1. Plant Structure, Growth, and Development
Chapter 35
Plant Structure, Growth, and Development

2. What you must know The function of xylem and phloem tissue.
The anatomy of a leaf
The anatomy of a root

3. Introduction to Plants
Kingdom: Plantae
Cell wall
Autotroph (photosynthesis)
Multicellular
Angiosperms (flowering plants)
~90% plants
Produce seeds within a fruit
Key adaptations: flowers & fruits

4. Plant Organization Organs Tissues Cell Types Roots Stems Leaves Dermal
Vascular
Ground
Cell Types
Xylem
Phloem
Parenchyma

5. I. Plant Organs Above ground Stems, leaves Underground (usually) Roots
Shoot
system
Underground (usually)
Roots
Root
system

6. A. Roots Anchors plant, absorbs H2O & minerals, stores sugars/starches
Root hairs – tiny extensions of epidermal cells, increase surface area for H2O and mineral absorption
Mycorrhizae: fungus + plant root symbiotic relationship
Root hairs

7. Fibrous Roots Taproots Mat of thin roots spread just below surface
Shallow
Increased surface area
One thick, vertical root
Many lateral (branch) roots
Firmly anchors
Stores food
Taproot
(carrot)
Fibrous Root
(scallion)

8. Modified Roots

9. Mangrove Forest in Florida

10. B. Stems Function: display leaves
Terminal bud: growth concentrated at top end of stem
Secretes hormone to prevent growth of axillary buds; growth directed upward, toward light
Axillary buds – located in V between leaf and stem; forms branches (lateral shoots)
Pinching/pruning – removing terminal bud

11. Modified stems Runner or stolin Rhizome Bulb – underground shoot
Aspen, strawberries, grass
Grow on surface
For asexual reproduction
Rhizome
Iris, ginger, potato, onion
Grow underground
Store food & DNA for new plant
Tuber: end of rhizome
Bulb – underground shoot
Onion
storage leaves

12. C. Leaves
Function: Photosynthetic organ
petiole
blade

13. Modified leaves

14. II. Plant Tissues

15. A. Dermal Tissue
Single layer, closely packed cells that cover entire plant
Protect against water loss & invasion by pathogens (viruses, bacteria)
Cuticle: waxy layer

16. B. Vascular Tissue Continuous throughout plant
Transports materials between roots & shoots
Xylem & Phloem

17. C. Ground Tissue Anything that isn’t dermal or vascular
Function: storage, photosynthesis, support
Pith: inside vascular tissue
Cortex: outside vascular tissue

18. III. Cell Types Xylem Conducts H2O and minerals up from root
Dead, tubular, elongated cells
Phloem
Conducts sugar & organic compounds from leaves to other parts of plant
Living cells aid movement of sugar
2 Cell Types: sieve tubes, companion cells

19. Xylem
Phloem

20. Plant Growth Types of Flowering Plants:
Annuals – 1 year life cycle
Biennials – 2 years
Perennials – continuous life cycle for many years
Meristem: perpetually embryonic tissues
Cells divide for plant growth
Apical meristem: growth at tips of roots & buds of shoots; cause primary growth (increase length)
Lateral meristem: growth thickens shoots and roots; secondary growth

21. Primary and Secondary Growth

22. Root Anatomy
Root Hairs
Zone of Maturation: primary growth becomes functionally mature
Zone of Elongation: cells elongate; push root tip ahead
Zone of Cell Division: apical meristem; new cells produced (mitosis)
Root cap: protects meristem as it pushes through soil

23. Primary Growth of a Root
Cortex
Vascular cylinder
Epidermis
Key
Zone of
maturation
Root hair
Dermal
Ground
Vascular
Zone of
elongation
Apical
meristem
Zone of cell
division
Root cap
100 µm

24. Primary Growth of Shoots
Shoot apical meristem: dome of dividing cells at tip of terminal bud; divide and elongate

25. Leaf Anatomy
Epidermis of underside interrupted by stomata (pores), flanked by guard cells (open/close stomata)
Mesophyll: ground tissue between upper/lower epidermis
Parenchyma: sites of photosynthesis

26. Secondary Growth = increase diameter
Involves lateral meristems
Vascular cambium: produces secondary xylem (wood)
Cork cambium: produces tough covering that replaces epidermis
Bark = all tissues outside vascular cambium

27. Primary and Secondary Growth of a Stem
in a two-year-old stem
Secondary phloem
Vascular cambium
Cork
cambium
Secondary
xylem
Late wood
Early wood
Periderm
Cork
Epidermis
Cortex
Pith
Primary
phloem
Primary xylem
Vascular cambium
Transverse section
of a three-year-
old Tilia (linden)
stem (LM)
Vascular
cambium
Primary phloem
Cortex
Epidermis
Xylem ray
Primary
xylem
Bark
Phloem ray
Growth
Pith
Xylem
ray
0.5 mm
0.5 mm
Primary
xylem
Primary and Secondary Growth of a Stem
Secondary xylem
Vascular cambium
Secondary phloem
Primary phloem
First cork cambium
Cork
Periderm
(mainly cork
cambia
and cork)
Growth
Primary
phloem
Secondary
phloem
Secondary
xylem (two
years of
production)
Vascular
cambium
Secondary
xylem
Vascular cambium
Secondary phloem
Primary
xylem
Bark
Most recent
cork cambium
Pith
Layers of
periderm
Cork