practical botany
TRANSCRIPT
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?