Download Parts of the Plant and Their Function

Parts of the Plant and Their Function HORTICULTURE UNIT 3

Objective & Standards  To recognize the main parts of a plant and describe

the function of each.  Hort2.1 Explain the basic principles of plant physiology and growth

Parts of a Plant  4 basic parts  Leaves  Stems  Roots  Flowers

Leaves  Produce and store all the food used by the plant  Shape and size help in plant identification  Fig 3-2 p. 27  Arrangement on the plant also differs among species  Fig 3-3 p. 28

External Leaf Structure

Internal Leaf Structure  Cuticle  Waxy outer layer of the leaf  Epidermis  the skin of the leaf  single layer of cells  Protects the leaf from losing too much moisture  Stoma  Small pore on the underside of the leaf that allow it to breathe, exchange gases and give off moisture

 Guard Cells  Open and close the stoma

Internal Leaf Structure

Transpiration  The evaporation of water through plant leaves and    

stems Necessary for plant survival Cools and maintains the flow of nutrients and manufactured food through the plant Plants transpire more when it is windy, hot and humidity is low if enough soil moisture is present Water is pulled up from the soil by forces of cohesion and adhesion

Transpiration When It is Dry  will slow or completely stops causing plants to wilt.  If wilting continues into evening then the plant

needs to be watered to prevent further damage to it.  During periods of drought the stomata close and photosynthesis slows or stops because no water or carbon dioxide moves through the leaf food factory

Transpiration When It is Wet  Plants force water from leaf vein tips to reduce water

pressure  This is why on windless humid mornings you will see water on leaf tips and edges this is called guttation

Photosynthesis  Process by which carbon dioxide and water in the

presence of light are converted to sugar and oxygen

LIGHT ENERGY 6 CO2 + 6 H2O + 672 kcal= C6H12O6 + 6O2 Carbon dioxide + water + light energy = glucose + oxygen

CHLOROPHYLL

Photosynthesis  Food manufactured in the leaves then moves

through the stem to the roots where it is used by the plant or stored in the stem/roots in the form of sugar, starch or protein  Therefore a good source of light energy and carbon dioxide, and water are important to optimum plant production

Respiration  Occurs 24 hours a day  Plants consumes carbon dioxide and releases oxygen  Produce more oxygen than is consumed through

respiration and growth and this excess oxygen is what is used by animals and people

Comparison of Photosynthesis and Respiration Respiration

Photosynthesis  Food manufactured  Sun’s energy is used  Carbon dioxide used by     

plant Oxygen given off Complex compounds form Produces sugars and starches Requires light Chlorophyll must be present

 Food consumed  Energy is released  Carbon dioxide is given     

off Oxygen used Simple compounds form Produces carbon dioxide and water Goes on day and night Carried on in all cells

Stems

Functions  Move water and minerals from roots to leaves  Move manufactured food from leaves to roots  Support of leaves and reproductive structures of the

plant

Cohesion & Adhesion  Cohesion- magnet like force that allows water

molecules to “stick” together and be pulled up the plant in the xylem tubes in a continuous column  Adhesion is the force that keeps the water clinging to the walls of the xylem tube

External Stem Structure

Internal Stem Structure  Xylem  Water and minerals travel up  Phloem  Manufactured food travels down

Dicot Stems  Xylem and phloem form two layers separated by the

cambium which produces all new cells  May continue to increase in diameter 

This is due to the cambium producing new phloem cells on the outside and new xylem cells on the inside

Monocot Stems  Only have one cotyledon  Have vascular bundles that contain both xylem and

phloem tissue  All cells are formed in the initial stages of stem growth and there is no further enlargement of stem size by formation of new cells

Roots

Functions of Roots  Anchor the plant  Hold the plant 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

Structure  Internal  Much like that of a stem; older roots of shrubs and trees have phloem on the outside a cambium layer and xylem on the inside  Both function just as they do in the stem  External  Root cap-initiates new growth and protects the root tip as it pushed down through the soil  Root hairs- absorb moisture and minerals that are conducted to the larger roots and to the stem of the plant

Root Structure

Types of Root Systems Fibrous Root

Tap Root

Flowers, Fruits & Seeds

Parts of the Flower  Complete Flower  

has both male and female parts Has 4 parts Sepals- green leaf-like parts of the flower that cover and protect the flower bud before it opens. They form the calyx after the flower opens.  Petals-actually leaves, bright color attracts insects for pollination  Stamens-male reproductive parts of flower-consist of a filament and anther  Pistil-located in the center of the flower, the female part of the flower and produce the eggs. If the eggs are fertilized they become seeds. 3 parts- stigma-sticky part on top of the style that catches the pollen, style- the tube that leads to the ovary, ovary-where the eggs develop and grow into fruit or a seed coat 

 Incomplete flowers only contain male or female parts

Cells and Cell Division

Cell Structure

Mitosis  Increases the number plant cells as the plant grows  Chromosome pairs duplicate in each new cell  Each new cell is identical to the old

Meiosis  Reproductive cell division  Results in the formation of gametes or mature sex cells  Pollen is transferred from the stamen to the pistil.  Pollination occurs when the pollen adheres to the stigma

and grows through the style to the ovary  Once the pollen is in the ovary fertilization takes place and one chromosome pair goes to one new gamete and the second to another.  Chromosomes are composed to a protein covering surrounding chains of DNA

Meiosis

Assignment  Complete the Unit 3 Self Evaluation-Short Answer,

Matching and Multiple Choice  DUE—Aug 26 end of period.

Activity  Flower Dissection. See worksheet for instructions