1. PLANT STRUCTURE & DEVELOPMENT
Chapter 35

2. Overview Roots – Underground Shoots – Leafs & Stems
3 Tissue types in the above
Dermal, Vascular, & Ground
5 Types of Differentiated Plant Cells
Parenchyma
Collenchyma
Sclerenchyma
Xylem
Phloem

4. Roots Multicellular organ Anchors plant Absorbs water & Minerals
May store sugar & starches

5. Fibrous Roots vs. Taproots
Fibrous Roots – mat of thin roots that are spread just below the root’s surface
Taproots – 1 thick, vertical root with many lateral roots that emanate from it

6. Questions Which root type is focused on absorption?
Which root type is focused on storage?
Fibrous roots are not efficient absorbers, so what structure is responsible for absorption?

7. Root Hairs Located at the tips of roots
Dramatically increase the surface area
Efficient absorption of H2O and minerals
Mycorrhizae – Symbiotic relationship
Root tips & fungus – assist in absorption
Found in vast majority of plants

8. Mycorrhizae

9. Shoots Consist of Stems & Leaves
Plant stuff that is above ground
Leaves – main photosynthetic organ in most plants
Stems
Function is to display the leaves
2 types of buds (growing parts)
Terminal (Apical) Bud – located at top end of stem
Growth usually occurs at this bud
Axillary Bud – located in the “v” between leaf and stem
Can potentially form a branch

11. Questions
What is the advantage to a plant to only grow at the apical and axillary buds?
A tree house was built between the stem and a branch without axillary buds. The growth rate of the apical buds is 2 feet per year, the growth rate of the axillary buds is 3 feet per year, and the tree house was built at a height of 10 feet. What will be the height of the tree house in 10 years?

12. Plant Organs (Leaf, Stem, & Roots)
3 Tissue types (Ground is on the next slide)
Dermal
Cover entire plant
Protect against water loss
Called Cuticle in the leaves
Nonspecific defense mechanism
Vascular
Continuous throughout the plant
Transports material between roots and shoots
Xylem – transports water & minerals up from the roots
Phloem – transports food from the leaves to rest of plant

13. Plant Organ Tissue Types
Ground
Any tissue that is neither dermal nor vascular
If the Ground tissue is located inside the vascular tissue called pith
Cortex – ground tissue located outside vascular tissue

15. 5 Types of Differentiated Cells
1. Paren(chyma) cells – Most abundant cell type
-- Present throughout the plant
-- perform most of the metabolic functions of the plant
(Photosynthesis & Respiration)
2. Collen(chyma) cells
-- Support growing parts of the plant
-- Grouped into cylinders
3. Scleren(chyma) cells
-- Occupy NonGrowing parts of plant
-- Tough cell walls for structural support

17. 4th Type of Plant Cells 4. Xylem – water conducting cells
-- 2 types: Tracheids & Vessels
-- Both types are dead at functional maturity
-- Tracheids found in ALL vascular plants
-- Long thin cells with lignin
-- Water moves through the pits
-- Vessels found primarily in angiosperms (flowering plants)
-- Have pits & perforated end walls for water movement 

18. Vessel Elements & Tracheids

19. 5th & Final Type of Plant Cell
5. Phloem – Sugar & other organic compounds
2 Types: Sieve-tube elements & Companion Cells
-- Both types are alive at functional maturity
Sieve Tubes
-- Consist of chains of cells
-- Called sieve-tube element
-- Highly modified for transport
-- Lack nucleus, ribosomes, & vacuoles

20. Phloem Continued Besides Sieve Tubes, there are also: Companion Cells
Provide for the molecular needs of the sieve-tube elements
Connected to the sieve-tube elements by plasmodesmata

22. Plant Growth Plant growth is indeterminant
Growth occurs throughout plant’s life
Embryonic, developing, and mature organs exist at all times during a plant’s life
Animal growth is determinant
Growth ceases after a certain size has been reached

23. Meristems Meristems are perpetually embryonic tissues
Responsible for indeterminate growth
Growth occurs only as a result of cell division in a meristem
2 Types of Meristems
Lateral Meristem – Thickening of shoots or roots
Thickening is called Secondary Growth
Apical Meristem – tips of roots and in buds of shoots
Sites of cell division
Allow the plant to grow and lengthen
Primary Growth – when plant grows at apical meristems
Lengthening is called Primary growth

25. Primary Growth lengthens …
Root Cap – protects delicate meristem of the root tip as it pushes through the soil
Secretes a polysaccharide lubricant
Root Tip – contains 3 zones of cells in various stages of growth

26. 3 Zones in root tip Zone of cell division Zone of elongation
Root apical meristem & derivatives
New root cells are produced in this region
Mitotic divisions
Zone of elongation
Cells elongate, sometimes significantly
Zone of maturation
Differentiation and functional maturation occurs

27. Roots -
Primary Growth

28. Lateral Roots emerge from the Pericycle (lies inside the endodermis)

29. What about shoots?
Apical meristem – dome of dividing cells at tip of terminal bud
Primary growth (Lengthening)
Accomplished by cell division and elongation

31. Primary Growth in Stems

32. How does grass continue growth after mowing?
 Mowing should destroy the apical meristems, so how would grass continue to grow if there were no “growth areas”?

33. 2 other meristems Intercalary Floral Primarily in monocots (grasses)
Response to grazing pressure
Floral
Flower growth
Determinate growth

34. Lateral Meristems Secondary growth 2 Types
Growth in the thickness of the shoot or root
2 Types
Vascular Cambium
Adds layers of tissue called 2ndary Xylem & phloem
Cork Cambium
Replaces the epidermis with the periderm (thicker & tougher)

36. Secondary Growth 2 lateral meristems are responsible for 2ndary growth
Vascular Cambium – produces 2ndary xylem (wood)
Cork Cambrium – produces a tough covering that replaces epidermis
Early in secondary growth
Bark – all the tissues outside the vascular cambium
Includes the phloem derived from the vascular cambium, cork cambium, & tissues derived from cork cambium

40. Question?
Why would the diameter of the plant have to increase as the plant grows?
Which diameter grows as a higher rate, xylem or phloem? Why?

41. Leaves… Stomata interrupts the underside of the leaf
Flanked by guard cells – open/close the stomata
Ground tissue is in between upper & lower epidermis, in the mesophyll
Ground tissue is composed of parenchyma cells
Site of photosynthesis are parenchyma cells

42. Leaf: Cross-Section

43. Angiosperms (Flowering Plants)
Classified by years in life cycle (germination  death)
Annuals – 1 year life cycle
Biennials – 2 year life cycle
Perennials – multiple year life cycle

44. Question Why would there be spaces in the spongy mesophyll?
Why would there not be spaces in the palisade mesophyll?