Plant Parts and their Functions

13.00 Describe principles of plant science as related to horticulture14.00 Compare the anatomical parts and distinguishing characteristics of horticultural plants

Plant Sciences

• Biology-the branch of science that deals with both plant and animal organisms and life processes– Zoology-the part of biology that deals

with animals– Botany the part of biology that deals

with plants

Plant Sciences

• Applied plant sciences are based on the purposes for which the plants are grown– Agronomy– Forestry– Horticulture

Agronomy

The science and practice of growing field crops such as cotton, wheat, tobacco, corn and soybeans.

Forestry

The science and practice of growing, managing and harvesting trees for building materials and other products.

Horticulture

The science and practice of growing, processing and marketing fruits, vegetables, and ornamental plants

Life Cycles of Plants

• Annual-a plant that completes its life cycle in one year

• Biennial-a plant that completes its life cycle in two years

• Perennial-a plant that lives more than two years

Leaf Retention

• Deciduous-loses leaves during the dormant season

• Evergreen-keeps leaves and remains green year-round

Plant Hormones

• Several types of hormones are used to help plants work more efficiently.– Inhibitors– cytokinins– gibberellias– auxins

Inhibitors

• Inhibitors hasten fruit ripening, retain seed germination and stem elongation.

Cytokinins

• Hormones that work with auxins to stimulate cell division.

Gibberellias

• Hormones that stimulate cell elongation, premature flowering, and breaking of dormancy.

Auxins

• Hormones that speed plant growth by stimulating cell enlargement

Moisture in Plants

• Turgid-plant is swollen or filled with moisture

• Wilted-plant is limp because it does not have enough moisture

Plant Parts

• Leaves• Stems• Roots• Flowers

Leaves-External

• Petiole-leaf stalk or part that connects the leaf to the stem

• Blade-the large, flat part of the leaf• Midrib-the large center vein• Veins-the structural framework of

the leaf• Margin-the edge of the leaf

Leaves-External

Leaves-Internal

• Upper and lower epidermis-skin of the leaf that prevents the loss of too much moisture

• Stomates-small openings under the leaf for breathing or transpiration

• Guard Cells-open and close stomates

Leaves-Internal

• Chloroplasts-small green particles that contain chlorophyll– gives leaves their green color– necessary for photosynthesis

Leaves-Internal

Leaves-Internal

Stems-External• Lenticels-breathing pores• Bud scale scars-show where terminal

buds have been located• Leaf Scars-show where leaves were

attached• Terminal bud-bud on the end of a stem• Axillary or lateral bud-bud on side of

stem

Stems-Internal

• Xylem-tissue that transports water and nutrients up from the roots to stems and leaves

• Phloem-tissue that transports food down from leaves to roots

Stems-Internal

PhloemPhloem

Xylem

Stems-Internal

• Cambium-thin, green, actively growing tissue located between bark and wood and produces all new stem cells

• Bark-old inactive phloem

• Heartwood-old inactive xylem

• Sapwood-new active xylem

Stems-Internal

Cambium

Heartwood

Sapwood

Bark

Stems-Internal

• Monocota-plant stems have vascular bundles that contain both xylem and phloem in each bundle– examples: corn, grasses

• Dicata-plant stems have the phloem layer and xylem layer separated by cambium– example: trees

Stems-Internal

Monocot Dicot

Roots-External

• Root cap-indicates growth of new cells

• Root hairs-absorb moisture (water) and minerals

Root images from a rice plant

Roots-Internal

• Much like stems in that they have a phloem, cambium, and xylem layer

• Phloem-the outer layer that carries food down the root

• Xylem-the inner layer that carries water and minerals up to the stem

Layers of Roots

• Fibrous-many branched shallow roots– are easier to transplant

• Tap-long root with few branched ones– more difficult to transplant

Flowers

• Sepals-Green parts that cover and protect flower bud before it opens

• Petals-are really leaves that are modified to attract insects for flower pollination, the pretty part that we call flowers

• Stamen-male part of the flower• Pistil-female part of the flower

Flowers

Parts of the Stamen

• Filament-short stalk that holds up the anther

• Anther-a sac-like structure that contains pollen, the male sex cells

Parts of the Pistil

• Ovules-the eggs or female sex cells that become seeds if fertilized

• Ovary-if fertilized becomes a fruit or seed coat

• Style-holds up the stigma and connects it to the ovary

• Stigma-sticky part on top of style where insects leave pollen

Parts of the PistilStigma

Style

Ovary

Complete-vs-Incomplete

• Complete flowers have both male and female parts

• Incomplete flowers have only male or female parts

What are the functions of these

plant parts?

Functions of Leaves

• Photosynthesis-manufactures food in green plants which is the beginning of the food chain for all living things

• Photosynthesis is the process by which carbon dioxide and water in the presence of light are converted to sugar and oxygen

Functions of Stems

• Translocation-moves water and minerals from roots up to the leaves and move food from the leaves down to the roots

• Supports branches, leaves, flowers, fruits and seeds

Functions of Roots

• Absorption-take water and nutrients from the soil and conduct them to the stem

• Anchor the plant and hold it upright• Store food for plant use• Asexual reproduction in some

plants

Functions of Flowers

• Produce seeds used for sexual reproduction

• Attract insects for pollination (Pollination is the transfer of pollen from anther to stigma.)

• Produce fruit to protect, nourish and carry seeds