Ch 30: Reproduction and Domestication of Flowering Plants

Question 1

Explain the function of flowers in angiosperms

Answer 1

reproductive shoots specialized for the transfer and reception of pollen

Question 2

Identify and describe the function of different parts of a flower (Key terms: sepal, petal, carpel, stamen, filament, anther, style, stigma, receptacle)

Answer 2

Sepals - protect the flower as it develops

Petals - attract pollinators

Carpel - produces ovules

Stamen - produces pollen

Filament - tube-like structure that supports the anther (pollen sac)

Anther - The part of a stamen that contains the pollen

Style - aid fertilization by allowing pollen tubes to travel to the egg and distribute sperm cells

Stigma - The part of the pistil where pollen germinates

Receptacle - The part of a flower stalk where the parts of the flower are attached

Question 3

Distinguish between perfect and imperfect flowers

Answer 3

Perfect flowers produce ovules and pollen in the same flower
Imperfect flowers produce pollen and ovules in separate flowers

Question 4

Describe the formation of the male gametophyte in angiosperms

Answer 4

• Development of the male gametophyte from microspores in the anther: Diploid microsporocyte divides via meiosis to form 4 microspores → microspores divide via mitosis → generative cells give rise to 2 sperm (pollen grains surrounded by spore wall)

Question 5

Describe the formation of the female gametophyte in angiosperms

Answer 5

Development of the female gametophyte from megaspores in the ovule: Ovules develop within ovary of carpel → Diploid megasporocyte cell divides via meiosis to form 4 haploid megaspores → 3 die, 1 megaspore → surviving megaspore does 3 rounds of mitosis to produce 1 cell with 8 nuclei → Cell forms embryo sac (female gametophyte) which includes 1 egg, 2 synergids that guide pollen tube, 3 antipodal cells (?), central cell with 2 nuclei

Question 6

Define the following key terms: megaspore, microspore, synergid, pollen grain, generative cell, tube cell, embryo sac, central cell

Answer 6

Megaspore - Megaspores areproduced inside megasporangium (ovules)

Microspore - Microspores aresmall haploid spores that develop into male gametophytes

Synergid - two specialized cells that lie adjacent to the egg cell in the female gametophyte of angiospermsand play an essential role in pollen tube guidance and function

Pollen Grain - Each pollen grain is a single cell containing two male gametes

Generative cell - formed at the first division of the microspore and divides in the pollen grain or pollen tube to form two sperm cells

Tube cell - The cell in the pollen grain that develops into the pollen tube

Embryo sac - a cell inside theovuleof a flowering plant where fertilization occurs and which becomes the femalegametophyte, containing theendospermnucleus and thefertilizedovumthat develops into the embryo

Central cell - characterizes the angiosperm female gametophyte (embryo sac or megagametophyte) in that it directly participates in “double fertilization” to initiate endosperm development

Question 7

Give examples of how flower morphology reflects mode of pollination

Answer 7

• Wind pollination does not require structures to attract pollinators
• Some flowers do not provide a reward, but instead they “trick” their pollinators into visiting them

Question 8

Distinguish between pollination and fertilization

Answer 8

Pollination is the transfer of pollen from the anther of one plant to the stigma of the same or another plant. Fertilization is the joining of a sperm (from the pollen grain) with the egg in the ovule.

Question 9

Explain the significance of double fertilization

Answer 9

Double fertilization is a mechanism to conserve resources: endosperm only developed in ovules where an egg has been fertilized; After double fertilization, the ovule develops into a seed, and the ovary develops into a fruit (with one or several ovules/seeds)

Question 10

Describe the structure and development of a seed

Answer 10

The seed consists of three components:embryo, endosperm (sometimes perisperm), and seed-coat. Both endosperm and embryo are the products of double fertilization, whereas the seed-coat develops from the maternal, ovular tissues.

Question 11

Describe the early stages of seed germination

Answer 11

During the beginning stage of germination,the seeds take up water rapidly and this results in swelling and softening of the seed coat at an optimum temperature. This stage is referred to as Imbibition. It starts the growth process by activation of enzymes.

Question 12

Explain why seed dormancy is adaptive

Answer 12

After they are formed, many seeds enter a period of dormancy: the embryo stops growing and all metabolical activities. Dormancy is advantageous because it allows for seeds to be dispersed and wait for favorable conditions to begin growth. In general seed dormancy is broken by presence of water → Germination is initiated by uptake of water

Question 13

Define imbibition

Answer 13

The uptake of water by dry seed

Question 14

Describe the function and structure of fruits

Answer 14

Fruits protect the seed and aid in dispersal; Fruits are the mature ovary of a flower

Question 15

Give examples of fruit and seed dispersal

Answer 15

Fruit structure and means of dispersal varies. Examples:

• Coconuts are dispersed by water
• Maple tree fruits and dandelion fruits are dispersed by wind
• Animals disperse fruits in different ways (ex: feces, transport)

Question 16

NOTES

Answer 16

Flowers referred to as “incomplete” are missing sepals, petals, stamens, or carpels.

Only if a pollen grain arrives at the stigma can fertilization subsequently take place.

In angiosperms, sperm are formed by mitosis in the pollen tube.

Seeds can remain dormant for a maximum of thousands of years before germinating.