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Plant reproduction.

Kinds of Plants

Plants can: a) grow 90 meters tall from a seed smaller than your thumbnail; b) produce seeds weighing over 9 kilograms; c) have flowers that can be smelled .8 kilometers away; d) all of the above.

If you picked "d", you know there is an amazing variety of plants. In fact, scientists have identified about 500,000 plant species. Plants range in size from single-celled diatoms (di-a-toms) to the giant sequoia (se-quoi-a) trees of California. How do all these wonderful plants reproduce (re-pro-duce), or make more of themselves?

How Do Plants Grow?

Many plants grow from seeds, which are produced by both flowers and cones. Flowering plants have male and female organs. The male organs, or stamens (sta-mens), have knobby tips called anthers (an-thers) that make tiny grains of pollen (pol-len). The female part of the flower, the pistil (pis-til), has 3 main parts--the stigma (stig-ma), the style, and the ovary (o-va-ry). Pollination (pol-li-na-tion) is the process where pollen from the stamens gets onto the sticky stigma. Then, the pollen travels down the tube-shaped style to the overy, and the ovules (ov-ules) in the ovary begin to ripen into seeds. Each seed will contain an embryo (em-bryo), the earliest stage of a plant, as well as food for the embryo. Later, the ovary will develop into a berry or fruit.

The color and smell of flowers attracts insects and birds. As they look for nectar (nec-tar), bees and birds carry pollen from one flower to another. Grasses and other small-flowered plants rely on wind and rain to move pollen.

How are Seeds Produced?

Many plants such as pine trees produce cones instead of flowers. These plants have both male pollen cones and female seed cones. Wind carries pollen from the pollen cone to the seed cone. After the pollen reaches an ovule on the seed cone, the ovule develops into a seed which later falls to the ground. The seed can then sprout and begin growing a new plant. This is called germination (ger-mi-na-tion). Seeds from flowers and cones need moisture and oxygen to germinate. Many seeds also need warmth and light.

Plants can also reproduce from stems, roots, and bulbs. Strawberry and spider plants grow new plants from their stems, or runners (run-ners). New trees or shrubs can grow from suckers (suck-ers), or stems which grow from the plant's roots. Many spring flowers such as iris and daffodils reproduce from rhizomes (rhi-zomes) or bulbs, which are types of underground stems. The "eyes" of potatoes are actually buds that can be planted and, later, become the mashed potatoes on your plate!

Background

With about 500,000 species of plants identified, it is no wonder that plants come in every size, shape, and color imaginable. They range in size from the giant sequoia trees of California, the largest living things on Earth, to single-celled diatoms visible only through a microscope. Plants live underwater, in deserts, in polar regions, and on other plants. Annual plants live for less than one year, while a bristlecone pine in California is believed to be between 4 and 5 thousand years old.

Plants are not only incredibly diverse, they are also incredibly important to us. People and animals could not survive without plants, which provide food, shelter, medicine, clothing, wood, paper, and oxygen in the air we breathe. How do these wonderful plants reproduce?

Sexual Reproduction

Sexual reproduction refers to plants that reproduce from seeds or spores. Seeds are produced by both flowering plants and cone-bearing plants. Flowering plants have male and female organs. The male organs, or stamens, have knobby tips called anthers that make tiny grains of pollen. The female part of the flower, the pistil, has 3 main parts--the stigma, the style, and the ovary. Reproduction occurs through pollination--the process whereby pollen from anthers comes into contact with the sticky stigma. The pollen then travels down the tube-shaped style to the ovary, and the ovules in the ovary begin to ripen into seeds. Each seed will contain an embryo, the earliest stage of a plant. Later, the ovary can develop into a berry or fruit.

Self-pollination occurs when pollen from the anthers falls onto the stigma of the same flower. Flowers are cross-pollinated when a flower receives the pollen from another plant of the same species. Flowers that are cross-pollinated generally produce larger, healthier plants.

Flowers also contain petals and sepals. Petals are often brightly colored, surrounding and protecting the pistil and stamens. Organs at the base of the petals produce nectar, a food for bees and birds. Sepals, usually green, surround the flower petals. Flowers that contain a pistil, stamens, petals, and sepals are complete flowers. Flowers missing one or more of these parts are incomplete.

Some species of plants, such as hollies and willows, have male and female flowers on separate plants. For these plants to be pollinated and bear fruit or berries, a female plant must be planted in close proximity to a male plant. These plants are classified as dioecious. Monoecious plants have male and female flowers on the same plant.

The color and smell of flowers attracts insects and birds. As they look for nectar, bees and birds carry pollen from one flower to another, causing pollination. Grasses and other small flowered plants rely on wind and rain to move pollen.

Seeds also come in many sizes, shapes, and colors, and their size has little to do with the eventual size of the plants they produce. For example, the seeds of giant sequoia trees, which may grow taller than 90 meters, are just 1.6 mm long. Tobacco seeds are so small that 2,500 fit in a pod just 19 mm long. The seeds of some coconut trees weigh as much as 9 kilograms.

Many plants such as pine trees produce cones instead of flowers. These plants have both male pollen cones and female seed cones. Wind carries pollen from the pollen cone to the seed cone. After the pollen reaches an ovule on the seed cone, the ovule develops into a seed which later falls to the ground. The seed can then germinate and begin growing a new plant.

Seeds from flowers and cones need moisture and oxygen to germinate. Many seeds also need warmth and light, although some seeds such as spinach and lettuce germinate best in cool temperatures. The period of time in which seeds will germinate, or are viable, varies greatly. Some willow seeds will only germinate for a period of several days, while in 1995 a lotus seed germinated after 1,300 years. If properly stored, corn, okra and parsley seeds will remain viable for a year; spinach, lettuce, and tomato will remain viable for 3 years; and cucumber and watermelon seeds remain viable for 5 or more years. Thus, home gardeners and farmers can safely use many seeds for more than one growing season.

Ferns reproduce from spores rather than seeds. These tiny spores grow on the undersides of the fern leaves. When the spores ripen and fall to the ground, the male and female cells of the spores can unite and new ferns begin to grow. Mosses also reproduce from spores.

Asexual Reproduction

Plants can also reproduce from stems, roots, and bulbs. Strawberry and spider plants grow new plants from their stems, or runners. New trees or shrubs can grow from suckers, or stems which sprout from the plant's roots. Many spring flowers such as iris and daffodils reproduce from rhizomes or bulbs, which are types of underground stems. The "eyes" of potatoes are actually buds that can be planted. When plants reproduce in this way, they will have the same characteristics of the parent plant. Plants produced from seeds may vary significantly, as they often have two "parents".

DID YOU KNOW??

Cockle burrs, which stick to animals and help the seeds to move to other places, were the inspiration for Velcro[R].

DID yOU KNOW??

The giant redwood tree grows from a seed only 1.6 millimeters long.

DID YOU KNOW??

some male insects are tricked into pollinating flowers that resemble female insects.

DID YOU KNOW??

Flowers pollinated by flies usually have a bad smell.

Level Pre-A

Main concepts: There are many kinds of plants, and they can reproduce in many ways. Flowers and cones make seeds. New plants can grow from seeds, bulbs, and stems.

Initiating Questions:

1. Do you know any plants that make seeds?

2. Do you ever eat plants that have seeds?

3. What kind of plants make cones?

Follow-up Questions:

1. What parts of plants make seeds?

2. Do seeds know which way to grow?

3. How can seeds get to other places?

Vocabulary

The words all have "ow". Have the students write "ow" in the blanks. Then read the words out loud. Flower and plow have short "o" sounds, while grow and mow have the long "o" sound.

Weekly Lab

Bean seeds germinate quickly and are large and easy for the children to handle. Plants' roots grow down and stems grow up because of a plant chemical called auxin. In nature, when seeds fall to the ground, they can land pointing in any direction, but the stems will always grow up and the roots down.

Storytelling

Have the students look at the picture and tell what they see. Have them relate the picture to their own experience. Have they ever planted seeds or bulbs? Do they have a spider plant at home?

Puzzle

The buds of potatoes are often called "eyes". When these are cut off of a potato and planted, they can grow new potato plants.

Bringing it Home

Good places to walk are by bushes, trees, tall grasses, and flower stalks. Woods and parks are good places to go seed hunting.

Math

Answers:

5+4 = 9; 5-4 = 1

DID YOU KNOW??

Tulip and daffodil bulbs will not sprout unless they are chilled firts.

DID YOU KNOW??

Some flowers open only at night and attract moths as pollinators.

Level A

Main concepts: People and animals need plants for food. Plants reproduce by seeds, stems, roots, and bulbs. Flowers and cones make seeds.

Initiating Questions:

1. What are ways that people and animals use plants?

2. What are some plants that make seeds?

2. Do you ever eat plants that have seeds?

3. What kind of plants make cones?

Follow-up Questions:

1. What parts of plants make seeds?

2. Do roots know which way to grow?

3. Do stems know which way to grow?

Vocabulary

Answer: the missing letters are r, o, s, e to spell rose. Ask the student if they know what a rose is. What other flowers can they name?

Weekly Lab

See Level Pre-A--WEEKLY LAB. In addition, the students will turn the jar on its side. The stems will bend to grow upward.

Math

Answer: The students can cross out half of the seeds in the drawing. There will be 3 left.

For the second question, 2 + 2 + 2 = 6.

Writing in Science

The students learned in the text that flowers and cones makes seeds, which grow new plants. Encourage them to think whether they have seen plants with cones. What kinds of plants (trees, bushes, etc. have they seen flowers on?

Puzzle

This is a long word, so students will feel a sense of accomplishment being able to write it with the help of the puzzle.

Bringing it Home

Potatoes can be grown from seed, but they can also grow from their "eyes", or buds This takes less time than growing from seed. If grown long enough, potato plants will develop pretty white flowers. Adult Supervision is Required.

DID YOU KNOW??

The largest living things are the giant sequoia trees, which live only in California.

Level B

Main concepts: Plants can grow in many environments. People and animals need plants. These plants reproduce in many ways. Plants reproduce from seeds, roots, stems, cones, and bulbs. Flowers and cones make seeds. Seeds need water to germinate.

Initiating questions:

1. Where can plants grow?

2. What kinds of plants make seeds?

3. What do seeds need to grow?

Follow-up questions:

1. How do seeds travel?

2. Besides seeds, what are ways plants can reproduce?

3. Can seeds begin growing in the dark?

Vocabulary

Remind students that a one-syllable word has a single sound, and give examples. Then have them unscramble the one-syllable plant words.

DID YOU KNOW??

The flower of the titan arum attracts dung beetles and can be smelled .8 km away.

Answers: seed, cone, root, stem, bulb

Weekly Lab

The students may need help poking holes in the bottom of the cartons with the pencil points. Place plates or trays under the egg cartons to catch water. Mustard seeds work well because they germinate quickly. Mustard seeds, like many other seeds, will germinate in the dark.

Math

Some seeds (lettuce, spinach, peas) germinate best in cool temperatures, while others (tomatoes, squash) germinate in warmer temperatures.

Answers: the bar graph shows that watermelons will germinate at a high of 40[degrees]C and a low of 16[degrees]C; carrots at a high of 35[degrees]C and a low of 4[degrees]C, with a difference of 31[degrees]C.

Writing in Science

This writing activity encourages students to think of all the different kinds of plants there are, and the different environments they live in.

Puzzle

For step 2, students will cross out the letter "p". After following all the steps, the students will be left with the letters r, o, t, o, which they will unscramble to spell root.

Bringing it Home

Many seeds can be found in kitchen cupboards, including celery seed, mustard seed, poppy seeds, etc. Cucumbers, strawberries, kiwi, lemon, apple, orange, green peppers are all good places to find seeds.

Level C

Main concepts: Plants are amazingly diverse. Plants reproduce from seeds, roots, buds, stems, bulbs, and rhizomes. Flowers have male and female parts. When conditions are right, seeds germinate.

Initiating questions:

1. What are some ways that humans and animals depend on plants?

2. What kinds of plants have cones? Flowers?

Follow-up questions:

1. What is pollination?

2. What are 2 things that plants need to germinate?

3. What is the name of the food that birds and insects get from flowers?

Vocabulary

This activity reinforces the meanings of the plant words, as well as the alphabetical order that words come in a dictionary.

Answers:

1. germination (sprouting of seeds)

2. nectar (food for bees and insects)

3. ovary (can become a fruit or berry)

4. pistil (female organ of a flower)

5: pollen (tiny grains from the stamen)

6: reproduction (ways that plants make more plants)

7. rhizome (type of underground stem)

8. stamen (male organ of a flower).

Weekly Lab

See Level B--WEEKLY LAB

Math

Answers:

1) 2 x 16 x 83 = 2,656

2) 224 divided by 16 = 14

Writing in Science

Students can stretch their imaginations, using rhyming words to write their own song about how plants grow.

Challenge

It is important not to let the paper touch the wet paper towels, or it will become soggy. The beans will lift the paper and a piece of cardboard, if it is not too heavy. The growing tip is strong because it is filled with water--like the fingers of a rubber glove become still and hard to bend when filled with water. The growing tips of plants can break through hard dirt and even come up through a tiny crack in a sidewalk.

Puzzle

Answer:

The map leads the way--maple

Shop in every store--pine

She will own books--willow

Jeff irks me--fir

DID YOU KNOW??

The pods of mountain wisteria can shoot their seeds up to 5 meters.

DID YOU KNOW??

Nuts, cucumbers, peas, and beans are actually fruits.

DID YOU KNOW??

The part of the carrot, beets, and radishes we eat are the roots,

Level D

Main concepts: Plants reproduce from seeds, roots, buds, stems, bulbs, and rhizomes. Flowers have male and female parts. Birds and insects help pollinate flowers. Seeds need moisture and oxygen to germinate. Some seeds also need warmth and light.

Initiating questions:

1. What are some ways that humans and animals depend on plants?

2. What kinds of plants have cones? Flowers?

3. Have you ever planted seeds? What time of year was it? Did you water the seeds?

Follow-up questions:

1. What is pollination?

2. What are 2 things that plants need to germinate?

3. What are the main parts of a flower?

Vocabulary

This activity reinforces the meanings of the vocabulary from the text, as well as gives the students practice in putting sentence in logical order and using connecting words.

Answers: The correct order of the sentences is 3, 5, 1, 2, 6, 4.

Weekly Lab

As seeds mature, they begin to dry out and go into a dormant, or resting, period. They germinate when certain conditions are met (which are different for different seeds). Inside the seed is the embryo for the emerging plant and a supply of stored food. Soaking the beans in dyed water will soften them and make the parts of the seed easier to see.

25 drops of food coloring

[ILLUSTRATION OMITTED]

1/2 cup water

[ILLUSTRATION OMITTED]

5 pinto beans or lima beans

[ILLUSTRATION OMITTED]

magnifying glass

[ILLUSTRATION OMITTED]

Math

Answers: $1.49 + $3.99 = $5.48; $0.65 x 30 = $19.50;

The difference in cost is $14.02.

Writing in Science

See WEEKLY LAB activity. Students should use a magnifying glass and try to draw what they can observe directly from the bean seed. Encourage students not to copy the printed illustration, but use it as a reference only, to help them identify and label the parts

Challenge

See Level C--CHALLENGE. Also, the mustard seeds will also lift paper.

Puzzle

See Level C--PUZZLE.

Answers:

Ros, enter now.--rose

Well, I'm Abe Anderson.--lima bean

Brad and Eli only drink tea.--dandelion

DID YOU KNOW??

More than half of all plant species are flowering.

DID YOU KNOW??

Wind can carry pollen up to 160 kilometers.

DID YOU KNOW??

Fruits help protect the seeds inside.

DID yOU KNOW??

The seeds of some coconut trees weigh 9 kilograms.

Level E

Main concepts: Plants reproduce from seeds, roots, buds, stems, bulbs, and rhizomes. Flowers have male and female parts. Seeds contain embryos, the earliest stage of plant development. Flowers that contain a pistil, stamen, petals, and sepals are complete; if they are missing one or more of these parts, they are incomplete.

Initiating questions:

1. How do flowers attract bees and insects? How does this benefit the plant?

2. Have you ever planted seeds? What time of year was it? Did you water the seeds?

3. What do seeds need to germinate?

Follow-up questions:

1. What is pollination?

2. What are the female parts of a flower? The male parts?

3. How do ferns reproduce?

Vocabulary

See Level D--VOCABULARY.

Answer: The order of the sentences is: 5, 2, 7, 3, 1, 4, 8, 6.

Weekly Lab

See Level D--WEEKLY LAB. Also, by putting wax on the opening in the seed coat, the water will not enter the seed as easily, and the seed will take longer to soften.

Math

Answers:

46 + 39 + 40 + 33 + 42 + 40 + 35 = 275 divided by 7 = 39.2; favorable for corn germination;

42 + 33 + 38 + 37 + 49 + 41 + 40 = 280 divided by 7 = 40[degrees]C; not favorable for squash germination.

Writing for Science

Discuss with the students that many pesticides kill a broad range of insects. Therefore, by spraying against beetles, one may also kill butterflies, lady bugs, bees, and other beneficial insects. Some ways to protect against bugs are with netting; by planting certain flowers such as marigolds that keep some pests away; making sure that plants are otherwise as healthy as possible, in good soil and with plenty of water; and by taking a "live and let live" attitude.

Challenge

The seeds of pine trees are contained in the scales of their cones, Each scale contains 2 seeds, attached to a papery wing on the inside of the pinecone. Use immature pinecones (small pinecones with tightly closed scales); mature pinecones may have already dropped their seeds. If it is too difficult to twist the cones, soak them in water for several hours first.

Puzzle

Across: anther, ovule, germination;

Down: stamens, ovary, petal;

Up: pistil, pollination;

Backwards: nectar, style, sepals, reproduction, embryo;

Diagonal: rhizome.

Weekly Resources

Helpful Sources for Planning Your Science Weekly Classroom Activities

Recommended Resources

* Ontario Science Center. Plants. Toronto, Canada: Kids Can Press, Ltd., 1994.

* Royston, Angela. How Plants Grow. Chicago, IL: Reed Professional & Professional Publishing, 1999.

* Heller, Ruth. The Reason for a Flower. Grosset & Dunlap, Inc.: New York, 1983.

* Raife Durant, Penny. Exploring the World of Plants. Franklin Watts Publishers, New York, 1995.

Internet Resources

http://theseedsite.co.ukseedparts.html

http://www.pbs.org.wnet/nature/plants/

http://www.botanical-online.com/lasplantasangles.htm

http://wayneword.palomar.edu/trmar98.htm

http://www.enchantedlearning.com/subjects/plants/label/plant/

http://ag.arizona.edu/pubs/garden/mg/botany/physiology.html

Vocabulary

FLY-pothesis is teaching the class about plant reproduction, but his sentences are mixed up. Help FLY-pothesis by putting his sentences in the right order.

--The female organ is called the pistil and the male organ, the stamen, makes pollen.

--They can reproduce from stems, buds, and roots.

--Then, the pollen travels down the style to the ovary.

--They can also reproduce from the seeds of flowers.

--Plants can reproduce in many ways.

-- Flowers have male and female organs.

--Finally, seeds begin to grow.

--This pollen gets on the stigma of the pistil.

DID yOU KNOW??

The pods of mountain wisteria can shoot their seeds up to 5 meters.

Weekly Lab

What's inside a seed? When seeds germinate, they don't "become alive". They start growing again after a resting period. Inside the seed is the embryo (em-bry-o), the earliest state in a new plant's life. Take a look.

You need: food coloring, cup, water, 8-10 pinto beans or lima beans, magnifying glass, candle, matches, aluminum foil, an adult's help

Step 1: Add 25 drops of food coloring to 1/2 cup of water and soak 5 of the beans overnight. What changes do you predict in the beans? The next day, remove the beans from the cup and use the magnifying glass to observe any changes.

Step 2: Put the beans back in the water and soak 2 more days. Using your thumbnail, carefully open some beans. Can you find all the parts of the developing plant shown in the drawing?

Step 3: Find the part of the seed where water entered. With help from an adult, put a drop of melted wax on several dry bean seeds. Then soak them in dyed water for 3 days. What do you predict will happen?

Step 4: Were your predictions correct? If not, how were your results different from your predictions? Explain what you observed.

Math

Corn will not germinate when temperatures are above 40 degrees centigrade ([degrees]C). Squash will not germinate above 38[degrees]C. Determine whether or not the mean temperatures for the first 2 weeks in June would be favorable for germination for corn and squash. (Mean, or average, is found by computing the sum of the numbers, then dividing by the number of numbers in the set). The temperatures for the first week in June were 46[degrees], 39[degrees], 40[degrees], 33[degrees] 42[degrees], 40[degrees], and 35[degrees]C. The temperatures the following week were 42[degrees], 33[degrees], 38[degrees], 37[degrees], 49[degrees], 41[degrees], and 40[degrees]C.

DID YOU KNOW??

Flowers pollinated by flies usually have a bad smell.</p> <pre>

June--week 1 June--week 2 Temperatures Temperatures

(Degrees C) (Degrees C) S -- -- M

-- -- T -- -- W --

-- T -- -- F --

-- J -- -- SUMS -- -- </pre>

<pre> June Number of Week 1

Week 1 days in week Mean Temperatures

(numbers in set) Temperature SUM -- /

-- = -- Is the mean temperature for the first week in June favorable for corn germination? [] yes [] no June Number of Week 2 Week 2

days in week Mean Temperatures (numbers in set) Temperature SUM -- / --

= -- Is the mean temperature for the second week in June favorable for squash germination? [] yes [] ne </pre> <p>Writing In Science

Your neighbor, Bugsy, really doesn't like bugs, so he uses a lot of pesticides. You are worried that if Bugsy keeps it up, there won't be many insects around to pollinate your garden. Write a letter to Bugsy, telling him how birds and insects help pollinate flowers. Can you suggest any other ways for Bugsy to handle his bug problem?

DID yOU KNOW??

some male insects are tricked into pollinating flowers that resemble female insects.

DID YOU KNOW??

The flower of the titan arum attracts dung beetles and can be smelled .8 km away.

Challenge

Find the seeds in a pinecone.

You need: newspaper, 2 old washcloths, and 3 immature pinecones

Step 1: Spread the newspaper on a table.

[ILLUSTRATION OMITTED]

Step 2: Wrap a washcloth around each end of a pinecone.

[ILLUSTRATION OMITTED]

Step 3: Grasp the washcloth-covered pinecone at each end.

[ILLUSTRATION OMITTED]

Step 4: Twist the pinecone several times to loosen its scales.

[ILLUSTRATION OMITTED]

Step 5: While holding the base of the cone with the washcloth, use your other hand to pull out some scales near the top of the cone. Each scale will have 2 seeds.

[ILLUSTRATION OMITTED]

newspaper

[ILLUSTRATION OMITTED]

2 washcloths

[ILLUSTRATION OMITTED]

3 pinecones

[ILLUSTRATION OMITTED]

pinecone scale

[ILLUSTRATION OMITTED]

2 seeds

[ILLUSTRATION OMITTED]

Puzzle

Find the 14 plant reproduction words. They can be forward, backward, up, down, or diagonal.

DID YOU KNOW??

Cockle burrs, Which stick to animals and help the seeds to move to Other places, Were the inspiration for Velcroo[R].

DID YOU KNOW??

Nuts, cucumbers, peas, and beans are actually fruits.

DID YOU KNOW??

Some flowers open only at night and attract moths as Pollinators,

DID YOU KNOW??

The largest living things are the giant sequoia trees, which live only in California.
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Date:Feb 23, 2006
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