BOTANY
The Study of Plants
Where Do Plants Fit In
• Living Things: Kingdoms
– Monera: Cells without nuclei and membranes;
bacteria
– Protista: cells with nuclei and organelles;
amoebae, algae, diatoms, slime molds
– Fungi: cell walls of chitin, mitosis and meiosis
different from Plantae, heterotrophs
– Plantae: mostly autotrophic, cell walls of cellulose
– Animalia: multicellular, no cell walls, no
photosynthesis
PLANT CLASSIFICATION
• Kingdom: Plantae
• Division: Tracheophyta (vascular)
• Class: Angiospermae (seeds in fruits)
• Order: Campanulatae
• Family: Asteraceae (Compositae)
• Genus: Coreopsis
• Species: lanceolata (lance-shaped)
Vascular Plants
• Gymnosperms: nonflowering (naked)
seed plants (mostly conifers)
• Angiosperms: (angos=vessel) flowering,
fruit-seed plants
• Monocots--one seed leaf: grasses
(grains), lilies, orchids, irises
• Dicots--two seed leaves: peas,
tomatoes, most deciduous trees
Scientific names
• Based on classification
• In angiosperms based on flower structure
• Uniformity among texts and discussions
• Often tell us something about the plant
Gymnosperms
• Fruitless seed plants: ovule not
enclosed in an ovary. (Ovary becomes
the fruit in angiosperms.)
• Modified leaves form scales of cones or
the fleshy coverings in yews and
junipers
Gymnosperm - Pine
Gymnosperm
Gymno vs Angiosperm
Flower Structure
SEEDS
• Develop from ovule
• Cotyledon--seed leaf
• Radicle--first root
Seed Germination
• Period of dormancy
• Factors: scarification, stored food
– Temperature: some require a period of
cold
– Moisture
– Light
– Oxygen (water logged soil may prevent
germination)
Vascular Plants
• Plants with:
– Roots
– Stems
– Leaves
– Vascular systems
ROOTS
•
•
•
•
Have no nodes
Never bear leaves or flowers directly
Have a root cap
Are the first structure to develop from a
seed
• Function: absorb water and nutrients
– Anchor the plant
– Furnish physical support for the stem
– Serve a food storage
ROOTS
Root Cap
• Not present in
“water roots”
Root growth in loose vs
compact soil
Mycorrhizae
• From mykes or fungus and rhiza or root
• Symbiotic relationships between fungi
and plant roots: the fungi get sugars or
food and the plants absorption of water
and minerals is greatly enhanced
• Occurs in >80% of vascular plants
Mycorrhizae
Specialized Roots
• Tap root: large main root taps deep for water,
develops from radicle and produces lateral
roots
• Fibrous root (a form of adventious root)
common in monocots and seedless plants
• Adventious root: not from radicle
• Aerial root arises from stem (ivy, orchid)
• Buttress root (Ficus)
• Suckers
• Pneumatophores provide oxygen in wet
areas
Plant Stems
• Support the weight of leaves
• Conduct water and minerals up to
leaves and food down to roots in the
vascular tissue
• Complex growth: produces leaves and
branches at nodes as well as lengthens
Plant Stem
Stem or Twig
Meristem or Cambium
• Site of cell division and growth located
between phloem and xylem
• At nodes and at the tip meristem tissue
forms buds.
• Meristem cells are undiffferentiated:
origin of all other cells
– Flower parts are modified leaves
Stem Cross Section
Woody Stem Cross Section
Apical Meristem
Specialized stems
• Rhizome: horizontal underground stem with
(nodes and buds); iris, bermudagrass
• Bulbs: shortened, compressed stem
surrounded by leaves (scales) that envelop a
flower bud
• Corm: similar to bulb with scales reduced to
dry covering
• Tuber: enlarged portion of underground stem;
potato with nodes as “eyes”
Rhizome
• The iris has a large fleshy underground
stem that runs parallel with the soil.
Leaves
• Site of photosynthesis. Plants are
photoautotrophs: they use light to make their
own organic compounds and oxygen.
• Light is the energy source and CO2 is the
carbon source.
• Plants also respire but the net effect is the
production of oxygen in excess of carbon
dioxide.
Leaf Structure
1.
2.
3.
4.
Cutin
5. Air space
Epidermis
6. Stoma
Palisade layer
Spongy parenchyma
Leaf Arrangement
• Simple. Opposite, alternate, whorled
• Compound: Leaflets Palmate, Pinnate
or Double Pinnate
• **Leaves attach to stems at nodes and
buds occur only at nodes.
• (a common error is to mistake a leaflet
for a leaf)
Simple leaf - Attachment
Leaf arrangement
Simple Leaves
Simple leaves
Compound Leaf with opposite
leaflets
Compound Leaves
Hybrid
• Hybrid: a plant or animal which is the
offspring of parents differing in one or
more characteristics. The parents may
be of the same or different species.
• Species:a group of individuals if nearly
identical structure and behavior which
can ordinarily interbreed and maintain
their characteristic in nature.
Genetic variability
• In a given species or variety a gene may
have quite a variable expression.
• Example: apple trees have so much
variability that to propagate a standard one
must use grafted stock. If one uses seeds
the two parent trees contribute such different
characteristics that one usually gets
something very different from either parent.
Gene Dominance
• If S is dominant over s when SS is mated to
ss all of the offspring will appear S. The
offspring will be Ss.
(The Ss is the hybrid.) If Ss is mated to Ss, the
offspring will be SS, Ss or ss and the ss will
appear different.
If there are multiple genes acting in such a way
the offspring of the hybrids may have many
differences from the hybrids.
Propagation from Seeds
• The offspring may vary from the parents
because of genetic variability or if the
parent was a hybrid.
• This may be desired in some cases, but
in apples usually the offspring are not
tasty.
PLANTS: Bryophytes
• Bryophytes (moss-plants) non-vascular.
Mosses, club mosses, liverworts
Cell walls of cellulose
Do not produce flowers
Seedless Vascular Plants
• Lycophyta: club mosses, selaginellas,
quillworts
• Sphenophyta: horsetails
• Pterophyta: ferns
Clubmoss
• Lycopodiums. Simplest vascular plants
Selaginella
•
Selagenella
•
Horsetail: Equisetum
•
Equisetum
•
Ferns
• Need moisture to complete the life cycle
but often grow in a variety of conditions
Ferns
• Maidenhair
Non-flowering Plants
• Can be interesting as well as beautiful
additions to outdoor and indoor
gardens.
• They often need high humidity and
some shade
– The north side of the house is often a good
habitat for selaginellas and ferns
Adaptations of Plants
• Drought tolerance
– Succulents have large vacuoles to store
water
– Waxy coats to avoid water loss
– Small leaves or needles to decrease
surface area (less effect from wind)
– Stomata close during the day (cacti)
– Hairs on leaves to collect moisture
Seed Dispersal
• Plumes: butterfly weed, dandilions,
maples
• Fruit: acorns, hollies, apples
• Water: coconuts
• Spines and barbs: beggar’s tick
• Explosive fruits: jewel weed
Asclepias
Butterfly weed
Bloodflower milkweed
•
Monarch on Milkweed