1. Plant Structure and Growth Topic 9.1

2. To review Study the chart on pg 239 for your different types of plants The seeded vascular plants include the angiosperms and gymnosperms Do you remember the difference between angiosperms and gymnosperms??? In this unit we will be referring to angiosperms unless otherwise noted.

3. 3 tissue systems in plants Dermal Vascular Ground

4. Dermal tissue Outer protective covering Single cell layer Root hairs are extensions of epidermal cells Most dermal tissue is covered by waxy cuticle which prevents water loss

5. Vascular tissue Includes xylem and phloem

6. xylem –xylem is dead at maturity, only secondary cell wall remains –Consist of 2 cell types, either vessel elements (wide/short) or tracheids (long, thin, tapered). –carries water and minerals –Pits between cells allow water to flow through

7. phloem Carries sucrose through cells called sieve- tube members. Alive at maturity but lack nuclei, ribosomes and vacuoles. Companion cells lie adjacent and provide for sieve tube members via plasmodesmata

8. Ground tissue (3 rd type!) Photosynthesis, support, storage “filler” tissue In dicots, center of stem is GT referred to as pith, outer stem GT is cortex.

9. Ground tissue made of 3 cell types Parenchyma – unspecialized cells. Lack secondary walls, have large central vacuole. Important in psyn and food storage. All plant cells begin as unspecialized parenchyma cells. Collenchyma – lack secondary walls but have thick primary walls. Form strands which support plant parts. Sclerenchyma – thick secondary walls w/ lignin (strength). Include fibers and sclerids

11. All 3 types of tissue originate from meristematic tissue. Meristematic tissue retains the ability to divide. If a meristematic cell divides one cell begins differentiation (the derivative) and the other cell remains meristematic (the initials) Where would you expect to find meristematic cells in a plant?

12. Plant organs

13. Roots Obtain water and minerals Anchor plant May store food Have a protective epidermis Cortex conducts water from soil to interior vascular tissue. May also store material Endodermis surrounds vascular tissue Vascular tissue

15. Shoot system – stem and leaves. Absorb light and carbon dioxide.

16. Shoot system Stem – alternating nodes (point of leaf attachment) w/ internodes in between. Axillary bud – at angle between leaf and stem Terminal bud – developing leaves and compacted nodes and internodes at tip of plant Apical dominance – when terminal bud inhibits growth of axillary bud.

17. Vascular tissue arranged in rings in dicots and scattered in monocots.

18. Leaves Blade – flat, photosynthetic Petiole – stalk of leaf monocots – leaves lack petiole, veins are parallel dicots – leaves have netted venation, petiole.

19. Leaf Anatomy Covering of wax over epidermis. Stomata, tiny pores surrounded by guard cells permit gas exchange Mesophyll – parenchyma and ground tissue containing chloroplasts. 2 layers, spongy (air spaces) and palisade (lots of chloroplasts) A branch of the vascular bundle continues into petiole and divides in leaf blade, providing support and transport

23. Monocot vs Dicot See page 242 to review

24. Modification of plant organs

25. Roots - 2 main types Taproot – one main vertical root with branch roots from main root Fibrous root – no main root. Roots are thinner and spread throughout soil. Good for preventing erosion

26. Root modifications Prop root – adventitious root growing from lower part of stem as a brace (corn) Storage root – parenchyma cells store carbohydrates and water (beet, carrot) Pneumatophore (air root) – extend above soil or water surface. Help with oxygen uptake (mangrove, cypress knee) Buttress root – at bottom of tree for stability (fig tree)

27. Prop Pneumatophore Buttress Storage

28. Stem Modifications Bulb – vertical underground stem with enlarged base for food storage (onion) Tuber – horizontal underground stem for starch storage (potato) Rhizome – horizontal stem just below surface for asexual reproduction (ginger) Stolon – horizontal above ground stem for asexual reproduction (strawberry)

29. Bulb Tuber Rhizome Stolon

30. Leaf Modifications Tendril – coil around objects for support (peas) Reproductive leaves – tiny plants form on leaf margins. Fall to ground and take root Bracts – AKA floral leaves. Surround flowers to attract pollinators. Spines – reduce water loss

31. Tendril Bract Reproductive Leaf Spine

32. Meristem – 2 types Apical meristem – found at tips of root and shoot. Produces primary tissue (non- woody) and primary growth (growth in length) Lateral meristem – produces secondary (woody) growth. 2 types: –Vascular cambium produces secondary xylem and phloem (see next slide) –Cork cambium produces cork cells of outer bark

33. Apical Meristem - shoot

34. Apical Meristem - Root

35. Secondary Growth Wood is the accumulation of secondary xylem with lignified walls. Growth rings occur due to seasonal cycles of growth (dormant, fast growth, slow growth) In secondary growth epidermis splits and is replaced by tissue made by cork cambium which produces cork cells with suberin – impregnated walls. This layer is called periderm. Lenticels are splits in periderm through which gas exchange occurs.

36. Bark = phloem + periderm In old trees, heartwood is old resin filled wood while sapwood is actively conducting

37. Auxins Plants have hormones too! Auxins (a class of hormones) are found in embryos (seeds), apical meristems and buds. They increase the flexibility of cell walls so shoots can bend toward light The auxin indoleacetic acid (IAA) collects on the side of the stem AWAY from the light causing that side to elongate and the plant to bend TOWARD light

39. Tropisms – growth or movement toward or away from a stimulus Phototropism – light Thigmotropism – touch Geotropism – gravity Chemotropism – chemicals Ex) plant shoots exhibit positive phototropism and roots exhibit negative phototropism