Childrens Illustrated Encyclopedia

411

Plants 411-

RepRoduction

Most plants reproduce sexually. pollen fertilizes the

ovules in the ovaries, which then become seeds.

other plants such as the potato can also

reproduce asexually by producing

tubers that are genetically the

same as the parent plant.

StRuctuRe of a plant

during its lifetime, a typical

flowering plant such as this

bean grows a stem, roots,

shoots, leaves, flowers,

and fruit. trees, which

are huge plants, have a

trunk—a stiff, woody stem.

life on eaRtH could not exist without plants. Humans and

animals need plants for food and oxygen. the cereal you eat for

breakfast, the orange juice you drink, even the jeans you wear, are

all derived from plants. trees provide us with wood for fuel,

furniture, and tools. in almost every country, flowers and vegetables

are grown in their millions for food and pleasure. Scientists use

plants to make drugs, such as digitalis (from foxgloves) and

morphine (from poppies). plants range from tiny mosses to

gigantic coniferous trees so tall you cannot see their tops. What

they all have in common is their unique ability to capture and

use the sun’s light as an energy source. this process is called

photosynthesis, and it powers all plant life and growth. More

than 210,000 plants are already known to us, from rare exotic

flowers to common garden vegetables. even more plants

await discovery, especially in tropical regions. today,

however, up to 144,000 different trees, flowers, and

other plants are in danger of extinction due to the

destruction of their natural habitats.

SteM

Sturdy

stem

supports

leaves and

flowers

and carries

water and

nutrients

to and from

leaves

and fruit.

RootS

from the soil, the roots take in water and

minerals, which pass to the different parts

of the plant, such as the flowers, through

tiny vessels in the stem. Roots also anchor

the plant firmly in the ground.

HoW a StRaWbeRRy

plant RepRoduceS

the parent strawberry plant sends

out runners along the ground.

buds and roots develop on these

runners and grow into new strawberry

plants. this is a form of asexual reproduction,

also called vegetative propagation.

photosynthesis

in order to grow, plants

use energy from sunlight.

this process is called

photosynthesis. a green

substance called chlorophyll

is contained in the cells of a

plant’s leaves. chlorophyll

captures energy in the light

waves from the sun, and

then carries out chemical

reactions in which carbon

dioxide gas from the air is

combined with water from

the soil. this process creates

sugars that the plant uses

for energy and growth.

Seed is inside

fruit (bean pod).

Guard cell

Palisade cell

containing

chloroplasts

Mesophyll cell

Stoma

fRuit

the fruit contains seeds that

eventually grow into new

plants. the large fruits on

this plant are called beans.

Phloem

(sap-carrying vessel)

Cortex

Xylem

(water-carrying vessel)

Root hair

Root cap

Inside a root

Parent

strawberry plant

Flower

Runner New strawberry plant

Light

energy

from sun

Carbon dioxide

is taken in from

air through tiny

holes called

stomata.

Water is taken

in from soil

through roots.

Oxygen is given off into

the air through stoma.

floWeRS

the flowers of

a plant contain

the reproductive

parts, the pollen

and ovule cells.

if pollinated, the

ovule develops

into a seed

leaveS

leaves capture energy from the sun and

use it in a process called photosynthesis

(along with carbon dioxide and water)

to produce sugars and oxygen.

Inside a leaf

Upper epidermis

Air spaces

Leaf vein

US_411_Plants_1.indd 411 12/02/16 11:19 am