Reproduction & Diversity of Seed Plants (Angiosperms & Gymnosperms)

These 50 question-and-answer flashcards review the core concepts, terminology, and examples presented in the lecture on seed plant reproduction, focusing on angiosperms, gymnosperms, and their unique life-cycle features.

How many cells make up a mature angiosperm pollen grain?

Three—two sperm cells and one pollen-tube cell.

Where are microsporangia located in angiosperms?

Inside the anthers of the flower’s stamen.

What structure carries sperm nuclei to the ovule in flowering plants?

The pollen tube produced by the pollen-tube cell.

During megasporogenesis in angiosperms, how many of the four meiotic products survive?

One functional megaspore; the other three degenerate.

How many nuclei and cells are present in a mature embryo sac (megagametophyte)?

Eight nuclei arranged in seven cells.

Which embryo-sac cell becomes the zygote after fertilization?

The egg cell.

What is the role of synergid cells in the embryo sac?

They secrete chemical signals that guide the growing pollen tube to the egg.

What are antipodal cells, and what is their known function?

Three cells at the chalazal end of the embryo sac; they appear to have little or no functional role.

Why are the two nuclei in the central cell called polar nuclei?

They originated at opposite poles of the embryo sac before migrating to the center.

Define double fertilization in angiosperms.

A process in which one sperm fuses with the egg to form a zygote, and a second sperm fuses with the two polar nuclei to form triploid endosperm.

What is produced by the first fertilization event in angiosperms?

A diploid zygote that develops into the embryo.

What is produced by the second fertilization (triple fusion) event?

A triploid cell that develops into nutrient-rich endosperm.

What is the ploidy level of angiosperm endosperm?

Triploid (3n).

Which tissue serves as the chief nutrient source for the developing angiosperm embryo?

The endosperm.

What seed part derives from the integuments of the ovule?

The seed coat.

After fertilization, what does the ovule mature into?

A seed.

After fertilization, what does the ovary mature into?

A fruit (unique to flowering plants).

What is the micropyle?

The small opening in the ovule through which the pollen tube enters.

What term describes a plant’s ability to recognize and reject incompatible pollen on the stigma?

Pollen incompatibility (an example of pre-zygotic reproductive isolation).

Why is heterospory an advantage for seed plants?

It produces distinct microspores and megaspores, enabling separate male and female gametophytes and paving the way for seeds.

Define dioecious as used for plants like cycads and ginkgo.

Having separate male and female individuals.

To which gymnosperm phylum does Ginkgo biloba belong?

Ginkgophyta.

Which gymnosperm genus is the natural source of the stimulant ephedrine?

Ephedra (in phylum Gnetophyta).

Which gnetophyte has only two strap-like leaves that grow for its entire life?

Welwitschia.

Which gymnosperm group bears exposed ovules on cone scales or similar structures?

Conifers (Phylum Coniferophyta) and other gymnosperms generally lack enclosed ovaries.

Name the three common pines in the Augusta area mentioned in lecture.

Longleaf pine, loblolly pine, and shortleaf pine.

What leaf types are characteristic of most conifers?

Needles or small scale-like leaves coated with protective waxes.

Which conifer is deciduous and known as the bald cypress?

Taxodium distichum.

List the three fundamental parts of a seed.

Embryo, food source (endosperm or cotyledons), and seed coat.

What is another name for the angiosperm female gametophyte?

The embryo sac or megagametophyte.

How many sperm cells are typically delivered by each angiosperm pollen grain?

Two.

Which cells chemically guide the pollen tube toward the ovule?

Synergid cells.

What is the ploidy of the angiosperm zygote?

Diploid (2n).

Which flower structure encloses and protects the ovules?

The ovary at the base of the pistil (carpel).

Where does pollen development begin in a flower?

Within microsporangia of the anther.

What happens to the endosperm during seed germination?

Enzymes break it down, releasing nutrients absorbed by the growing embryo.

Why can the stigma digest pollen from other species?

The plant’s recognition proteins identify foreign pollen and trigger rejection, ensuring species-specific fertilization.

What is the function of the pollen-tube nucleus?

It directs growth of the pollen tube toward the embryo sac.

Which gymnosperm group with large landscaping cones is often toxic to pets?

Cycads; their tissues contain carcinogens and other toxins.

Why are cycads hazardous for household animals?

They contain toxins and carcinogens that can cause illness if ingested.

Why is the placement of Gnetophyta controversial in plant phylogeny?

Morphological traits once linked it to angiosperms, raising debate about whether gymnosperms are paraphyletic; DNA evidence now keeps it with gymnosperms.

Pollen rejection at the stigma exemplifies which type of reproductive barrier?

Pre-zygotic (specifically, gametic) isolation.

Define cotyledon.

Seed leaf; an embryonic leaf that may store or absorb nutrients.

How many cotyledons are found in a monocot seed such as corn?

One.

How many cotyledons are found in a dicot seed such as a bean?

Two.

During seed development, which tissue stores proteins and carbohydrates for the embryo?

Endosperm (or cotyledons once endosperm is absorbed in many dicots).

What is the role of the pollen-tube nucleus inside the growing tube?

It controls tube elongation and direction toward the embryo sac.

What term describes the fertilization involving one sperm and two polar nuclei?

Triple fusion (part of double fertilization).

What is the common name for the male gametophyte of flowering plants?

Pollen grain.

Through which floral structures must a pollen tube grow to reach the ovule?

Down the style and through the micropyle of the ovule.