Anatomy & Growth of Angiosperms

1. Anatomy & Growth of Angiosperms

2. Two plant groups: monocots & eudicots

3. Structure Reflects Function http://www.fugu-sg.org/~elia/cambodia/templesfacesweb/pages/A3_Embracing_Roots.htm

4. Structure of a plant determined by: • 1. Genetics • 2. Environment – two time scales: • a. Long-term: accumulation of adaptations that enhanced survival & reproduction (evolution by natural selection) • b. Short-term: plasticity = wide range of phenotypes for each genotype. Allows plants to adjust to changing environment (ex. Shorter plant in dry year so that it can still reproduce)

5. Muscle cell Parenchyma cell Cells Tissues Muscle tissue Dermal tissue Organs Heart Leaves Circulatory system Systems Shoot system

6. Three organs: Roots, stems, leaves • 1. Roots • a. Collect water & minerals from soil • b. Anchor plant • c. Store food (carb’s from photosynthesis) to be used for flowering & fruiting • d. Covered with root hairs – increased surface area for absorption

7. Fig 35.2

8. Modified Roots – Fig 35.4 Prop roots Aerial strangler roots Storage root Buttress roots Pneumatophores

9. 2. Stems/shoots • a. Support, transport • b. Some photosynthesis • c. Two types of shoots • * Vegetative – leaves only • * Reproductive – produces flowers • Two parts of the stem: • * Node – point of leaf attachment • * Inter-node – stem segments between nodes

10. Two types of buds Apical dominance = the presence of an apical bud inhibits the growth of axillary buds. - remove or depress apical bud, axillary buds begin to grow. 1. Terminal bud – contains a shoot apical meristem; shoot growth is concentrated here 2. Axillary buds – in angle (axil) between leaf & branch, contain meristem with potential to become a vegetative shoot. Mostly dormant.

11. Modified Shoots (stems): • Stolons – above-ground runners • Rhizomes – below-ground runners Asexual, vegetative propagation • Bulbs – swollen underground shoots • Tubers – swollen rhizomes Stores food for later growth

12. Fig 35.5

13. 3. Leaves – main photosynthesis organs • Petiole • Blade http://www.knotweed.co.uk/japknot_Info.htm

14. Modified leaves Compound, doubly compound – why??

15. Tendrils Fig 35.7 – Modified leaves Spines Succulents

16. Three main tissues: Dermal, Vascular, & Ground Fig 35.8

17. 1. Dermal tissue or epidermis A. single layer of tightly packed cells covering the young parts of the plant. B. Functions in protection C. Root hairs are specialized epidermal extensions D. Secretes waxy cuticle of the leaf

18. 2. Ground Tissue • A. Fills the space between dermal and vascular tissue systems. • B. Diverse functions: • photosynthesis • storage • support pith In eudicots: cortex

19. 3. Vascular Tissue A. function in transport between roots & shoots, and structural support of plant • a. Xylem: H2O & minerals transported up to shoot system • b. Phloem: Food transported to roots & non-photosynthetic parts such as the flowers

20. The Plant Cell Fig 7.8

21. The Plant Cell • Same as animals, except: • a. No lysozomes (digestive organelle) • b. Cell walls: maintains shape, structural support, protects from damage. Made of cellulose, protein, & sometimes lignin • c. Chloroplasts • d. Vacuole – storage, waste breakdown, growth! • e. Plasmodesmata – holes in cell wall, creates channels to connect cytoplasm of adjacent cells

22. 5 Differentiated Plant Cell Categories 1. Parenchyma 4. Water-conducting cells of the xylem 3. Schlerenchyma 5. Sugar-conducting cells of the phloem 2. Collenchyma

23. 1. Parenchyma • A. Least specialized cell. Can differentiate into other cell types • B Primary cell walls only - thin and flexible • C. Lack secondary plant cell walls • D. Most metabolically active – lots of chloroplasts for PSN (PhotoSyNthesis) • E. Starch, carbohydrate production & storage in stems

24. 2. Collenchyma A. Primary walls are unevenly thickened B. Usually lack secondary walls. C. Usually grouped in strands to support young parts of plants without restraining growth D. Flexible, elongate with growing shoots

25. 3. Schlerenchyma A. Function in mechanical support B. Have rigid and thick secondary walls strengthened with lignin. C. May be dead at functional maturity – ??? D. Cell walls left behind as skeleton • Two types, both function in support: • Fibers - long, slender, tapered cells occurring in bundles. • Sclereids - short, irregularly-shaped. Ex. hard seed coats

26. Lignin:

28. Fig 35.9

29. 4. Water conducting cells of the xylem: A. 2 types: tracheids & vessel elements

30. Tracheids a. are long, thin tapered cells having lignin-hardened secondary walls with pits. b. Dead at maturity c. Water flows from cell to cell (laterally) through pits in cell wall d. Support function

31. Vessel Elements a. are wider, shorter b. Arranged end-to-end to form tubes c. End walls are perforated for free flow of water d. More efficient as water conductors than tracheids

32. Fig 35.9

33. 5. Sugar-conducting cells of the phloem • 2 types: • A. Sieve-tube members: • a. Chains of cells arranged end-to-end • b. Alive at functional maturity • c. Lack a nucleus, ribosomes, vacuole • d. Cells separated by perforated sieve plates – allow sugar movement • B. Companion cells • a. Load sugars into the sieve tube member • b. nucleus and ribosomes also serve the sieve-tube member.

34. Fig 35.9

35. Growth & Development http://www.cneccc.edu.hk/subjects/bio/album/Chapter20/PLANT_GROWTH.html

36. Development is the sum of all the changes that progressively elaborate the plant’s body.

37. Three processes of development: 1. Growth = increase in mass, due to cell division & elongation 2. Cellular differentiation = generation of different cell types 3. Morphogenesis – creation of body form & organization.

38. 1. Growth A. Cell division in itself does not mean an increase in growth. B. Cell division yields no expansion of size. • C. Cell elongation increases growth.

39. Cell elongation • 1. due to water uptake • 2. Direction of expansion = perpendicular to alignment of cellulose microfibrils in cell wall • 3. Enzymes weaken cross-link between microfibrils, allowing cell to expand.

40. Fig 35.24

41. Cell division 1. Occurs in meristems 2. The plane of cell division is an important determinant of plant form

42. Fig 35.22

43. Plant growth vs. Animal growth • 1. Unlike animals, plants: • A. Embryonic, developing, and mature organs exist together at the same time on one plant. • B. Grow until they die, called indeterminate growth. Some determinate parts: leaves, flowers.

44. Three types of life cycles: • 1. Annual – complete life cycle (germination through fruiting) in one year or less. Examples: grasses, crops, wildflowers • 2. Biennial – complete life cycle in two years (first year = vegetative, second year = reproductive). Some need a cold winter period to initiate flowering from vegetative state. Ex. carrots • 3. Perennial – live year after year, do not die after reproduction. Examples: trees, shrubs, some grasses. Causes of death = fire, disease

45. How is indeterminate growth possible?????

46. Meristems • 1. region of the plant with continuous cell division (i.e. perpetually embryonic tissue) • 2. Two types of meristems: • A. Apical meristem – located at the root and shoot tips, responsible for growth in length (called primary growth) • B. Lateral meristems – extend lengthwise along the axis of the stem & roots. Responsible for growth in girth in older parts of the plant (called secondary growth). Exist only in perennials

47. Fig 35.10

48. Primary Growth of Roots 1. Occurs at root tip (Root Apical Meristem) 2. Root cap – layer of cells that protect the RAM as it pushes through the soil

49. 3 zones moving upward from RAM: • 1. Zone of cell division – contains the RAM • 2. Zone of cell elongation – cells elongate, thereby pushing the root tip through the soil • 3. Zone of maturation – cells differentiate and become functionally mature (i.e. become part of one of the 3 tissue systems)

50. Fig 35.12