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Ch. 31 – Plant Structure, Growth and Differentiation

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Presentation on theme: "Ch. 31 – Plant Structure, Growth and Differentiation"— Presentation transcript:

1 Ch. 31 – Plant Structure, Growth and Differentiation

2 Plant Body Root system Shoot system Underground Anchor and absorb
Vertical stem, leaves (flowers, fruits w/seeds) photosynthesis

3 Reproductive shoot (flower)
Fig. 35-2 Reproductive shoot (flower) Apical bud Node Internode Apical bud Shoot system Vegetative shoot Blade Leaf Petiole Axillary bud Stem Figure 35.2 An overview of a flowering plant Taproot Lateral branch roots Root system

4 Plant Cells and Tissues
Ground tissue system – majority Photosynthesis, storage, support Vascular tissue system Conduction, strength, support Dermal tissue system Covering, protection All 3 are Interconnected throughout the plant

5 Dermal tissue Ground tissue Vascular tissue Fig. 35-8
Figure 35.8 The three tissue systems Dermal tissue Ground tissue Vascular tissue

6 Ground Tissue System Parenchyma, collenchyma, sclerenchyma tissue
Primary cell wall – secreted by growing cell; stretches and expands as cell grows Secondary cell wall – secreted when cell stops growing; thick and strong (inside primary)

7 Parenchyma Living, metabolizing Most common Soft parts Function
Photosynthesis – green chloroplasts Storage – starch, oil, water, salt Secretion – resins, tannins, hormones, enzymes, nectar Can differentiate if plant injured (i.e. xylem cells)

8 Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm
Fig a Figure Examples of differentiated plant cells Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm

9 Parenchyma

10 Collenchyma Flexible, structural support (nonwoody parts)
Elongated cells Alive at maturity Primary CW – unevenly thick, thicker in corners Near stem surface, leaf veins

11 Collenchyma cells (in Helianthus stem) (LM)
Fig b 5 µm Figure Examples of differentiated plant cells Collenchyma cells (in Helianthus stem) (LM)

12 Collenchyma

13 Sclerenchyma Structural support
Primary and secondary CW (strong and hard, extreme thickening, so can’t stretch, elongate) Cells dead at maturity 2 types: Sclereids – variable shape, nut shells, pits of stone fruits, pears gritty (clusters of sclereids) Fibers – long, tapered – patches, clumps; wood, inner bark, leaf veins

14 Sclerenchyma

15 Sclereid cells in pear (LM)
Fig c 5 µm Sclereid cells in pear (LM) 25 µm Cell wall Figure Examples of differentiated plant cells Fiber cells (cross section from ash tree) (LM)

16 Vascular tissue Embedded in ground tissue Transport Xylem and phloem

17 Xylem Conducts water, dissolved nutrient minerals roots  stems, leaves Support Angiosperms – tracheids, vessel elements - conduct parenchyma cells - storage fibers - support

18 Tracheids and vessel elements
Dead at maturity  hollow, CW remain Tracheids – long, tapering, patches/clumps; water passes from 1 tracheid to another by pits (thin areas where sec. wall did not form) Vessel elements – larger in diameter than tracheid; end walls have perforations; stacked  water goes between; stack = vessel; pits in side walls for lateral water transport

19 Vessel Tracheids Pits Tracheids and vessels (colorized SEM)
Fig d Vessel Tracheids 100 µm Pits Tracheids and vessels (colorized SEM) Figure Examples of differentiated plant cells Perforation plate Vessel element Vessel elements, with perforated end walls Tracheids

20 Phloem Conducts food Support Angiosperms
Sieve tube members, companion cells – conduct Fibers – support Parenchyma cells

21 Sieve tube members Conduct food in solution
Joined end-to-end  long tubes CW ends = sieve plates; cytoplasm extends between cells Living at maturity – many organelles shrink/disintegrate Can function w/o nuclei

22 Companion cells Adjacent to each sieve tube member (stm) Assists stm
Living w/ nucleus – directs activities of both cells Plasmodesmata between stm and companion Helps move sugar into stm

23 longitudinal view (LM) 3 µm
Fig e Sieve-tube elements: longitudinal view (LM) 3 µm Sieve plate Sieve-tube element (left) and companion cell: cross section (TEM) Companion cells Sieve-tube elements Plasmodesma Figure Examples of differentiated plant cells Sieve plate 30 µm 10 µm Nucleus of companion cells Sieve-tube elements: longitudinal view Sieve plate with pores (SEM)

24 Food conducting

25 Dermal tissue system Epidermis and periderm Protective covering
Herbaceous – single layer = epidermis Woody – epidermis splits w/ growth Periderm – layers thick, under epidermis; replaces epidermis in stems, roots, composing outer bark

26 Epidermis Unspecialized dermal cells Special guard cells + trichomes
Single layer, flat cells Usually no chloroplasts  transparent Allow light through

27 (a) Cutaway drawing of leaf tissues
Fig a Key to labels Dermal Ground Cuticle Sclerenchyma fibers Vascular Stoma Upper epidermis Palisade mesophyll Figure Leaf anatomy Bundle- sheath cell Spongy mesophyll Lower epidermis Cuticle Xylem Phloem Vein Guard cells (a) Cutaway drawing of leaf tissues

28 Surface view of a spiderwort (Tradescantia) leaf (LM)
Fig b Guard cells Stomata pore 50 µm Epidermal cell Figure Leaf anatomy (b) Surface view of a spiderwort (Tradescantia) leaf (LM)

29 Cross section of a lilac (Syringa) leaf (LM)
Fig c Upper epidermis Key to labels Palisade mesophyll Dermal Ground Vascular Spongy mesophyll Lower epidermis 100 µm Figure Leaf anatomy Vein Air spaces Guard cells (c) Cross section of a lilac (Syringa) leaf (LM)

30 Cuticle Aerial parts Secreted by epidermal cells Waxy – water loss
Slows diffusion of CO2 – stomata help Stomata Open – day – photosynthesis, evaporative cooling Closed – night Closed in day if drought

31 Trichomes Outgrowths or hairs Many shape, sizes, functions Ex:
Roots hairs – increase SA Salty env. – remove excess salt Aerial parts – increase light reflection, cooler Protections – stinging nettles

32 Growth at Meristems Cell division Cell elongation Cell differentiation
Increase # cells Cell elongation Vacuole fills, increase pressure on CW, expands Cell differentiation Specialize into cell types Meristems = where plant cells divide, mitosis No differentiation

33 2 kinds of Growth Primary growth Secondary growth
Increase stem, root length All plants, soft tissues Secondary growth Increase width Gymnosperms, woody dicots Wood + bark

34 Primary growth in stems
Fig 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 Axillary bud meristem Periderm Cork cambium Figure An overview of primary and secondary growth Cortex Pith Primary phloem Primary xylem Root apical meristems Secondary phloem Secondary xylem Vascular cambium

35 Primary growth Increase in length
Apical meristem – tips of roots + shoots (buds) Buds = dormant embryonic shoot (develop into branches next spring Root tip Root cap – protective layer of cells, covers root tip Root apical meristem – directly behind root cap Cell elongation – behind meristem, push tip ahead, some differentiation

36 Cortex Vascular cylinder Epidermis Key to labels Zone of
Fig Cortex Vascular cylinder Epidermis Key to labels Zone of differentiation Root hair Dermal Ground Vascular Zone of elongation Figure Primary growth of a root Apical meristem Zone of cell division Root cap 100 µm

37

38 Root with xylem and phloem in the center (typical of eudicots)
Fig a1 Epidermis Key to labels Cortex Dermal Endodermis Ground Vascular Vascular cylinder Pericycle Figure Organization of primary tissues in young roots Xylem 100 µm Phloem (a) Root with xylem and phloem in the center (typical of eudicots)

39 Root with xylem and phloem in the center (typical of eudicots)
Fig a2 (a) Root with xylem and phloem in the center (typical of eudicots) Endodermis Key to labels Pericycle Dermal Ground Vascular Xylem Phloem Figure Organization of primary tissues in young roots 50 µm

40 Root with parenchyma in the center (typical of monocots)
Fig b Epidermis Cortex Endodermis Vascular cylinder Key to labels Pericycle Dermal Core of parenchyma cells Ground Vascular Figure Organization of primary tissues in young roots Xylem Phloem 100 µm (b) Root with parenchyma in the center (typical of monocots)

41 Shoot apex = terminal bud
Shoot meristem Give rise to leaf primordia and bud primordia

42 Shoot apical meristem Leaf primordia Young leaf Developing vascular
Fig Shoot apical meristem Leaf primordia Young leaf Developing vascular strand Figure The shoot tip Axillary bud meristems 0.25 mm

43 Cross section of stem with vascular bundles forming
Fig a Phloem Xylem Sclerenchyma (fiber cells) Ground tissue connecting pith to cortex Pith Figure Organization of primary tissues in young stems Key to labels Epidermis Cortex Dermal Vascular bundle Ground 1 mm Vascular (a) Cross section of stem with vascular bundles forming a ring (typical of eudicots)

44 Cross section of stem with scattered vascular bundles
Fig b Ground tissue Epidermis Key to labels Figure Organization of primary tissues in young stems Vascular bundles Dermal Ground Vascular 1 mm (b) Cross section of stem with scattered vascular bundles (typical of monocots)

45 Secondary Growth Increase in width
Make secondary tissues: sec. xylem, sec. phloem, periderm Lateral meristem – cells divide, not elongate 2 types: Vascular cambium Between wood and bark Make sec. xylem (wood) + sec. phloem (inner bark)

46 Vascular cambium Growth Vascular cambium X X C P P Secondary phloem
Fig Vascular cambium Growth Vascular cambium X X C P P Secondary phloem Secondary xylem X X C P X C P C C C C C X C C Figure Secondary growth produced by the vascular cambium After one year of growth After two years of growth C C C

47 Growth ring Vascular ray Heartwood Secondary xylem Sapwood
Fig Growth ring Vascular ray Heartwood Secondary xylem Sapwood Fig Anatomy of a tree trunk Vascular cambium Secondary phloem Bark Layers of periderm

48

49 Cork cambium In outer bark Form cork to outside +parenchyma (storage)
Periderm = cork, parenchyma, cork cambium

50 Bark – outermost covering of woody stems
Everything outside of vascular cambium 2 regions: Living inner bark of secondary phloem Mostly dead outer bark of periderm

51 Primary and secondary growth in a two-year-old stem Primary xylem
Fig a3 Pith (a) Primary and secondary growth in a two-year-old stem Primary xylem Vascular cambium Epidermis Primary phloem Cortex Cortex Primary phloem Epidermis Vascular cambium Growth Vascular ray Primary xylem Secondary xylem Pith Secondary phloem First cork cambium Cork Periderm (mainly cork cambia and cork) Most recent cork cambium Figure Primary and secondary growth of a stem Cork Secondary phloem Bark Layers of periderm Secondary xylem

52 Cross section of a three-year- old Tilia (linden) stem (LM)
Fig b Secondary phloem Bark Vascular cambium Cork cambium Late wood Secondary xylem Periderm Early wood Cork 0.5 mm Figure Primary and secondary growth of a stem Vascular ray Growth ring (b) Cross section of a three-year- old Tilia (linden) stem (LM) 0.5 mm

53 You should now be able to:
Compare the following structures or cells: Dermal, vascular, and ground tissues Parenchyma, collenchyma, sclerenchyma, water-conducting cells of the xylem, and sugar-conducting cells of the phloem Sieve-tube element and companion cell Describe in detail the primary and secondary growth of the tissues of roots and shoots Describe the composition of wood and bark


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