Reproduction and Aging

What 2 thing stimulate flowering?

1. Plant age

2. Enviro signals

_____ ______ ensures time for reproductive events + fruit initiation

Seasonal flowering

Timing is crucial for some plants to receive ______, reipen fruit, and disseminate seeds

pollen

Delays allow for more ________ production to support the energy-density floral cycle

biomass

Some plants will flower once they reach a specific _____

age

Plants that flower once they reach a specific age is determined by the development of _______ and not environmental conditions

nodes

1 example of a plant that flowers at a specific age

Garden peas

Early determinate garden peas initiate the production of flower buds once they have produced _____ (#) nodes

8

Late determinate garden peas initiate production of flower buds once they have produced _____ (#) nodes

16

Once the determined # of nodes is reached, the genes that control flower development are _________

activated

What is phase change?

Change in plant from vegetative growth to reproductive phase

Juvenility

Characterized by the inability to flower + reproduce seeds

What is juvenility generally determined by?

Plant size or # of nodes or leaves

How long can plant juvenility last?

It can be short (weeks) or long (decades)

What is one way to visually identify juvenility vs maturity?

Differences in leaf shape are noticeable in many plants in regards to phase of development?

Maturity (adult)

Characterized by the ability to flower + reproduce seeds

Flowering in mature plants still must be induced by ______ or _____ stimulus

1. enviro

2. genetic

Duration of juvenile phase (years) of apple

6-8

Duration of juvenile phase (years) of orange

6-7

Duration of juvenile phase (years) of grapefruit

6-8

Duration of juvenile phase (years) of pear

8-12

Duration of juvenile phase (years) of scotch pine

5-10

Duration of juvenile phase (years) of douglas fir

15-20

Duration of juvenile phase (years) of norway spruce

20-25

Duration of juvenile phase (years) of english oak

25-30

Duration of juvenile phase (years) of european beech

30-40

2 most common enviro signals (for flower induction + intiation)

1. Temp

2. Light (day length)

What are two examples of plants that respond to cold temperature?

1. Winter wheat

2. Orchardgrass

What are two examples of plants that respond to day length?

1. Poinsettia

2. Soybean

Day length

the # of hours of light received during the day

Vernalization

Low temp signals floral induction + initiation in some plants

What temps are most effective for vernalization?

0 - 10^oC or 32 - 50^oF

How much time (of low temps) are required for vernalization?

Several weeks

Exposure to extended periods of temps above 10^oC may ________ ___ ______ of vernalization

reverse the process

Light (photoperiod)

The effect of the # of hours of light received per day on flowering

In regards to photoperiod, the specific # of hours of ______ per day is difference for each plant species

light

Plants that respond to photoperiod are called _________

Photoperiodic

2 photoperiodic classes

1. Long day

2. Short day

Long day plants

Plants that flower when the photoperiod (day length) is greater than some critical time

Short day plants

Plants that flower when the photoperiod (day length) is shorter than some critical time

Ex of long day plant

Tickseed

Ex of short day plant

Poinsettia

Phytochrome

Photoreceptor proteins that absorb specific wavelengths of light

Red wavelengths

650-680 nm

Far-red wavelengths

710-740 nm

2 forms of phytochrome

1. Pr (phytochrome red)

2. Pfr (phytochrome far-red)

Which form of phytochrome absorbs red light?

Phytochrome red

Which form of phytochrome is not biologically active?

Phytochrome red

Which form of phytochrome absorbs far-red light?

Photochrome far-red

Which form of phytochrome is biologically active?

Phytochrome far-red

Biologically active (in regards to phytochrome)

Causes the response to happen

Once activated, Pfr can regulate the _____ _____

flowering response

What is the signal that stimulates long-day plants to flower?

Light

In long day plants, flower is initiated once what is reached?

The critical photoperiod

Pfr travels from the cytoplasm to the nucleus where it binds to specific regions of plant DNA that control flowering. This must process must occur _____ for ______ ______ before flower initiation occurs.

1. daily

2. several weeks

Can the prcoess of flower induction and initation be reversed or inhibited? How?

Yes, by changing the daylength

In short day plants like poinsettias, the concentration of Pfr should be ____ which allows flowering to occur

low

3 stages of flower formation and development

1. Floral Induction

2. Floral Initiation

3. Floral Development

Floral induction

Stage when plant cells are ready to receive the signal to flower

When does floral induction occur?

After the cell matures (phase change)

Floral initiation

Stage when “induced meristematic cells” change from forming vegetative organs to floral reproductive organs

Floral development

Stage when floral initials develop into fully formed flower buds

Meosis I

Chromosomes replicate, sort, and separate into 2 daughter cells with the orginal ceullar chromsome content

Meiosis II

• Chromosomes do not replicate

• Homologous chromosomes align across from each other

• Daughter cells formed at the end are haploid (1n)

• Form the pollen grains (anthers) and the egg (ovules)

Anthesis

When flowers open and pollen is shed through the anther wall

Most plants must _____ their flowers before pollen transfer can occur

open

Pollination

Transfer of pollen from an anther to a stigma

How large are pollen grains?

Microscopic, about 15 to 100 microns

Pollen is transferred to the stigma by what 3 things?

1. Insects: honeybees, hummingbirds, butterflies, moths

2. Wind

3. Other: water, snails, slugs, birds, bats

Fertilization

Union of an egg + a sperm (gametes) to form a zygote

When does fertilization occur?

After the pollen grain has germinated and grown down the style to the ovary

Double fertilization

1. Union of sperm + egg → zygote → embryo

2. Union of sperm + polar nuclei (2) → endosperm → food

Gymnosperms

Reproductive organs are cones

2 forms of fertility

1. Self-fertile

2. Self-sterile (incompatibility)

Self-fertile

• Plant can set fertile fruit + seed with its own pollen or pollen from the same clone

• Pollen pollinates the stigma from the same flower or plant

Self-sterile (incompatibility)

• Plant cannot set fertile fruit + seed with its own pollen or pollen from the same clone

• Pollen from another plant (different clone) is required for fertile fruit + seed formation

Fruit growth begins following…

fertilization and fruit set

Fruit growth + development is influenced by what 3 enviro factors

1. Temp

2. Light

3. Soil moisture

How does (low) temperature affect fruit growth?

It impact pollination/fertilization by influencing pollinators + pollen viability, which affect fruit set

How does light affect fruit growth?

Influences the production of carbs in leaves

How does soil moisture affect fruit growth?

Influences water uptake + the movement to developing fruit

Fruit growth + development is influenced by what 3 plant growth regulators?

1. Auxins

2. Gibberellins

3. Ethylene

What 4 things do auxins do in regards to fruit growth + development?

1. Fruit set + cell division

2. Often originates from seeds

3. Cell enlargement

4. Seed development

What do gibberellins do in regards to fruit growth + development?

Stimulate cell enlargement + expansion

What does ethylene do in regards to fruit growth + development?

Fruit ripening

5 ex of climacteric fruit

1. Bananas

2. Tomatoes

3. Apples

4. Avocados

5. Peaches

Climacteric fruit

Characterized by a burst in respiration + release of ethylene near the end of ripening

Thinning

Growers remove some fruit to improve fruit size + quality

Plants typically set ____ fruit than needed

more

–Plants cannot support a high number of fruit, so some naturally ____ 2 or 3 times during the year

drop

2 ways fruits thinning is performed

1. By hand (organic method)

2. By applying specific plant growth regulators

Senescence

A terminal, irreversible deteriorative change in living organisms, leading to cellular and tissue breakdown and death

Senescence occurs in what parts of plants (4)?

1. Leaves

2. Seeds

3. Flowers

4. Fruits

Annuals’ pattern of senescence

The whole plant dies at the end of one growing season, usually after reproductive growth ends

Herbaceous perennials’ senescence

• Leaves + stems die at the end of the growing season + resume growth the next spring

• Roots remian alive + grow for many years

Deciduous woody plants’ senescence

• Leaves senesce, die + drop every year

• Stems + roots remian alive + grow for many years

Reduction of _______ triggers leaf senescence

photoperiod

Why does the reduction of photoperiod trigger leaf senescence?

Ethylene blocks auxin transport in leaves which triggers leaf abcission

4 physiological changes that cause senescence

1. Decline in photosynthesis

2. Pollination + fertilization

3. Transfer of stored nutrients to flowers + fruit

4. Changes in plant growth regulators

Fruit set

When a flower on a plant is successfully pollinated + begins to grow into fruit instead of falling off