1. Lecture # 16 Date _____ 8Chapter #35~ Plant Structure and Growth

2. Angiosperm structure 8Three basic organs: 8Roots (root system) 8fibrous: mat of thin roots 8taproot: one large, vertical root 8Stems (shoot system) 8nodes: leave attachment 8internodes: stem segments 8axillary bud: dormant, vegetative potential 8terminal bud: apex of young shoot 8apical dominance: inhibits axillary buds 8Leaves (shoot system) 8blade 8petiole

3. Plant Organ Systems 8Dermal (epidermis): single layer of cells for protection 8cuticle 8Vascular (material transport) 8xylem: water and dissolved minerals roots to shoots 8tracheids & vessel elements: xylem elongated cells dead at maturity 8phloem: food from leaves to roots and fruits 8sieve-tube members: phloem tubes alive at maturity capped by sieve plates; companion cells (nonconducting) connected by plasmodesmata 8Ground (photosynthesis, storage, support): pith and cortex

4. Plant Tissue Cell Types 8Parenchyma primary walls thin and flexible; no secondary walls; large central vacuole; most metabolic functions of plant (chloroplasts) 8Collenchyma unevenly thick primary walls used for plant support (no secondary walls ; no lignin) 8Sclerenchyma support element strengthened by secondary cell walls with lignin (may be dead; xylem cells); fibers and sclereids for support

5. Plant Growth 8Life Cycles 8annuals: 1 year (wildflowers; food crops) 8biennials: 2 years (beets; carrots) 8perennials: many years (trees; shrubs) 8Meristems 8apical: tips of roots and buds; primary growth 8lateral: cylinders of dividing cells along length of roots and stems; secondary growth (wood)

6. Primary growth 8Roots 8root cap~ protection of meristem 8zone of cell division~ primary (apical) meristem 8zone of elongation~ cells elongate; pushes root tip 8zone of maturation~ differentiation of cells (formation of 3 tissue systems)

7. Primary Tissues of Roots 8Stele~ the vascular bundle where both xylem and phloem develop 8Pith~ central core of stele in monocot; parenchyma cells 8Cortex~ region of the root between the stele and epidermis (innermost layer: endodermis) 8Lateral roots~ arise from pericycle (outermost layer of stele); just inside endodermis, cells that may become meristematic

8. Primary Tissues of Stems 8Vascular bundles (xylem and phloem) 8Surrounded by ground tissue (xylem faces pith and phloem faces cortex) 8Mostly parenchyma; some collenchyma and sclerenchyma for support

9. Primary Tissues of Leaves 8Epidermis/cuticle (protection; desiccation) 8Stomata (tiny pores for gas exchange and transpiration)/guard cells 8Mesophyll: ground tissue between upper and lower epidermis (parenchyma with chloroplasts); palisade (most photosynthesis) and spongy (gas circulation)

10. Secondary Growth 8Two lateral meristems 8vascular cambium ~ produces secondary xylem (wood) and secondary phloem (diameter increase; annual growth rings) 8cork cambium ~ produces thick covering that replaces the epidermis; produces cork cells; cork plus cork cambium make up the periderm; lenticels (split regions of periderm) allow for gas exchange; bark~ all tissues external to vascular cambium (phloem plus periderm)

11. Summary of primary & secondary growth in a woody a stem Apical meristem of stem PRIMARY PRIMARY LATERAL SECONDARY MERISTEMSTISSUES MERISTEM TISSUES ProtodermEpidermis Secondary phloem Primary phloem Vascular Procambiumcambium Secondary Primary xylem xylem Ground meristemGroundPith & tissue:CortexCork cambium Cork Periderm

12. Lecture #16 Date ______ 8Chapter 36~ Transport in Plants

13. Transport Overview 81- uptake and loss of water and solutes by individual cells (root cells) 82- short-distance transport from cell to cell (sugar loading from leaves to phloem) 83- long-distance transport of sap within xylem and phloem in whole plant

14. Whole Plant Transport 81- Roots absorb water and dissolved minerals from soil 82- Water and minerals are transported upward from roots to shoots as xylem sap 83- Transpiration, the loss of water from leaves, creates a force that pulls xylem sap upwards 84- Leaves exchange CO2 and O2 through stomata 85- Sugar is produced by photosynthesis in leaves 86- Sugar is transported as phloem sap to roots and other parts of plant 87- Roots exchange gases with air spaces of soil (supports cellular respiration in roots)

15. Cellular Transport 8Water transport √ Osmosis; hyper-; hypo-; iso- 8Cell wall creates physical pressure: √water potential solutes decrease; pressure increase 8Water moves from high to low water potential 8Flaccid (limp, iostonic); 8Plasmolysis (cell loses water in a hypertonic environment; plasma membrane pulls away); 8Turgor pressure (influx of water due to osmosis; hypotonic environment)

16. Transport within tissues/organs 8Tonoplast vacuole membrane 8Plasmodesmata (components) cytosolic connection 8Symplast route (lateral) cytoplasmic continuum 8Apoplast route (lateral) continuum of cell walls 8Bulk flow (long distance) movement of a fluid by pressure (xylem)

17. Transport of Xylem Sap 8Transpiration: loss of water vapor from leaves pulls water from roots (transpirational pull); cohesion and adhesion of water 8Root pressure: at night (low transpiration), roots cells continue to pump minerals into xylem; this generates pressure, pushing sap upwards; guttation

18. Cohesion of Water

19. Transpirational Control 8Photosynthesis-Transpiration compromise…. 8Guard cells control the size of the stomata 8Xerophytes (plants adapted to arid environments)~ thick cuticle; small spines for leaves

20. Translocation of Phloem Sap 8Translocation: food/phloem transport 8Sugar source: sugar production organ (mature leaves) 8Sugar sink: sugar storage organ (growing roots, tips, stems, fruit) 81- loading of sugar into sieve tube at source reduces water potential inside; this causes tube to take up water from surroundings by osmosis 82- this absorption of water generates pressure that forces sap to flow alon tube 83- pressure gradient in tube is reinforced by unloading of sugar and consequent loss of water from tube at the sink 84- xylem then recycles water from sink to source