Fall Leaves: Brilliant Survival

music
ambience: walking and crunching of leaves

The brilliant colors of Fall are not just a visual treat, they’re nature’s way of preparing trees for the winter. I’m Jim Metzner, and this is the Pulse of the Planet. Nina Bassuk is the Director of the Urban Horticultural Institute at Cornell University.

“For deciduous trees, trees that lose their leaves, they’re starting to respond to the shortened day length and the cool nights and they’re responding by losing their leaves. Otherwise, if the cold weather comes and they don’t change, those leaves will be killed. And so they’re starting to wall off, where the leaves are attached to the branches. And in doing so the leaves start to move their sugars into the plant and start to change color in preparation for winter. In deciduous trees there are pigments in the leaves that are actually sensing the change in day length from the long summer days to the shorter late summer and early fall days. And it’s that sensing of the day length change that starts to really make that Fall color occur. It’s absolutely critical that they do this in order to prepare themselves for winter. If they don’t, they’re going to be killed by the early frost. So this is a preparation otherwise they will be killed.”

Some trees respond to winter with a different strategy.

“Well evergreens have adapted to keep their leaves all winter. In doing so, they have certain chemicals in the leaves that prevent them from experiencing freezing damage – kind of an antifreeze that exists in those leaves that enable them to keep them all year round. And deciduous trees don’t have that.”

Most of us are awe struck when we see the vibrant hues of a Cherry, an Ash or a Maple tree in the Fall. Throughout the Spring and Summer, the chlorophyll in the leaves of these trees obscures all its colors except for green. Only with its death, can a leaf’s true beauty be visualized by the human eye.

Pulse of the Planet is presented by DuPont, bringing you miracles of science for 200 years, with additional support provided by the National Science Foundation. I’m Jim Metzner.

music

Fall Leaves: Brilliant Survival

A magnificent display of autumnal leaves is nature's cue that trees are preparing for the winter ahead.
Air Date:10/08/2002
Scientist:
Transcript:


music
ambience: walking and crunching of leaves

The brilliant colors of Fall are not just a visual treat, they’re nature’s way of preparing trees for the winter. I’m Jim Metzner, and this is the Pulse of the Planet. Nina Bassuk is the Director of the Urban Horticultural Institute at Cornell University.

"For deciduous trees, trees that lose their leaves, they're starting to respond to the shortened day length and the cool nights and they're responding by losing their leaves. Otherwise, if the cold weather comes and they don’t change, those leaves will be killed. And so they're starting to wall off, where the leaves are attached to the branches. And in doing so the leaves start to move their sugars into the plant and start to change color in preparation for winter. In deciduous trees there are pigments in the leaves that are actually sensing the change in day length from the long summer days to the shorter late summer and early fall days. And it's that sensing of the day length change that starts to really make that Fall color occur. It's absolutely critical that they do this in order to prepare themselves for winter. If they don't, they're going to be killed by the early frost. So this is a preparation otherwise they will be killed."

Some trees respond to winter with a different strategy.

"Well evergreens have adapted to keep their leaves all winter. In doing so, they have certain chemicals in the leaves that prevent them from experiencing freezing damage - kind of an antifreeze that exists in those leaves that enable them to keep them all year round. And deciduous trees don't have that."

Most of us are awe struck when we see the vibrant hues of a Cherry, an Ash or a Maple tree in the Fall. Throughout the Spring and Summer, the chlorophyll in the leaves of these trees obscures all its colors except for green. Only with its death, can a leaf’s true beauty be visualized by the human eye.

Pulse of the Planet is presented by DuPont, bringing you miracles of science for 200 years, with additional support provided by the National Science Foundation. I’m Jim Metzner.

music