BOTANY
General Overview
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4 Main Groups of Land Plants:
o Bryophytes  Non-Vascular
 Mosses
 Flagellated Sperm
 Gametophyte is the dominant phase; the sporophyte is dependent on the gametophyte
o Pteridophytes  Vascular but Seedless
 Ferns
 Flagellated Sperm
 Sporophyte is the dominant phase; the gametophyte is FREE-LIVING
o Gymnosperms  Vascular with Seeds
 Conifers (ex. Pine Trees)
 Non-Flagellated Sperm
 Sporophyte is dominant and the gametophyte is retained in the sporophyte
o Angiosperms  Vascular with Seeds, Fruits, and Flowers
 Flowering Plants
 Non-Flagellated Sperm
 Sporophyte is dominant and the gametophyte is retained in the sporophyte
Seeds  multicellular; sporophyte embryo and food supply; can be dormant; prevents against desiccation;
aids in dispersal for the plant; develops from the ovule
Flowers  Specialized for reproduction
o Sepals
o Petals
o Stamens (male reproductive part – produces microspores, which develop into the male gametophyte)
o Carpals/Pistils (female reproductive part – produces megaspores, which develops into the female
gametophyte)
 Seed forms from ovule
 Fruit forms from the ovary
Double Fertilization  pollen contains two sperm cells; one fertilized the egg to make the diploid zygote, one
fertilizes the two polar nuclei to form the endosperm (food source); the purpose of double fertilization is to
synchronize the development of the food storage with the development of the embryo
Monocots vs. Dicots 
Monocots
Dicots
EmbryosOne Cotyledon (seed leaf)
Two cotyledons (seed leaves)
Leaf veinsParallel
Netlike
Stemsvascular bundles – random
vascular bundles – ring
RootsFibrous
Taproot
Flowers Multiples of 3
Multiples of 4 or 5
EvolutionMonophyletic
Polyphyletic
Plant Parts:
o Roots  anchor plant, absorb water (root hairs!), store food
o Shoots  stems and leaves
o Stem  nodes and internodes; axillary buds and terminal buds (meristems!)
Plant Tissues:
o Dermal  Epidermis; can secrete waxy cuticle (on leaves!)
o Vascular  Xylem and Phloem
 Xylem – transports water; uses tracheids and vessel elements; goes “up” from roots
 Phloem – transports “food” (sugars); uses sieve tube cells and companion cells; goes from
source to sink; active transport (translocation)
o Ground  Neither dermal nor vascular; photosynthetic, storage, support; pith (center) and cortex
(outside) in dicots
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Plant Cells:
o Parenchyma  least specialized; thin, flexible, primary cell walls; all cells start as parenchyma
o Collenchyma  thicker, but uneven primary cell walls; supports young parts of plants; no secondary
cell walls
o Sclerenchyma  thick secondary cell walls made of lignin; supports plants; very rigid
Meristems:
o Allows for lifelong growth
o Two types:
 Apical meristems  found in the tips of roots and buds of shoots; allows for primary growth
(length)
 Protoderm = makes dermal tissue (epidermis)
 Procambium = makes the stele (vascular tissue – primary xylem and phloem)
 Ground = makes ground tissue
 Lateral meristems  thickens the plant; found in woody plants
 Vascular cambium = makes secondary xylem (WOOD!) and secondary phloem
 Cork Cambium = makes the tough covering for stems which replaces the epidermis
(ex. Bark)
o Primary growth order:
 Root cap  zone of cell division  zone of elongation  zone of maturation
Water Potential determines the direction of movement in plants
o ALWAYS goes from higher to lower
o Adding solute = lowers water potential
o Adding pressure = increases water potential
Movement in Vascular Tissue:
o Xylem 
 Root Pressure (push) – water flows into the stele (many solutes) and therefore pushes the
water upward, can result in “guttation”
 Transpiration (pull) – due to adhesion/ cohesion/ H-bonding; water is lost by transpiration
(evaporation) through the stomata and is therefore pulled up from other cells by osmosis; this
is the MAIN mechanisms for xylem flow
o Phloem 
 Source to Sink
 Uses energy (translocation); occurs in sieve tube cells and is helped by companion cells
Life Cycle = “Alternation of Generations”
Sporophyte (2n)
Meiosis
Spores (n)
Microspore – male
Megaspore - female
Mitosis
Gametophyte (n)
Pollen – male
Embryo Sac - Female
Mitosis
Mitosis
Zygote (2n)
Vocabulary Terms to Know:
Stomata
Root Hairs
Companion Cells
Fertilization
Guard Cells
Translocation (phloem)
Sieve Tube Elements/Cells
Gametes (n)
Sperm – male
Egg - female
Charophyceans
Tracheids
Stele
Guttation
Vessel Elements
Mesophyll Tissue
Signal Transduction  Greening (roots, shoots and leaves)
 Growth hormones and enzymes for photosynthesis
Hormones
Tropism  growth response toward or away from a stimulus
Auxin
Cytokinins
Gibberellins
Abscisic Acid
Ethylene
Brassinosteroids
Elongation and apical dominance
Commercially for herbicide or fruit growth
Induce growth, stimulate germination
Can delay senescence (aging)
Stimulate growth in leaves and stems
Flower and fruit development including bolting
Maintains dormancy (inhibits germination)
Reduces drought stress by closing stomata
Gas produced during stress (obstacle) and ripening (positive feedback)
Role in apoptosis and leaf abscission
Similar to steroid hormones in animals
Promotes cell elongation and retards leaf abscission
Light responses
Photomorphogenesis (growth and development)  blue and red (phytochromes)
Circadian rhythym  cycle with 24 hour frequency
Photoperiodism  relative length of day/night and physiological response (critical night length)
Other responses
Gravity (root – positive gravitropism; shoots – negative gravitropism)
Stress
Drought  reduce transpiration (guard cells lose turgor, stomata close)
Heat  heat shock proteins help scaffold folding
Cold  change in membrane fluidity (increase unsaturated fatty acids)
Plant Defense
Herbivory : physical and chemical
Pathogen:
gene to gene (avirulent)
hypersensitive (localized)
SAR (systematic acquired resistance)