Plant Growth

1
Plant Growth
2
Meristems

• Perpetually embryonic tissues in regions of
  growth
• Types
• apical meristems primary growth
• lateral meristems secondary growth

3
Figure 35.12 Locations of major meristems an
overview of plant growth
4
Meristems

• Regions of active cell division
• Apical meristems at tips or apex of roots and
  buds of shoots
• for PRIMARY GROWTH
• Lateral meristems cylinders of dividing cells
  extending along length of roots and shoots
• for SECONDARY GROWTH

5
Figure 35.13 Morphology of a winter twig
6
Root Growth

• 3 zones
• Zone of cell division
• Zone of elongation
• Zone of maturation

7
Figure 35.14 Primary growth of a root
8
Primary tissues of roots page 732

• Epidermis -- dermal
• Cortex -- ground
• Stele -- vascular
• Endodermis -- ground
• Pericycle -- vascular
• Pith -- vascular
• Xylem -- vascular
• Phloem -- vascular

9
Figure 35.15 Organization of primary tissues in
young roots
10
Primary tissues of stems

• Epidermis -- dermal
• Cortex -- ground
• Vascular Bundle vascular
• sclerenchyma, phloem, xylem
• Pith -- ground

11
Figure 35.18 Organization of primary tissues in
young stems
12
Tissues of Leaves

• Cuticle
• Upper epidermis
• Palisade parenchyma
• Spongy parenchyma
• (contains veins xylem and phloem)
• Lower epidermis
• (contains guard cells)
• Cuticle

13
Figure 35.19 Leaf anatomy
14
Function of Guard Cells
Section 23-4
Guard cells
Guard cells
Inner cell wall
Inner cell wall
Stoma
Stoma Open
Stoma Closed
15
Secondary Growth

• Laterial meristems add girth in stems and roots
• Produces secondary vascular tissue and periderm
• Vascular cambium see page 735
• Cork cambium see pages 736-737

16
Figure 35.21 Secondary growth of a stem (Layer 1)
17
Figure 35.21 Secondary growth of a stem (Layer 2)
18
Figure 35.21 Secondary growth of a stem (Layer 3)
19
Figure 35.22 Anatomy of a three-year-old stem
20
Figure 35.23 Anatomy of a tree trunk
21
Figure 35.24 A summary of primary and secondary
growth in a woody stem
22
Pathway

• Pollination ? fertilization?
• growth ? morphogenesis ? differentiation
• (these last 3 produce the plant body)

23
Figure 35.26 The plane and symmetry of cell
division influence development of form
24
Figure 35.27 The preprophase band and the plane
of cell division
25
Figure 35.28 The orientation of plant cell
expansion
26
Figure 35.29 A hypothetical mechanism for how
microtubules orient cellulose microfibrils
27
Positional Information and growth

• Signals of some kind that indicate each cells
  location withing an embryonic structure
• Ex. Polarity
• Ex. Cellular differentiation
• Ex. Phase changes

28
Figure 35.35 Organ identity genes and pattern
formation in flower development
29
Figure 35.36 The ABC hypothesis for the
functioning of organ identity genes in flower
development