CH 38 ANGIOSPERM REPRODUCTION AND BIOTECHNOLOGY FLOWERS OF DECEIT by sdfgsg234

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									                      CH 38: ANGIOSPERM REPRODUCTION AND BIOTECHNOLOGY


FLOWERS OF DECEIT

There is often a mutualistic relationship between plant flowers and insects: the plant provides nectar for the
insect and the insect assists with pollination. There are many instances, however, where the design of the
flower mimics an insect’s reproductive structures. Insects are attracted to the flower, assist with pollination,
but receive no benefit from the flower.



38.1 FLOWERS, DOUBLE FERTILIZATION AND FRUITS ARE UNIQUE                                FEATURES OF THE
ANGIOSPERM LIFE CYCLE

Plant life cycles are governed by alternation of generations. Diploid sporophytes produce gametophytes that, in
turn, produce haploid gametes. Fertilization then results in new diploid zygotes, which will develop into new
sporophytes. The three “F’s” of the Angiosperms = flowers, fertilization (double) and fruit production.

FLOWER STRUCTURE AND FUNCTION

 Floral Organs

    Sepals

    Petals

    Stamens

    Carpels

    Pistil

 Receptacle

 Complete Flower

 Incomplete Flower

 Stamen

    Anther

    Filament

 Carpel

    Stigma

    Style




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   Ovary



POLLINATION AND (DOUBLE) FERTILIZATION

 1-Pollen grains land on the stigma of the carpel.

 2-Stigmatic fluids (1) hold the pollen grain in place and (2) soften and open the surface of the grain.

 3-Pollen tube emerges from the grain and grows down into the style.

 4-Two haploid sperm form from the sperm cell nucleus while growth is proceeding.

 5-The pollen tube cell directs growth and all pollen production.

 6-The pollen tube penetrates the ovule at a small opening termed the micropyle, which is on the surface of
 the ovule.
 7-One sperm cell fertilizes the ovule and the other combines with the remaining embryo sac cells to form
 the endosperm tissue. “Double fertilization”.
 8-Endosperm tissue nourishes the developing seeds.



Some flowers are monoecious (separate sexes located on one plant) and others are dioecious (separate sexes in
separate plants).

GERMINATION OF SEEDS- INCLUDES IMBIBITION

Fertilization follows pollination in as little as an hour or as long as several months. Many seeds enter a
dormancy period after their formation. Dormant seeds may retain their viability (ability to break out of
dormancy and begin growth).

The initiation of the growth process requires: (1) ambient temperatures, (2) uptake of moisture (imbibition)
and (3) possibly oxygen and light. If the environment is positive, germination will begin and then these
structures develop from the seed:

 Radicle

 Hypocotyl

 Epicotyl

   Plumule

 Cotyledons

 Seed Coat

 Protective Sheaths:




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    Coleoptile

    Coleorhiza



FRUIT FORM AND FUNCTION

In angiosperms a fruit encloses all seeds. Uneaten fruits provide nutrients to the potential plants they contain.
If eaten by animals, fruits may assist with seed dispersal.

 (1) Simple Fruits

                       (A) Fleshy

    Berry

    Drupe

                       (B) Dehiscent (Fruit that splits open to release seeds)

    Follicle

    Legume

    Capsule

                       (C) Indehiscent (Fruit that does not split open to release seeds)

    Grain

    Achene

    Nut

 (2) Aggregate Fruits

 (3) Multiple Fruits

 (4) Accessory Fruits




38.2 FLOWERING PLANTS REPRODUCE SEXUALLY, ASEXUALLY OR BOTH

Higher plants such as flowering plants do not rely solely on sexual reproduction. Some asexual alternatives
include:

 Vegetative Propagation




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    Cuttings

    Grafting

    Test-Tube Cloning

 Fragmentation

 Stolons

 Tuber

 Rhizomes

 Bulbs

 Corm

 Parthenogenesis

    Apomixis




38.3 HUMANS MODIFY CROPS BY BREEDING AND GENETIC ENGINEERING

Plant biotechnology specialists are working on methods to great crops that are resistant to destructive pests,
contain more nutrients “per bite”, provide more usable food per acre, and so on.

Their ultimate goals include:

    (1) Reduction of world hunger and malnutrition and
    (2) Reduction of fossil fuel dependency (development of biofuels).

There are many potential problems involved with plant biotechnology, such as

    (1) Issues of human health,
    (2) Possible effects on nontarget organisms and
    (3) Transgene escape.




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