Parts of Plants and

their Functions

Objectives• Note contributions of plants to the life cycle on

earth• List and describe the purpose of the four main

parts of plants• Explain process of photosynthesis• Explain process of respiration• Explain major structural differences between

dicot and monocot stems• Describe process of pollination

Importance of Plants• Without plants, life on earth would not exist• Plants are the source of food for humans and

animals, directly or indirectly• Plants produce oxygen and are the major

producers• Plants help keep us cool, renew the air, slow

wind, hold soil in place, shelter wildlife, beautify space, perfume the air, furnish building materials, and fuel

ROOTS

Root Functions• Anchor the plant and hold upright• Absorb water and minerals from the soil

and conduct them to the stem• Store large quantities of plant food• Propagate or reproduce some plants• The first three are essential to all plants

Root Structure• The internal structure of a root is similar to a

stem• Older roots of shrubs and trees have a phloem

on the outside, a cambium layer, and xylem (wood) on the inside

• A phloem is the old outer layers of corklike bark

• The phloem carries manufactured food down to the root for food and storage

• The xylem carries water and minerals up to the stem

• External structures of roots are different form stems

• Roots have a root cap that produce new cells which lubricate a path and protect the cap as new roots push its way through the soil

• Behind the root cap are many root hairs which absorb moisture and minerals for larger roots and the stem

• Side roots of increasing size form as the plant grows older

• Roots are important agricultural cash crops• Carrots, beets, radishes and sweet potatoes are

roots• Roots also serve for propagation• Dahlia, peony, and sweet potato have tuberous

root clumps that can be separated will sprout new roots and plants

Fibrous Roots• Fibrous root plants are very easy to

transplant• Roots are smaller, shorter and more

compact, allowing more roots to be saved

Tap Roots• Tap root systems have longer and fewer

roots• Tap roots are usually cut off

during transplanting which loses root hairs and the ability absorb

water and nutrients • Tap roots will conduct and store

water and nutrients but not absorb it

• Roots will move toward moisture in the soil• Central roots grow downward because of

the force of gravity• This is know as geotropism and is controlled by the root tip