1. Chapter 35 Plant Structure, Growth, and Development

2. What you must know The function of xylem and phloem tissue. The specific functions of tracheids, vessels, sieve-tube elements and companion cells. The correlation between primary growth and apical meristems versus secondary growth and lateral meristems.

3. Introduction to Plants Kingdom: Plantae  Plants: Cell wall Autotroph (photosynthesis) Multi-cellular  12 Divisions (Phylum) 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 groups: Monocots & Dicots

4. Monocots compared to dicots

5. MonocotDicot One cotyledon (seed leaf) Two cotyledon Parallel veins in leaves Netted veins in leaves Fibrous root system Taproot Floral parts in multiples of 3 Floral parts in multiple layers of 4 or 5 Complex vascular arrangement Ring vascular arrangement Eg. grass, corn, palm, onion, tulip, bamboo Eg. bean, pea, rose, sunflower

6. Concept 35.1 The plant body has a heirarchy of organs, tissues, and cells Basic Organs Roots Stems Leaves Types of Tissue Dermal Vascular Ground Cell Types Parenchyma Collenchyma Sclerenchyma Xylem Phloem

7. I. PLANT ORGANS

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

9. A. Roots  Anchors plant, absorbs H 2 O & minerals, stores sugars/starches  Root hairs – tiny extensions of epidermal cells, increase surface area for H 2 O and mineral absorption  Mycorrhizae: symbiosis with fungi Root hairs

10. Fibrous RootsTaproots Mat of thin roots spread just below surface One thick, vertical root Shallow Many lateral (branch) roots Increased surface area Firmly anchors Monocots Stores food in root Dicots Fibrous Root (scallion) Taproot (carrot)

11. Modified Roots

12. Mangrove forest in Florida

13. 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

14. Stolons. Storage leaves Bulbs. Tubers. Stem Roots Node Root Rhizomes. Rhizome Modified Stems

15. 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

16. C. Leaves Main photosynthetic organ Has blade & petiole petiole blade

17. Simple vs. Compounds Leaves

18. Modified leaves

19. II. PLANT TISSUES

20. Three Tissue Systems

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

22. B. Vascular Tissue Continuous throughout plant Transports materials between roots & shoots 1. Xylem: transport H 2 O and minerals up from root 2. Phloem: transports food from leaves to other parts of plant

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

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

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

26. Plant Growth & Development Growth: irreversible increase in mass from cell division and expansion Development: sum of all changes that elaborate an organism’s body (make it more complex) PlantAnimal FasterSlower Mostly H 2 OMakes new cytoplasm Indeterminate  meristemsDeterminate Annual (1 year) Biennials (2 years) Perennials (many)

27. Concept 35.2 Meristems generate cells for growth Meristem: perpetually embryonic tissues Indeterminate growth (throughout plant’s life) Cell division to make new cells  Apical meristem: growth areas at tips of roots & buds; cause primary growth (increase in length)  Lateral meristem: growth thickens shoots and roots; secondary growth

28. Primary and Secondary Growth

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

30. Key Dermal Ground Vascular Epidermis Root hair Cortex Vascular cylinder Zone of maturation Zone of elongation Zone of cell division Apical meristem Root cap 100 µm Primary Growth of a Root

31. Primary Growth of Shoots Shoot apical meristem: dome of dividing cells at tip of terminal bud; divide and elongate

32. Leaf Organization epidermis of underside interrupted by stomata (pores) Mesophyll: ground tissue between upper/lower epidermis Parenchyma: sites of photosynthesis

33. 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

35. Primary and secondary growth in a two-year-old stem Epidermis Cortex Growth Xylem ray Vascular cambium Primary phloem Pith Primary xylem Phloem ray Epidermis Cortex Vascular cambium Primary phloem Pith Primary xylem Vascular cambium Primary phloem Primary xylem Secondary phloem Secondary xylem First cork cambium Cork Growth 0.5 mm Vascular cambium Secondary phloem Secondary xylem Transverse section of a three-year- old Tilia (linden) stem (LM) Late wood Early wood 0.5 mm Cork cambium Cork Periderm Xylem ray Bark Vascular cambium Primary phloem Secondary phloem Secondary xylem Periderm (mainly cork cambia and cork) Primary xylem Pith Vascular cambium Secondary phloem Secondary xylem (two years of production) Cork Bark Layers of periderm Most recent cork cambium Primary and Secondary Growth of a Stem