Читать книгу Can You Hear the Trees Talking? - Peter Wohlleben - Страница 12

Leaves are very important to trees, because trees use their

leaves to make their food. When trees are hungry–and they're

always hungry–they just hold their leaves up to the light.

LEAVES

MIX

WATER

WITH

CERTAIN

PARTS of the air to

make

sugar. To do that, they need energy, and they get this

energy from light.

Wait a minute. Leaves use air? Does this mean

they can breathe just like you?

Yes,

leaves breathe in

and out—through their mouths, which they can open

and shut. These mouths even have

lips,

just like yours.

But there is one big difference.

A tree doesn't have just

one mouth

—

it has

thousands. They're

all very tiny, and

they're located on

the undersides of

the leaves. When

it's very hot and

dry, trees close their

mouths because they

lose lots of water

when they breathe,

just like you do. (You

can see this if you breathe on a windowpane—the

moisture from your breath will fog the glass.)

Larches ace one

of

just three conifers that turn yellow

in the fall and shed their needles

for

the winter.

*

If you

close your mouth, you won't suffocate, because

you can still breathe through your nose. When it's dry

outside and a tree shuts its many mouths, it doesn't

suffocate either, because it can still take in air through

its bark and roots,

The upper surface of

the

leaves has

a

waxy coating,

which often makes them shiny. The sun shines on the

tops of the leaves, and because the leaves are so

thin,

they can easily dry out. The wax makes them

thicker so they can hold in moisture, and this keeps

them healthy.

The leaves of each species of tree look different.

Hornbeam leaves, for example, have notched edges

like a saw. Others—such as oak leaves—have wavy

edges.

There's also a big difference between deciduous

trees and conifers. Deciduous trees have big, flat

leaves, The leaves of conifers are narrow and pointed,

like needles—and they

can

prick

you.

This is how coni-

fers protect themselves so that deer won't eat them.

In the winter, deciduous trees drop their leaves,

but conifers hold onto their needles. They do this

because many of them live where it's very

cold.

The

winters are long and the summers are very short. So

it's better for the trees to stay green the whole time,

That way they can start to make sugar whenever a

warm day arrives. If they had to wait to grow new

leaves first, summer would be over before they had

time to make any

food.

Flat leaves are very sensitive, and they really don't

like cold weather. The leaves of deciduous trees such

as oak and beech would freeze on the first frosty day.

That's why these trees drop their leaves before winter.

The needles of spruce trees and other conifers contain

oil that protects them from freezing.

*

But there are a few conifers that behave like decidu-

ous trees: the larch, the dawn redwood, and the bald

cypress. In the

fall,

their needles turn yellow and fall

off. That's why a lot of people think these trees are

dead when they see them in winter.

Really, they're just sleeping

through the cold time

of year.

TREES

LIVE

IN

MANY

DIFFERENT

environments–

dry or wet. hot or cold–ond the shape and

size of their leaves

is

important.

In

tropical rain

forests, large leaves with pointed tips shed

water easily when it rains. In desert regions,

feathery leaflets with a small surface area

lose moisture slowly in the hot sun.

HOW TREES WORK

Leaves Large

and Small

This

is

what tree mouths look

like

under

a

microscope.