Plant Kingdom

1. Plant Kingdom BIO 1004 Flora

2. What Is a plant? • Eukaryotic • Multicellular • Photosynthetic • Contains chlorophyll a and b • Has cellulose cell walls • Live in a variety of terrestrial habitats • And a few shallow aquatic habits • Exhibits alternation of generations

3. Plant Diversity

4. The Evolution of Plants • Primitive plants • Lack vascular tissue to carry water • Usually live in moist situations • Have dominant gametophyte generation • More advanced plants • Have specialized cells that transport water • Typically live in dryer situations • Have dominant sporophyte generation

5. The Evolution of Plants

6. Nonvascular Plants • Commonly known as the bryophytes • Include • Mosses, hornworts, liverworts • Common features • Lack vascular tissue • Do not have true roots or leaves • Sperm swim to egg • Are small and confined to moist habitats

7. Moss Life Cycle

8. Kinds of Nonvascular Plants • Mosses • Grow as a carpet of many individual gametophyte plants • Each individual is less than 5 cm tall. • Liverworts and hornworts • Form flat sheets only a few cells thick • Cells of hornworts only contain one large chloroplast.

9. The Significance of Vascular Tissue • Vascular tissue allows plants to transport water and nutrients throughout the plant • Vascular tissue is associated with development of • Leaves for photosynthesis • Stems for positioning leaves and transporting materials • Roots for absorbing water and minerals • An increase in plant size • The appearance of a waterproof coating on the plant surfaces • Two types of vascular tissue • Xylem • Phloem

10. Xylem • A series of dead, hollow cells that form tubes • Vessel elements • Form long tubes with cells end-to-end • Tracheids • Tapered cells with holes • Overlap to form a sieve-like tube • The walls of these cells are strengthened by cellulose and lignin. • Transports water and minerals from the soil to the leaves

11. Xylem

12. Phloem • Carries organic molecules produced in the leaves to the rest of the plant • Sugar • Amino acids • Consists of two types of cells • Sieve-tube elements • Lack a nucleus and organelles, but have cytoplasm • Have holes in the end walls for the transport of material • Companion cells • Connected to sieve-tube elements • Assist in actively transporting sugars and amino acids out of the leaf cells and into the sieve-tube elements

13. Phloem

14. The Development of Roots, Stems, and Leaves • The appearance of vascular tissue allowed for the development of specialized plant parts. • Roots are specialized for absorption. • Stems are specialized for transport. • Leaves are specialized for photosynthesis.

15. Roots • Underground parts of a plant that • Anchor in the soil • Absorb water and nutrients • Move the nutrients into the vascular system • Grow from the tips • Explore new areas of soil for water and nutrients • Root tips have root hairs that increase their absorptive surface. • Important storage sites for food • Many plants store carbohydrates in their roots during the growing season to be used during the winter and the following spring.

16. Kinds of Roots

17. Stems • Above-ground structures that • Support the leaves • Transport raw material from the roots to the leaves • Transport manufactured material from the leaves to other parts of the plant • Vary greatly in form and function • Tree trunks are large and support branches. • Vine stems are flexible and require support. • Dandelion stems are short. • Some stems are underground.

18. Stems • The structure of cell walls allows the stem to support the leaves. • Herbaceous plants • Cell walls are made of cellulose interwoven into a box. • When cells are full of water, the cell walls will not stretch. • This makes the cells turgid, stiff, and able to support weight. • Woody plants have especially thick cell walls. • Cellulose cell walls are strengthened with lignin. • Allows woody plants to grow tall and withstand wind

19. Stems • Stems contain a lot of vascular tissue. • Stems also • Have waterproof layers • Can be waxy or woody (bark) • Some store food • Sugar cane • Yams • Potatoes • Some photosynthesize

20. Leaves • Specialized for photosynthesis • Have large surface area to collect sunlight • Relatively thin to allow light penetration • Have bundles of vascular tissue to support leaf tissue and provide transport • Water and minerals transported to the leaf • Sugar produced by photosynthesis from the leaf • Are arranged to minimize shading of lower leaves • Covered by a waxy coating to minimize water loss

21. The Structure of a Leaf

22. Leaves • Transpiration, stomates, and photosynthesis • Transpiration involves several processes • Water evaporates and exits leaves through stomates. • The negative pressure caused by evaporation of water from leaves helps pull water and nutrients from the roots. • Role of stomates • Stomates must be open to allow water and oxygen to exit, and carbon dioxide to enter leaves and allow for photosynthesis. • Stomates can close to regulate water loss in drought or during dry part of the day

23. Stomates

24. Seedless Vascular Plants • Include • Whisk ferns • Horsetails • Club mosses • Ferns • Have vascular tissue • Are not limited to aquatic environments • Do not have seeds • Have flagellated sperm • Must have moist conditions to reproduce

25. Fern Life Cycle

26. Kinds of Seedless Vascular Plants • Ferns • Most common seedless vascular plant • Whisk ferns • Lack roots and leaves • Anchored by an underground stem • Modifications of the stem serve the functions of roots and leaves.

27. Kinds of Vascular Seedless Plants • Horsetails • Low-growing plants with jointed stems • Most photosynthesis occurs in the stems. • Have silicon dioxide in their cell walls • Called (and used as) scouring brushes by pioneers • Club mosses • Usually evergreen • Low-growing, branching plants • Some are called ground pines.

28. Seed-Producing Vascular Plants • Gymnosperms and angiosperms produce seeds. • A seed is a specialized structure that contains • An embryo • Stored food • A protective outer coating (seed coat) that prevents drying • Seeds allow plants to live in dry habitats. • Germinate and grow when conditions are right • Aid in dispersal • Seed development is accompanied by the development of a life cycle with pollen • Pollen is a male gametophyte generation which contains sperm nucleus • Pollen resists drying and can be transported through air, which allows plants to reproduce without water for a swimming sperm.

29. Gymnosperms • Gymnosperm means “naked seed”. • Produce seeds that are not enclosed (naked) • Produce seeds in cones • Woody, perennial plants

30. Kinds of Gymnosperms • Cycads • Woody plants with a ring of fern-like leaves at the top • Live in tropical regions • Ginkgo • Ginkgo biloba is the only living species. • A tree with fan-shaped leaves • Used in many herbal medicines

31. Kinds of Gymnosperms • Conifers • Trees and shrubs that bear cones • Have needle-shaped leaves • Called evergreens because they do not lose their leaves all at one time • Do shed needles throughout the year • Used in the production of lumber

32. Several Gymnosperms

33. Angiosperms • Produce flowers • Have vascular tissue, seeds, and pollen • Have seeds enclosed in a fruit • A modification of the ovary wall

34. Flower Structure • Composed of highly modified leaves • Petals and sepals surround pistils and stamens. • Petals and sometimes sepals are large and showy in insect-pollinated plants. • Flowers of insect-pollinated plants typically produce nectar and odors to attract insects. • Much variation in structure of flowers

35. Flower Structure (continued) • Specialized for sexual reproduction • Female parts in the center • Pistil (stigma, style, and ovary) • Ovary produces eggs • Male parts surround the pistil. • Stamens (filament and anther) • Anther produces pollen which contains sperm nucleus. • Perfect flowers have both pistils and stamens. • Imperfect flowers have either pistils or stamens.

36. Flower Structure

37. Pollination Strategies • Wind pollination • Plants with inconspicuous flowers are usually wind-pollinated. • Produce many flowers and much pollen • Grasses and sedges • Many trees such as aspens, birches, and oaks • Responsible for hay fever • Some people have allergic reactions to certain kinds of pollen.

38. Strategies for Pollination • Animal pollination • Plants with showy flowers are usually animal-pollinated. • Flowers attract insects, birds, and small mammals. • These flowers usually produce nectar. • Also produce odors that attract animals • The animals feed on the nectar and pick up the pollen. • Then move to another plant for more nectar, transferring the pollen

39. Wind- and Insect-Pollinated Flowers

40. Fruit • A modification of the ovary that contains seeds • Involved in dispersal of seeds • Many fruits are nutritive to animals. • The animals eat the fruit and ingest the seeds. • The seeds pass through the digestive tract unharmed and get “planted” in the animals’ feces. • Other fruits burst open and release light seeds that are dispersed by wind. • Other fruits have sticky surfaces that cling to animals that pass by.

41. Types of Fruits

42. Angiosperm Diversity • Classified as either monocots or dicots • Cotyledons (seed leaves) store food for the growing embryo. • They emerge as the first leaves. • Monocot and dicot refers to the number of cotyledons found in the seeds of the species. • Monocots have one cotyledon (grasses, lilies, etc). • Dicots have two cotyledons (beans, apples, etc).

43. Embryos in Dicots and Monocots

44. Monocots vs. Dicots

45. Angiosperm Diversity • Monocots • A few monocots are woody—yucca, palms • Most monocots are herbaceous. • Wheat, rice, corn, sweet potatoes, onions, bananas, etc. • Dicots • Herbaceous dicots include such plants as mints, carrots, cabbages, mustards, tomatoes, and potatoes. • Woody dicots include most broad-leave trees and shrubs. • Many woody dicots drop their leaves in winter or during dry periods—they are deciduous.

46. Growth of Woody Plants • All gymnosperms and many dicots are woody plants. • Woody plants are perennials that have the ability to grow continuously for many years. • They get taller and grow in diameter each year. • Growth in length occurs at the tips of the roots and stems. • Growth in diameter occurs by adding new xylem and phloem to the outside of the stem.

47. Growth of Woody Plants • Grow in diameter by adding new xylem and phloem to the outside of the stem • Vascular cambium is located between xylem and phloem and responsible for growth in diameter. • Produces a new layer of xylem and phloem each year • Cambium cells go thought mitosis, making two cells. • One cell remains cambium; the other cell forms vascular tissue—either xylem to inside or phloem to outside. • The accumulation of xylem is known as wood. • The bark of the tree contains the phloem.

48. A Cross Section of Woody Stem

49. Plant Responses to Their Environment • Plants are constantly changing in response to changes in their environment. • They produce flowers at certain times of year. • Grow toward the light • Can mount an attack against a competitor

50. Tropisms • Growth toward or away from a stimulus • Phototropism • Growing toward light • Involves a hormone called auxin • The tip of the stem produces auxin • Transported into the stem on the shaded side • Stimulates cells on that side to divide and elongate • Causes the stem to bend toward the light