Final Lecture Exam Ch 40 - Bio 104

What represents an evolutionary innovation with their production of flowers and fruits

Angiosperms

Once plants are competent to reproduce, a combination of factors -including what determines when a flower is produced

light, temperature, and both promotive and inhibitory internal signals

________ _________ changes allow plants to obtain competence to respond to external or internal signals

-May be morphologically obvious or very subtle

Internal developmental

What gene prevents early flowering in Arabidopsis?

embryonic flower (emf)

What happens to emf mutants in Arabidopsis?

They flower immediately.

What is the default state of flowering in plants?

Flowering is the default state.

What have many mechanisms evolved to do in relation to flowering?

Delay flowering.

What gene can induce the juvenile-to-adult transition in plants?

LEAFY (LFY)

In which plant was the LEAFY (LFY) gene cloned?

Arabidopsis

What type of promoter was used to replace LFY in the study?

A viral promoter

What effect does overexpressing LFY have on flowering time in aspen?

It causes flowering to occur in weeks instead of years.

Four genetically regulated pathways to flowering have been identified. What are they?

The light-dependent pathway

The temperature-dependent pathway

The gibberellin-dependent pathway

The autonomous pathway

What is the Light-Dependent Pathway keyed to?

Changes in the proportion of light to dark in the daily 24-hr cycle (day length)

When do short-day plants flower?

When daylight becomes shorter than a critical length

When do long-day plants flower?

When daylight becomes longer than a critical length

When do day-neutral plants flower?

When mature, regardless of day length

What are obligate long-day plants?

Plants that require long nights to flower.

What are obligate short-day plants?

Plants that require short nights to flower.

What are facultative long-day plants?

Plants that can flower with varying day lengths, but may flower more rapidly with longer days.

What are facultative short-day plants?

Plants that can flower with varying day lengths, but may flower more rapidly with shorter days.

Using light as a cue allows plants to do what?

flower when abiotic conditions are optimal

Manipulation of ______ in greenhouses ensures that short-day poinsettias flower in time for the winter holidays

photoperiod

What type of light does phytochrome respond to?

Red light

What type of light does cryptochrome respond to?

Blue light

What happens when phytochrome or cryptochrome undergoes a conformational change?

It triggers a cascade of events that leads to the production of a flower.

In Arabidopsis, which gene is regulated by phytochrome?

CONSTANS (CO)

What does phytochrome regulate in relation to CONSTANS (CO)?

The transcription of CO.

What is the role of CONSTANS (CO) protein?

CO protein is a transcription factor that turns on other genes.

How does blue light affect CONSTANS (CO) protein levels?

Blue light acting via cryptochrome stabilizes CO during the day and protects it from ubiquitination.

What happens to CONSTANS (CO) protein levels at night?

Levels of CO are lower at night because of targeted protein degradation by ubiquitin.

What gene does CONSTANS (CO) help express?

CONSTANS (CO) results in the expression of LFY.

What is the significance of the LFY gene?

LFY is one of the key genes that tells a meristem to switch over to flowering.

What is vernalization?

A period of chilling required by some plants before flowering.

What is the effect of chilling on winter wheat?

Winter wheat will not flower without a period of chilling.

Can seeds be chilled and then planted in spring?

Yes, seeds can be chilled and then planted in the spring.

What effect do decreased levels of gibberellins have on flowering in some species?

They delay flowering.

Which gene does gibberellin bind to that supports flowering?

The LFY gene.

How does gibberellin affect LFY gene expression?

It induces an increase in LFY gene expression.

What is the autonomous pathway in plants?

A flowering pathway that does not depend on external cues except for basic nutrition.

What effect does the autonomous pathway presumably have on flowering?

It presumably delays flowering.

What regulates when flowering occurs in the autonomous pathway?

A balance between floral promoting and inhibiting signals.

How can you test determination for flowering in the autonomous pathway?

By changing the environment and ascertaining whether developmental fate has changed.

What are the four flowering pathways that lead to an adult meristem becoming a floral meristem?

They activate or repress the inhibition of floral meristem identity genes.

What are the two key genes involved in floral meristem identity?

LFY and AP1

What do floral meristem identity genes turn on?

Floral organ identity genes.

What are the four concentric whorls defined by floral organ identity genes?

Sepal, petal, stamen, and carpel.

ABC Models explain how 3 classes of floral organ identity gene scan specify 4 distinct organ types. List these classes

Class A genes alone - Sepals

Class A and B genes together - Petals

Class B and C genes together - Stamens

Class C genes alone - Carpels

What are the other two classes in the ABC Model

Class D genes are essential for carpel formation

Class E genes SEPALATA (SEP)

What is the calyx of a flower?

The calyx consists of flattened sepals.

What is the corolla of a flower?

The corolla consists of petals.

What is the androecium in a flower?

The androecium is the collective term for all the stamens (male structures) of a flower.

What are the components of a stamen?

A stamen consists of a filament and an anther.

What is the gynoecium in a flower?

The gynoecium is the collective term for all carpels (female structures) of a flower.

What are the components of a carpel?

A carpel consists of an ovary, style, and stigma.

Where are ovules produced in a flower?

Ovules are produced in the ovary.

What are the 2 Trends in Floral Specialization

Floral parts together

Floral parts lost or reduced

Primitive flowers are

Advanced flowers are

radially symmetrical

bilaterally symmetrical

In angiosperms, the ______ ________ is very small and is completely enclosed within the tissues of the parent sporophyte

gametophyte generation

Reproductive organs of angiosperms differ from thoseof animals in two ways

Both male and female structures usually occur together in the same individual

Reproductive structures are not permanent parts of the adult individual

Pollen Formation

Anthers contain four microsporangia which produce microspore mother cells (2n)

Microspore mother cells produce microspores (n)through meiosis

Microspore develops by mitosis into pollen

Generative cell in the pollen grain will later divide to form two sperm cells

What type of cell undergoes meiosis within each ovule to form megaspores?

Diploid megaspore mother cell

How many haploid megaspores are produced from the meiosis of a megaspore mother cell?

Four haploid megaspores

How many megaspores typically survive after meiosis?

Usually only one megaspore survives

What happens to the surviving megaspore after it enlarges?

It undergoes repeated mitotic divisions to produce eight haploid nuclei

What is formed from the eight haploid nuclei after mitotic divisions?

A seven-celled embryo sac

What evolutionary strategy involves the separation of stamens and pistils in space?

Promotion of outcrossing

What type of plants produce only ovules or only pollen?

Dioecious plants

What type of plants produce male and female flowers on the same plant but may mature at different times?

Monoecious plants

What is the term for a mechanism that prevents self-fertilization in plants?

Self-incompatibility

What is self-incompatibility?

Self-incompatibility increases outcrossing.

How do pollen and stigma recognize each other in self-incompatibility?

Pollen and stigma recognize each other as being genetically related, and pollen tube growth is blocked.

What controls self-incompatibility?

Self-incompatibility is controlled by alleles at the S locus.

What are the two types of self-incompatibility?

1. Gametophytic self-incompatibility 2. Sporophytic self-incompatibility

What is gametophytic self-incompatibility?

It depends on the haploid S locus of the pollen and the diploid S locus of the stigma.

What is sporophytic self-incompatibility?

If the alleles in the stigma match either of the pollen parent's S alleles, the haploid pollen will not germinate.

What is double fertilization?

A process that occurs only in angiosperms involving two sperm cells.

What are the two key developments resulting from double fertilization?

Fertilization of the egg and formation of endosperm that nourishes the embryo.

What initiates embryo development?

Embryo development begins once the egg cell is fertilized.

What does the growing pollen tube do in angiosperm embryos?

The growing pollen tube enters the angiosperm embryo sac and releases two sperm cells.

What happens to one of the sperm cells released by the pollen tube?

One sperm fertilizes the central cell with its polar nuclei and initiates endosperm development.

What does the other sperm cell released by the pollen tube do?

The other sperm fertilizes the egg to produce a zygote.

What follows fertilization in embryo development?

Cell division soon follows, creating the embryo.

What is the nature of the first zygotic division?

The first zygotic division is asymmetrical.

What does the small cell formed during the first zygotic division develop into?

The small cell divides repeatedly to form a ball of cells that will become the embryo.

What does the large cell formed during the first zygotic division develop into?

The large cell divides repeatedly to form an elongated structure called a suspensor.

What is the function of the suspensor in early development?

The suspensor transports nutrients to the embryo.

What axis forms during the first zygotic division?

The root-shoot axis forms at this time.

What do the cells near the suspensor become?

Cells near the suspensor become the root.

What do the cells at the opposite end of the suspensor become?

Cells at the other end become the shoot.

What type of cell division is observed in the zygote of the brown alga Fucus?

Asymmetrical cell division

What develops on one side of the embryo in Fucus zygote development?

A bulge

What does the smaller cell that results from cell division in Fucus develop into?

A rhizoid that anchors the alga

What does the larger cell that results from cell division in Fucus develop into?

The thallus, or main algal body

How is the axis first established in the zygote of Fucus?

By the point of sperm entry

Can the axis established in the Fucus zygote be changed?

Yes, it can be changed by environmental signals

What determines the three-dimensional shape and form in plants?

Regulating the amount and pattern of cell divisions.

What is established at a very early stage in plant development?

The vertical axis (root-shoot axis).

What is the second axis established in plants?

The radial axis (inner-outer axis).

What do the first cells in plant development divide to produce?

A solid ball of cells.

What do apical meristems establish in plants?

The root-shoot axis