1. Parts of the Plant and Their Function
Horticulture
Unit 3

2. 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

3. Parts of a Plant
4 basic parts
Leaves
Stems
Roots
Flowers

4. 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

5. External Leaf Structure

6. 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

7. Internal Leaf Structure

8. 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

9. 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

10. 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

11. 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 kcal= C6H12O6 + 6O2
Carbon dioxide + water + light energy = glucose + oxygen
CHLOROPHYLL

12. 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

13. 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

14. Comparison of Photosynthesis and Respiration
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

15. Stems

16. 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

17. 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

18. External Stem Structure

19. Internal Stem Structure
Xylem
Water and minerals travel up
Phloem
Manufactured food
travels down

20. 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

21. 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

22. Roots

23. 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

24. Structure Internal External
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

25. Root Structure

26. Types of Root Systems
Fibrous Root
Tap Root

27. Flowers, Fruits & Seeds

28. 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

29. Cells and Cell Division

30. Cell Structure

31. 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

33. 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

34. Meiosis

35. Assignment
Complete the Unit 3 Self Evaluation-Short Answer, Matching and Multiple Choice
DUE—Aug 26 end of period.

36. Activity
Flower Dissection. See worksheet for instructions