Angiosperm Success and Plant Tissues Post Mount Saint Helens Eruption

1. Plant Tissues Chapter 29

2. Mount Saint Helens Eruption • Volcano is located in southwestern Washington state • In 1980 it erupted, blowing 500 million metric tons of rock and ash outward • Ash and lava devastated about 40,500 acres of what had been forest

3. Recovery • Plants moved into the empty habitat almost immediately • Fireweed and blackberry were early colonists • In less than ten years, willow and alders were on the scene

4. Success of the Angiosperms • The angiosperms are seed-bearing vascular plants • In terms of distribution and diversity, they are the most successful plants on Earth • The structure and function of this plant group help explain its success

5. Shoots and Roots • Shoots • Produce food by photosynthesis • Carry out reproductive functions • Roots • Anchor the plant • Penetrate the soil and absorb water and dissolved minerals • Store food

6. Angiosperm Body Plan EPIDERMIS • Ground tissue system • Vascular tissue system • Dermal tissue system VASCULAR TISSUES GROUND TISSUES SHOOT SYSTEM ROOT SYSTEM Figure 29.2 Page 506

7. Cutting Specimens radial transverse tangential

8. Meristems • Regions where cell divisions produce plant growth • Apical meristems • Lengthen stems and roots • Responsible for primary growth • Lateral meristems • Increase width of stems • Responsible for secondary growth

9. activity at meristems Apical Meristems new cells elongate and start to differentiate into primary tissues Shoot apical meristem new cells elongate and start to differentiate into primary tissues Root apical meristem activity at meristems Figure 29.4 Page 507

10. Tissue Differentiation Protoderm Ground meristem Procambium Epidermis Ground tissue Primary vascular tissue

11. Lateral Meristems • Increase girth of older roots and stems • Cylindrical arrays of cells vascular cambium cork cambium thickening Figure 29.2 Page 506

12. Tissue Differentiation Vascular cambium Cork cambium Secondary vascular tissue Periderm

13. Simple Tissues Made up of only one type of cell Parenchyma Collenchyma Sclerenchyma

14. Parenchyma: A Simple Tissue • Most of a plant’s soft primary growth • Pliable, thin walled, many sided cells • Cells remain alive at maturity and retain capacity to divide • Mesophyll is a type that contains chloroplasts

15. Collenchyma: A Simple Tissue • Specialized for support for primary tissues • Makes stems strong but pliable • Cells are elongated • Walls thickened with pectin • Alive at maturity

16. Sclerenchyma: A Simple Tissue • Supports mature plant parts • Protects many seeds • Thick, lignified walls • Dead at maturity • Two types: • Fibers: Long, tapered cells • Sclereids: Stubbier cells

17. Complex Tissues Composed of a mix of cell types Xylem Phloem Epidermis

18. Xylem • Conducts water and dissolved minerals • Conducting cells are dead and hollow at maturity vessel member tracheids Figure 29.8  Page 509

19. Phloem: A Complex Vascular Tissue • Transports sugars • Main conducting cells are sieve-tube members • Companion cells assist in the loading of sugars sieve plate sieve-tube member companion cell Figure 29.8  Page 509

20. Epidermis: A Complex Plant Tissue • Covers and protects plant surfaces • Secretes a waxy, waterproof cuticle • In plants with secondary growth, periderm replaces epidermis

21. Monocots and Dicots: 1 cotyledon 2 cotyledons 4 or 5 floral parts 3 floral parts Netlike veins Parallel veins 3 pores 1 pore Vascular bundles dispersed Vascular bundles in ring Figure 29.10  Page 509

22. Shoot Development immature leaf shoot apical meristem procambium protoderm procambium ground meristem epidermis cortex primary phloem procambium Figure 29.11  Page 510 primary xylem pith

23. Internal Structure of a Dicot Stem • Outermost layer is epidermis • Cortex lies beneath epidermis • Ring of vascular bundles separates the cortex from the pith • The pith lies in the center of the stem Figure 29.13 Page 510

24. Internal Structure of a Monocot Stem • The vascular bundles are distributed throughout the ground tissue • No division of ground tissue into cortex and pith Figure 29.13 Page 510

25. Common Leaf Forms DICOT MONOCOT petiole axillary bud blade node sheath blade node Figure 29.14 Page 511

26. Adapted for Photosynthesis • Leaves are usually thin • High surface area-to-volume ratio • Promotes diffusion of carbon dioxide in, oxygen out • Leaves are arranged to capture sunlight • Are held perpendicular to rays of sun • Arranged so they don’t shade one another

27. Leaf Structure UPPER EPIDERMIS cuticle PALISADE MESOPHYLL xylem SPONGY MESOPHYLL phloem LOWER EPIDERMIS one stoma CO2 O2 Figure 29.16 Page 513

28. Mesophyll:Photosynthetic Tissue • A type of parenchyma tissue • Cells have chloroplasts • Two layers in dicots • Palisade mesophyll • Spongy mesophyll

29. Leaf Veins: Vascular Bundles • Xylem and phloem; often strengthened with fibers • In dicots, veins are netlike • In monocots, they are parallel

30. Root Systems Fibrous root system of a grass plant Taproot system of a California poppy Figure 29.17 Page 514

31. Root Structure • Root cap covers tip • Apical meristem produces the cap • Cell divisions at the apical meristem cause the root to lengthen • Farther up, cells differentiate and mature Figure 29.17 Page 514

32. Internal Structure of a Root • Outermost layer is epidermis • Root cortex is beneath the epidermis • Endodermis, then pericycle surround the vascular cylinder • In some plants, there is a central pith

33. Function of Endodermis • Ring of cells surrounds vascular cylinder • Cell walls are waterproof • Water can only enter vascular cylinder by moving through endodermal cells • Allows plant to control inward flow

34. Root Hairs and Lateral Roots • Both increase the surface area of a root system • Root hairs are tiny extensions of epidermal cells • Lateral roots arise from the pericycle and must push through the cortex and epidermis to reach the soil new lateral root Figure 29.19 Page 515

35. Secondary Growth • Occurs in all gymnosperms, some monocots, and many dicots • A ring of vascular cambium produces secondary xylem and phloem • Wood is the accumulation of these secondary tissues, especially xylem

36. What Happens at Vascular Cambium? • Fusiform initials give rise to secondary xylem and phloem • Ray initials give rise to horizontal rays of parenchyma

37. Secondary Growth Ongoing cell divisions enlarge the inner core of secondary xylem and displace vascular cambium toward the stem Figure 29.21 Page 517

38. Formation of Bark • All tissues outside vascular cambium • Periderm • Cork • New parenchyma • Cork cambium • Secondary phloem

39. Woody Stem secondary phloem HEARTWOOD SAPWOOD periderm BARK vascular cambium Figure 29.24 Page 519

40. Annual Rings • Concentric rings of secondary xylem • Alternating bands of early and late wood • Early wood • Xylem cells with large diameter, thin walls • Late wood • Xylem cells with smaller diameter, thicker walls

41. Types of Wood • Hardwood (oak, hickory) • Dicot wood • Xylem composed of vessels, tracheids, and fibers • Softwood (pine, redwood) • Gymnosperm wood • Xylem composed mostly of tracheids • Grows more quickly