Plant Tissues. Chapter 28 Part 1

Transcription

1 Plant Tissues Chapter 28 Part 1

2 Impacts, Issues Drought Versus Civilization Without plants, we would die prolonged drought can destroy crops and civilizations

3 28.1 Components of the Plant Body The unique organization of tissues in flowering plants is part of the reason why they are the dominant group of the plant kingdom

4 The Basic Body Plan Shoots Aboveground plant parts such as stems, leaves, and flowers Roots Structures that absorb water and dissolved minerals, store food, and support the plant Usually grow down and outward in the soil

5 Plant Tissue Systems Ground tissue system Photosynthesis, storage, and structural support of other tissues Vascular tissue system Distributes absorbed water and mineral ions and products of photosynthesis Dermal tissue system Covers and protects exposed plant surfaces

6 Body Plan: Tomato Plant

7 shoot tip (terminal bud) lateral (axillary) bud young leaf flower node internode node dermal tissue vascular tissues ground tissues SHOOTS ROOTS leaf seeds in fruit withered seed leaf (cotyledon) stem primary root lateral root root hairs root tip root cap Fig. 28-2, p. 476

8 Animation: Tissue systems of a tomato plant

9 Eudicots and Monocots Flowering plants are divided into two classes with tissues organized into different patterns Eudicots have two cotyledons (seed leaves) Monocots have one cotyledon

10 Eudicots and Monocots

11 A In seeds, two cotyledons (seed leaves of embryo) B Flower parts in fours or fives (or multiples of four or five) Leaf veins usually forming a netlike array Pollen grains with three pores or furrows Vascular bundles organized in a ring in ground tissue In seeds, one cotyledon (seed leaf of embryo) Flower parts in threes (or multiples of three) Leaf veins usually running parallel with one another Pollen grains with one pore or furrow Vascular bundles throughout ground tissue Fig. 28-3, p. 477

12 Animation: Eudicots and monocots

13 Introducing Meristems All plants tissues arise at meristems (regions of rapidly dividing, undifferentiated cells) Growth in apical meristems at tips of shoots and roots (primary growth) increases length In some plants, growth in lateral meristems (secondary growth) thickens roots and shoots

14 Apical and Lateral Meristems

15 Fig. 28-4a, p. 477

16 shoot apical meristem (new cells forming) cells dividing, differentiating three tissue systems developing three tissue systems developing cells dividing, differentiating root apical meristem (new cells forming) a Many cellular descendants of apical meristems are the start of lineages of differentiated cells that grow, divide, and lengthen shoots and roots. Fig. 28-4a, p. 477

17 Fig. 28-4b, p. 477

18 vascular cambium cork cambium thickening b In woody plants, the activity of two lateral meristems vascular cambium and cork cambium result in secondary growth that thickens older stems and roots. Fig. 28-4b, p. 477

19 28.2 Components of Plant Tissues Different plant tissues form just behind shoot and root tips, and on older stem and root parts Tissue systems are organized as simple tissues (one cell type) or complex tissues (two or more cell types)

20 Simple Tissues Parenchyma makes up most primary growth Functions in secretion, storage, photosynthesis (mesophyll), and tissue repair Collenchyma supports growing plant parts Pectin provides flexibility Sclerenchyma contains lignin for support Cells (fibers, sclereids) are dead at maturity

21 Simple Tissues

22 collenchyma parenchyma Fig. 28-7a, p. 479

23 lignified secondary wall Fig. 28-7c, p. 479

24 Complex Tissues: Vascular Tissues Xylem carries water and ions through the plant Consists of two types of cells that are dead at maturity: tracheids and vessel members Lignin-filled secondary walls Phloem conducts sugars, other organic solutes Sieve tubes connect end to end at sieve plates Companion cells load sugars into sieve tubes

25 Vascular Tissues

26 one cell s wall pit in wall sieve plate of sievetube cell companion cell a b c parenchyma vessel of xylem phloem fibers of sclerenchyma Fig. 28-8, p. 479

27 Complex Tissues: Dermal Tissues Epidermis Usually a single outer layer of cells that secrete a waxy, protective cuticle May contain specialized cells that form stomata for gas exchange Periderm Replaces epidermis in woody stems and roots

28 Plant Cuticle

29 leaf surface cuticle epidermal cell photosynthetic cell Fig. 28-9, p. 479

30 Flowering Plant Tissues

31 Studying Plant Parts: Tissue Specimens Tissue specimens are cut along standard planes

32 radial: tangential: transverse: Fig. 28-6, p. 478

33 Tissues in a Buttercup Stem

34 sclerenchyma (fibers) parenchyma epidermis xylem phloem Fig. 28-5, p. 478

35 Key Concepts Overview of Plant Tissues Seed-bearing vascular plants have a shoot system, which includes stems, leaves, and reproductive parts; most also have a root system Such plants have ground, vascular, and dermal tissues Plants lengthen or thicken only at active meristems

36 28.3 Primary Structure of Shoots Inside the soft, young stems and leaves of both eudicots and monocots, the ground, vascular, and dermal tissue systems are organized in predictable patterns

37 Behind the Apical Meristem Terminal buds Main zones of primary growth in shoots Naked or encased in modified leaves (bud scales) Form leaves at nodes Lateral buds (axillary buds) Dormant shoots in leaf axils Form side branches, leaves, or flowers

38 Apical Meristem and Primary Growth

39 Fig (a-c), p. 480

40 immature leaf shoot apical meristem a Sketch of the shoot tip in the micrograph at right, tangential cut. The descendant meristematic cells are color-coded orange. b Same tissue region later on, after the shoot tip lengthened above it cortex primary phloem primary xylem pith c Same tissue region later still, with lineages of cells lengthening and differentiating Fig (a-c), p. 480

41 Fig d (1), p. 480

42 immature leaf youngest immature leaf apical meristem epidermis forming lateral bud forming vascular tissues forming pith Fig d (1), p. 480

43 Fig d (2), p. 480

44 Inside the Stem Vascular bundles Multistranded cords of vascular tissues threaded lengthwise through ground tissues of all shoots Two distinct patterns of vascular bundles Eudicot stems: Cylinders run parallel with stem, divide ground tissue into cortex and pith Monocot stems: Bundles distributed throughout ground tissue

45 Eudicot and Monocot Stems

46 Fig a, p. 481

47 vessel in xylem meristem cell epidermis cortex vascular bundle pith A Stem fine structure for alfalfa (Medicago), a eudicot sieve tube in phloem companion cell in phloem Fig a, p. 481

48 Fig b, p. 481

49 collenchyma sheath cell air vessel in space xylem epidermis vascular bundle pith B Stem fine structure for corn (Zea mays), a monocot sieve tube in phloem companion cell in phloem Fig b, p. 481

50 Animation: Stem organization

51 Animation: Apical meristems

52 Animation: Cutting tissue specimens

53 Animation: Ground tissues

54 Animation: Vascular tissues