a dicotyledons

type of angiosperm and is characterized by having two embryonic leaves, or cotyledon

Examples of dicotyledons

1. common garden plants

2. tress

3. been seed

Whats germination

many seeds require physical “abuse” to germinate

Scarification occurs when seed coats are

1. abraded by soil particles over time

2. heated by fire

3. exposed to digestive action

4. broken down by mircrobes

What is scarification

weakening or altering the coat of a seed to encourage germination

What are pollination syndromes

are flower traits that evolve to facilitate pollination

• different modes of pollination favor different structures, colors, scents

Co-evolution between flowers and pollinators

they evolve together, but to maximize their individual fitness, not to help the other organism

• plants evolve to maximize pollen transfer for minimum reward output

• pollinators evolve to obtain as much reward as possible

What is nectar

a sugar solution produced by plants to attract pollinators

Where do flowers hold nectar

in nectaries

Bee pollination

• flower parts visible

• often colored, but not red

• has nectar guides

• sweet floral odor

What are nectar guides

• help bees find nectaries

• some are visible only in UV range

Fly pollination

• flowers resemble carrion

• reddish to purple-brown color

• strong foul odor

• no nectar guides

Moth pollination

• open at night

• usually white

• strong/sweet odor

• lots of nectar

Hummingbird pollination

• flowers produced nectar, hidden in long floral tube

• often red, orange, or yellow

• no odor

• often lack landing platforms

Wind pollination

• don’t need to attract pollinators

• petals, sepals reduced

• lots of pollen produced

• pollen is lightweight, non-sticky

• stigma is large, often feathery

Complete table of the summary of pollinator syndromes