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