Plants

1. Plants The Important parts.

2. Basic Vocab you need to know! • seed - an embryo and nutrients surrounded by a protective coat • Megasporangia produce megaspores that give rise to female gametophytes • Microsporangia produce microspores that give rise to male gametophytes and develop into pollen

3. Common in all seed plants • Reduced gametophytes • Heterospory = magasporangia make female gametophytes and microsporangia make male gametophytes • Ovules • Pollen • Seeds provide some evolutionary advantages over spores: • They may remain dormant for days to years, until conditions are favorable for germination • They may be transported long distances by wind or animals

4. Pollination is the transfer of pollen to the part of a seed plant containing the ovules • In what ways could pollen be dispersed?

5. Fig. 30-3-2 Femalegametophyte (n) Spore wall Egg nucleus (n) Male gametophyte(within a germinatedpollen grain) (n) Dischargedsperm nucleus (n) Micropyle Pollen grain (n) (b) Fertilized ovule

6. Flowers • A flower is a specialized shoot with up to four types of modified leaves: • Sepals, which enclose the flower • Petals, which are brightly colored and attract pollinators • Stamens, which produce pollen on their terminal anthers • Carpels, which produce ovules • A carpel consists of an ovary at the base and a style leading up to a stigma,where pollen is received

7. Fig. 30-7 Stigma Carpel Stamen Anther Style Filament Ovary Petal Sepal Draw and label this in your notes! You will need to know this! Ovule

8. Fruit AKA Ovaries • A fruittypically consists of a mature ovary but can also include other flower parts • Fruits protect seeds and aid in their dispersal

9. Fig. 30-8 Tomato Ruby grapefruit What are the various methods in which seeds can be dispersed? Nectarine Hazelnut Milkweed

10. Fig. 30-9 Wings Seeds within berries Barbs

11. Angiosperm Diversity • Cotyledon - seed leaves (found within a seed, the embryo consists of a root and two cotyledons) • The two main groups of angiosperms are monocots (one cotyledon) and eudicots (“true” dicots) AKA dicots • The clade eudicot includes some groups formerly assigned to the paraphyletic dicot (two cotyledons) group

13. Fig. 30-13n MonocotCharacteristics EudicotCharacteristics You will need to know these characteristics from this and the next slide! Embryos Two cotyledons One cotyledon Leafvenation Veins usuallyparallel Veins usuallynetlike Stems Vascular tissueusually arrangedin ring Vascular tissuescattered

14. Fig. 30-13o MonocotCharacteristics EudicotCharacteristics Roots Taproot (main root)usually present Root systemusually fibrous(no main root) Pollen Pollen grain withone opening Pollen grain withthree openings Flowers Floral organsusually inmultiples of three Floral organs usuallyin multiples of four or five

15. Systems • Rootsare multicellular organs with important functions: • Anchoring the plant • Absorbing minerals and water • Storing organic nutrients • taproot system consists of one main vertical root that gives rise to lateral roots, or branch roots

16. Fig. 35-4 Prop roots “Strangling” aerial roots Storage roots Buttress roots Pneumatophores

17. A stem is an organ consisting of • An alternating system of nodes, the points at which leaves are attached • Internodes, the stem segments between nodes • An axillary budis a structure that has the potential to form a lateral shoot, or branch • An apical bud, or terminal bud, is located near the shoot tip and causes elongation of a young shoot • Apical dominancehelps to maintain dormancy in most nonapical buds

18. Fig. 35-2 Reproductive shoot (flower) Apical bud Node Internode Apical bud Shoot system Vegetative shoot Blade Leaf Petiole Axillary bud Stem Taproot Lateral branch roots Root system

19. The leafis the main photosynthetic organ of most vascular plants • Leaves generally consist of a flattened bladeand a stalk called the petiole, which joins the leaf to a node of the stem • Monocots and eudicots differ in the arrangement of veins, the vascular tissue of leaves • Most monocots have parallel veins • Most eudicots have branching veins

20. Fig. 35-6 (a) Simple leaf Petiole Axillary bud Leaflet (b) Compound leaf Petiole Axillary bud (c) Doubly compound leaf Leaflet Petiole Axillary bud

21. Lateral meristems add thickness to woody plants, a process called secondary growth • There are two lateral meristems: the vascular cambium and the cork cambium • The vascular cambiumadds layers of vascular tissue called secondaryxylem (wood) and secondary phloem • The cork cambiumreplaces the epidermis with periderm, which is thicker and tougher

22. Fig. 35-11 Primary growth in stems Epidermis Cortex Shoot tip (shoot apical meristem and young leaves) Primary phloem Primary xylem Pith Lateral meristems: Vascular cambium Secondary growth in stems Cork cambium Periderm Axillary bud meristem Cork cambium Cortex Primary phloem Pith Primary xylem Secondary phloem Root apical meristems Secondary xylem Vascular cambium

23. Primary Growth of Roots • The root tip is covered by a root cap, which protects the apical meristem as the root pushes through soil • Growth occurs just behind the root tip, in three zones of cells: • Zone of cell division • Zone of elongation • Zone of maturation Video: Root Growth in a Radish Seed (Time Lapse)

24. Fig. 35-13 Cortex Vascular cylinder Epidermis Key to labels Zone of differentiation Root hair Dermal Ground Vascular Zone of elongation Apical meristem Zone of cell division Root cap 100 µm

25. Fig. 35-14a2 (a) Root with xylem and phloem in the center (typical of eudicots) Endodermis Key to labels Pericycle Dermal Ground Vascular Xylem Phloem 50 µm

26. Fig. 35-14b Epidermis Cortex Endodermis Vascular cylinder Key to labels Pericycle Dermal Core of parenchyma cells Ground Vascular Xylem Phloem 100 µm (b) Root with parenchyma in the center (typical of monocots)

27. Response in Plants

28. Water Pressure and Osmosis • Water potentialis a measurement that combines the effects of solute concentration and pressure • Water potential determines the direction of movement of water • Water flows from regions of higher water potential to regions of lower water potential – this sounds familiar!!! OSMOSIS!!!!

29. Water potential is abbreviated as Ψand measured in units of pressure called megapascals (MPa) • Ψ = 0 MPa for pure water at sea level and room temperature • Turgor pressure is the pressure exerted by the plasma membrane against the cell wall, and the cell wall against the protoplast – Look up what this is right now! – What is it?

30. Water and minerals can travel through a plant by three routes: • Transmembrane route: out of one cell, across a cell wall, and into another cell • Symplastic route: via the continuum of cytosol • Apoplastic route: via the cell walls and extracellular spaces

31. Mechanisms of Stomatal Opening and Closing • Changes in turgor pressure open and close stomata • These result primarily from the reversible uptake and loss of potassium ions by the guard cells

32. Fig. 36-17 Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed Radially orientedcellulose microfibrils Cellwall Vacuole Guard cell (a) Changes in guard cell shape and stomatal opening and closing (surface view) Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed H2O H2O H2O H2O H2O K+ H2O H2O H2O H2O H2O (b) Role of potassium in stomatal opening and closing

33. Fig. 36-17a Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed Radially orientedcellulose microfibrils Cellwall Vacuole Guard cell (a) Changes in guard cell shape and stomatal opening and closing (surface view)

34. Fig. 36-17b Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed H2O H2O H2O H2O H2O K+ H2O H2O H2O H2O H2O (b) Role of potassium in stomatal opening and closing

35. Stimuli for Stomatal Opening and Closing • Generally, stomata open during the day and close at night to minimize water loss • Stomatal opening at dawn is triggered by light, CO2 depletion, and an internal “clock” in guard cells • All eukaryotic organisms have internal clocks; circadian rhythms are 24-hour cycles

36. Bulk Flow by Positive Pressure: The Mechanism of Translocation in Angiosperms • In studying angiosperms, researchers have concluded that sap moves through a sieve tube by bulk flow driven by positive pressure Animation: Translocation of Phloem Sap in Summer Animation: Translocation of Phloem Sap in Spring

37. Fig. 36-20 Source cell(leaf) Vessel(xylem) Sieve tube(phloem) Loading of sugar 1 H2O Sucrose 1 H2O 2 Uptake of water 2 Bulk flow by positive pressure Bulk flow by negative pressure Unloading of sugar 3 Sink cell(storageroot) Water recycled 4 3 4 Sucrose H2O

38. Concept 39.2: Plant hormones help coordinate growth, development, and responses to stimuli • Hormones are chemical signals that coordinate different parts of an organism

39. The Discovery of Plant Hormones • Any response resulting in curvature of organs toward or away from a stimulus is called a tropism • Tropisms are often caused by hormones

40. Phototropism – plant’s response to light Video: Phototropism

41. Fig. 39-5b RESULTS Darwin and Darwin: phototropic response only when tip is illuminated Light Tip covered by opaque cap Site of curvature covered by opaque shield Tip removed Tip covered by trans- parent cap

42. The term auxin refers to any chemical that promotes elongation of coleoptiles • Auxin is involved in root formation and branching • Auxin affects secondary growth by inducing cell division in the vascular cambium and influencing differentiation of secondary xylem

43. Cytokinins are so named because they stimulate cytokinesis (cell division) Control of Cell Division and Differentiation • Cytokinins are produced in actively growing tissues such as roots, embryos, and fruits • Cytokinins work together with auxin to control cell division and differentiation

44. Control of Apical Dominance • Cytokinins, auxin, and other factors interact in the control of apical dominance, a terminal bud’s ability to suppress development of axillary buds • If the terminal bud is removed, plants become bushier

45. Fig. 39-9 Lateral branches “Stump” after removal of apical bud (b) Apical bud removed Axillary buds (c) Auxin added to decapitated stem (a) Apical bud intact (not shown in photo)

46. Gibberellins have a variety of effects, such as stem elongation, fruit growth, and seed germination Stem Elongation • Gibberellins stimulate growth of leaves and stems • In stems, they stimulate cell elongation and cell division

47. Fruit Growth • In many plants, both auxin and gibberellins must be present for fruit to set • Gibberellins are used in spraying of Thompson seedless grapes

48. Fig. 39-10 (b) Gibberellin-induced fruit growth Gibberellin-induced stem growth

49. Germination • After water is imbibed, release of gibberellins from the embryo signals seeds to germinate

50. Fig. 39-11 Gibberellins (GA) send signal to aleurone. 1 Sugars and other nutrients are consumed. 2 3 Aleurone secretes -amylase and other enzymes. Aleurone Endosperm -amylase Sugar GA GA Water Radicle Scutellum (cotyledon)