July 2012 – Page 4 – Growing With Science Blog

Our mystery seeds from last week came from the ironwood tree, Olneya tesota.

This unique tree gets its common name from the extreme hardness of its wood. Because there are a number of other trees with the same common name, it is sometimes called desert ironwood.

Desert ironwood is a small, shrubby tree found throughout the Sonoran Desert. The lower branches droop, giving a lovely form in its natural state.

The bark of the younger trunks and branches are pale gray to green at the tips.

It is a legume, having compound leaves of narrow, elliptical leaflets.

As with many desert plants, it is well armed, with many pairs of curved spines.

Desert ironwoods produce many lovely purplish-pink flowers in the spring. See Firefly Forest for a photograph of ironwood flowers.

The seed pods mature on the plant and then fall off.

The clue I mentioned that you might have noticed in the the mystery seed photograph last week was a drying leaf toward the bottom of the shot.

You can grow new trees from these seeds, but people often chose to purchase larger trees because desert ironwoods are very slow growing.

If you travel through the low desert you will often see dead ironwood trees. That is because the wood contains strong chemicals that prevent decay after the tree has died and the wood remains in place, sometimes for hundreds of years.

For more detail, see Natural History of the Desert Ironwood Tree (Olneya tesota) from the Arizona-Sonora Desert Museum.

Have your children ever wondered about the crops they have seen growing in fields? Or have they heard recent news stories about how the droughts in certain areas are having an impact on crops? Let’s use their curiosity as an opportunity for learning. Today I will start with a few agricultural science activities for elementary-aged children, with corn (maize) as a primary example. You can use these as a jumping off point to investigate other cropsÂ Look for blog posts of activities for older children and young adults coming up soon.

What is Agriculture?

Agriculture, or farming, is growing plants, fungi, and animals for food, clothing, shelter, fuel, and other products humans use to survive.

Agricultural Science Activity 1. Reading science-related books

Encourage children to acquire new vocabulary, gain knowledge, and practice reading skills by reading childrenâ€™s nonfiction books related to agricultural crops, such as these books about corn:

The Life and Times of Corn by Charles Micucci

Corn by Gail Gibbons

From Kernel to Corncob by Ellen Weiss

Glorious Grasses, The Grains by Meredith Sayles Hughes

Corn Is Maize (Let’s-Read-and-Find-Out Science 2) by Aliki

Ask the children to share what they learned. Write a paragraph about something interesting about corn, such as why corn seeds must be planted by people in order to grow.

Agricultural Science Activity 2. Collecting and interpreting data by counting corn kernels

Gather:

ears of corn*, and/or
plastic bags of loose popcorn with different numbers of seeds to represent cobs of corn – can be up to 600 seeds (allowing for three digit addition), and/or
photographs/illustrations of corn ears
paper and pencil to record results
marker to mark kernels (optional)

*Ears of corn may be available fresh at the grocery store. Dried corn on the cob may be available where birdseed or animal food is sold (check ahead of time). Decorative corn and popcorn on the cob are often available online.

Ask the children to estimate how many kernels are on each cob. After recording the estimates, have the children count the number of kernels and record counts for several ears. If they have difficulty counting ears, the children might want to mark each kernel as they count it. If counting loose popcorn, move kernels from one pile to another to avoid mix-ups. To practice skip counting, have them make piles of 5 or 10 kernels.

Add the total number of kernels from all the cobs and dividing by the number of cobs to get an average.

You can also incorporate fractions by using colored corn. What fraction of the cob had red kernels? What fraction has blue?

If possible, have the children compare different types or varieties of corn to see if the average number of kernels varies.

Agricultural Science Activity 3. Plant science

If you can’t take a “field” trip to an actual farm,

Gather:

photographs of common crop plants
seeds from common crop plants (be aware that crop seeds may be treated with pesticides and use the recommended precautions) -Seeds are often available in garden supply and animal feed stores. Some seeds, like alfalfa, may be available at health food stores for sprouting.
actual crop plants (see if a nearby gardener or farmer is willing to contribute live samples)

Explore the basic structures of plants. Identify and examine the roots, stems, leaves and flowers. Describe the life cycles of each crop and how the plants change with the season. Match the seed to the plant that grows from it. Find out when the seeds are planted and when the crop is harvested in your region.

Soak some corn and alfalfa seeds (substitute beans if alfalfa isn’t available). Examine the seeds daily over a week or so as they germinate. Use a microscope or hand lens, if available. Identify the plant structures as they emerge. Compare and contrast the germination of corn (which is botanically a monocot) to the alfalfa (a dicot). See characteristics of monocots and dicots and popcorn science for more details.

If you soak a corn seed, you might be able to cut it open lengthwise with an utility knife (adults only). See if you can see the white area, or endosperm, where the starch is stored. The endosperm is the food reserve for the embryo, which is the baby plant. Another structure supporting the embryo is the cotyledon. Corn has one cotyledon, beans and other dicots have two.

Agricultural Science Activity 4. The chemistry of corn – investigating cornstarch

The endosperm of the corn seed contains a great deal of starch. Let’s take a look at some of its properties.

Gather:

cornstarch
water
vegetable oil
dropper for oil
microwave safe bowl
plastic close-top bag
access to a microwave

Second part, optional:

iodine (see iodine chemistry post)
paper plate
spoon

First, mix a bit of cornstarch with water in the bowl. If your children have never experienced cornstarch goo or “oobleck,” then let them free explore the properties of cornstarch and water. Cornstarch and water form a complex material that feels like a solid when it is compressed, but returns to the liquid state when the pressure is released. Very cool! (Discovery Channel has a discussion of Non-Newtonian Fluids and a video).

Second, if you have iodine available, show that the powder is indeed starch. {Note about safety(see iodine chemistry post):Â read all the product warnings on the label before using. Iodine is used as a disinfectant, but it can stain skin and clothes (it can also be toxic in higher concentrations.) Be sure to wear gloves and closed-toe shoes when working with it. Clean up spills and dispose of all food used in this demonstration immediately and completely so the tested items will not be accidentally consumed by humans or pets. } Place a small amount of cornstarch goo onto a paper plate with a spoon. Add a drop or two of iodine, using the dropper provided in the iodine bottle (check). If starch is present the iodine will turn from reddish-brown to blue-black in color. Be sure to dispose of the paper plate immediately and safely.

Third, follow the instructions in this video to make cornstarch plastic (more instructions at corn plastic website).