Biotechnology

Only available on StudyMode
  • Topic: Seed, Flowering plant, Pollen
  • Pages : 8 (1531 words )
  • Download(s) : 72
  • Published : January 23, 2013
Open Document
Text Preview
Chapter 38: Angiosperm Reproduction and Biotechnology I. Overview: Flowers of Deceit
1. Angiosperm flowers can attract pollinators using visual cues and volatile chemicals 2. Many angiosperms reproduce sexually and asexually
3. Symbiotic relationships are common between plants and other species

II. Concept 38.1: Flowers, double fertilization, and fruits are unique features of the angiosperm life cycle 1. Diploid (2n) sporophytes produce spores by meiosis; these grow into haploid (n) gametophytes 2. Gametophytes produce haploid (n) gametes by mitosis; fertilization of gametes produces a sporophyte 3. Angiosperms- sporophyte is dominant generation, the large plant * gametophytes are reduced in size and depend on the sporophyte for nutrients 4. Angiosperm life cycle- the “three Fs”: flowers, double fertilization, and fruits A. Flower Structure and Function

1. Flowers -reproductive shoots of the angiosperm sporophyte; they attach to a part of the stem called a. receptacle- where flower attaches to the stem
b. Flowers has four floral organs: sepals, petals, stamens, and carpels c. Stamen consists of a filament topped by an anther with pollen sacs that produce pollen d. Carpel has a long style with a stigma on which pollen may land e. Ovary at the base of the style, containing one or more ovules f. Pistil- single carpel or group of fused carpels

Stamen

Anther

Filament

Stigma

Carpel

Style
Ovary
Receptacle
Sepal
Petal
(a) Structure of an idealized flower

Fig. 38-5a
Stigma

Pollen tube
2 sperm
Style
Ovary
Ovule
Micropyle
Egg
Pollen grain
Polar nuclei

Structure of the Carpel 2. Types of flowers
a. Complete flowers contain all four floral organs
b. Incomplete flowers lack one or more floral organs
c. Inflorescences- Clusters of flowers
B. Development of Male Gametophytes in Pollen Grains
1. Pollen develops from microspores in the microsporangia (pollen sacs) of anthers 2. If pollination succeeds, a pollen grain produces a pollen tube- grows down into the ovary and discharges sperm near embryo sac 3. The pollen grain consists of the two-celled male gametophyte and the spore wall C. Development of Female Gametophytes (Embryo Sacs)

1. megaspores are produced in the ovule by meiosis
2. develop into embryo sacs, the female gametophytes
D. Pollination
1. Pollination is the transfer of pollen from anther to stigma 2. Can be by wind, water, bee, moth and butterfly, fly, bird, or bat 3. Double Fertilization
a. Pollen grain lands on stigma &makes a pollen tube extending from style to ovary b. Double fertilization -two sperm leave the pollen tube & enter embryo sac c. One sperm fertilizes the egg

d. The other combines with polar nuclei, makes triploid (3n) food-storing endosperm Ovule
Polar nuclei
Egg
Synergid
2 sperm

Endosperm
nucleus (3n)
(2 polar nuclei
plus sperm)
Zygote (2n)
(egg plus sperm)

E. Seed Development, Form, and Function
1. Fertilized ovules developed into seeds
2. The ovary develops into fruit enclosing the seed(s)
3. Endosperm Development
a. Happens first
b. Most monocots & some eudicots stores nutrients for seedling in endosperm c. Some eudicots store food in the cotyledons
4. Embryo Development
a. First mitotic division is transverse & splits fertilized egg into a basal cell and a terminal cell Fig. 38-7
Ovule

Endosperm
nucleus
Integuments
Zygote

Zygote
Terminal cell

Basal cell
Basal cell

Proembryo
Suspensor
Cotyledons

Shoot
apex
Root
apex
Seed coat
Endosperm

Suspensor

F. Structure of the Mature Seed - dormant
1. seed coat- hard, protective outer coat
2. Structure...
tracking img