Parts of the plant and their functions Importance

Parts of the plant and their functions

Importance of plants • Without plants life on earth would not exist

Plants: • Primary source of food for people and animals • Produce oxygen • help to keep us cool • renew the air

Plants: • slow wind speed • provide a home for wildlife • beautify surroundings • perfume the air • furnish building materials and fuel

Parts of a plant • Four basic parts – leaves – stems – roots – flowers

Leaves • the food factory of the plant • produce the food used by the plant or stored for later use

Shape and size of leaves • vary among plants • used for identification of plants

Leaf arrangement • alternate • opposite • whorled – arranged in a circle around the stem

External leaf structure • petiole - leaf stalk • leaf blade (leaf) – has veins – forms structural framework of the leaf

Midrib • large center vein from which all other leaf veins extend

Margins • edges of leaves • assists in plant identification

Internal leaf structure • epidermis – skin of the leaf – single layer of cells – protects leaf from loss of too much moisture

Guard Cells • open and close the small pore on the underside of the leaf

Stomates • allow the plant to breathe and transpire – give off moisture

Chloroplasts • contain chlorophyll • located inside the food making cells

Photosynthesis • process by which CO 2 and H 2 O in the presence of light are converted to sugar and oxygen

Chemical formula • 6 CO 2 + 6 H 2 O • -----> in reaction with sunlight and chlorophyll ------> • C 6 H 12 O 6 (glucose) + 6 O 2

food • manufactured in the leaves moves downward through the stem to the roots – used by the plant – stored in stem or root and leaf in the form of sugar, starch or protein.

Respiration • plants respire 24 hours a day • consume O 2 and give off CO 2 • plants produce more O 2 through ps. Than they consume during respiration and growth.

Stems • have two main functions – movement of water and minerals from the roots upward and movement of manufactured food down

Stem functions • support of leaves and reproductive structures

Stems also • used for food storage and reproduction of plants involving cuttings • Green stems manufacture food just as leaves do

External Stem Structure • lenticels- breathing pores • bud scale scars-indicate where terminal bud has been located previous year.

Leaf Scars • shows where leaf was attached • Distance between the two represents one year of growth.

Internal Stem Structure • phloem- bark, carries manufactured foods down. • Xylem- wood, carries water and minerals up. • Cambium- separates the 2 and produces all new cells. • Characteristic of dicots

Internal Stem Structure • dicot- dicotyledon, a plant with 2 seed leaves

Monocot • Monocotyledon - a plant with one seed leaf. • Have vascular bundles, contain both xylem and phloem in each small bundle

Monocot • stems have no cambium • cells enlarge to create size of mature stem

Economic Importance • food • building materials

Roots • Usually underground • functions: –anchor plant and hold upright –absorb water and minerals form soil and conduct to stem –store food, & propagation

Root Structure • internal –similar to stems –older roots have xylem, phloem and cambian

external –root cap • produces continuous supply of new cells • protects roots as they push through soil

Structure • root hairs –absorb moisture and minerals • small roots

Functions other than water and mineral absorption • cash crops for food –carrots –beets –radishes –sweet potatoes • propagation

Type of root systems • fibrous-grasses –easier transplanting –shorter, smaller, more compact • lap root-carrot –longer and fewer roots

Flowers, Fruits, and Seeds • pollination- color of flower attracts insects to fertilize flower – beginning of fruit and seed formation • fruits and seed are attractive to birds who eat and spread seeds. – Reproduces plant – some seeds carried on animals coats

Parts of the Flower • differ in size, shape, and color, some basic parts • sepal –green leaf-like part, covers and protects bud before opening

Petals • are actually leaves • usually bright colors to attract pollinating insects.

Parts of the Flower • stamens –male part of flower –has two parts • filament-stalk

Anther • anther- sac-like structure on top of filament, contains pollen

Parts of the Flower • Pistil - female part • in the center of flower • has three parts

Pistil • three parts • stigma - top - sticky • style - tube leading from stigma to ovary

Ovary • egg cells develop here • grows to become fruit or seedcoat

Types of Flowers • complete –contains 4 main parts

Incomplete • does not have all 4 main parts

Perfect • has stamens and pistils

Imperfect • lacks stamens or pistils

Types of Flowers • monoecious –stamens and pistils are found in separate flowers on the same plant • ex: Corn

dioecious • male or staminate flowers found on one plant, female or pistilate flowers on another plant • ex: holly