1. PLANTS

2. What are plants?  Eukaryotic (have a nucleus)  Have cell walls made of cellulose  Carry out photosynthesis using the pigment chlorophyll a and chlorophyll b  Belong to the kingdom Plantae

3. What do plants need to survive  Sunlight – make food through photosynthesis  Gas Exchange (CO2 and O2)  Water and Minerals  PHOTOSYNTHESIS  6 CO 2 + 6 H 2 O → C 6 H 12 O 6 + 6 O 2 Carbon dioxide + Water + Light energy → Glucose + Oxygen

4. Plant evolution  The ancestor to today’s plants were similar to green algae  Plants are divided into 4 major groups

5. Alternation of generations  The lifecycle of plants has 2 phases  Gametophyte (haploid – N)  Sporophyte (diploid – 2N)  During evolution – the size of the gametophyte decreased and sporophyte increased

6. Types of plants  1) Bryophytes (Mosses and others)  2) Ferns  3) Gymnosperms --------------  4) Angiosperms

7. Bryophytes  Found in damp places  Have specialized reproductive cells that require water for reproduction.  Lack vascular tissue – water/nutrient carrying tissue supported by lignin  Lack support to grow tall

8. Moss life cycle

9. Seedless vascular plants - Ferns and relatives  Have vascular tissue which makes it possible to move fluids through the plant (against gravity)  Phloem = carries nutrients  Xylem = carries water  Do not have seeds – reproduce through spores  Reproductive cells need water for fertilization

10. Gymnosperms – cone bearing plants  First seed plants – allows the plant to  Reproduce without water  Protect the embryo in a seed  Provide nutrients to the embryo  Reproduction occurs through pollination  Pollen (the male gametophyte) is transferred to the female cone

11. Gymnospserm lifecycle

12. Angiosperms – flowering plants  Reproduce sexually through flowers  Ovaries in flowers develop into fruits to help disperse seeds  Flowers attract pollinators and reproduction is more efficient than the wind pollination of gymnosperms

13. Monocot vs. dicot

15. Chapter 28 Plant Structure and Function  Plants have tissues and organs too!!!!!  TISSUES = dermal, vascular and ground  ORGANS = Roots, stems and leaves

16. Plant growth  Where do plants grow????  Meristems = regions of cells in which mitosis produces new cells that are ready for differentiation  Apical meristem = rapidly growing regions at the tip of the stem and roots

17. Meristems  All plants tissues arise at meristems (regions of rapidly dividing, undifferentiated cells)  Growth in apical meristems at tips of shoots and roots (primary growth) increases length  In some plants, growth in lateral meristems (secondary growth) thickens roots and shoots

18. Apical and Lateral Meristems

19. Apical Meristem and Primary Growth

20. Simple Tissue (Ground) Tissue  Ground tissue = produces and stores sugars and contributes to the support of the plant  Parenchyma = thin cell walls, contain a large vacuole, in leaves have chloroplasts (mesophyll)  Collenchyma = thicker cell walls Supports rapidly growing plant parts (make up “strings” of celery)  Sclerenchyma = thickest cell walls – resist stretching, cloth, rope, nutshells, seed coats

21. Types of tissue – Dermal Tissue  Dermal tissue = the protective outer covering in a plant  Epidermis - Usually a single outer layer of cells that secrete a waxy, protective cuticle  May contain specialized cells that form stomata for gas exchange  Periderm - Replaces epidermis in woody stems and roots

22. Vascular Tissue  Vascular tissue = supports the body and transports water and nutrients  Xylem- carries water and ions through the plant  Consists of two types of cells that are dead at maturity: tracheids and vessel members  Lignin-filled secondary walls  Phloem conducts sugars, other organic solutes  Sieve tubes connect end to end at sieve plates  Companion cells load sugars into sieve tubes

23. Flowering Plant Tissues

24. Studying Plant Parts: Tissue Specimens  Tissue specimens are cut along standard planes

25. Roots  Root Function  Support a plant  Anchor it to the ground  Store food  Absorb water from the soil  Absorb nutrients from the soil

26. 28.5 Primary Structure of Roots  Roots mainly function to provide plants with a large surface area for absorbing water and dissolved mineral ions  Support a plant  Anchor it  Store food  Root hairs  Fine extensions of root epidermis that increase the surface area for absorption

27. Roots cont.  Types of roots  Taproot – carrots, beets, dandelions  Fibrous root - grasses  Root pressure – roots actively pump nutrients into the root. Water moves in by osmosis. This causes a pressure that causes water to move up the plant into the stem

28. Eudicot and Monocot Root Structures  Taproot system (eudicots)  A primary root and lateral branchings  Central vascular cylinder  Fibrous root system (monocots)  Adventitious and lateral roots  Vascular cylinder divides root into cortex and pith

29. Stems  Functions of stems  Produce leaves, branches and flowers  Hold up the leaves to the sun  Transport substances throughout the plant

30. Inside the Stem  Vascular bundles  Multistranded cords of vascular tissues threaded lengthwise through ground tissues of all shoots  Two distinct patterns of vascular bundles

31. Tissues in a Buttercup Stem

32. Structure of Wood

33. Seasonal Growth  Vascular cambium is inactive in cool winters or long dry spells, and active when warmth or moisture returns  In regions where seasonal change is pronounced, alternating bands of early and late wood form “tree rings”

34. Seasonal Growth

35. 28.7 Tree Rings and Old Secrets  The number and relative thickness of a tree’s rings hold clues to environmental conditions – such as annual rainfall – during its lifetime  Tree rings are used to date archaeological ruins, study ecology, and provide evidence about wildfires, floods, landslides and glaciers

36. Historical Evidence  Settlements in North Carolina (1587) and in Virginia (1610) experienced severe drought

37. Leaves  Anatomy of a Leaf  Stomata (next slide)  Mesophyll – where photosynthesis occurs  Cuticle – waxy cover to protect/prevent water loss  All leaves are metabolic factories where photosynthetic cells produce sugars – but they vary in size, shape, surface specializations, and internal structure

38. Mesophyll – Photosynthetic Ground Tissue  Mesophyll=Photosynthetic parenchyma with air between cells  CO2 diffuses in and oxygen diffuses out through stomata  Plasmodesmata connect adjacent cells  Single layer or double layer (palisade and spongy mesophyll)

39. Veins – The Leaf’s Vascular Bundles  Veins  Vascular bundles in leaves, strengthened with fibers, containing xylem and phloem  Two distinct patterns  Eudicots: Large veins branch into networks of smaller veins  Monocots: Veins of similar size run parallel to the leaf axis

40. Leaves – stomata  Stomata – openings in the leaf that allow CO2, water, and O2 to diffuse in and out of the leaf  Guard cells = cells that surround the stomata and regulate their opening and closing

41. Homeostasis and stomata  Plants keep stomata open just enough so that gas exchange can occur for photosynthesis but not so much that they lose too much water  When water is abundant water flows into the leaf. This increases water pressure in the guard cells and opens them.  When water is scarce, pressure decreases and the stomata close

42. Water transport in plants  Transpiration = water loss from a plant through its leaves  Water leaves through open stomata  Dry cell walls pull water from deeper in the leaf and pulls water from the roots, stem and leaf through xylem  Water “sticks” to water (cohesion) and other molecules (adhesion)  Even small trees can lose 100L of water/day  What conditions increase transpiration???  Hot  Dry  Wind

43. How does water move up the plant?  Capillary action – the tendency of water to rise in a thin tube

44. 29 Reproduction in flowering plants  Parts of a flower  Sepals = enclose the flower before the bud opens and protects the flower  Petals = attract pollinators to the flower often brightly colored inside the sepals

45. Parts of a flower (cont.)  Parts of a flower  Stamen = male parts of the flower Anther – produce pollen Filament – a stalk that holds up the anther  Carpels (pistil) = female parts of the flower Stigma – sticky structure designed to capture pollen Style – a stalk that holds up the stigma

46. Angiosperm gamete production

47. Angiosperm lifecycle

48. Fruit and seed development  Fruit = a thickened ovary wall that encloses seeds  Seed Dispersal =  Animals = seeds with tough coats are encased in a sweet fleshy fruit Apples, grapes  Wind = lightweight fruits that allow them to be carried in the air Dandelions  Water = buoyant fruits that allow them to float coconuts

49. Seed Dormancy and Germination  Dormancy = the embryo is alive but not growing  Germination = growth of the plant embryo following dormancy

50. Advantages of Dormancy  Allows for long distance dispersal  Allows seeds to germinate in ideal growth conditions  Some seeds only germinate under extreme conditions  Some pine cones remain sealed until the high temps generated by forest fires cause the cones to open

51. Plant Hormones  Hormones = chemical signals produced by an organism that affect the growth, activity, and development of cells and tissues  Auxin – stimulate cell elongation and growth of roots Produced in the shoot apical meristem and transported When light hits a part of a plant, auxins build up in the shaded region, causing the plant to bend toward the light Growth of lateral buds is inhibited by auxin (if you cut off the top of a plant, the lateral buds grow more quickly.

52. Cytokinins  Cytokinins = hormones produced in the growing roots and developing fruits and seeds.  Often produce effects opposite of auxins  Stimulate cell division  Interact with auxins to balance root and shoot growth  Stimulate regeneration of tissues damaged by injury

53. Giberellin, abscisic acid, ethylene  Giberellins  Found in meristems of shoot, root, and seed embryo  Stimulate growth, promote germination  Abscisic Acid  Found in terminal buds and seeds  Inhibits cell division  Promotes seed dormancy  Ethylene  Found in fruit tissues and aging leaves and flowers  Stimulates fruits to ripen  Causes plants to seal off and drop leaves

54. Tropisms  Tropism = plants response to environmental stimuli  Phototropism – tendency of a plant to grow toward light  Gravitropism – response of a plant to gravity  Thigmotropism – response of a plant to touch

55. Rapid responses  Some plants can also adjust quickly to their environment  Venus fly trap  Mimosa (folds leaflets in a few seconds when touched)

56. Response to seasons  How do plants know when to flower, drop leaves, etc? Photoperiod = the number of hours of light/dark a plant receives (pigment phytochrome)  Winter Dormancy -  Deciduous plants turn off photosynthetic pathways  Transport materials from leaves to roots  Seal off leaves  Chlorophyll breaks down allowing other pigments to be seen (brown, yellow, etc.)