Know the overview of the flowering plant life cycle. Fig. 31.3
The Sporophyte (diploid) stage is the dominant stage producing microscopic
spores that produce the gametophytes. The male gametophyte (haploid) is
the pollen grain that is dispersed but the female gametophyte (haploid)
lives parasitically in the sporophyte flower tissue.
Know the components of a flower. Fig. 31.3
The flower in Fig. 31.3 is a complete flower with, male and female components
and other structures given. Flowers may only have components of this complete
design. For example: Some plant species will have male flowers and one plant
and female flowers on another plant.
The male gametophyte, the pollen grains develop in the athers, a part of
the stamen structure.
The female gametophyte develops in the ovary of the carpel.
Flowers with both male and female structures are called perfect flowers
and others are imperfect flowers containing male or female structures.
Note: Be able to recall (in human cells) the cell production of mucus
in response to the presence of pollen on the surface of the cell.
Take a look at the surface of the pollen in Fig. 31.5.
Different pollen surfaces are specific to the plant species that produced
it.
Be able to summarize the complete process in Fig. 31.6 including double
fertilization.
Cells in the pollen sacs of the anther divide by meiosis and produce
haploid microspores. These become the pollen grains. Sperm nuclei form in
the pollen grain that will travel through the pollen tube to fertilize tissue
in the female gametophyte.
In the ovules of the ovary, meoitic cell divisions form haploid megaspores.
Further mitotic divisions of this haploid tissue leads to the embryo sac,
the female gametophyte. Within the embryo sac, one cell is the egg and another
cell with two nuclei, is the cell that will develop into the endsperm, the
nutritive tissue for the embryo as it develops.
Pollination is when the pollen grains are transfered to the stigma.
Fertilization occurs when sperm nuclei fuse with cells of the embryo sac.
Double fertilization occurs:
1. pollen tube and nucleus with two sperm cells penetrate the embryo sac.
2. the sperm nuclei fertilize both: (therefore-double fertilization)
a. egg is fertilized by the sperm nuclei, the resulting zygote is a diploid
embryo.
b. two nuclei endosperm mother cell will produce the endosperm nutritive
tissue.
Know Fig. 31.6 and be sure to read: A Coevolutionary Tale - Commentary of
Theory
The embryo of a dicot develops codyledons, or seed leaves. The endosperm
nutritive materials are transfered into these codyledons for storage until
germination.
In moncots the endosperm is left until germination, when the codyledon transfers
enzymes to the endosperm to break down and distribute the nutrients of the
endosperm to the growing seedling.
Be able to locate the embryo and the cotyledons - is it a monocot or dicot??
Seed is the mature ovule containing the embryo, the food reserves, and the
seed coat.
The seed is a protected area for embryo development.
The ovule's integument thickens and hardens into a seed coat.
The fruit develops from the ovary and assoicated tissue around the seeds.
Fruit descriptions involve fruits that dry or fleshy, patterns of the incorporation
of ovaries and associated tissue (note: one ovary - simple, or multiple
ovaries - compound), and flower combinations (pineapples).Fig. 31.8
Examples: Table 31.1 - Fleshy (apple) or dry & hard (walnut)
Fleshy fruit has three divisions: endocarp (tissue around the seed[s]),
mesocarp (middle, fleshy part), and the exocarp (skin) [All together refered
to as: pericarp]
Modifications specific for each plant are linked to different means of
seed dispersion. Fruit function as the means of seed dispersion.
Types of dispersal:
1. wind-dispersed fruit - (The pericarp might be extended like "wings"
to catch the wind.)
2. water-dispersed fruit (example: coconuts)
3. animal-dispersed fruit - eaten by animals and the seeds coats are only
slightly digested and thus dispersed by the animal in its feces and prepared
for germination.
You should be able to put forth an hypothesis for this question after reading this section presenting the flowering of the giant saguaro in Arizona.
Plants can reproduce without fertilization through various modes of vegetative
growth. Table 31.2 This is the result of mitotic divisions of plant parts
(on the plant or separated from the plant) leading to the production of
a complete individual, a clone of the parent plant. Fig. 31.11
Parthenogenesis - the embryo develops from an unfertilized egg. It is prompted
by the presence of pollen on the stigma, and chemicals may prompt the fusing
of two eggs in the embryo sac to initiate the embryo development.
Tissue taken from a plant and treated with growth factors, can be induced to produce a mass of dividing cells that can result in vegetative reproduction. Even differentiated cells can be induced. Induction often involves exposing the plant tissue to growth promoting chemicals that are in the plant naturally but are here exposed to tissues that are prompted to produce a new plant. Fig. 31.12