BOTANY

The Study of Plants

Where Do Plants Fit In

• Domains:– Bacteria: most prokaryotes (no nucleus or

intracellular organelle)– Archaea: have many biochemical differences from

bacteria and often live in extreme environments– Eukaryotes (true nucleus):

• Fungi• Plantae• Animalia

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Plant Classification• Non-vascular Plants - lack tissues to transport

water and sap:• Green algae• liverworts• Mosses

– Leaves are a single layer of cells

Vascular Plants

Tube like structures distribute water, nutrientsand food throughout the plant. Ferns – Spores, (no seeds)Gymnosperms – “Naked” seeds (mostlyconifers)Angiosperms – Flowers and seeds

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Gymnosperm - Pine

Angiosperms

Monocotyledons – One seed leaf grasses, lilies, palms, yuccas, agaves Reproductive parts in threes or multiple of three Three petals etcDicotyledons –Two or more seed leaves Most deciduous trees & herbaceous plants Reproductive parts in fours or fives: four or five petals

Monocots and Dicots

A practical note: Some herbicides act

differently on dicots vs monocots.

Scientific names• Based on classification • In angiosperms based on flower structure• Uniformity among texts and discussions• Often tell us something about the plant

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-further classification

Annuals: Complete a life cycle in one year. Most vegetables, grains, some ornamental plants. Plant may germinate in fall, live through the winter and die after makingseeds the next year. Example: Poppies(An “annual” in our zone may be able to live more than one year if grown intropics.)

Biennials complete a life cycle in two years.Perennials live longer than one year. Herbaceous perennials die back to regrow the following growing season. Many ornamental garden plants. Asparagus. Woody perennials, either deciduous or evergreen, do not die back.

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Vascular Plants• Plants with:– Roots– Stems– Leaves– Vascular systems: extend from root tips up

the stems and out into the leaves.

ROOTS• Have no nodes• Never bear leaves or flowers directly• Have a root cap• Function: absorb water and nutrients– Anchor the plant

– Furnish physical support for the stem– Serve a food storage

Root Cap• Not present in “water roots”

ROOTS

Root growth in loose vscompact soil

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

Mycorrhizae• From mykes or fungus and rhiza or root• Symbiotic relationships between fungi and

plant roots: the fungi get sugars or foodand the plants absorption of water andminerals 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 lateralroots

• 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 vasculartissue

• Complex growth: produces leaves andbranches at nodes as well as lengthens

Plant Stem

Stem or Twig

Vascular Cambium• Produces phloem peripherally which

transports sap to the roots and back fromthe roots in early spring or late winter

• Produces xylem internally which transportswater

• If completely interrupted, the plant will die

Meristem or Cambium

• Site of cell division and growth locatedbetween phloem and xylem. If this is destroyedthe stem cannot form new cells for transport of water andsap.

• At nodes and at the tip meristem tissueforms buds.– Flower parts are modified leaves

Stem Cross Section

Woody Stem Cross Section

Apical Meristem

Plant Stem Tip

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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 drycovering

• 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 theirown organic compounds and oxygen.

• Light is the energy source and CO2 is thecarbon source.

• Plants also respire but the net effect is theproduction of oxygen in excess of carbondioxide.

Leaf Structure

• 1. Cutin, 4. Spongy parenchyma• 2. Epidermis 5. Air space• 3. Palisade layer 6. Stoma

•

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 leaves

Leaf arrangement

Compound Leaves

Sexual Reproduction

Occurs in all plants. Involves meiosis or halvingthe number of chromosomes so that sperm andova are produced. These then unite to produce anew combination of chromosomes and genes.

Gymnosperm

Flower Structure

Gymno vs Angiosperm

Pollination and Fertilization

Pollination: Pollen is carried by wind, insect,bird, water….from the anther to a stigma.Fertilization: The sperm cell unites with the eggcell in the ovule.

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)

Seed Dispersal• Plumes: butterfly weed, dandilions, maples• Fruit: acorns, hollies, apples

• Water: coconuts• Spines and barbs: beggar’s tick• Explosive fruits: jewel weed

Hybrid• Hybrid: a plant or animal which is the

offspring of parents differing in one ormore characteristics. The parents may beof the same or different species.

• Species:a group of individuals if nearlyidentical structure and behavior which canordinarily interbreed and maintain theircharacteristic in nature.

Red crossed with white producespink (hybrid) flowers

Genetic variability• In a given species or variety a gene may have

quite a variable expression.

• Example: apple trees have so much variabilitythat to propagate a standard one must usegrafted stock. If one uses seeds the two parent

trees contribute such different characteristicsthat one usually gets something very differentfrom either parent.

Gene Dominance• If S is dominant over s when SS is mated to ss

all of the offspring will appear S. The offspringwill be Ss.

(The Ss is the hybrid.) If Ss is mated to Ss, theoffspring will be SS, Ss or ss and the ss willappear different.

If there are multiple genes acting in such a way theoffspring of the hybrids may have manydifferences from the hybrids.

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 usegrafted stock. If one uses seeds the two parenttrees contribute such different characteristicsthat one usually gets something very differentfrom either parent.

Gene Dominance• If S is dominant over s when SS is mated to ss

all of the offspring will appear S. The offspringwill be Ss.

(The Ss is the hybrid.) If Ss is mated to Ss, theoffspring will be SS, Ss or ss and the ss willappear different.

If there are multiple genes acting in such a way theoffspring of the hybrids may have manydifferences from the hybrids.

Propagation from Seeds• The offspring may vary from the parents

because of genetic variability or if theparent was a hybrid.

• This may be desired in some cases, but inapples usually the offspring are not tasty.

PLANTS: Bryophytes• Bryophytes (moss-plants) non-vascular,

seedless: Mosses: sphagnum, rockmosses, “true mosses, Liverworts,Hornworts

Cell walls of cellulose Do not produce flowers

MOSS

• MOSS

Moss Cultivation• Mosses need moisture to complete their

life cycle. Many can survive dry periodsbut the spores need water.

• Generally does well in shade, often growson rocks.

• Grows in wide range of pH.• Plant other garden plants first then add the

moss

LIVERWORT•

Seedless Vascular Plants• Lycophyta: club mosses, selaginellas,

quillworts• Sphenophyta: horsetails• Pterophyta: ferns

Clubmoss• Lycopodium

Selaginella

Selaginella

Equisetum (Horsetail)

Equisetum

Ferns

• Need moisture to complete the life cycle

but often grow in a variety of conditions

Life Cycle of Fern

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

Galls

Oak Leaf Gall Urchin Gall

Monarch on Milkweed• Monarchs prefer more than one species of

milkweed