Understanding Basic Plant Anatomy and Growth Cycles

1. Plant Anatomy Chapter 35

2. Basic plant anatomy 1 • root • root tip • root hairs

3. 1 Roots • Roots anchor plant in soil, absorb minerals & water, & store food • fibrous roots (1) • mat of thin roots that spread out • monocots • tap roots (2) • 1 large vertical root • also produces many small lateral, or branch roots • dicots • root hairs (3) • increase absorptive surface area 2 3

4. Basic plant anatomy 2 • root • fungi at tips of the roots Mycorrhizae • -Symbiotic relationship • shoot (stem) • buds • terminal or apical buds-located at the top • axillary buds-located at the V formed b/t leaf and stem

5. Modified shoots stolons (strawberries) rhizome (ginger) tuber (potato) bulb (onion)

6. Leaves • Function of leaves • photosynthesis • energy production • CHO production • gas exchange • transpiration simple vs. compound

8. Putting it all together • Obtaining raw materials • sunlight • leaves = solar collectors • CO2 • stomates = gas exchange • H2O • uptake from roots • nutrients • uptake from roots

9. Plant TISSUES • Dermal • epidermis (“skin” of plant) • single layer of tightly packed cells that covers & protects plant • Ground • bulk of plant tissue • photosynthetic mesophyll, storage • Vascular • transport system in shoots & roots • xylem & phloem

10. Plant CELL types in plant tissues • Parenchyma • “typical” plant cells = least specialized • photosynthetic cells, storage cells • tissue of leaves, stem, fruit, storage roots • Collenchyma • unevenly thickened primary walls • support • Sclerenchyma • very thick, “woody” secondary walls • support • rigid cells that can’t elongate • dead at functional maturity If I’d onlyhad triplets!

11. Xylem and Phloem Xylem- water conducting cells. xylem vessels- found mostly in angiosperms have pits for water movement. xylem tracheids- long thin cells strengthen with lignin

12. Vascular tissue vessel elements • Xylem • move water & minerals up from roots • dead cells at functional maturity • only cell walls remain • need empty pipes to efficiently move H2O • transpirational pull vessel element dead cells Aaaah… Structure–Functionagain! tracheids

13. Phloem: food-conducting cells • carry sugars & nutrients throughout plant sieve tube companion cell sieve plate plasmodesmata living cells

14. Phloem: food-conducting cells • sieve tube elements & companion cells

15. Aaaah… Structure–Functionagain! Phloem • Living cells at functional maturity • cell membrane, cytoplasm • control of diffusion • lose their nucleus, ribosomes & vacuole • more room for specialized transport of liquid food (sucrose) • Cells • sieve tubes • sieve plates — end walls — have pores to facilitate flow of fluid between cells • companion cells • nucleated cells connected to the sieve-tube • help sieve tubes

16. Plant Growth Chapter 35

17. Life Cycle of Plants • Annuals- in one year Ex:Wildflowers, crops • Biennials- completed in 2 years Ex: radishes and carrots • Perennials- continues for many years Ex. Trees

18. Growth in Plants • Specific regions of growth: meristems • stem cells: perpetually embryonic tissue • regenerate new cells • apicalshoot meristem • growth in length • primary growth • apical root meristem • growth in length • primary growth • lateral meristem • growth in girth • secondary growth

19. Apical meristems shoot root

20. Root structure & growth protecting the meristem

21. Shoot growth protecting the meristem Young leaf primordium Apical meristem Older leaf primordium Lateral bud primordium Vascular tissue

22. Primary xylem Growth in woody plants Primary phloem • Woody plants grow in height from tip • primary growth • apical meristem • Woody plants grow in diameter from sides • secondary growth • lateral meristems • vascular cambium • makes 2° phloem & 2° xylem • cork cambium • makes bark Epidermis Lateral meristems Secondary xylem Primary phloem Primary xylem Secondary phloem Annual growth layers Bark

23. corkcambium vascularcambium Why are early & late growth different? Vascular cambium • Phloem produced to the outside • Xylem produced to the inside bark phloem xylem late early last year’s xylem

24. Woody stem cork cambium How old is this tree? vascular cambium late early 3 2 1 xylem phloem bark

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

26. Plant hormones Ch:39 • auxin • gibberellins • abscisic acid • ethylene • and more…

27. Auxin (IAA) • Effects • controls cell division & differentiation • phototropism • growth towards light • asymmetrical distribution of auxin • cells on darker side elongate faster than cells on brighter side • apical dominance

28. Gibberellins • Family of hormones • over 100 different gibberellins identified • Effects • stem elongation • fruit growth • seed germination plump grapes in grocery stores have been treated with gibberellin hormones while on the vine

29. Abscisic acid (ABA) • Effects • slows growth • seed dormancy • high concentrations of abscisic acid • germination only after ABA is inactivated or leeched out • survival value: seed will germinate only under optimal conditions • light, temperature, moisture

30. Ethylene • Hormone gas released by plant cells • Effects • fruit ripening • leaf drop • like in Autumn • apoptosis One bad apple spoils the whole bunch…

31. Fruit ripening • Adaptation • hard, tart fruit protects developing seed from herbivores • ripe, sweet, soft fruit attracts animals to disperse seed • Mechanism • triggers ripening process • breakdown of cell wall • softening • conversion of starch to sugar • sweetening • positive feedback system • ethylene triggers ripening • ripening stimulates more ethylene production

32. Apoptosis in plants What is the evolutionary advantage of loss of leaves in autumn? • Many events in plants involve apoptosis • response to hormones • ethylene • auxin • death of annual plant after flowering • senescence • differentiation of xylem vessels • loss of cytoplasm • shedding of autumn leaves

33. Don’t take this lying down… Ask Questions!!