34.1 Angiosperm Reproduction (p. 700; Fig. 34.1)
A.
Asexual Reproduction
1.
The forms of vegetative reproduction are runners, rhizomes, suckers, adventitious plantlets.
B.
Sexual Reproduction
1.
Angiosperm life cycles involve alternation of generations, with the sporophyte as the dominant generation and the gametophyte developing within the tissues of the sporophyte.
2.
Both microgametophytes (male gametophytes) and megagametophytes (female gametophytes) are housed within the same structure, the flower.
3.
Flower production is seasonal and not a permanent feature of the mature sporophyte.
4.
Pollen grains are the male gametophytes while embryo sacs are the female gametophytes.
34.2
Structure of the Flower ( p. 701; Fig. 34.2)
1.
The male parts of a flower consist of stamens and anthers; pollen grains develop within the anthers.
2.
The female parts of a flower consist of carpels; each carpel is composed of a stigma that collects pollen, a style, and an ovary that houses the ovules in which embryo sacs develop.
3.
Pollen Formation a.
Pollen grains develop from microspores that form in the pollen sacs. b.
Within the pollen sacs, the microspore mother cells undergo meiosis to form microspores; microspores undergo mitosis to form pollen grains.
4. Egg Formation a.
Eggs develop in the ovules of the angiosperm flower; within each ovule is a megaspore mother cell. b.
Each megaspore mother cell undergoes meiosis to produce four haploid megaspores, only one of which survives. c.
The lone megaspore undergoes mitotic divisions and produces 8 haploid nuclei; one will function as the egg nuclei and two are polar nuclei.
34.3 Gametes Combine Within the Flower (p. 704; Figs.34.3, 34.4, 34.5)
1. Pollination a.
Pollination is the process by which pollen arrives at the stigma. b.
Pollinators include various insects or birds that are attracted to the flowers by scents and colors, and are often rewarded for their efforts by sugary nectar. c.
Coevolution of flowers and pollinators can be seen in a wide variety of plants and animals. d.
Wind-pollinated flowers are not fragrant or colorful, and typically produce very large amounts of pollen to ensure that at least some of it arrives at the female stigma.
2. Fertilization a.
In angiosperms, fertilization occurs in a unique process called double fertilization. b.
Once pollen grains reach the stigma, a pollen tube grows down through the style until it reaches the ovule. c.
One of the cells of the pollen within the pollen tube becomes two sperm cells; one of the sperm cells unites with the egg cell to produce the zygote, and the other sperm cell fuses with two polar nuclei. d.
The two polar nuclei and the sperm cell fuse and divide rapidly, becoming nutritious endosperm.
34.4 Seeds (p. 706; Fig. 34.6)
A.
The entire series of events that occur between fertilization and maturity is called development.
B.
In many plants, embryo development is arrested soon after apical meristems and the first leaves (cotyledons) are differentiated.
C.
The integuments surrounding the embryo develop into an impervious seed coat that protects the embryo throughout its period of dormancy.

D.
Resumption of metabolic activity within the seed leads to germination.
34.5 Fruit (p. 707; Fig. 34.7)
A.
In some plants, the ovary surrounding the ovule develops into fruit.
B.
Fruits aid in seed dispersal, as animals eat the fruit and defecate or drop the seeds at some distance away from the parent plant; dry fruits can be dispersed by wind, and hard fruits can be dispersed by water.
34.6 Germination (p. 708; Fig. 34.8)
A.
When the time is right for the embryo to resume its growth, the seed coat absorbs water, and the embryo becomes metabolically active once again.
B.
Oxygen is needed during germination for most seeds, although some seem able to germinate in anaerobic conditions.
34.7
Growth and Nutrition (p. 709; Fig. 34.9)
A. Macronutrients
B. Micronutrients
C. Indentifying Essential Nutrients
34.8 Plant Hormones (p. 710; Figs. 34.10, 34.11, Table 34.1)
A.
After germination, a plant’s further development depends on its meristematic tissues.
B.
As plants grow, cells differentiate.
C.
But one critical difference remains between plant cells and animal cells: once animal cells differentiate, they cannot be anything other than what they are in their differentiated form.
D.
Some plant cells, on the other hand, can be induced to form whole new plants.
E.
Plant growth is regulated by chemical messengers, known as hormones.
F.
At least five major hormones have been found; others also exist but are less well understood.
34.9 Auxin (p. 712 Figs. 34.12, 34.13, 34.14)
A.
The hormone auxin is a primary growth hormone that is more abundant in shaded portions of stems.
B.
Phototropism, or seeming to grow toward the light, is a commonly observed phenomenon in many plants.
1.
The shaded side of the stem elongates faster, causing the plant to lean toward the light.
C.
Synthetic auxins are used as herbicides (such as 2, 4-D) because the plants can be induced to literally growth themselves to death.
(p. 714)
34.10 Photoperiodism and Dormancy (p. 714)
A.
Plants respond to environmental stimuli in a variety of ways.
B.
Photoperiodism
1.
Plants respond to patterns of light and dark as the seasons progress, a phenomenon referred to as photoperiodism.
2.
Day length cues plants to flower.
3.
Some plants flower when days are shorter, others as the days become longer.
4.
Still other plants are day-neutral and produce flowers when conditions are favorable, regardless of day length.
C.
The Chemical Basis of Photoperiodism
1.
One class of chemicals, the phytochromes, are pigment molecules that influence flowering in plants.
D.
Dormancy
1.
When environmental conditions are unfavorable to growth, the capacity to become dormant is critical to the survival of certain plants.
2.
Annual plants overwinter as seeds.
34.11 Tropisms (p. 715; Fig. 34.15)
A.
Tropisms are growth responses of plants to external stimuli and control patterns of growth and appearance.
B.
Gravitropism
1.
Stems grow downward and shoots upward as a response to gravity, or gravitropism.

C.
Thigmotropism
Thigmotropism occurs when plants respond to being touched