Ask Dr. Universe: How do leaves make themselves?

Dr-Universe-230WENATCHEE, Wash. – Last fall, my friend Lee Kalcsits and I went exploring in the apple orchards of Wenatchee. The apples were ripe and the leaves were changing from green to gold. We plucked a few leaves and took them back to his lab.

“You know, if you take a stem, pull away all the mature leaves and slice it from the top down, you can look at it under the microscope,” said Kalcsits, a scientist at Washington State University in Wenatchee who studies all kinds of trees.

Dr.-Universe-with-leavesHe slid a tiny piece of the stem under his microscope and took a closer look.

“What it looks like is these tiny, moon-shaped leaves,” he said. “They get smaller and smaller until you get this dome-shaped structure and that’s the meristem.”

The meristem is the part of a plant where leaves begin to form, he explained.

Read all of this answer from Dr. Universe at


A service of Washington State University, Ask Dr. Universe answers some of the most interesting, tough and smart questions from curious kids all around the world.