Plant Structures & Taxonomy

1. Plant Structures & Taxonomy Plant Science Unit 1

2. Introduction* • Plants are a basic part of the food chain • Without plants the web of life cannot exists and most animals and humans would die.

3. Plant Parts • Stems • Branches • Leaves • Flowers • Fruit • Nuts

4. Basic necessities of Plant Life • For a plant to survive these basic needs must be met. • Light • Water • Air • Minerals

5. Roots • The largest part of the plant

6. Adventitious Roots • Seen above ground • Prop up plants

7. Tap Roots • Main root of the plant • Grows straight down • Heavy and thick • Food storage organs so are often used for human and livestock food • Able to survive periods of drought • Do not stabilize the soil well • Examples of plants with taproots • Carrots • Sugar beets

8. Fibrous Roots • Generally thin • Somewhat hair like • Numerous • Normally very shallow • Hold the soil well • Dry out more easily & can not tolerate drought conditions • Grasses & corn are good examples of fibrous root systems.

9. Root Tissues • A knowledge of the parts that make up the root is helpful in diagnosing disease and other dysfunctions of plants.

10. The Root

11. Root Cap • Outermost part of the root • Protects the tender, outer growing tip as the root penetrates the soil • A tough set of cells that are able to withstand the course conditions that the root encounters as it pushes its way through the soil • As the root cap wears away the cells are replaced by more cells that develop at the root tip.

12. Area of Cell Division • Provides new cells that allow the root to grow longer • Cells multiply in two directions • tougher cells replace those on the root cap • more tender cells are produced in the back of the tougher ones and are used as the root grows longer • Thin—about the thickness of a strand of hair

13. Area of Cell Elongation • Become longer and specialized • Begin to look like the older cells • Start to do their specific job.

14. Xylem & Phloem • The most important cells in the root • Xylem • Responsible for carrying the water and nutrients that are in the soil to the upper parts of the plant • Phloem • Functions as the pipeline that carries the manufactured food from the down to the leaves & other plant parts, including the roots, where it is used or stored.

15. Area of Cell Maturation • Cells become fully developed • Root hairs emerge • Small, microscopic roots • Rise from existing cells located on the root surface • Job is to take in water and nutrients • Small, tender and break easily • Once broken off they cannot re-grow or be replaced.

16. Stems • First thing seen by a casual observer • Noticeable when leaves are gone • Easily seen as plants grow • Support the leaves, flowers, and fruit

17. Types of Stems* • Above ground Stems • Woody • Herbaceous • Modified stems • Bulbs • Corms • Rhizomes • Tubers

18. Woody Stems • Tough • Often have bark • Able to survive cold winter climates

19. Herbaceous Stems • Succulent • Often green • Will not survive winter in cold climates

20. Bulbs • Shortened stems surrounded by modified leaves called scales. • Examples are: • Easter Lilies • Onions

21. Corms • Thickened • Compact • Fleshy • Ex. Gladiolas

22. Rhizomes • Thick stems that run below the ground • Examples: Johnson grass & Iris

23. Tubers • Thickened, underground stems that store carbohydrates • We often eat this type of stem I LOVE taters!

24. Parts of Stems • Have the same internal parts as roots • The xylem and phloem run the length of the stem and into the branches of the plant • In a subclass of plants called dicotyledons the xylem and phloem occur together in tissues called vascular bundles • In another subclass called monocotyledons the xylem and phloem occur in separate areas

25. Parts of the Plant Stem • External Parts • The node • Internodes • Axillary bud • Lenticels • Terminal bud • Internal Parts • Some of the same internal parts of the roots. • Xylem and phloem continue to run the length of the stem and in to all branches

27. The Node • Portion of the stem that is swollen or slightly enlarged where buds and leaves originate

28. The Internodes • The area between the nodes

29. Axil & Axillary Bud • Axil Bud • The angle above a leaf stem or flower stem and the stalk • Axillary Bud • Grows out of the axil • Function is to develop into a leaf or branch

30. Lenticels • Pores in the stem that allow the passage of gases in and out of the plant

31. Terminal Bud • Located on the tip or top of the stem or it’s branches • May be a vegetative or flowering bud

32. Vegetative Bud • Produces the stem and leaf of the plant

33. Flowering Bud • Produces flowers

34. Leaves • Manufacture food for the plant by using light energy • Leaves are capable of adjusting their angle of exposure to the sun • Some plants leaves will turn to allow full sunlight to shine on the leaf surface as the position of the sun changes during the day. • This process is known as phototropism • Without phototropism plants would grow less

35. Leaf Margins • Edge of leaf • Allow plants to be identified by the edge, shape, and arrangement of the leaves • named or described according to the toothed pattern on each leaf edge

36. Leaf Shape & Form • Varies with species. • Useful in identification of plants.

37. Types of Leaves • Vary according to species • Also used to ID species • Single leaf arising from a stem is called a simple leaf • Two or more leaves arising from a stem are called compound leaves

38. Leaf Parts • Petiole • The petiole is the stem of the leaf; it may be almost absent or very long • Blade • Wide portion; it may be many shapes and sizes

39. Internal Structure • Internal parts of the leaf: • Cuticle • Epidermis • Palisade cells • Spongy layer • Chloroplasts • Mesophyll • Stoma • Guard Cells

40. Cuticle • Top most layer of the leaf • Waxy • Functions as a protective covering for the rest of the leaf

41. Epidermis • Surface layer on the lower & upper side • Protects the inner leaf

42. Palisade Cells & Spongy Layer • Give the leaf strength • Manufacture food • Contain chloroplasts

43. Stoma • Special cells located in the lower epidermis • Allow for the exchange of carbon dioxide & oxygen as well as some water

44. Guard Cells • Surround the stoma • They are responsible for opening and closing the stoma

45. Flowers • Primary function is to produce seeds • Not all flowers are really flowers • The poinsettia and flowering dogwood have modified leaves called bracts • Protect the flower parts & attract insects for pollination

46. Flower Structure* • Composed of many parts –see handout • Filament • Anther • Pollen • Stigma • Style • Ovary • Petals • Sepals

47. Male Flower Parts • Stamen • It is made up of the filament, anther and pollen • The filament supports the anther • The anther produces the pollen • Pollen is the male sexual reproductive cell

48. Female Flower Parts • The pistil • Made up of the stigma, style and ovary • Stigma receives the pollen from the male • Pollen travels down the style and into the ovary • The ovary contains the ovules or eggs • Once fertilized by the pollen the eggs will ripen into seeds. • http://www.youtube.com/watch?v=L4Ig8J2b2Ag&feature=related

49. Perfect vs. Imperfect Flower • Must have all the parts mentioned previously. • Imperfect flowers are missing one or more of the parts

50. Flowering Plants in Horticulture • In plant breeding the anther sac is removed from the plant to prevent pollination • It may be destroyed or used to pollinate another flower to create a new variety. • Many hybrids are created this way.