Practical Botany

Learning Objectives

Learn the structures and characteristics of plants.

Understand how plants are named or classified.

Understand the growth processes of plants.

Learn practical applications of botanical knowledge.

The Cell -the basic unit of life

Plant Cell

Vegetative: Roots Stems Buds Leaves

Reproductive: Flowers Fruit Seeds

Major plant parts

Roots Anchor the plant

Absorb water and nutrients

Store sugars from photosynthesis

Need oxygen to break down sugars for growth

Modified Roots

Sweet potatoes Beets

Transport water and nutrients

Site of flower and leaf attachment

Support structure

Stems

Underground Modified Stems

BULBS – ONION, TULIP TUBERS - POTATOModified leavesModified stem

Many bulbs are modified stems

Vegetative bud

Flower bud

Mixed bud

Buds – axillary vs. terminal

Leaves

Simple vs. Compound Leaf*

Arrangement of leaves on a stem

Whorled leaf arrangement

Catalpa Bedstraw (Galium)

Broadleaf flower anatomy

Attract pollinators

Contain reproductive structures

Fruits arise from the mature ovaries

Dioecious vs. monoecious

Pistil

Perfect flower

Monoecious vs. Dioecious

MONOECIOUS DIOECIOUS

Alder Persimmon

Some types of inflorescences

Fruits are enlarged ovaries left after other flower parts drop

Fleshy Drupe (peach) Pome (apple) Berry Achene (strawberry)

Dry Nuts Pods – beans and peas

Fruits – function in seed distribution

Water uptake (imbibition) causes seed to swell

Germination requires: Oxygen Proper temperature

(70-80°F)

Seeds

Naming/Classifying Horticultural Plants

Plant families

Plants within a family have similar characteristics

Helps to narrow the field when identifying plants

Kingdom

Division

Class

Order

Family

Genus

Species

Scientific classification

Genus – close genetically

Species – easily interbreed

Binomialnomenclature

Varieties and Cultivars

Variety – naturally occurring Ex. Brassica oleraceae var. botrytis

(common name: broccoli)

Cultivar – product of plant breeding Ex. Acer platanoides ‘Crimson Sentry’

(common name: Crimson Sentry Norway maple)

Why use scientific names?

Universal

Unambiguous

Everybody knows what you’re talking about.

Chinese elm(Ulmus parvifolia)

Spore-bearing (ferns, mosses, hornworts)

Seed-bearing

Angiosperms

Seed leaves called cotyledons

Other ways plants are classified

Gymnosperms (naked seeds – cone-bearing)

Angiosperms (enclosed seeds – flowering plants)

Monocots (one seed leaf)

Dicots (two seed leaves)

Vascular plants

Most horticultural plants are vascular plants: Stems Leaves Roots Conducting tissues

Non-vascular plants

Bryophytes Liverworts Mosses Hornworts

Marchantia polymorpha

Common weed in nursery production

Monocots vs. Dicots*

Monocots vs. Dicots*

dicotmonocot

Why do we care?

Monocots = grasslike plants

Dicots = broadleaf plants

Selective herbicides

Classification by lifecycle* Annuals – complete their lifecycle in one

growing season

Biennials – require two growing seasons to flower; often sold and cultivated as annuals

Perennials – live for more than two growing seasons Herbaceous perennials Woody perennials

Annuals go through an entire lifecycle in one season

True annuals vs. frost-tender perennials True annuals live through only one lifecycle

regardless of climate Frost-tender perennials are native in climates

with warm winters – they are cultivated as annuals in our cold-winter climate

Winter annuals are grown in mild-winter climates and are planted in fall for winter bloom

Annuals

Require two years to complete their lifecycle

First season growth results in a small rosette of leaves near the soil surface

Second season growth: Stem elongation Flowering Seed formation

Biennials

Digitalis - Foxglove

Plants that live and flower more than two growing seasons Trees and shrubs are woody perennials - go

through a dormant phase each winter Bulbs (ex. Tulips) – leaves yellow and die back

after flowering – sugars are transported to and stored in the bulb for flowering the next growing season

Perennial garden flowers – plants die back to the ground and enter a dormant phase over winter – grow back from the root crown in spring

Grasses – grow from the crown

Perennials

Plant Growth

Cambium (a meristem found only in woody plants)*

Phloem –practical aspectsGIRDLING DISRUPTS PHLOEM TRANSPORT

SYSTEMIC HERBICIDES MOVE THROUGH THE PHLOEM

Photosynthesis

Plants use light + CO2 and water to make sugar.

Sugars are used by the plant for growth or stored.

Translocation

Water and soil nutrients are transported up through xylem.

Sugars are transported through phloem.

Occurs through the phloem tissue

Primary sink = Roots – CHO storage

2nd sink - Developing flowers, fruits, and seeds

3rd sink are growing points called meristems

Source to sink movement

Electron micrograph of a growing point

Root hairs absorb water and nutrients

Cell elongation pushes the root through the soil

Meristem produces new root cells

Roots Tips

Grasses

or spike

Roots need oxygen

Soil compaction

RootingDepthRoot

Hair

Stomate

2CO

Nutrients Absorption

Transpiration

Gas exchange occurs through leaf pores called stomata

CO2 is taken up and O2 is released

Water moving out through stomata keeps leaves cool

Enlarged leaf structure

Stomate

Increase Transpiration

Intense sunlight

Wind

High temperature

Low relative humidity

Plant Development

Stages of Plant Development

Seed germination – Start of life for many plants

Juvenility – Stage of life cycle when plants put on root and shoot growth

Maturity – Flowering and sexual reproduction occurs during this stage

Dormancy - way for plants to survive unfavorable conditions

Senescence – Aging of the plant or its parts

Development ruled by hormones

Auxins (IAA, IBA) – control growth of stems, roots

Cytokinins – work with auxins

Abscisic Acid (ABA) – affects bud growth, and seed, bud dormancy

Gibberellins (GA) – important in seed germination

Ethylene – affects fruit ripening

Germination

MONOCOTYLEDON DICOTYLEDON

Traits of Juvenility

HEDERA HELIX (ENGLISH IVY)

STAYS IN JUVENILE STAGE FOR 10 YEARS!

Leaf form (Ivy)

Growth form (suckers or water sprouts)

Thorns (Locust tree)

Leaf retention (in young trees, ex. oaks)

Juvenile Mature

Juvenile plant parts are easier to propagate

Adventitious roots

Budding

Flowering

HAMNER AND BONNER (1920’S)

PHOTOPERIOD RESPONSE Induction

Cool temperature - vernalization

Night-length (long-day vs. short-day plants)

Initiation Vegetative meristems

change to flower meristems

Development Pollination Fertilization

Self-pollination vs. cross-pollination

Fertilization usually required for fruit development

Exception: Parthenocarpy (produces seedless fruit)

Fertilized ovary becomes the fruit

Pollination and Fertilization

Fruit ripening

Change in fruit color

Softening of the fruit

Change in flavor from sour to sweet

Plant hormone ethylene is involved

Ripening tomato fruit

Senescence

Senescence = aging

Annual plants begin senescence after flowering

Sometimes only part of a plant will senesce

Mediated by ethylene

Fall leaf color caused by senescence of chlorophyll (green) pigments allowing other pigments to show

Slowed or interrupted plant growth

Winter dormancy in cold-winter areas

Dry-season dormancy in Southwest and on coasts

Seeds usually enter a period of dormancy after plant senescence.

Breaking seed dormancy: Cold-moist

stratification Heat Scarification of seed

coat Gibberellins

Seed dormancy

Nicking seed coat 24 hours later

Auxins and Apical Dominance

Response to pruning*

Removing the apical bud release apical dormancy and results in growth of axillary buds below the cut.

Response to pruning*

The effect of heading cuts differs, depending on bud arrangement.

Questions?