1. Plant structure, growth, & development ~ 35

2. 1. Plants have a hierarchical organization consisting of organs, tissues, and cells
3 basic organs
Roots, stems, leaves
Shoot System
Stems
Raises or separates leaves to expose
to sunlight
Leaves
Main photosynthetic organ
Root System
Anchors a vascular plant in
the soil
Absorbs minerals & H2O
Stores carbohydrates

3. Dermal, Vascular, and Ground tissues = Tissue System
Tissue system connects all of the plants organs
Dermal Tissue System
Epidermis, cuticle, periderm
Outer protective covering
Vascular Tissue System
Xylem, phloem, stele
Long distance transport of materials
btwn root & shoot systems
Ground Tissue System
Pith, cortex
Specialized cells for storage, photosynthesis
and support

4. Differentiated Cell Types

5. Differentiated Plant Cells
Parenchyma Cells
Typical plant cell w/ lg central vac
Metabolic functions, synthesizing, & storing organic products
Collenchyma cells
Flexible Support & strength w/o restraining growth (young parts of plant shoot), grouped in strands

6. Water Conducting cells of xylem
Sclerenchyma Cells
Support & hardness
Much more rigid than Collenchyma lignin in cell walls
Water Conducting cells of xylem
Support; harden as die at maturity
Hardening of tracheids & vessel elements tubes to transport water; migrate btwn cells thru pits
Sugar Conducting cells of Phloem
Transport sugars throughout; alive at maturity
Chains of cells = sieve-tube elements & sieve plates facilitate flow of sugars throughout plant

7. 2. Meristems generate cells for primary & secondary growth
Intermediate Growth
Growth occurs throughout life of plant
Meristems
Apical
Primary Growth
Roots to extend in soil
Shoots expose to sunlight
Tips of roots, buds & shoots
Lateral
Secondary Growth
Growth in thickness
Vascular cambium, Cork cambium
Determinate Growth
Leaves, thorns, flowers stop growing after reach certain size

8. 3. Primary Growth Lengthens Roots & Shoots
Primary growth of roots
Growth occurs behind root cap in three overlapping zones
Cell Division
Elongation
Differentiation/Maturation

9. Primary growth of shoots Apical meristem
Dome shaped mass of dividing cells at the shoot tip
Shoot elongation due to lengthening of cells below shoot tip
Leaf primordia
Development of leaves
Tissue Organization
of Stems

10. Tissue Organization of Leaves
Epidermis
Upper & lower
Pores = stomata
Gas exchange
Prevent loss of water
Guard cells regulate opening/closing of stomata
Mesophyll
Ground tissue (middle tissue)
Layers of parenchyma cells
Vascular Tissue
Xylem & phloem reinforcing shape of leaf = Vein
Bundle sheath cells protect Vein

11. 4. Secondary Growth Increases the Diameter of Stems and Roots in Woody Plants
Secondary growth (thickness produced from lateral meristems) occurs in stems and roots of woody plants, rarely in leaves
Tissues produced by vascular cambium & cork cambium
V.Cambium  adds secondary xylem (= wood) and phloem
Inc vascular flow and support for shoots
C.Cambium  tough, thick covering of wax protect the stem from water loss, insects, bacteria, fungi

12. Growth rings Gymnosperms Angiosperms Temperate regions
Layers of sec. xylem accum
Tracheids, vessels, fibers
Walls of sec xylem heavily
lignified= hardness & strength
of wood
Gymnosperms
Tracheids only
Angiosperms
Tracheids & vessel elements
Temperate regions
Early wood (spring; lrg cells) & late
wood (summer; sml cells)
V.Cambium inactive in winter
Forms seasonal rings

13. 5. Growth, Morphogenesis, and Cell Differentiation Produce the Plant Body
Growth – inc in size by cell division
Morphogenesis = creation of plant shape
Tissue, organ, organism its shape & position of cell types
Development of specific patterns = Pattern Formation
Cell fate
Lineage-based determined early in development
Position-based  cell’s final position in an emerging organ determines what kind of cell it will become
Differentiation = cells with same genes become different from one another
Gene expression; Hox genes in animals = MADS-box in plants for transcription factors

14. Organ identity genes Meristem identity genes Organ identity genes
Vegetative growth  flowering (floral meristems)
Organ identity genes
Regulate development of floral pattern
ABC Hypothesis
3 classes of genes direct the formation of 4 types of floral organs via gene activation for expression
A  sepals & petals
B  petals & stamens
C  stamens & carpels