Chapter 38  Angiosperm Reproduction and Biotechnology

Student Guided Notes

Concept 38.1 Flowers, double fertilization, and fruits are key features of the angiosperm life cycle

Sporophyte and gametophyte generations alternate in the life cycles of plants.

  • The life cycles of angiosperms and other plants are characterized by an alternation of generations, in which haploid (n) and diploid (2n) generations take turns producing each other.
  • The diploid plant, the sporophyte, produces ______by ______.
  • These spores divide by ______to form ______, multicellular male and female haploid plants that produce ______ (______and ______).
  • ______results in diploid ______, which divide by ______to form new ______.
  • In angiosperms, the ______is the dominant generation—the large, conspicuous, long-lived plant we see.
  • Angiosperm gametophytes are the smallest of all plants, consisting of only a few cells.

Flowers are specialized shoots that bear the reproductive organs of the angiosperm sporophyte.

  • The four floral organs are the ______, and ______. (REFER TO CHAPTER 30 NOTES)

The male gametophytes of angiosperms are ______.

In the sporangia, the diploid microsporocyte(microspore mother cell) forms four haploid ______by ______.

  • Each microspore then undergoes ______to produce a male ______consisting of only two cells: the ______and the ______.
  • Together, these two cells and the spore wall constitute a pollen grain. (POLLEN GRAIN = ______!)
  • A pollen grain may be transferred to a receptive stigma, where the tube cell produces the ______, that delivers sperm to the ______.
  • As the pollen tube elongates quickly through the style, the generative cell divides to produce ______, which remain inside the tube cell.
  • The pollen tube grows into the ______, where it releases the sperm cells near the female gametophyte.

The female gametophyte of an angiosperm is an embryo sac.

  • The development of the embryo sac occurs in the tissue within each ovule called the ______. (EMBRYO SAC = ______)
  • The diploid megasporocyte (or megaspore mother cell) forms four haploid ______by meiosis.
  • Only ______megaspore survives; the others degenerate.
  • The nucleus of the surviving megaspore divides by mitosis ______times without cytokinesis, resulting in one large cell with ______haploid nuclei.
  • At one end, two cells called synergids flank the egg cell and help ______.
  • At the opposite end of the embryo sac are three ______ of unknown function.
  • The other two nuclei, called ______, share the cytoplasm of the large central cell of the embryo sac.

OVERVIEW

-Development of Pollen (male gametophyte)

  • In sporangia (pollen sacs) are diploid cells (called microsporocytes) that divide by meiosis to form haploid microspores, which give rise to pollen (male gametophyte)
  • Two cells: ______cell = produces sperm; ______cell = produces pollen tube
  • Pollen = ___ sperm

-Development of Embryo Sac (female gametophyte)

  • Ovary → ovule → megasporocyte → goes thru meiosis forming 4 megaspores – only 1 survives
  • One end of the embryo sac has 1 egg and 2 synergids (which are used for attraction/ guidance of pollen tube)

- ____ antipodal cells

- ____ polar nuclei

- ____ egg

- ____synergids

Double fertilization gives rise to the zygote and endosperm.

  • Synchronizes ______with ______
  • 1 sperm + egg = 2n ______
  • 1 sperm + 2 polar nuclei = 3n ______(FOOD!)
  • BOTH sperm fertilize nuclei in the female gametophyte

(REFER TO Chapter 30 Notes)

The ovule develops into a seed containing an embryo and a supply of nutrients.

  • After double fertilization, the ovule develops into a ______, and the ovary develops into a ______enclosing the seed(s).

The embryo develops within the seed.

  • During the last stages of maturation, a seed dehydrates until its water content is only about 5–15% of its weight.
  • The embryo stops growing and enters ______ until ______.
  • The embryo and its food supply are enclosed by a protective ______ formed by the integuments of the ovule.

Seed dormancy is an adaptation for tough times.

  • The conditions required to break seed dormancy and resume growth and development vary among species.
  • Some seeds germinate as soon as they are in a ______.
  • Others remain dormant until some specific environmental cue causes them to break dormancy.
  • Germination of seeds depends on imbibition, ______.
  • Imbibition causes the expanding seed to ______and triggers metabolic changes in the ______that enable it to resume growth.
  • The first organ to emerge from the germinating seed is the ______, the ______.
  • Next, the ______must break through the soil surface.

The ovary develops into a fruit adapted for seed dispersal.

  • As the seeds are developing from ovules, the ovary of the flower is developing into a fruit, which protects the enclosed seeds and aids in their dispersal by ______or ______.
  • During fruit development, the ______wall becomes the pericarp,______.
  • Fruits are classified into types, depending on their ______.
  • Simple fruit → develops from a single ovary; ex. cherry, soybean
  • Aggregate fruit → single flower, several carpals; ex. blackberry
  • Multiple fruit → tightly clustered group of flowers; ex. pineapple

Concept 38.2 Flowering plants reproduce sexually, asexually, or both

  • Many plants clone themselves by ______reproduction (also called clonal reproduction), in which ______.
  • Detached vegetative fragments of some plants can develop into whole offspring.
  • In ______(making cuttings of plants), a parent plant separates into parts that re-form into ______.
  • This can also occur naturally!
  • A different method of asexual reproduction, called apomixis, is found in ______and some other plants.
  • These plants produce seeds ______.

Both sexual and asexual reproduction have advantages and disadvantages.

  • Many plants are capable of both sexual and asexual reproduction, and each offers advantages in certain situations.
  • If a plant is well suited to a stable environment, asexual reproduction has advantages.
  • A plant can clone many copies of itself rapidly.
  • Generally, the clones produced by ______reproduction are not as frail as the seedlings produced by ______reproduction.
  • The clones are usually ______of the parent plant, which is why asexual reproduction in plants is also known as ______.
  • Seeds produced by sexual reproduction can disperse to new locations and wait for favorable growing conditions.
  • Seed dormancy suspends growth until hostile environmental conditions are reversed.
  • The major advantage of sexual reproduction is increasing the ______of offspring.

Plants have various mechanisms that prevent self-fertilization.

  • The various barriers that prevent self-fertilization contribute to genetic variety by ensuring that the sperm and egg come from different parents.
  • The most common anti-selfing mechanism is self-incompatibility, ______.
  • If a pollen grain from an anther happens to land on a stigma of a flower on the same plant, a ______.
  • The self-incompatibility systems in plant are analogous to the ______of animals.
  • Both are based on the ability of organisms to distinguish ______.
  • The key difference is that the animal immune system rejects ______, whereas self-incompatibility in plants is a rejection of ______.
  • Plant breeders frequently hybridize different varieties of a crop plant to combine the ______and counter the ______that can result from ______.

Vegetative propagation of plants is common in agriculture.

  • In a multicellular organisms, any cell that can ______is said to be totipotent.
  • Transgenic plants are ______. (in other words: genes from two of more species in one plant)
  • Test-tube culture makes it possible to regenerate a GM plant from a ______.
  • Transgenic plants can also happen naturally (not just by genetic engineering).

Concept 38.3 People modify crops by breeding and genetic engineering including the following examples:

Humans have created new plant varieties by artificial selection.

  • Humans have intervened in the reproduction and genetic makeup of plants for thousands of years.
  • ______by humans has created plants that could not survive or reproduce in the wild.
  • For domesticated crop plants, genetic modifications began long before humans started altering crops by artificial selection (for example: wheat groups undergo natural hybridization.)
  • The term plant biotechnology has two meanings.
  • In the general sense, it refers to ______(or substances obtained from plants) to make ______—an endeavor that began in prehistory.
  • In a more specific sense, it refers to ______.
  • The terms ______and ______ have become synonymous in the media.
  • Unlike traditional plant breeders, ______are not limited to transferring genes between ______or varieties of the same species.

In summary: There is much debate about plant biotechnology  political, economic and ethical issues

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