Bright colors wait patiently to emerge for autumn shows
BY BRAVETTA HASSELL World Scene Writer
Saturday, October 06, 2012
10/06/12 at 4:42 AM
In Mrs. Muñozcano’s first-grade class, you know it's fall because Halloween is coming. Not long after that is Thanksgiving. There's a field trip to a pumpkin patch. Parents make you swap your shorts and T-shirts for sweaters and jeans, the students say.
And oh, yes, the leaves change colors, too.
Lately, Carla Muñozcano's Hoover Elementary School class has been going on leaf walks, walking around the school property and making observations about nature. Few trees have really started turning, but in the coming weeks, many will be putting on a show.
On a recent afternoon, about 20 or so students are sitting cross-legged on the classroom carpet to review what makes leaves green and what makes them turn other colors in the fall.
Lying on a nearby tabletop are some drying leaves, and on a bulletin board not too far away is a sprawling tree with different colored leaves, a sun and labels with words such as "photosynthesis" and "chlorophyll" written on them.
Muñozcano stands ahead of them both, getting ready to pass out green construction paper leaves that are "hiding" something.
Don't open them, she tells the boys and girls.
"I think I know (what's in them)," one little voice says.
"Can we keep it?" asks another. Muñozcano reminds everyone to think to themselves about what could be inside the leaves.
"What's inside here is what's really inside all of these leaves," she says.
Seeds, bugs and veins are posed as answers and then Sydney Smith says she thinks colors are inside.
"You think it's like rainbow colors?" Muñozcano asks.
"No," Sydney says with a certainty. "I think it's like fall colors."
A classmate raises his hand to mark his agreement.
Out come the kind of "wows" and "ahhs" that only a magic trick could elicit, when the students are told they can open their leaves.
The fall effect
Across town in a bit of a different academic setting, University of Tulsa botany professor Estelle Levetin explains what's "hiding" in tree leaves - what accounts for the color change we see in the fall.
It's the type of explanation Muñozcano's first-graders might be relieved to know they won't hear for some years but touches on many of the topics they learned this week.
In the spring and summer, leaves are normally green because of an abundance of chlorophyll, Levetin explains. It's the pigment that allows plants to carry out photosynthesis - the process in which plants use sunlight to turn carbon dioxide and water into sugar and produce oxygen.
"Well, as the days start to get shorter and the nights get longer, the trees are actually starting to prepare for winter. And that's the trigger, the change in day length," Levetin says.
When this begins to happen, the leaves stop synthesizing chlorophyll and the green starts to fade.
Carotenoids, yellow and orange pigments that were always in the leaf but masked by the chlorophyll, start to show up.
The fading of the green pigment to reveal yellows and oranges accounts for a great part of the color change, Levetin explains.
And as for the reds and reddish-purples seen on some leaves, she says the excess sugar in some leaves is converted into another pigment called anthocyanin - red. In certain plants, when the weather is clear and sunny but cool during the fall they form anthocyanins.
That's why you have everything from green, yellow, orange and then beautiful red and reddish purple.
Levetin attributes tree leaves that turn straight to brown to tannins: "It's not really a pigment. It's a compound in the leaves that as (the leaf) ages, the tannins increase."
So the particular color is often a characteristic of what pigments are abundant. Sometimes one family of trees will offer a range of color in the fall, while others are known for turning only one specific color.
Ginko trees, which Levetin has at home, will turn "absolutely beautiful golden yellow. ... Never any other color."
On the other hand, while some maples turn yellow, many turn red.
"Sweetgum can be anywhere from golden yellow to red, even on the same tree," says Levetin, adding that she is unsure why pigmentation can vary on one tree.
In preparing for winter, plants do some amazing things, Levetin says. "And this is just kind of their shut down system."
Back in Mrs. Muñozcano's room, after the students have discovered the squares of orange, yellow and brown hiding in the leaves and learned the conditions that makes leaves change colors in the fall, a student sums up the lesson.
A tree isn't dying when fall comes, he says. It's just sleeping so it can get ready for the summer.
"Plants need many hours of sunlight and warmth," Muñozcano explains. And when photosynthesis stops, the plant stops producing the green coloring.
The green fades, and yellows and oranges and browns are revealed. Red can be made, too, although that process gets a little complicated and is left out of the lesson for now.
"(The colors) were there already, they were just hiding under the leaf," says Sydney, reflecting on what she'd learned. Before she'd just thought leaves died and changed colors.
Saving fall color
With Oklahoma weather having been what it has for the past couple summers, the most observable result of the drought is leaf burn. What fall color we do get may be less brilliant because of the damage. Still, there are many opportunities as the days continue to shorten and nights lengthen, to not only enjoy fall leaf color but also collect and keep it.
There are a variety of ways to preserve fall leaves but probably the least labor and material intensive is the book method.
Once you've collected your leaves, get them as dry as possible by blotting them between two sheets of paper towels.
Replace the towels and, using a book, place a leaf (with towels) between the pages of a large book - perhaps a telephone book or other heavy duty book that won't ruin if there is excess moisture from the leaves leftover.
Once you've put a few leaves in one book, stack several more books on top for enough pressure to press the leaves. Make sure your homemade leaf press is kept in a dry place.
Keep leaves in the press for at least seven days and feel free to replace your paper towels from time to time.
- Adapted from Yankee Magazine
Original Print Headline: The Magic Of Leaves
Bravetta Hassell 918-581-8316
Fall leaves show the progression
from green to red. STEPHEN
Hoover Elementary School first-grade student Jay Montgomery discovers colors “hiding” in leaves. The orange and yellow square cutouts represent
pigments that exist in plants. BRAVETTA HASSELL/Tulsa World
Hoover Elementary first-grader Mason Shepherd works on his leaf activity book. BRAVETTA HASSELL/Tulsa World
Hoover Elementary School teacher Carla Muñozcano explains
to her first-grade class that carotenoids — the yellow and orange
pigments — are always in leaves but only show themselves when
photosynthesis stops. BRAVETTA HASSELL/Tulsa World