Caso 4 - Background Information
Flowers are key in the process of seed production. Flower structure
can vary greatly, but there are a number of basic parts.
The female portion of the flower is generally located at the
center. It is called the pistil and is made up of three parts.
The top part of the pistil is called the stigma and is sticky
so it will trap and hold pollen.
In flowering plants, the flower functions in sexual reproduction.
The essential flower parts are the male parts called the stamens
and the female part called the pistil. The stamen has two parts:
anthers and filaments. Pollen is produced at the ends of the stamens
on structures called anthers. These are generally yellow in color.
Anthers are supported by a thread-like structure called a filament.
The pistil has three parts: stigma, style, and ovary. The stigma
is the sticky surface at the top of the pistil; it traps and
holds the pollen. The style is the tube-like structure that supports
the stigma. The style leads down to the ovary which contains the
ovules.
During the process of pollination, pollen moves from the male
parts to the female parts. Pollen grains land on the stigma and
a tiny tube grows from it and down the style into the ovary. Sperm
cells travel down the tube from the pollen grains and join with
an egg cell in the ovule resulting in fertilization. The fertilized
ovule becomes the seed and the ovary becomes the fruit.
Other parts of the flower that are important are the petals
and sepals. Petals act as attractants to pollinators and are usually
the reason why we buy and enjoy flowers. The sepals are the green
petal-like structures located at the base of the flower. Sepals
help protect the developing bud.
During the flower exploration exercise, it is best to use flowers
that have obvious and large flower parts. Flowers such as iris,
tulip, lilies, amaryllis, snapdragon, and gladiolus are best to
use for the dissection part of the lesson. When dissecting, have
students record the number of various parts they find in the flower.
Flowers of related plants will have a characteristic number
of petals. You might also introduce the concept of composite flowers.
These flowers look like one flower but are actually made up of
hundreds of separate flowers. Flowers of a sunflower, chrysanthemum,
dandelion, and daisy are members of this group. When these flowers
are dissected, you will find many separated small flowers grouped
together to look as if they were one.
When selecting flowers to dissect, try to get a variety of flowers
so students can compare the shape, size, quantity, and color of
the various parts and record them while working on Caso 4.
Flowers may contain either all male parts or all female parts.
These flowers are called imperfect. Melons, cucumbers, pumpkins,
and holly are examples of imperfect flowers because there are
flowers present on the plant that contain either all male parts
or all female parts.
Perfect flowers contain both male and female parts in the same
flower. Peas, beans, and iris are examples of perfect flowers.
Since flowers can't move, they need to be able to attract pollinators.
Flowers attract pollinators with sweet nectar, bright colors,
and shapes and structures that accommodate particular pollinators.
Petalless flowers accommodate wind pollination. Some flowers may
also be open at specific times of the day to take advantage of
certain pollinators that prefer to work during specific hours.
Examples would include night blooming plants that are pollinated
by bats.
Plants without flowers
The simplest plants do not flower. Plants such as ferns, mosses,
and lichens produce spores instead of seeds. Spores are microscopic
specks or living material enclosed in a tough, protective wall.
Ferns produce their spores on the undersides of the leaves (fronds)
in structures called sporangia.
Studying non-flowering plants during this lesson can be an interesting
side-bar. The variety and diversity of ferns is interesting. A
collection can be started and leaf shapes and size can be compared.
Mosses and lichens can also be collected and studied. These can
be collected in shady areas, on rocks, or on tree bark. Discussion
can start on how plants growing on rocks get nutrients.
Spores can be used to grow ferns. Ripe spores will be brown
in color and easily separate from the fronds. Shake the spores
over a petri dish filled with damp sphagnum moss. Don¹t cover
the spores. Put the lid on the petri dish and place it in a warm
spot. Spores germinate and grow very slowly, so patience is key
in this activity. If you have access to a microscope, use it to
look at the spores. You will find them to be a variety of shapes
and unique to each fern variety.
Plants from parts
Plants from parts is a form of asexual or vegetative propagation.
Unlike reproduction from seed, only one parent is involved and
the offspring produced is exactly like the parent. You are producing
clones. Some of the structures that plants use to reproduce vegetatively
include tubers (potato), bulbs (tulip), runners (strawberry),
rhizome (iris), cuttings (coleus), offsets (daylily), and crowns
(asparagus).
How to Make Plantenstein
The Plantenstein activity makes use of a variety of propagation
forms to produce a "face." The majority of propagation
methods will be vegetative with some seeds (sexual) being used.
The activity suggests the use of grass seed for "hair,"
plantlets or runners for "eyes," a bulb for the "nose,"
a cutting for the "mouth," a leaf cutting for the "tongue,"
and pieces of tuber for the "ears." All of these parts
have the ability to produce a new plant. Not all will root and
grow at the same time or the same rate. When the plant part roots
and starts to grow, it can be noted on a chart. In a week, you
should see grass seed germinate and bulbs grow, in 10-14 days
the tuber should sprout, and in two weeks the plantlets should
root. The leaf cutting will take the longest, about four weeks.
In order to assure success, all the plant parts should be placed
in the container filled with moist potting media. An 8-inch by
10-inch container is a good size as it allows room to work. After
the material is planted, place the container in a large plastic
bag to maintain a uniform moisture level. After the cuttings have
rooted, dig them out of the community container and put them into
individual pots. This will allow them to develop into mature plants.
What you will need:
You may want to take photographs to show the stages of development
of Plantenstein.
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