Introduction to Plants
Kingdom: Plantae
Plants:
 Cell wall
 Autotroph (photosynthesis)
 Multi-cellular
12 Divisions (Phyla)
 Anthophyta = Angiosperms (flowering plants)
 Largest # of species (~250,000 - 90% plants)
 Seed plants: product seed w/in a fruit
 Key adaptations: flowers & fruits
 Sporophytes are trees, shrubs, herbs that
flower
 2 main groups: Monocots & Dicots
Monocots vs. Dicots
Monocot
Dicot
• One cotyledon (seed leaf)
•Two cotyledon
• Parallel veins in leaves
•Netted veins in leaves
• Fibrous root system
•Taproot
• Floral parts in multiples of 3
•Floral parts in multiple layers of 4
or 5
• Complex vascular arrangement
•Ring vascular arrangement
• Eg. grass, corn, palm, onion, tulip,
•Eg. bean, pea, rose, sunflower
bamboo
Concept 35.1 The plant body has a heirarchy of organs,
tissues, and cells
Basic Organs
• Roots
• Stems
• Leaves
Types of Tissue
• Dermal
• Vascular
• Ground
Cell Types
• Parenchyma
• Collenchyma
• Sclerenchyma
• Xylem
• Phloem
Shoot
system
•Above ground
•Stems, leaves
Root
system
•Underground (usually)
•Roots
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: symbiosis with fungi
Root hairs
Fibrous Roots
Taproots
•Mat of thin roots spread just
below surface
•One thick, vertical root
•Shallow
•Many lateral (branch) roots
•Increased surface area
•Firmly anchors
•Monocots
•Stores food in root
•Dicots
Fibrous Root
(scallion)
Taproot
(carrot)
Roots
B. Stems

Alternating system of nodes (leaf
attachment) and internodes
 Function: display leaves
 Terminal bud – growth concentrated at
apex (tip)
 Apical dominance: terminal bud
prevents 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
Stems
Modified stems
• Runner or stolin
– 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
C. Leaves
◦
◦
◦
◦
epidermis of underside interrupted by stomata (pores)
Mesophyll: ground tissue between upper/lower epidermis
Parenchyma: sites of photosynthesis
Cuticle: waxy layer
Three Tissue
Systems
A. Dermal Tissue
• Single layer, closely packed cells that cover
entire plant
• Protect against water loss & invasion by
pathogens
• Cuticle: waxy layer
• Epidermis, periderm
B. Vascular Tissue
• Continuous throughout plant
• Transports materials between roots & shoots
1. Xylem: transport H2O and minerals up from root
2. Phloem: transports food from leaves to other
stele parts of plant
C. Ground Tissue
•
•
•
•
Anything that isn’t dermal or vascular
Function: storage, photosynthesis, support
Pith: inside vascular tissue
Cortex: outside vascular tissue
III. Cell Types
A. Parenchyma: most abundant
 Perform metabolism, synthesizes & stores
organic products
B. Collenchyma: grouped in cylinders, support
growing parts of plant
C. Sclerenchyma: rigid support cell
D. Xylem: water conduction
 Tracheids, vessel elements – dead, tubular,
elongated cells
E. Phloem: sugar, organic cmpd. conduction
 Sieve tubes, plates, companion cells – alive
cells which aid movement of sugar
WATER-CONDUCTING CELLS OF THE XYLEM
PARENCHYMA CELLS
Vessel
Parenchyma cells in Elodea leaf,
with chloroplasts (LM)
Tracheids
100 µm
60 µm
Pits
COLLENCHYMA CELLS
80 µm
Cortical parenchyma cells
Tracheids and vessels
(colorized SEM)
Vessel
element
Vessel elements with
perforated end walls
Tracheids
SUGAR-CONDUCTING CELLS OF THE PHLOEM
Collenchyma cells (in cortex of Sambucus,
elderberry; cell walls stained red) (LM)
Sieve-tube members:
longitudinal view
(LM)
SCLERENCHYMA CELLS
5 µm
Companion
cell
Sclereid cells in pear (LM)
Sieve-tube
member
Plasmodesma
25 µm
Sieve
plate
Cell wall
Nucleus
Cytoplasm
Companion
cell
30 µm
15 µm
Fiber cells (transverse section from ash tree) (LM)
Sieve-tube members:
longitudinal view
Sieve plate with pores (LM)
Primary and Secondary Growth
(apical vs. lateral meristems)
Concept 35.3 Primary growth lengthens roots and
shoots
Root Hairs
Zone of Maturation: growth & differentiation complete;
fully mature cells
Zone of Elongation: cells elongate; push root tip ahead
Zone of Cell Division: apical meristem; new cells produced
Root cap: protects meristem as it pushes through soil; also
secretes polysaccharide lubricant
Concept 35.4 Secondary growth adds girth to
stems and roots in woody plants
• Involves lateral meristems
– Vascular cambium: produces secondary xylem
(wood)
– Cork cambium: produces tough covering that
replaces epidermis
• Bark = all tissues outside vascular cambium