BIOL 371 Vascular Seed Plants

What are angiosperms?

Covered seeds

Are angiosperms gametophyte or sporophyte dominant?

sporophyte

What do angiosperms reproductive organs contain?

flowers containing haploid spores

What is the ovule?

Sporophyte structure that houses and protects the megaspore that gives rise to the
female gametophyte, the embryo sac

What is the embryo sac?

The embryo sac is the female gametophyte of a flowering plant (angiosperm). In most flowering plants, a mature embryo sac contains eight nuclei distributed among seven cells.

Where do ovules typically develop in angiosperms?

the ovary

What does the ovary do?

Houses and protects the ovule

can aid in dispersal and nourishment of the seeds

What happens to the ovule after fertilization?

the ovule becomes the seed, and the ovary becomes the fruit

What are sieve tubes and companion cells?

Sieve tubes and companion cells work together as a crucial vascular partnership in plant phloem. Sieve tubes act as hollow pipelines that transport sugars, while companion cells provide the necessary metabolic energy and logistical support to keep the enucleated sieve tubes alive and functioning.

How do angiosperms allow for efficient transport of water and nutrients?

• vessel elements

• sieve tubes and companion cells

What characteristics do flowers offer in angiosperms?

• compact reproductive organs

• often hermaphroditic/bisexual

• attractive to pollinators

What is the double fertilization in angiosperms?

production of both embryo and nutritive tissue (endosperm) by utilizing both sperm cells

When does nutritive tissue develop?

only if pollination is succesfull (fertilization occurs)

Where is the ovary?

the base of the carpal

What part of the plant becomes the fruit after fertilization?

the ovary

What is the carpel/pistil an what is it made up of?

the female reproductive parts that are made up of the stigma, style and ovary/ovaries

What is the stamen and what is it made up of?

the male reproductive parts made up of the anther and filaments

What is the Stigma?

The stigma is the sticky or feathery uppermost tip designed to catch pollen grains during pollination.

What is the Style?

The style is the slender, stalk-like tube that connects the stigma to the ovary. It provides a pathway for the pollen tube to grow down to the egg cells.

Angiosperm reproduction cycle

Sporophyte (flowering plant, 2n) → flowers → anthers & ovules → meiosis → microspores + megaspore → pollen grain (male gametophyte) + embryo sac (female gametophyte) → pollination → pollen tube → double fertilization → zygote (2n) + endosperm (3n) → seed (in fruit) → germination → new sporophyte (2n)

Mature flowering plant (sporophyte, 2n) develops flowers containing stamens (male) and carpels/pistils (female).

Stamens contain anthers with microsporangia, where meiosis produces haploid microspores (n).

Microspores develop into pollen grains (male gametophytes), each containing sperm cells.

Carpels (pistils) contain an ovary with ovules. Inside each ovule is a megasporangium, where meiosis produces four megaspores (n), but three degenerate, leaving one functional megaspore.

The functional megaspore undergoes three rounds of mitosis without cytokinesis forming a single large cell with eight nuclei.

Then cytokinesis occurs to form the female gametophyte (embryo sac), which contains 7 cells. The egg cell, the central cell composed ofo two nuclei (becoming the endosperm) and 5 remaining cells that end up degenerating.

Pollen from the pollen sac is released. Pollination occurs when a pollen grain lands on the stigma. The pollen grain germinates and grows a pollen tube through the style to the ovule, carrying two sperm cells.

Double fertilization occurs: one sperm fertilizes the egg to form the zygote (2n), while the other fertilizes the central cell to form the endosperm (3n).

The zygote develops into an embryo, and the ovule becomes a seed containing the embryo and endosperm. The ovary develops into a fruit.

The seed disperses and germinates into a seedling, which grows into a mature flowering plant (sporophyte, 2n), completing the cycle.

What is the seed made up of from inner to outer?

embryo (2n), endosperm (3n) and seed coat (integument)

What is the endosperm?

a trinucleate cell that will give rise to triploid endosperm which is a nutritive tissue that will nourish the developing embryo

What guides pollen tube growth?

pollen attractant released from the embryo sac

How can angiosperms be pollinated either than just wind?

through specific animal pollinators

How do pollinators undergo coevolution with angiosperms?

• plants evolving to attract pollinators through things like showy, mimicry, scent, nectar

• animals evolve various parts of their body for pollination like tounges or other mouth parts

What are integuments?

2n protective seed coat

In what plants is the the embryo smaller?

In grains and in some eudicot seeds, the endosperm fills most of the seed and the embryo is small.

How do seeds attain dormancy?

Seeds will fully dry prior to dispersal to attain dormancy

Monocot vs Eudicot vasculature

monocot: Bundles of vascular tissue scattered in stem

eudicot: Bundles of vasculature arranged in a ring

Monocot vs Eudicot veins

monocot: Parallel-veined leaves common

eudicot: reticulate veins

Monocot vs Eudicot floral parts

monocot: floral parts in groups of 3

eudicot: floral part sin groups of 4 or 5

Monocot vs Eudicot root system

monocot: fibrous root system

eudicot: branching roots with strong tap root

Monocot vs Eudicot pollen grain

monocot: pollen grain with 1 aperature → monocolpate

eudicot: pollen grain with 3 aperature → tricoplate

What are cotyledons?

A cotyledon is the first embryonic leaf that appears from a germinating seed. Also known as a "seed leaf," it provides essential nutrients to the developing seedling and frequently acts as its first photosynthetic organ until the true leaves can grow.

What are monocots vs eudicots?

• Monocots (Monocotyledons): Plants that have exactly one seed leaf (e.g., corn, wheat, grasses, and lilies).

• Eudicots: Plants that have two seed leaves (e.g., beans, sunflowers, and most broadleaf trees).

Monocot vs Eudicot endosperm

monocot: endosperm majority

eudicot: little/no endosperm

gymnosperms vs angiosperm reproductive organs

gymnosperms: unisexual cones

angiosperms: bisexual flowers

gymnosperms vs angiosperm seeds

gymnosperms: naked at maturity

angiosperms: contained at maturity

gymnosperms vs angiosperm integuments

gymnosperms: single integument covers ovule

angiosperms: two integuments cover ovule

gymnosperms vs angiosperm female gametophyte cell number

gymnosperms: 100s of cells

angiosperms: 7 cells most often

gymnosperms vs angiosperm microsporangia

gymnosperms: microsporangia housed on male cones

angiosperms: housed inside anthers

gymnosperms vs angiosperm main pollen dispersal method

gymnosperms: wind

angiosperms: animal pollinators and wind

gymnosperms vs angiosperm main pollination time

gymnosperms: about 2 years

angiosperms: minutes-hours

gymnosperms vs angiosperm sperm cells used

gymnosperms: 1 sperm cell for fertilization

angiosperms: 2 sperm cells for fertilization

gymnosperms vs angiosperm nutritive tissue

gymnosperms: the remanent female gametophyte (n)

angiosperms: endosperm (3n)

gymnosperms vs angiosperm xylem composition

gymnosperms: tracheids

angiosperms: tracheids and vessels

gymnosperms vs angiosperm phloem composition

gymnosperms: sieve elements

angiosperms: sieve tubes and companion cells

When do seeds germinate?

Seeds will germinate when they are in suitable conditions (i.e. when they have sufficient water and access to resources)

How do seeds know when the appropriate conditions are met?

• Absorbance of red light activates Phytochrome B

• Repeated/extended Red Light exposure converts sufficient amounts of Phytochrome to

the active state to initiate seed germination

• Reabsorption of far-red light inactivates the Phytochrome

• Lack of light also causes Phytochrome to revert to inactive form

*Far-red light is not absorbed well by plants → reception of Far-red light alone indicates plant coverage overhead (Red light absorbed above) and not enough light for photosynthesis

Why do seeds need to sense whether or not they will receive enough light to photosynthesize?

• Germination will use up all of the nutritive tissue present in the seeds

• If the plant is unable to photosynthesize once it emerges then it will quickly die