Introduction to Plants

1. Introduction to Plants Kingdom: Plantae • Plants: • Cell wall • Autotroph (photosynthesis) • Multi-cellular • 12 Divisions (Phyla) • Anthophyta= Angiosperms (flowering plants) • Largest # of species (~250,000 - 90% plants) • Seed plants: product seed w/in a fruit • Key adaptations: flowers & fruits • Sporophytes are trees, shrubs, herbs that flower • 2 main groups: Monocots& Dicots

2. Monocots vs. Dicots

4. Concept 35.1 The plant body has a heirarchy of organs, tissues, and cells

5. Above ground • Stems, leaves Shoot system • Underground (usually) • Roots Root system

6. A. Roots • Anchors plant, absorbs H2O & minerals, stores sugars/starches • Root hairs – tiny extensions of epidermal cells, increase surface area for H2O and mineral absorption • Mycorrhizae: symbiosis with fungi Root hairs

7. Fibrous Root (scallion) Taproot (carrot)

8. Roots

9. B. Stems • Alternating system of nodes (leaf attachment) and internodes • Function: display leaves • Terminal bud – growth concentrated at apex (tip) • Apical dominance: terminal bud prevents growth of axillary buds; growth directed upward, toward light • Axillary buds – located in V between leaf and stem; forms branches (lateral shoots) • Pinching/pruning – removing terminal bud

10. Stems

11. Modified stems • Runner or stolin • Aspen, strawberries, grass • Grow on surface • For asexual reproduction • Rhizome • Iris, ginger, potato, onion • Grow underground • Store food & DNA for new plant • Tuber: end of rhizome • Bulb – underground shoot • Onion • storage leaves

12. C. Leaves • epidermis of underside interrupted by stomata (pores) • Mesophyll: ground tissue between upper/lower epidermis • Parenchyma: sites of photosynthesis • Cuticle: waxy layer

13. Three Tissue Systems

14. A. Dermal Tissue • Single layer, closely packed cells that cover entire plant • Protect against water loss & invasion by pathogens • Cuticle: waxy layer • Epidermis, periderm

15. B. Vascular Tissue • Continuous throughout plant • Transports materials between roots & shoots • Xylem: transport H2O and minerals up from root • Phloem: transports food from leaves to other parts of plant stele

16. C. Ground Tissue • Anything that isn’t dermal or vascular • Function: storage, photosynthesis, support • Pith: inside vascular tissue • Cortex: outside vascular tissue

17. III. Cell Types • Parenchyma: most abundant • Perform metabolism, synthesizes & stores organic products • Collenchyma: grouped in cylinders, support growing parts of plant • Sclerenchyma: rigid support cell • Xylem: water conduction • Tracheids, vessel elements – dead, tubular, elongated cells • Phloem: sugar, organic cmpd. conduction • Sieve tubes, plates, companion cells – alive cells which aid movement of sugar

18. WATER-CONDUCTING CELLS OF THE XYLEM PARENCHYMA CELLS 100 µm Tracheids Vessel Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm Pits COLLENCHYMA CELLS Cortical parenchyma cells Tracheids and vessels (colorized SEM) 80 µm Vessel element Vessel elements with perforated end walls Tracheids SUGAR-CONDUCTING CELLS OF THE PHLOEM Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM) Sieve-tube members: longitudinal view (LM) SCLERENCHYMA CELLS 5 µm Companion cell Sclereid cells in pear (LM) Sieve-tube member 25 µm Plasmodesma Sieve plate Cell wall Nucleus Cytoplasm Companion cell 30 µm 15 µm Fiber cells (transverse section from ash tree) (LM) Sieve-tube members: longitudinal view Sieve plate with pores (LM)

19. Primary and Secondary Growth(apical vs. lateral meristems)

20. Concept 35.3 Primary growth lengthens roots and shoots Root Hairs Zone of Maturation: growth & differentiation complete; fully mature cells Zone of Elongation: cells elongate; push root tip ahead Zone of Cell Division: apical meristem; new cells produced Root cap: protects meristem as it pushes through soil; also secretes polysaccharide lubricant

21. Concept 35.4 Secondary growth adds girth to stems and roots in woody plants • Involves lateral meristems • Vascular cambium: produces secondary xylem (wood) • Cork cambium: produces tough covering that replaces epidermis • Bark = all tissues outside vascular cambium

23. What does a plant need?

24. Solute transport across plant cell plasma membranes

25. Osmosis • **Water potential (ψ): H2O moves from high ψ  low ψpotential, solute conc. & pressure • Pure water: ψ = 0 MPa • Plant cells: ψ = 1 MPa • Water potential equation: ψ = ψS + ψP • Solute potential (ψS) – osmotic potential • Pressure potential (ψP) – physical pressure on solution; turgor pressure • Bulk flow: move H2O in plant from regions of high  low pressure ** Review AP Lab 1

26. Flaccid: limp (wilting) • Plasmolyze: shrink, pull away from cell wall (kills most plant cells) due to H2O loss • Turgid: firm (healthy plant) Plasmolysis Turgid Plant Cell

27. Vascular Tissues: conduct molecules

28. Apoplast = continuum of cell walls/extracellular spaces Symplast = continuum of cytosol

29. Absorption of H2O and minerals • Root hairs: increase surface area of absorption at root tips • Mycorrhizae: symbiotic relationship between fungus + roots • Increase H2O/mineral absorption The white mycelium of the fungus ensheathes these roots of a pine tree.

30. Transport of H2O and minerals from root hairs xylem

32. Guttation: exudation of water droplets seen in morning (not dew), caused by root pressure

33. Stomata regulate rate of transpiration • Stomata – pores in epidermis of leaves/stems, allow gas exchange and transpiration • Guard cells – open/close stoma by changing shape • Take up K+ lower ψ take up H2O  pore opens • Lose K+  lose H2O  cells less bowed  pore closes

34. Cells stimulated open by: light, loss of CO2 in leaf, circadian rhythms • Stomata closure: drought, high temperature, wind

35. Sugar Transport • Translocation: transport of sugars to phloem by pressure flow • Source  Sink • Source = produce sugar (photosynthesis) • Sink = consume/store sugar • Via sieve-tube elements • Active transport of sucrose

36. Nutritional Requirements Essential element: required for plant to complete life cycle and produce another generation • Macronutrients (large amounts): CHNOPS + K, Ca, Mg • Nitrogen = most important! • Micronutrients (small amounts): Fe, Mn, Zn, Cu, etc.

37. Mutualistic Relationships: • Rhizobium bacteriasupply nitrogen at roots (fix atmospheric N2 to usable N) • Plant supplies sugar & amino acids • Mycorrhizae (plant + fungus)

38. Unusual nutritional adaptations: epiphytes, parasitic plants, canivorous plants Epiphyte: grow on another plant, absorb H2O from rain through leaves

39. Parasitic Plants: not photosynthetic; absorb sugar and minerals from living hosts

40. Carnivorous Plants: photosynthetic, but obtain some nitrogen and minerals by digesting small animals

41. Angiosperms have 3 unique Features: • Flowers • Fruits • double Fertilization

42. Alternation of Generations:Sporophyte (2n)  (meiosis)  Spores (mitosis)  gametophytes  (mitosis) gametes (n)  (fertilization)

46. Pollination: transfer pollen from anther to stigma • Pollen tube grows down into ovary

47. Double Fertilization • Union of 2 sperm cells with different cells of embryo sac • One sperm + egg  zygote (2n) • One sperm + 2 polar bodies  endosperm (triploid 3n) • Endosperm = nutrition for embryo plant • Ovule develops into seed; ovary develops into fruit • Seed = embryo + endosperm

48. Stigma Stigma Self-incompatibility: prevent reject own pollen or closely related individual Anther with pollen Pin flower Thrum flower “Pin” and “thrum” flower types reduce self-fertilization

49. The development of a eudicot plant embryo

50. Fruit • Protects enclosed seed(s) • Aids in dispersal by water, wind, or animals