HOW DOES YOUR GARDEN GROW?

Lesson 2: Plant reproduction without seeds, Vegetative Reproduction

Aim:  How can you produce new plants without seeds?

Do Now: Using classroom resources, give three examples of vegetative reproduction.

Answer:  Growing new plants from roots, stems and leaves or by artificial means such as grafting. 

Motivation:  Display onion and tulip bulbs, an avocado, a white potato, a willow tree branch and African violet or philodendron plants for the students to examine.

Discussion: 

1.         Tulips grow from seeds and produce roots, stems and leaves. Plants with true roots, stems and leaves are called vascular plants. Elicit from the class “If you were in a rain forest and saw a tall plant would you think it was a vascular or non-vascular plant?” Answer: A tall plant is a vascular plant.   Non- vascular plants such as mosses live close to the ground because they do not have true roots, stems and leaves. They have rhizoids that anchor them to the ground. They absorb water and minerals form the ground.  These plants do not grow very tall.  Tulips are vascular plants that can be grown from bulbs.  The bulbs produce several smaller bulbs toward the end of their growing season. If you dig the bulbs up, break them apart and plant them again, several new plants will grow.  A “bulb” is actually an underground stem with thick leaves.  Growing plants from bulbs is one form of vegetative reproduction.

2.         Vegetative reproduction is the growth of new plants from a part of a parent plant. Roots, stems or leaves can be broken off a parent plant and placed in soil or water until a new root system appears.  Vegetative reproduction is an example of asexual reproduction. When a new plant forms it is produced from just one parent. During mitosis a parent cell divides to produce a new identical cell with the same set of chromosomes.  As cell division continues, a new plant is produced identical to the parent plant.  Vegetative reproduction can also take place by artificial means.  Grafting is the third type of vegetative reproduction. A branch is taken from one tree and attached to the branch of another tree.  You could graft several different pear branches onto one pear tree.  That tree could grow many different varieties of pears. Note: This is a good time to review mitosis vs. meiosis with the class.

Demonstration: The teacher will demonstrate some methods of vegetative reproduction: 1) Break off a leaf from an African Violet plant and place it in a pot of moist soil. You can do the same with a philodendron or Swedish Ivy plant. 2) Place a branch from a pussy willow bush (or weeping willow tree) in a bucket of water until roots form, than plant in soil. 3) Suspend an avocado halfway in water by inserting toothpicks or place a white potato, cut in half on a plate of water and watch as roots and stems form. 4) Plant tulip bulbs and observe as the plant grows. Use several different bulbs for variety.  Later, after they bloom dig up the bulb and observe.  Assign groups of students to monitor and care for the plants.  Each group should check their plant daily and record the environmental conditions (low sunlight, dry soil or cool temperature) in their journals.  As the plant begins to grow, changes in height should be measured and recorded as well as any other noticeable changes.      

Summary:  Vegetative reproduction is a form of asexual reproduction. This process is useful to farmers and gardeners. The end result will be a “clone” of the parent plant.

Evaluation: The children will work in pairs and share information found on web sites and software applications.  They will answer the following questions that will demonstrate their knowledge of vegetative reproduction. 1) What is the meaning of vegetative reproduction?  2) Why might a farmer graft the branch of one variety of fruit (apple, pear) onto the tree of another variety? 3) What is a hybrid?  These questions help the students reflect on the experiment and understand how natural phenomena’s are explained. 

Performance Standards: For reference see The Board of Education City of New York, Performance Standards in Science, first edition.  This lesson is in alignment with the new standards. 

Life Sciences Concepts: The students will become skilled in scientific investigation by demonstrating scientific competence, completing secondary research and completing fieldwork. The students will demonstrate understanding of life cycles of organisms and understanding of change over time. Communication skills are developed when children explain the purpose and procedure of their experimentation to other students.   

Homework:  Students are to grow their own plants by vegetative reproduction. This exercise will demonstrate understanding of the classroom lesson.  Geranium stems, pussy-willow branches, carrot tops, potatoes or other cuttings, roots, stems or leaves can be used. They should try to root plants that have not been used in the classroom.  The children should keep a growth-log, recording their daily observations. A scientific report should be included with charts, graphs, photographs or drawings of the growth process. For additional research, visit at least one web site and include information on the type of vegetative reproduction used in the experiment.  The assignment needs a 2-week time frame to complete.  Plants and reports should be brought into the classroom to share with peers.

Software: Grolier Multimedia Encyclopedia, Encyclopedia of Science 2.0. Look up vegetative reproduction to answer question #1 (evaluation).

Additional Links:

www.kidsgardening.com  (digging deeper) articles for the teacher about growing plants, plant sales, and fundraising events. (See: Rent-a-Plant and Plant Sale Grows Kid)

This site also has information on obtaining e-mail addresses that allows you to hook-up with teachers and students who share your interest in gardening. You may want to become pen pals with another school.  This is a great way to develop writing skills while learning about different cultures, communities and gardening techniques.

www.encyclopedia.com (search = grafting) to answer the question #2 on grafting and question # 3 What is a hybrid?

Obsession with Orchids, a PBS broadcast available on videotape, discusses how new breeds of orchids are created artificially by mating one type of flower with another. The primary reason for grafting is to propagate HYBRIDS that do not bear seed or do not grow true from seed. This video is 60 minutes long and can be viewed over two days. You can obtain lesson plans that can be used with this show by contacting PBS.

Materials: plastic cups, water, potting soil and toothpicks.  Potatoes, carrots, cactus, an African violet or Swedish ivy plant and assorted bulbs should be on hand. A weeping willow or pussy willow branch can be used if available.

Note:  This is a good lesson for a science or ecology club.  The children can grow plants by vegetative reproduction and sell them for a profit.  Each team can design cards that explain how the new plant was developed. Vegetative reproduction is an inexpensive and fast way to produce new plants.