Plants in Review

1. Plants in Review AP Biology 2010-11

2. Life Emergent Properties Organization Energy Use Regulation/Homeostasis Evolution Response to Environment Growth & Development Reproduction

3. Biological Levels of Organization BiosphereEcosystemCommunity Population Organism Organ systems Organs  Tissues Cells Organelles Macromolecules Atoms Subatomic Particles

4. Organization Evolution of Roots and Leaves • Roots are organs that anchor vascular plants • They enable vascular plants to absorb water and nutrients from the soil • Roots may have evolved from subterranean stems • Leaves are organs that increase the surface area of vascular plants, thereby capturing more solar energy that is used for photosynthesis

5. According to one model, microphylls evolved first, as outgrowths of stems Overtopping growth Megaphyll Vascular tissue Sporangia Microphyll Webbing develops. Other stems become re- duced and flattened. (a) Microphylls (b) Megaphylls • Microphylls, leaves with a single vein • Megaphylls, leaves with a highly branched vascular system

6. Plant Tissues in Leaf Guard cells Key to labels Stomatal pore 50 µm Dermal Epidermal cell Ground Cuticle Sclerenchyma fibers Vascular Stoma (b) Surface view of a spiderwort (Tradescantia) leaf (LM) Upper epidermis Palisade mesophyll Spongy mesophyll Bundle- sheath cell Lower epidermis 100 µm Cuticle Xylem Vein Phloem Vein Air spaces Guard cells Guard cells (a) Cutaway drawing of leaf tissues (c) Cross section of a lilac (Syringa)) leaf (LM)

7. Ground tissues internal to the vascular tissue is pith; ground tissue external to the vascular tissue is cortex 1) Parenchyma Cells • Mature parenchyma cells • Have thin and flexible primary walls • Lack secondary walls • Are the least specialized • Perform the most metabolic functions • Retain the ability to divide and differentiate BioFlix: Tour of a Plant Cell

8. 2)Collenchyma Cells • Collenchyma cells are grouped in strands and help support young parts of the plant shoot • They have thicker and uneven cell walls • They lack secondary walls • These cells provide flexible support without restraining growth

9. 3) Sclerenchyma Cells • Sclerenchyma cells are rigid because of thick secondary walls strengthened with lignin • They are dead at functional maturity • There are two types: • Sclereids are short and irregular in shape and have thick lignified secondary walls • Fibers are long and slender and arranged in threads

10. Energy Plant Cell Specialization in Leaf Guard cells Key to labels Stomatal pore 50 µm Dermal Epidermal cell Ground Cuticle Sclerenchyma fibers Vascular Stoma (b) Surface view of a spiderwort (Tradescantia) leaf (LM) Upper epidermis Palisade mesophyll Spongy mesophyll Bundle- sheath cell Lower epidermis 100 µm Cuticle Xylem Vein Phloem Vein Air spaces Guard cells Guard cells (a) Cutaway drawing of leaf tissues (c) Cross section of a lilac (Syringa)) leaf (LM)

11. Energy Photosynthesis Chloroplasts Adaptations Carbon-Fixation C3- Calvin Cycle in Mesophyll cells C4-Spatial: corn, crabgrass, sugarcane Malate to Bundle Sheath Cells Decreases photo-respiration CAM-Temporal:cacti, succulents, xerophytes Decreases water loss • 1. Thylakoid in Grana stacks: • ETC- Light Dependent PSII(P680), PSI(P700); Photolysis, NADPH redoxATP synthase, chemiosmosis • Pigments: Chlorophyll a & b, Xanthophyll, Carotene • 2. Stroma: Calvin-Benson Cycle • Light Independent 2G3P Glucose Rubisco (RuBP carboxylase) Questions #1

12. Casparian strip Root Cells & Specialization Endodermal cell Pathway along apoplast Pathwaythroughsymplast Casparian strip Plasmamembrane Apoplasticroute Vessels(xylem) Symplasticroute Roothair Epidermis Endodermis Stele(vascularcylinder) Cortex

13. Regulation Transport: Osmosis & Water Potential (a) (d) (b) (c) Positivepressure Increasedpositivepressure Negativepressure(tension) 0.1 Msolution Purewater H2O H2O H2O H2O ψP = 0ψS= 0 ψP = 0ψS= −0.23 ψP = 0ψS= 0 ψP = 0.23ψS= −0.23 ψP= 0ψS = 0 ψP = 0.30ψS= −0.23 ψP = −0.30ψS= 0 ψP = 0ψS= −0.23 ψ ψ= 0 MPa ψ= 0 MPa ψ= 0.07 MPa ψ= −0.30 MPa ψ= −0.23 MPa ψ= 0 MPa = −0.23 MPa ψ= 0 MPa Video: Turgid Elodea

14. Cell wall Cytosol Vacuole Plasmodesma Vacuolar membrane Plasma membrane (a) Cell compartments Key Apoplast Apoplast Transmembrane route Symplast Apoplast Symplast Symplastic route Apoplastic route (b) Transport routes between cells

15. Transport in Xylem and Phloem • Vascular plants have two types of vascular tissue: xylem and phloem • Xylem conducts most of the water and minerals and includes dead cells called tracheids (thus Tracheophytes) • Phloem consists of living cells and distributes sugars, amino acids, and other organic products • Water-conducting cells are strengthened by lignin and provide structural support • Increased height was an evolutionary advantage

16. Cohesion and Adhesion in the Ascent of Xylem Sap • The transpirational pull on xylem sap is transmitted all the way from the leaves to the root tips and even into the soil solution • Transpirational pull is facilitated by cohesion of water molecules to each other and adhesion of water molecules to cell walls Animation: Transpiration Animation: Water Transport

17. Xylemsap Mesophyllcells Outside air ψ = −100.0 Mpa Stoma Stoma Leaf ψ(air spaces) = −7.0 Mpa Watermolecule Transpiration Leaf ψ(cell walls) = −1.0 Mpa Atmosphere Adhesionby hydrogenbonding Xylemcells Cellwall Water potential gradient Trunk xylem ψ = −0.8 Mpa Cohesionby hydrogenbonding Cohesion andadhesion inthe xylem Watermolecule Roothair Trunk xylem ψ = −0.6 Mpa Soilparticle Soil ψ = −0.3 Mpa Water Water uptakefrom soil

18. Growth & Development Apical meristem Developing leaves Apical meristem of shoot Apical meristem of root Shoot Root 100 µm 100 µm Video: Root Growth in a Radish Seed (Time Lapse)

19. Concept 29.1: Land plants evolved from green algae: Morphological and Molecular Evidence of Evolution Evolution • Green algae called charophytes are the closest relatives of land plants • Land plants share four key traits only with charophytes: • Rose-shaped complexes for cellulose synthesis • Peroxisome enzymes • Structure of flagellated sperm • Formation of a phragmoplast • In charophytes a layer of a durable polymer called sporopollenin prevents exposed zygotes from drying out • The movement onto land by charophyte ancestors provided unfiltered sun, more plentiful CO2, nutrient-rich soil, and few herbivores or pathogens • Land presented challenges: a scarcity of water and lack of structural support • Fossil evidence (spores and tissues) indicates that plants were on land at least 475 million years ago

20. Fig. 29-4 Red algae ANCESTRAL ALGA Chlorophytes Viridiplantae Charophytes Streptophyta Plantae Embryophytes

21. Derived Traits of Plants • Four key traits appear in nearly all land plants but are absent in the charophytes: • Alternation of generations (with multicellular, dependent embryos) • Walled spores produced in sporangia • Multicellular gametangia • Apical meristems • Additional derived traits such as a cuticle and secondary compounds evolved in many plant species • Symbiotic associations between fungi and the first land plants may have helped plants without true roots to obtain nutrients

22. Alternation of Generations and Multicellular, Dependent Embryos Reproduction • Plants alternate between two multicellular stages, a reproductive cycle called alternation of generations • The gametophyte is haploid (1n) and produces haploid gametes by mitosis • Fusion of the gametes gives rise to the diploid (2n) sporophyte,which produces haploid (1n) spores by meiosis

23. Gamete from another plant Gametophyte (n) Mitosis Mitosis • The gametophyte is haploid and produces haploid gametes by mitosis • Fusion of the gametes gives rise to the diploid sporophyte,which produces haploid spores by meiosis n n n n Spore Gamete MEIOSIS FERTILIZATION Zygote 2n Mitosis Sporophyte (2n) Alternation of generations

24. Spores Sporangium Longitudinal section of Sphagnum sporangium (LM) Sporophyte Gametophyte Sporophytes and sporangia of Sphagnum (a moss)

25. Fig. 29-5d Archegonium with egg Female gametophyte Antheridium with sperm Male gametophyte Archegonia and antheridia of Marchantia (a liverwort)

26. Land plants can be informally grouped based on the presence or absence of vascular tissue • Most plants have vascular tissue; these constitute the vascular plants • Nonvascular plants are commonly called bryophytes • Seedless vascular plants can be divided into clades • Lycophytes(club mosses and their relatives) • Pterophytes(ferns and their relatives) • Seedless vascular plants are paraphyletic, and are of the same level of biological organization, or grade

28. Concept 29.2: Mosses and other nonvascular plants have life cycles dominated by gametophytes Origin of land plants (about 475 mya) 1 Origin of vascular plants (about 420 mya) 2 Origin of extant seed plants (about 305 mya) 3 Liverworts • phylum Hepatophyta • phylum Anthocerophyta • phylum Bryophyta Nonvascular plants (bryophytes) Land plants Hornworts ANCES- TRAL GREEN ALGA 1 Mosses Lycophytes (club mosses, spike mosses, quillworts) Seedless vascular plants Vascular plants 2 Pterophytes (ferns, horsetails, whisk ferns) Gymnosperms 3 Seed plants Angiosperms 50 500 450 400 0 350 300 Millions of years ago (mya)

29. Bryophyta Raindrop Sperm “Bud” Antheridia Male gametophyte (n) Key Haploid (n) Protonemata (n) Diploid (2n) “Bud” Egg Gametophore Spores Archegonia Female gametophyte (n) Spore dispersal Rhizoid Peristome FERTILIZATION Sporangium (within archegonium) MEIOSIS Seta Zygote (2n) Capsule (sporangium) Mature sporophytes Foot Embryo Archegonium Young sporophyte (2n) 2 mm Animation: Moss Life Cycle Female gametophytes Capsule with peristome (SEM)

30. Concept 29.3: Ferns and other seedless vascular plants were the first plants to grow tall • Bryophytes and bryophyte-like plants were the prevalent vegetation during the first 100 million years of plant evolution • Vascular plants began to diversify during the Devonian and Carboniferous periods • Vascular tissue allowed these plants to grow tall • Seedless vascular plants have flagellated sperm and are usually restricted to moist environments

31. Origins and Traits of Vascular Plants • Fossils of the forerunners of vascular plants date back about 420 million years • These early tiny plants had independent, branching sporophytes • Living vascular plants are characterized by: • Life cycles with dominant sporophytes • Vascular tissues called xylem and phloem • Well-developed roots and leaves

32. Life Cycles with Dominant Sporophytes • In contrast with bryophytes, sporophytes of seedless vascular plants are the larger generation, as in the familiar leafy fern • The gametophytes are tiny plants that grow on or below the soil surface Animation: Fern Life Cycle

33. Key Haploid (n) Diploid (2n) Antheridium Spore (n) Young gametophyte Spore dispersal MEIOSIS Sporangium Mature gametophyte (n) Sperm Archegonium Egg Mature sporophyte (2n) New sporophyte Sporangium Zygote (2n) FERTILIZATION Sorus Gametophyte Fiddlehead

34. Classification of Seedless Vascular Plants • There are two phyla of seedless vascular plants: • Phylum Lycophyta includes club mosses, spike mosses, and quillworts • Phylum Pterophyta includes ferns, horsetails, and whisk ferns and their relatives Pterophytes(Phylum Pterophyta) Athyrium filix-femina, lady fern Psilotum nudum, a whisk fern Equisetum arvense, field horsetail Vegetative stem Strobilus on fertile stem 25 cm 1.5 cm 2.5 cm

35. The Significance of Seedless Vascular Plants • The ancestors of modern lycophytes, horsetails, and ferns grew to great heights during the Devonian and Carboniferous, forming the first forests • Increased photosynthesis may have helped produce the global cooling at the end of the Carboniferous period • The decaying plants of these Carboniferous forests eventually became coal

36. Overview: Transforming the World • Seed plants form a clade and can be divided into further clades: • Gymnosperms, the “naked seed” plants, including the conifers • Angiosperms, the flowering plants

37. Concept 30.2: Gymnosperms bear “naked” seeds, typically on cones • The gymnosperms have “naked” seeds not enclosed by ovaries and consist of four phyla: • Cycadophyta (cycads) • Gingkophyta (one living species: Ginkgo biloba) • Gnetophyta (three genera: Gnetum, Ephedra, Welwitschia) • Coniferophyta (conifers, such as pine, fir, and redwood)

38. Phylum Cycadophyta • Individuals have large cones and palmlike leaves • These thrived during the Mesozoic, but relatively few species exist today Cycas revoluta

39. Phylum Ginkgophyta • This phylum consists of a single living species, Ginkgo biloba • It has a high tolerance to air pollution and is a popular ornamental tree Ginkgo bilobaleaves and fleshy seeds

40. Phylum Gnetophyta • This phylum comprises three genera • Species vary in appearance, and some are tropical whereas others live in deserts Ephedra Gnetum

41. Ovulate cones Welwitschia

42. Living seed plants can be divided into two clades: gymnosperms and angiosperms • Gymnosperms appear early in the fossil record and dominated the Mesozoic terrestrial ecosystems • Gymnosperms were better suited than nonvascular plants to drier conditions • Today, cone-bearing gymnosperms called conifers dominate in the northern latitudes

43. PLANT GROUP Mosses and othernonvascular plants Ferns and other seedlessvascular plants Seed plants (gymnosperms and angiosperms) Reduced, independent(photosynthetic andfree-living) Reduced (usually microscopic), dependent on surroundingsporophyte tissue for nutrition Gametophyte Dominant Reduced, dependent ongametophyte for nutrition Sporophyte Dominant Dominant Gymnosperm Angiosperm Sporophyte(2n) Microscopic femalegametophytes (n) insideovulate cone Microscopic femalegametophytes (n) insidethese partsof flowers Sporophyte(2n) Gametophyte(n) Example Microscopic malegametophytes (n) insidethese partsof flowers Microscopic malegametophytes (n) inside pollencone Sporophyte (2n) Sporophyte (2n) Gametophyte(n)

44. You should now be able to: • Describe four shared characteristics and four distinct characteristics between charophytes and land plants • Distinguish between the phylum Bryophyta and bryophytes • Diagram and label the life cycle of a bryophyte • Explain why most bryophytes grow close to the ground and are restricted to periodically moist environments

45. Describe three traits that characterize modern vascular plants and explain how these traits have contributed to success on land • Explain how vascular plants differ from bryophytes • Distinguish between the following pairs of terms: microphyll and megaphyll; homosporous and heterosporous • Diagram and label the life cycle of a seedless vascular plant