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

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

AsclepiasButterfly weed

Bloodflower milkweed

•

Monarch on Milkweed