Bean plants provide a variety of experiences dealing with plants and the plant kingdom. Such experiences could include
Flowering plants can be divided into two groups on the basis of their seed structure.
There are other differences between monocots and dicots. Monocots have parallel veins in the leaves. Dicots have a veination pattern resembling a net. Monocots generally grow from the base of the plant. Dicots generally grow from the tips of the branches and near the leaves. Refer to the table below.
|Cotyledons in the seed||One||Two|
|Growth region||base of stem||shoot tips and leaf axils|
The axil is the angle that the leaf makes with the stem. Growth from this position is the result of an axillary bud.
There are also microscopic differences between monocot and dicot plants.
A bean seed is kidney-shaped with a protective layer on the outside called a test. Examination with a magnifier will show the other structures which include the hilum and the micropyle.
Inside the seed one can observe the two cotyledons which contain the embryonic plant between them. The following parts should be visible when the seed is split open.
1. Students take a bean seed and examine it with a magnifier. They draw the outside of the bean seed in their Science Journals and they label the parts.
2. Students carefully separate the been seed and open it like a book with the hilum serving as the hinge. Using a magnifier, they observe the internal parts of the bean seed. They draw and identify the parts of the bean seed in their Science Journals including
In their Science Journals, students describe each part of the bean seed, what the name of the part is, where it is located and what its function is.
3. The place of the bean seed in the pod can be seen by opening a pod carefully. It is best to split the pod open along the thinner seam so as to leave the bean seeds still attached within.
Students open string bean pods for study although pea pods could be used as well. They observe the points at which the seeds are attached. Drawings and descriptions are written in their Science Journals.
Students draw each of their observations in their Science Journals. Each drawing should be labeled properly. The figures above can serve as guides.
1. Students describe the function of each part of the bean seed. This can be done as a table which the students write in their Science Journal.
What it does
|test||protects the seed|
|hilum||attaches the seed to the bean pod|
|micropyle||permits entry of water for germination|
|embryo||germinates into a new plant|
These descriptions can also be written out in the form of a paragraph using complete sentences.
2. Students compare bean seeds with corn seeds. The corn seeds are studied with magnifiers to observe similarities and differences. Observations are written in their Science Journals.
3. Students brainstorm about other plants with similar seeds. There are other types of beans which have very similar anatomy. There are also closely related species such as peas and peanuts.
Safety Notice: Some children are violently allergic to peanuts. Teachers should be sure that no one would have an allergic reaction if peanuts are brought into the classroom for study.
As an alternative to bringing lots of fresh plants to school, students can do research on the Internet about plants. Observations and results are written in their Science Journals.
Bean seeds are planted in the ground. They absorb water and the embryonic plant begins to grow and develop. The root grows downward first to begin absorbing water. Energy for growth is provided by food stored in the cotyledons.
After a few days, the stalk of the plant begins to emerge from the ground. Then, the cotyledons are exposed as the epicotyl emerges. The embryonic leaves develop and deploy. They are heart-shaped.
1. Students describe the materials they are about to use and what they will be doing with each.
2. The paper coffee cups should have holes punched in the bottom to permit proper drainage of the soil. Paper cups are suggested because they are more environmentally compatible than plastic foam cups.
3. Each student fills a container with soil and plants a bean seed. Follow the directions provided on the seed package. Water the bean seeds according to the instructions on the package.
1. Students observe their bean seeds daily to see what happens. Usually, the beans begin to sprout after several days. Daily observations are written in their Science Journals. Once the plants have germinated and deployed their seed leaves, they can be observed once or twice per week.
2. Students observe the following events.
In their Science Journals students draw their bean plants as they grow. The drawings are labeled in each case with the date, the age of the plant (number of days old the plant is) and the parts. Students write in their Science Journals about the sequence of events in the germination of a bean seed and what occurs during each event.
1. Students plant corn seeds to observe their germination process. They write in their Science Journals about the ways in which bean germination and corn germination are different.
2. Students study the development of the bean root as the bean seed germinates. This is done by permitting a bean seed to germinate in a closed dish (such as a petri dish) with a piece of moist filter peper or paper towel on the bottom of the dish. The dish must be kept closed and the paper must be kept moist as the seed germinates. Students observe that the root emerges from the seed first and begins to absorb water from the moist paper. If petri dishes are not available, try an ordinary dish covered with household kitchen wrap.
Roots grow from the tip. Just behind the tip of the root is an area where specialized root hair cells develop. Root hair cells can be seen using magnifiers. They increase the surface area of the root for more efficient absorption of water.
Students draw the germinating bean seed in their Science Journals. They write about the function of each of the parts.
3. Students observe that roots grow longer using the zone of elongation. Refer to the figure below.
The zone of elongation occurs immediately behind the root tip and the zone of cell division (also known as the root tip meristem).
Students use the seeds that are germinating in the dishes. They use a pen with a sharp point and dark, black ink. Pencils usually do not work. Felt tip pens make a mark that is too wide.
Students line up the tip of the root with a metric ruler. Then, using the pen with the sharp point and the dark, black ink, they make 10 marks on the root spaced about 1 mm apart.
The measure the roots daily for several days to see that the distance between the marks increases. They can mark from the root to a graph in their Science Journal. The graph will show an increase in the length of the marked region of the root over time.
Be sure to keep the paper moist and the dish with the seedling covered when it is not being observed. This will prevent the root from drying out.
4. Crops such as beans are started by planting seeds just the way it was done in the classroom. Nowadays we purchase seeds from seed companies in stores. Students research how seeds were preserved and kept for planting in the days before there were seed companies. They write about the way these things used to be done in their Science Journals.
When a bean seed is planted, the following events take place.
Once the bean plant has emerged, it grows from buds located at the tip of the stalk and in the axils. An axil is the angle formed beteen a leaf and the stem. The terminal buds at the tip make the plant grow taller. The axillary buds make the plant bushier.
The point where cotyledons or leaves are attached is called a node. The cotyledons are attached at the first node. The heart-shaped seed leaves are attached at the second node. The bean plant will develop leaves at the third node and later on at others.
The seed leaves of the bean plant are heart-shaped. All other leaves produced by the bean plant are made by the terminal bud on the shoot tip. These leaves are trifoliate and contain three leaflets.
The first trifoliate leaf develops at the third node.
In this activity students measure the distance of the first and second internodes over a period of several weeks.
As this is a long experiment, make sure that the plants are checked and watered at least twice per week.
1. The bean seedlings are first measured when the cotyledons are fully emerged from the soil. The measurements are repeated on a weekly basis for a period of 4 or 5 weeks on the same day of the week. Students write their data in their Science Journals.
2. Students make a data table in their Science Journals in which to record their measurements. The observations are timed one week apart.
|Time (weeks)||Length of Internodes (mm)|
3. The first measurement is made when the cotyledons have just emerged from the soil and the heart-shaped seed leaves are deploying. At this point the first internode can be measured in millimeters. The second internode has not yet developed so its length is 0 mm. Students continue their measurements of the length of the internodes for 4 or 5 weeks. Each week they record the internode lengths in the data table.
1. After the experiment is completed, the students will have a completed data table containing internode lengths. Students make a graph with Time (weeks) on the x-axis and Length of internode (mm) on the y-axis.
The length of the internode depends on the time. Therefore length is the dependent variable (because its value depends on something else--in this case, time) and time is the independent variable (because you can measure it but you cannot control it.)
2. Students draw the graph in their Science Journals. A completed graph should have two lines on it, one for the first internode and one for the second internode. The write about the way the lengths of the internodes they measured changed over time.
1. As a comparison, students grow corn plants. Because the corn plant develops from the base, there are no obvious internodes that can be measured. While making comparisons between bean plants and corn plants, students write notes about their observations in their Science Journals.
Higher plants are often called the flowering plants because they reproduce by means of flowers. The flowers of flowering plants can be sorted into three major groupings.
In a flower such as the bean, there is a female structure called the pistil (note the spelling) which is located in the center of the flower. At the base of the pistil is the ovary where the ovules (eggs) are formed.
At the base of the flower on the outside are little green sepals. The sepals resemble small leaves but are not leaves. The are structures that protect the flower at the time when it is developing as a bud.
The pistil is fertilized by pollen which is produced by the male parts of the flower which are called the stamens. On the outside of the flower are the petals. In many flowers the petals are brightly colored to attract insects. The insects visit different flowers and carry pollen with them on their bodies. The pollen fertilizes the pistil of the flower.
After fertilization takes place, the petals and stamens are no longer needed. They dry up and fall off the plant. The pistil remains attached as development continues.
The pistil has the ovary at the base. The ovary contains the developing seeds. As the seeds develop the ovary develops into a structure known as a fruit.
It is important for students to distinguish between the various uses of the same word in different contexts. In biology, a fruit is a mature ovary that contains developed seeds inside. Examples include
Most people are familiar with the produce section of the supermarket. Some produce classified as vegetables is considered to be fruits by biologists. String beans and pea pods are examples.
1. When bean plants are grown in pots for five or six weeks, they begin to flower. Students make drawings of bean flowers in their Science Journals. They label the parts of the flowers as directed.
2. Students write about the life cycle of the bean plant and describe each of the stages below.
1. Students research and study other types of flowers and flowering plants. Examples could include pine trees, maple trees and grass plants.
2. Students investigate methods of pollination. They collect pictures of plants and their flowers. The pictures of flowers are sorted according to their means of pollination, for example using insects or wind. Students compare the appearance of the flowers and relate the appearance to the mode of pollination. For example, bean plants have colored petals while corn plants have tassels and silks on different parts of the plant. The tassels produce the pollen while the silks are connected to the ovules.
3. Students make a list of items found in the produce department of the supermarket. The items are sorted on the basis of what parts of the plant they are.
4. Students investigate how seeds are dispersed. Different plants rely on different agents to assist in seed dispersal. Some examples are
4. If a variety of different maple seeds are available (meaning seeds from different species of maple trees) students drop them from the balcony of the stairwell in the school and measure how much time it takes for each type to fall to the floor. The different types of maple trees are compared using a bar graph. Or, they can select several seeds from the same tree and see if they all take exactly the same time to fall or slightly different times (this becomes a good statistical study to do with older students).