intro to horticulture · – affects flower initiation, vegetative development, or onset of...
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Introduction to Horticulture
University of California Cooperative ExtensionPamela Geisel
Statewide Coordinator Master Gardener Program Farm Advisor, Environmental Horticulture
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NTRODUCTION TO HORTICULTURE
Botany– structure and life phenomena exhibited by
plants– Agronomy– Horticulture
• hortus (garden)• colere (to cultivate)
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NTRODUCTION TO HORTICULTURE
What makes up a plant?– living factories that produce their own food– serve as food source for nearly all other living
organisms• cells• photosynthesis• water (85 - 90 % by weight)
– Solvent for mineral and sugar transport
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Leaves, stems, roots, flowers, fruits, and seeds are known as plant organs. Each organ is an organized group of tissues that work together to perform a specific function.
Sexual reproductive parts produce seed; they include flower buds, flowers, fruit, and seeds.
Vegetative parts include roots, stems, shoot buds, and leaves; they are not directly involved in sexual reproduction. Vegetative parts often are used in asexual forms of reproduction such as cuttings, budding, or grafting.
INTRODUCTION TO HORTICULTUREExternal plant parts-roots, stems, buds, leaves, flowers, fruits and seeds
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NTRODUCTION TO HORTICULTURE
Plant Classification– Growth Habit– Structure or Form– Leaf retention– Climatic Adaptation– Use– Botanical or Scientific Classification
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NTRODUCTION TO HORTICULTURE
Plant Classification– Growth Habit
• Annuals– complete a life cycle (seed to flowering to re-seeding) in one
growing season and then die• Perennials
– may go through repeated flowering and seeding cycles before dying
– may grow for several years before flowering and dying• Biennials
– How do they differ?
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NTRODUCTION TO HORTICULTURE
Plant Classification– Structure or Form
• Herbaceous -- tender stemmed species• Woody -- hard fibrous stems
– Form» Vine» Shrub» Tree (includes tree shape also…weeping, vase, etc.)
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NTRODUCTION TO HORTICULTURE
Plant Classification– Leaf retention
• Deciduous• Evergreen
– broad-leaved -- azaleas, some magnolias– needle-leaved -- pine, redwood
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NTRODUCTION TO HORTICULTURE
Plant Classification– Climatic Adaptation
• Perennial plants are classified according to minimum temperatures they will tolerate
– tropical, subtropical, temperate• Cool- and warm-season plants
– cool season grow best with average daytime temperatures of 55o to 75o F (carrot, asparagus, spinach, broccoli)
– warm season grow best with average daytime temperatures of 65o to 95o F (tomato, sweet corn)
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NTRODUCTION TO HORTICULTURE
Plant Classification– Use
• Fruits• Herbs• Vegetables
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NTRODUCTION TO HORTICULTURE
Plant Classification– Botanical or Scientific Classification
• Genus + specific epithet (species)– Red Raspberry (common name)– Rubus idaeus, or Rubus ideaus
• Grouped according to similarities in morphology
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NTRODUCTION TO HORTICULTURE
Plant Classification– Botanical or Scientific Classification
• Varieties• Cultivars• Clone
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NTRODUCTION TO HORTICULTURE
Plant Classification– Most horticulturally important plants belong to
• Coniferphyta - cone-bearing plants– gymnosperms - seeds exposed at base of scales
• Anthrophyta - true flowering plants– angiosperms - seeds buried in fruit developed from ovary– further divided into
» Monocots - “one seed leaf” - Gramineae grasses» Dicots - “two seed leaves” - Rosaceae
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NTRODUCTION TO HORTICULTURE
Plant Classification– Monocots - “one seed leaf”
- Gramineae grass– Dicots - “two seed leaves” -
Rosaceae• What are some of the
differences?
Monocots Dicots
Vascular tissues scattered in stem
Vascular tissues in circular pattern
Flower parts in three
Flower parts in 4-5 or multiples
Leaf veins parallel
Leaf veins branched
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NTRODUCTION TO HORTICULTURE
Plant Growth– Irreversible increase in plant size due to
increased cell number and/or sizeThree Critical Processes for Growth– Photosynthesis– Respiration– Transpiration
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NTRODUCTION TO HORTICULTURE
Plant Growth– Photosynthesis
• Process by which green plants produce their own carbohydrates and obtain chemical energy
• Plant cells, in presence of chlorophyll and light, convert carbon dioxide (CO2) and water (H2O) to carbohydrates
• Net result is transformation of light energy into chemical energy
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NTRODUCTION TO HORTICULTURE
A model ofPhotosynthesis
urtesy of Ohio State University
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NTRODUCTION TO HORTICULTURE
Plant Growth– Photosynthesis
• Energy is “stored’ in chemical bonds• By-product is evolution of free oxygen (O2)
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NTRODUCTION TO HORTICULTURE
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NTRODUCTION TO HORTICULTURE
Plant Growth– Photosynthesis
• Requirements– Stomata must be
open to allow CO2 to enter leaf
– Adequate light must reach leaf
– Water must be available to the plant
– Mineral nutrients must be available to plant
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NTRODUCTION TO HORTICULTURE
How might thisaffect plant
growth?
urtesy of Ohio State University
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NTRODUCTION TO HORTICULTURE
Plant Growth– Photosynthesis
• Fate of carbohydrates produced– combined with minerals to synthesize more
complex compounds for cell growth– converted to more complex carbohydrates
(sugars and starches) or fats and stored (where?)
– biologically combusted to release stored chemical energy, a process called respiration
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NTRODUCTION TO HORTICULTURE
Plant Growth– Respiration
• occurs in cells through complicated series of reactions regulated by enzymes
• uses oxygen• releases CO2 and water
C6H12O6 + 6 O2 energy 6 CO2 +6 H2O
+ Energy
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NTRODUCTION TO HORTICULTURE
Plant Growth– Respiration
• rate dependent on– temperature– availability of oxygen and carbohydrates
• occurs at all times in living material, even after harvest
• post-harvest respiration affects how fruits and vegetables are stored
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NTRODUCTION TO HORTICULTURE
Plant Growth– Cycling of Photosynthesis and Respiration
• What conditions would impact cycling?
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NTRODUCTION TO HORTICULTURE
Plant Growth– Cycling of Photosynthesis and Respiration
• Photosynthesis requires light, and ceases at night• Respiration occurs all the time, but is driven by
temperature– it nearly doubles for every 18oF rise in temperature
between 40oF and 96oF
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NTRODUCTION TO HORTICULTURE
Plant Growth– Cycling of Photosynthesis and Respiration
• Rate of photosynthesis must exceed rate of respiration
• Why?• What happens when water is limited?
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NTRODUCTION TO HORTICULTURE
A model ofphotosynthesis
urtesy of Ohio State University
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NTRODUCTION TO HORTICULTURE
Plant Growth– Respiration
• occurs in cells through complicated series of reactions regulated by enzymes
• uses oxygen• releases CO2 and water
C6H12O6 + 6 O2 energy 6 CO2 +6 H2O + Energy
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NTRODUCTION TO HORTICULTURE
Plant Growth– Water and Nutrient Uptake
• Most of water and nutrient uptake occurs in roots• Some nutrient uptake requires roots to expend
energy• Water uptake is largely passive and in response to
a gradient
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NTRODUCTION TO HORTICULTURE
How might thisaffect water and nutrient uptake?
urtesy of Ohio State University
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NTRODUCTION TO HORTICULTURE
Plant Growth– Transpiration
• Evaporative loss of water vapor from plant leaves through stomata
• Related to translocation through xylem
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NTRODUCTION TO HORTICULTURE
Porous pot analogy to plant transpiration
urtesy of Ohio State University
soil
Stem-xylem
leaf
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NTRODUCTION TO HORTICULTURE
Diagram of leaf cellsand leaf epidermis
with stoma
urtesy of Ohio State University
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NTRODUCTION TO HORTICULTURE
Stoma inepidermal peel ofchrysanthemum
urtesy of Ohio State University
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NTRODUCTION TO HORTICULTURE
Diagram of thecross-section of
a woody perennialplant
urtesy of Ohio State University
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NTRODUCTION TO HORTICULTURE
• Plant Growth– Transpiration
• Rate depends on– environmental factors (which ones?)– degree of stomatal opening– amount of available soil water
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NTRODUCTION TO HORTICULTURE
• Plant Growth– Transpiration
• In temperate plants transpiration ceases. – When?– Why?
• How is transpiration different in succulents?• Transpiration is affected by wind….
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NTRODUCTION TO HORTICULTURE
• Plant Growth– Transpiration
• Helps to cool plants during day• Transports minerals from soil and organic
compounds produced in roots
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NTRODUCTION TO HORTICULTURE
Impacts of avascular wiltdiseaseon maple
urtesy of Ohio State University
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NTRODUCTION TO HORTICULTURE
Plant Growth– Translocation
• Movement of water, nutrients, food etc. from one part of the plant to another
• Can occur from cell to cell, and in intercellular spaces
• Mostly occurs in xylem (water and nutrients) and phloem (carbohydrates)
• Why are many insects phloem feeders?
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NTRODUCTION TO HORTICULTURE
Plant Development– Dormancy
• Plant parts that are alive but not growing• Mechanism to survive adverse conditions• In order to survive, must contain stored food
reserves to support what process?• Can be physical or physiological
– Day length --Hard seed coat– Chill hours --Closed cone
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NTRODUCTION TO HORTICULTURE
Reproductive Development– The goal for many horticultural plants
• Flowers• Fruits• Seeds
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NTRODUCTION TO HORTICULTURE
Reproductive Development– Flower Induction
• From our old friend the meristem• Timing differs among species
– annuals may flower within weeks of germination– many woody perennials initiate flowers in previous year– Why is this important for your lilacs?
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NTRODUCTION TO HORTICULTURE
Reproductive Development– Flower and Fruit Development
• Controlled by day length, light intensity, temperature, soil moisture content, nutritional status of plant
• Pollination - self-, cross- (wind, insect)• Fertilization
– Only fraction of flowers normally mature– “drop” at petal fall– “June drop” 4 to 6 weeks after petal fall
– Fruit Quality and Ripening
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NTRODUCTION TO HORTICULTURE
Reproductive Development– Fruit Quality and Ripening
• Sugars and aromatic compounds begin to accumulate• Some fruits picked when physiologically mature but not fully
ripe– Tomato, banana, avocado, apples
• Other fruits must be allowed to mature on plant– grapes, citrus, strawberries
• What conditions promote ripening? (Hint - our old friend photosynthesis)
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NTRODUCTION TO HORTICULTURE
How Plants Function– Plant responses to
• daylength• light intensity• light quality• temperature
– Interactions of photoperiod and temperature• soil moisture conditions• carbon dioxide and oxygen concentrations• nitrogen nutrition• stress
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NTRODUCTION TO HORTICULTURE
How Plants Function– Plant responses to
• Daylength– affects flower initiation, vegetative development, or onset
of dormancy in some plants– Plant leaves are sensors of critical photoperiods
» Short-day plants - light period less than 12 hours long (chrysanthemum, poinsettia, strawberry)
» Long-day plants - light period more than 14 hours long (fuchsia, spinach, perennial ryegrass)
» Day neutral - processes not affected by day length (fruits and nuts, grapes, corn)
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NTRODUCTION TO HORTICULTURE
How Plants Function– Which of these requirements can we change
in the garden?• daylength• light – intensity and quality• temperature• soil moisture conditions• carbon dioxide and oxygen concentrations• nitrogen nutrition• stress
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ant responses to stress:
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eaf dema aused by ood-duced eration eficit
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Marginal Necrosis
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Sunburn on Tree Trunk
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Acute Lack of Water
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NTRODUCTION TO HORTICULTURE
Review:Plant ClassificationPhotosynthesisRespirationTranspirationTranslocation
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Thank You---Any Questions?