BIO306 Exam 1 Notes
Plants provide food, fuel, and fiber for humans.
All caloric intake comes from plants, sustaining all life on Earth.
Plants provide air and water purification and habitats. They prevent erosion, provide pharmaceuticals, and give beauty to spaces.
Plants undergo photosynthesis, converting carbon dioxide and water in the presence of sunlight into oxygen and sugars.
The source of photosynthesis is leaves, and the sink is fruit.
Seeds go through three stages for germination:
Uptake of water
Formation of enzyme systems
Metabolism of storage products
For a seed to germinate, three requirements must be met:
The seed is viable
Environmental conditions are favorable
Dormancy is overcome
Plants react to their environments in many ways
Phototropism…movement in response to light
Thigmotropism…movement in response to touch
Gravitropism…movement in response to gravity
Dormancy…the temporary suspension of visible plant growth
Quiescence…dormancy due to lack of necessary external environmental factors
Rest…dormancy due to internal limitations
Dormancy can be positive and negative in crop production.
Dormancy is good because wheat grains can lay Dormant in storage
Dormancy is bad because weeds can lay dormant in fields for years
Senescence…a failure of plant reactions preceding cell death
By delaying senescence we can allow crops to grow and produce longer, as well as allowing flowers and fruits to last longer
Without horticulture there would be a very different landscape in regards to the plants around us and the foods available to us.
Agriculture…production of plants and animals to meet basic needs of the human population
Forestry…planting, managing, or caring for forests
The word “horticulture” comes from hortus cultura meaning garden cultivation
Horticulture differs from agriculture or forestry in that there is more intensive management where the individual plant is important and there is a higher gross return per unit area per time.
Horticulture…the cultivation of a crop that is highly valued and intensely managed where the individual plant matters
Cultivation of edible plants began 7,000 to 10,000 years ago.
Agriculture lead to an available and dependable food supply, which in turn lead humans to be able to become scientists, artists, and engineers. All quality of life increased.
Around 3,000 B.C.E. preparation, irrigation, and pruning of plants took place in Egypt. Irrigation lead to the ability to create extensive and planned gardens
Irrigation spread through Mesopotamia, Babylonia, and Assyria and by 1800 B.C.E. 10,000 square miles were under cultivation to feed 15 million people.
Greek philosophers contributed to the study of crops, such as Theophrastus, who is considered the father of botany.
Romans made no major horticultural advancements, but they did use and improve on the technology of conquered peoples. This included grafting, budding, legume rotation, storage of fruits and vegetables, and the creation of the first greenhouse-like structure.
Arabian cultures established botanical gardens between 800 and 1300 C.E.
Monks perpetuated science through the Middle Ages and the Renaissance period brought forth new scientific discoveries.
There are many ideas regarding how humans developed agriculture, including various cultures believing it to be a divine gift.
Early societies grew figs, dates, grapes, and olives as well as roses, ornamentals, and medicinal plants.
The Chinese developed cultural practices for tea, oranges, and Ephedra.
In the Americas, Pre-Incans in Peru cultivated corn, potatoes, cacao, tomatoes, peppers, and beans about 5,000 years ago.
Borlaug lived from 1914 to 2009 and fathered the Green Revolution
Borlaug is credited with prevented the starvation of one billion people by developing disease resistant wheat varieties for tropical nations
The Green Revolution occurred from the 1940s to the 1970s when populaitons were rising and crop yeilds were stagnating
The Green Revolution arose out of necessity and resulted in the modernization of agriculture, leading to enhanced crop yields, increased food security, and reduced hunger.
8000 B.C.E….domestication occurs
3500 B.C.E….Egyptians begin using irrigation
1492…European discovery of the New World
1800…Chemical fertilizers first used
1862…US Merrill Land Grant College Act establishes agricultural institutions and the USDA is introduced
1866…Mendel describes inheritance
1887…The Hatch Act established an agricultural experiment station in each state
1930…the first plant patent is given
1970…Normal Borlaug fathers the Green Revolution
1982…the first GMO crop is created
New cultivars are continuously improving crop quality and yield as well as pest and environmental resistance.
Created understanding of plant-water relationships helps improve the efficiency of irrigation systems.
Light can be used to trigger or delay flowering.
Temperature control increases production efficiency of greenhouses.
Plant nutrition improves through fertilizers delivered in specific ways at specific rates.
Rhizosphere soil-free mixes
Integrated pest management is more environmentally friendly.
Plant growth regulators can be applied to control height, branching, flowering, and fruit size
Horticultural engineering can automate processes and implement remote sensing.
Post-harvest refrigeration and controlled atmosphere extends the viability of food.
There are numerous ways that one can find a career in horticulture:
Creating and distributing supplies such as pots, chemicals, tractors, and processing equipment
Grower services including pest control, nutrient analysis, and greenhouse maintenance
Production of crops includes skilled and unskilled labor, GMO creation, and tissue culturing
Marketing of crops is crucial, as producing a crop is useless if there is no market for it
In 1862 the Morrill Act was signed and the USDA was created, causing a boom in horticultural research
The Hatch Act of 1887 led to experiment stations in every state
In 1889 the US Department of Agriculture was elevated to cabinet status
Furthering studies in horticulture can include plant sciences, animals science, engineering, and social sciences
Horticulture is closely related to applied plant sciences and agronomy, as well as forestry.
Horticulture can be broken down into three sections:
Ornamental horticulture
Floriculture
Landscaping
Interiorscaping
Olericulture (vegetables)
Pomology (fruits and nuts)
Ornamental horticulture…growing plants for natural beauty
Floriculture…production, transportations, and use of flowers and foliage plants
Floriculture accounts for more than half of all non-food horticulture.
Floriculture crops are primarily grown in greenhouses in temperate climates and are very time sensitive, including Easter lilies, poinsettias, and Christmas cactus.
Landscape horticulture…production, design, and marketing of landscapes
Nurseries are very importnat in landscape horticulture.
Interiorscaping…growing plants for inside usage, including indoor malls and medical offices
Olericulture…vegetable production, harvesting, storage, processing, and marketing
Olericulture is very complex and competitive.
Pomology…growing, harvesting, storing, processing, and marketing of fruits and nuts
Post-harvest preservation is a major aspect of pomology
Many jobs are available within horticulture including:
Florist
Golf course superintendent
Cooperative extension specialist
Crop consultant
Teaching
Research
Botanical gardens and arboreta
Landscape architect
Theophrastus was the first person to classify plants
Carolus Linnaeus was the creator of the current classification system that is now regulated by the International Code of Botanical Nomenclature
The classification system assigns organisms into kingdom, phylum, class, order, family, genus, and species (King Phillip Came Over From Germany Stoned)
Scientific names are typically preferred over common names as common names can be misleading and refer to a number of different species.
There are many different ways to group horticultural plants together
Dicots vs. monocots
Kinds of stems
Stem types are described as physical hardness
Herbaceous…stems that are not woody and are short lived
Vines…herbaceous plants that twine
Woody plants…dense, sturdy, long lived plants
Liana…woody plants that twine
Climate
Warm season and cool season are often categories used for grass and vegetables that define optimal conditions for growth and survival
Plants can be cold hardy or tender
Soil moisture
Hydrophytes…aquatic plants such as water lilies
Xerophytes…drought tolerant plants such as cacti
Mesophytes…plants that prefer intermediate soil moisture, a group including most plants
Unique characteristics
Halophytes…plants that thrive in high salt soils
Basophilic…plants that prefer basic soils
Acisophilic…plants that prefer acidic soils
Life Cycle
Annuals…plants which go from seed to seed in one season
Biannuals…plants that have a two season life cycle
Winter annuals…plants that germinate in the fall, overwiner, and flower in the spring
Perennials…plants that live two or more seasons
Foliage
Deciduous…plants that drop their leaves
Evergreen…plants that hold leaves all year long
Usage
Edible…plants whose primary usage is consumption
Amenity…plants that provide aesthetic primarily
Forma…subdivision of a species differing only slightly
Variety…subclassifications of the traditional species
Plant verists are listed as the genus and species name followed by their variety, such as Scilla sibirica var. alba.
Cultivar…a group of plants within a species often distinguished by flower, fruit, or vegetative characteristics that can be patented
Cultivars can be listed of ‘Hidcote’ or cv. Hidcote, but should be kept separate.
Hybrid plants names should be preceded by a capital X (Petunia X hybrida)
Cultigen…plant or group of plants originated in domestication with no native form
Cultigens include brussels sprouts, cabbage, and corn
Line…sexually reproduced cultivar
Clone…population of plants derived asexually from one individual
Horticulture is the manipulation of plants and their environment
Plants are bred for particular characteristics and growth
A plant’s environment includes both abiotic and biotic factors
Atmospheric environment includes wind, light, temperature, and rainfall
Edaphic environment refers to underground conditions
Plants are influenced by genetics primarily and their environment secondarily. Their environment impacts growth and development.
Wind is an abiotic facor that impacts aboveground plant growth
Higher winds lead to plants that are smaller, more compact, and with a tougher cuticle.
Wind cools a plant, reduces moisture, and reduces disease by making plants more resistant to mechanical stress, pathogens, and pests
Wind can cause destruction of plants, spread spores, pests, and seeds, and cause salt spray.
Light is majorly important to plant growth
Light can be defined by its itensity (quantity), color (quality), and the length of the dark period (photoperiod).
Light quantity…the amount of light within particular wavelengths
The main source of light for plants is the sun and the highest amount of light is at noon.
Light can be absorbed or reflected off of a leaf; only a small amount is used in photosynthesis
Photon…discrete particle of energy
Light compensation point…where carbon dioxide ficed by photosynthesis is equal to that lost by respiration. At this point a plant maintains tissue but does not grow.
Light saturation point…the point where light is no longer the limiting factor. Varies by species and number of leaves per individual.
Light quality refers to its wavelength
Plants absorb light from the visible spectrum. Chlorophylls, carotenoids, and phycobilin absorb light from specific wavelength
Leaves absorb blue and red light and reflect green light.
Photosynthesis takes place in the chloroplasts.
Light reactions are driven by light energy and occur in the grana.
Photosynthesis required carbon dioxide, water, and light, and yields glucose and oxygen as a waste product.
Stomatal opening is regulate by guard cells and facilitates carbon dioxide entering the leaves as well as water exiting.
Field plants need to be spaced ideally for maturity. This leads to wasted space when plants are young.
As a rule of thumb, bigger plants should be placed in the back or to the north and smaller plants should be in the front or to the south.
Horticultural crops are often pruned for enhanced light interception, particularly for more light to hit the middle of the tree.
Pruning properly allows for more photosynthesis, more sugars, higher yields, and more fruit color.
Ornamental hedges are pruned for aesthetic, but also light capture. Keeping bottoms wider ensures that the tops don’t shade lower leaves.
Etiolation…exaggerated plant stem growth in the absence of light
Etiolatoin results in visible internode elongation and yellow tissues
Etiolation does not occur in monocots, rather leaves just get bigger
Cuttings from etiolated leaves root easier
Blanching…when plants or plant parts are covered to be devoid of light.
Cauliflower heads are covered with leaves to keep the head white in an example of blanching.
Plants can etiolate in response to blanching treatment
An excess of red and far red light can lead to phytochrome responses in plants. This is a light quality issue.
Phytochrome resonses are essentially etiolation, but due to lower quality light rather than lower quality.
This occurs in plants so that they can outcompete surrounding competitors that may be shading them.
Light can stimulate anthocyanin production, making fall leaves more colorful and fruits more red.
Photoperiodism…a plant’s response to daylength where darkness is the critical portion
Day neutral plants…plants that flower across a wide range of day lengths
Some day neutral plants flower more or less in response to day length, called quantitative long or short plants.
Long day plants…plants that flower when nights do not meet a critical length
Short day plants…plants that flower when nights are more than a certain critical length
Alternating day length plants…plants that need short days followed by long days or vice versa
Understanding photoperiodism allows plants to be produced in any hemisphere at any time.
Critical night length aries by species and by cultivar of a species.
Storage organ development can also depend on photoperiodism, such as in onion and garlic, which depend on a long day (short night)
Plants can be very sensitive to light when it comes to photoperiodism, with some being able to be reset by a flashlight.
Many horticultural crops need full sun
Rapidly shifting an individual from shade to sun or vice versa can cause issues with scorching and mortality
A variety of supplemental lighting can be used to improve plant growth
High intensity discharge lamps are very expensive, but can last up to 24,000 hours, be used in windowless warehouses, and increased rose production by 240%
Fluorescent lamps are used in seed germination and tissue culture. They are less intense but can be used to lengthen the day
Incandescent lamps are too hot and have improper wavelengths, so they are primarily used to control the photoperiod
LED lights are expensive, but last longer, use less energy are harder to break, and can be put closer to plants than other light options.
Temperature is the most important factor in plant distribution. It also plays a major role in plant physiology, impacting growth, development, flowering, dormancy, yield, and color.
Hardy plants are less sensitive to temperature.
Tender plants cannot tolerate cold temperatures.
Many horticultural crops are divided into cool season, intermediated season, and warm season.
Most plants can survive from 0 to 50 degrees celsius, but 10 to 30 degrees celsius is optimal.
The USDA breaks the country into zones 1-11 based on annual minimum temperatures. Zones do not factor in maximum or mean temperatures.
Plants can be grown outside of their zones by using protection, placing them in sheltered areas, and burying them with soil and snow.
Soil temperature impacts seed germination, root growth, water uptake, and disease.
Plant roots stop growing when soil temperature is below 41 degrees Fahrenheit.
Sandy soils warm more quickly than clay soils due to differences in water content. Soil temperature is also impacted by air temperature, wind, and solar radiation.
Optimum soil temperature is 59-86 degreed Fahrenheit
Soil temperature can be modified by applying plastic mulch in light or dark colors to achieve the desired effect, altering soil moisture, heating irrigation water, or using heating pads.
Thermoperiodicity…When plants grow better with alternating day and night temperatures
In 1944 it was discovered that tomatoes grow much less when they are constantly at 80 degrees Fahrenheit than when the day was 80 degrees Fahrenheit and the night was 68 degrees Fahrenheit.
Thermoperiodicity is especially important to plant height
Recommendations regarding thermoperiodicity vary based on species, market, and sunny vs. cloudy.
Lilies, poinsettias, and chrysanthemums grow taller if night temperatures are constant and day temperatures are increased, but shorter if the night is increased and the day is constant.
The difference between night and day is DIFF, calculated by subtracting the night temperature from the day temperature.
Growing degree days relate to development and reproduction of plants and insects. They are also known as heat units.
Growing degree days are used for organisms that cannot maintain their own temperature, where their development is predicted by temperature and time.
Growing degree days help people know when to scout for pests or market crops.
Minimum development threshold…minimum temperature at which growth occurs
Maximum development threshold…maximum temperature at which growth occurs
A growing degree day is 24 hours at 1 degree above the minimum development threshold
Biofix date…date at which you being calculations, including seedling emergency, calendar date, first trapping, etc.
Degree days= ((daily maximum temperature + daily minimum
temperature)/2)-minimum threshold temperature
A plant needs a certain number of degree days to exist.
Buds of woody plants go to pre-dormancy in the summer, which is broken if the plant needs more growth. By winter the buds are dormant. If a plant is placed in a greenhouse after this, buds will not grow unless overcome by a chilling period.
There is a minimum number of hours that a temperature must be below a certain threshold for buds to break dormancy.
Chilling period varies by species and cultivar.
Endodormancy…imposed by internal blocks in seeds and buds, regulated by hormones and removed by winter chilling (rest)
Ectodormancy…plants refrain from growing until external conditions are satisfied (quiescence)
Both endodormancy and ectodormancy work together to prevent bud break during the wrong time of year.
We can overcome dormancy by calculating chilling hours and the heat units required for buds to break once chilling hours are reached.
Chilling injury can occur to tropical plants at temperatures as warm at 59 degrees Fahrenheit (non-freezing temperatures).
While tropical plants are susceptible to cold at any time, temperate plants have different tolerances depending on whether they are growing or dormant.
Two main freeze events can threaten plants that grow in temperate regions.
Advective freeze…mass of cold air moved in by strong winds often leading to temperatures below freezing for a full day or more.
It is difficult to protect plants from advective freezes as they are very windy and have long durations.
Radiational cooling…clear nights and calm winds that last a few hours.
Protection
There are multiple ways to protect from radiational cold events as they typically only last a few hours on either side of the sunrise.
Row covers…protection from radiational cooling that can offer 1-3 degrees C of protection. Woven materials protect more than paper or plastic
Torches…a method of protection from cooling events that uses open flames throughout plantings, used widely in European vineyards
Helicopters…can be used to protect crops from cooling by mixing the air
Irrigation may be used to protect plants. Overhead irrigation begins at a very specific time using low volume sprinklers. As the water freezes, it gives off heat that warms plant tissues. Irrigation must continue until the ice is melted. This method is only effective for short periods within a few degrees of freezing.
Sunscald…damage of thin market trees which occurs when temperatures are below freezing, sun hits the bark and raises the temperature, thawing the tissues, and freezing conditions return as soon as the sun is no longer on the tissues. The cells die and the bark splits.
Frost cracking…splitting of turns due to extremely cold temperatures
Very high temperatures can kill plants
High head with direct sunlight can cause sunburn or sunscald.
Rapid changes in temperature can cause injury to plants, sometimes even including cold water falling on leaves.
Temperatures are important to consider when selecting a site, with many factors impacting it such as air, slope, altitude, bodies of water, and latitude.
Frost pockets…low areas where cold air settles
Cool air is more dense than warm air and thus will flow downhill. Fruit orchards are usually planted on slopes to avoid cool air.
Altitude…the elevation of the site
For every 300m increase in altitude, the air temperature can drop by 5 degrees celsius, and higher altitudes have higher thermoperiodicity.
Variables at particular latitudes make prime locations for fruit production.
Large bodies of water can be useful for crop production due to the temperature moderation provided by the heat capacity. Warm water in the fall protects from early frosts, cool water in spring prevents buds bursting before a cold snap, and summer and winter temperatures are much less extreme.
70% of the Earth’s surface is water and many ancient civilizations were built near water.
Water is important for plants so that they can perform photosynthesis. Requirements vary by crop, region, and development state. Herbaceous plants are 80-90% water by weight, woody plants are 50% water by weight, and tomatoes are 95% water.
200 to 1000 grams of water can be needed to produce 1 gram of dry matter.
Water has unique properties that make it even more useful for plants.
High specific heat stabilizes extreme temperatures
Water is a universal solvent, helping transport nutrients, fertilizers, sugars, and hormones
Surface tension
Turgor pressure keeps plants erect
Water in guard cells open stomata
Transpiration…loss of water from a plant as vapor. Loss occurs through stomatal openings
Evapotranspiration…evaporation loss of water from plants and soil influenced by humidity
When soil is saturated, all pores are full of water moving along gravitational potential
When soil is not saturated, water moves by metric potential
Water enters plants through root tips.
Field capacity…when water is only held in small pores, reached when large pores are drained by gravity
Permanent wilting point…the point when water will not longer be able to be absorbed
Incipient wilting…occurs when plants temporarily wilt and then recover without additional water
Water penetration of soil is important in irrigation as runoff is not desired and standing water reduces oxygen to plants
Irrigation…supplemental meeting of water needs of a crop
There are many different ways to irrigate plants
Hand watering is simple and low cost, but has variable success and requires a lot of labor.
Furrow irrigation…irrigation where ditches are placed between crop rows and gates are open to release water
Requires ground to have slope, not suitable for well draining soils, and does not wet foliage
Flood irrigation…irrigation that covers most of a field
Most inefficient form of irrigation
High volume irrigation
Overhead irrigation using sprinklers
Circular pivot sprays in a circular pattern
Lateral system walks through a field
Common in fields as good airflow is needed if it is used in a greenhouse
Wind can distort patterns
Evaporation loss is high, equipment is expensive, and salt can build up in soils
Low volume irrigation
Trickle or drip systems
Conserves water, limits weeds, reduces disease issues, more uniform, and fertilizers can be added
Clogging can be problematic, coyotes may destroy systems, and they are expensive
Subirrigation…applying water below the root zone
Floor flood
Plants are on a floor or bench and flooded for 15 minutes at a time
Efficient for water and fertilizer, low labor and cost
Pathogens become problematic very quickly
Open irrigation system…water is not reused
Closed irrigation system…water is recycled repeatedly
Nursery crops mostly involve the sale of woody ornamental plants in one of the fastest growing segments of agriculture
In the USA there are both wholesale and retail nurseries
Wholesale nurseries have fewer crops on a larger scale and sell to other nurseries whereas retail nurseries often sell these plants.
Product mix…type of plants to be grown
Container production and field production are used, but the trend is leaning towards container stock.
Less labor required
More control
High density of crop
Quicker recovery
More marketable
Plants are grown in pots
Very valuable in the market
Pots need to last a long time
Ground needs to be level
Issues with root binding
Pots are expensive
Roots are not are protected in the winter
Plants should be grouped together or border pots can be placed
Alternatively, pots can be buried in the ground
Fields need tilled before planting
Cover crops may be used to make soil more fertile
Plants must be spaced for maximum size because they cannot be moved
Space for equipment must be considered as well
Plants may be sold “balled and burlapped” with a ball of soil dug up and wrapped or bare root, which risks transplant shock
Greenhouses may be used to control the environment
Cold frames have no heat
Shadehouses only protect from the elements
The first use of flowers is documented in 2800 B.C.E. Egypt
Flower petals are used during ceremonies in Greece in 600 B.C.E.
Flowers are used in India, China, and Japan for religious ceremonies
In the 1920s corsages began to be used
Flowers are detached and used in arrangements
Cut flowers have very short lifespans
Both woody and herbaceous plants are used
Vase life…how long a cut flower will last
There are different stages or development that are optimal for harvesting in different plants and all species have their own vase life
Once cut one should minimize a flower’s exposure to heat and ethylene and should recut stems and place in warm, high quality water
Interiorscaping…ornamental plants for functional and aesthetic purposes
Interior plants filter the air, reduce noise, and look nice.
Lighting is key in interiorscaping.
Plants provide food, fuel, and fiber for humans.
All caloric intake comes from plants, sustaining all life on Earth.
Plants provide air and water purification and habitats. They prevent erosion, provide pharmaceuticals, and give beauty to spaces.
Plants undergo photosynthesis, converting carbon dioxide and water in the presence of sunlight into oxygen and sugars.
The source of photosynthesis is leaves, and the sink is fruit.
Seeds go through three stages for germination:
Uptake of water
Formation of enzyme systems
Metabolism of storage products
For a seed to germinate, three requirements must be met:
The seed is viable
Environmental conditions are favorable
Dormancy is overcome
Plants react to their environments in many ways
Phototropism…movement in response to light
Thigmotropism…movement in response to touch
Gravitropism…movement in response to gravity
Dormancy…the temporary suspension of visible plant growth
Quiescence…dormancy due to lack of necessary external environmental factors
Rest…dormancy due to internal limitations
Dormancy can be positive and negative in crop production.
Dormancy is good because wheat grains can lay Dormant in storage
Dormancy is bad because weeds can lay dormant in fields for years
Senescence…a failure of plant reactions preceding cell death
By delaying senescence we can allow crops to grow and produce longer, as well as allowing flowers and fruits to last longer
Without horticulture there would be a very different landscape in regards to the plants around us and the foods available to us.
Agriculture…production of plants and animals to meet basic needs of the human population
Forestry…planting, managing, or caring for forests
The word “horticulture” comes from hortus cultura meaning garden cultivation
Horticulture differs from agriculture or forestry in that there is more intensive management where the individual plant is important and there is a higher gross return per unit area per time.
Horticulture…the cultivation of a crop that is highly valued and intensely managed where the individual plant matters
Cultivation of edible plants began 7,000 to 10,000 years ago.
Agriculture lead to an available and dependable food supply, which in turn lead humans to be able to become scientists, artists, and engineers. All quality of life increased.
Around 3,000 B.C.E. preparation, irrigation, and pruning of plants took place in Egypt. Irrigation lead to the ability to create extensive and planned gardens
Irrigation spread through Mesopotamia, Babylonia, and Assyria and by 1800 B.C.E. 10,000 square miles were under cultivation to feed 15 million people.
Greek philosophers contributed to the study of crops, such as Theophrastus, who is considered the father of botany.
Romans made no major horticultural advancements, but they did use and improve on the technology of conquered peoples. This included grafting, budding, legume rotation, storage of fruits and vegetables, and the creation of the first greenhouse-like structure.
Arabian cultures established botanical gardens between 800 and 1300 C.E.
Monks perpetuated science through the Middle Ages and the Renaissance period brought forth new scientific discoveries.
There are many ideas regarding how humans developed agriculture, including various cultures believing it to be a divine gift.
Early societies grew figs, dates, grapes, and olives as well as roses, ornamentals, and medicinal plants.
The Chinese developed cultural practices for tea, oranges, and Ephedra.
In the Americas, Pre-Incans in Peru cultivated corn, potatoes, cacao, tomatoes, peppers, and beans about 5,000 years ago.
Borlaug lived from 1914 to 2009 and fathered the Green Revolution
Borlaug is credited with prevented the starvation of one billion people by developing disease resistant wheat varieties for tropical nations
The Green Revolution occurred from the 1940s to the 1970s when populaitons were rising and crop yeilds were stagnating
The Green Revolution arose out of necessity and resulted in the modernization of agriculture, leading to enhanced crop yields, increased food security, and reduced hunger.
8000 B.C.E….domestication occurs
3500 B.C.E….Egyptians begin using irrigation
1492…European discovery of the New World
1800…Chemical fertilizers first used
1862…US Merrill Land Grant College Act establishes agricultural institutions and the USDA is introduced
1866…Mendel describes inheritance
1887…The Hatch Act established an agricultural experiment station in each state
1930…the first plant patent is given
1970…Normal Borlaug fathers the Green Revolution
1982…the first GMO crop is created
New cultivars are continuously improving crop quality and yield as well as pest and environmental resistance.
Created understanding of plant-water relationships helps improve the efficiency of irrigation systems.
Light can be used to trigger or delay flowering.
Temperature control increases production efficiency of greenhouses.
Plant nutrition improves through fertilizers delivered in specific ways at specific rates.
Rhizosphere soil-free mixes
Integrated pest management is more environmentally friendly.
Plant growth regulators can be applied to control height, branching, flowering, and fruit size
Horticultural engineering can automate processes and implement remote sensing.
Post-harvest refrigeration and controlled atmosphere extends the viability of food.
There are numerous ways that one can find a career in horticulture:
Creating and distributing supplies such as pots, chemicals, tractors, and processing equipment
Grower services including pest control, nutrient analysis, and greenhouse maintenance
Production of crops includes skilled and unskilled labor, GMO creation, and tissue culturing
Marketing of crops is crucial, as producing a crop is useless if there is no market for it
In 1862 the Morrill Act was signed and the USDA was created, causing a boom in horticultural research
The Hatch Act of 1887 led to experiment stations in every state
In 1889 the US Department of Agriculture was elevated to cabinet status
Furthering studies in horticulture can include plant sciences, animals science, engineering, and social sciences
Horticulture is closely related to applied plant sciences and agronomy, as well as forestry.
Horticulture can be broken down into three sections:
Ornamental horticulture
Floriculture
Landscaping
Interiorscaping
Olericulture (vegetables)
Pomology (fruits and nuts)
Ornamental horticulture…growing plants for natural beauty
Floriculture…production, transportations, and use of flowers and foliage plants
Floriculture accounts for more than half of all non-food horticulture.
Floriculture crops are primarily grown in greenhouses in temperate climates and are very time sensitive, including Easter lilies, poinsettias, and Christmas cactus.
Landscape horticulture…production, design, and marketing of landscapes
Nurseries are very importnat in landscape horticulture.
Interiorscaping…growing plants for inside usage, including indoor malls and medical offices
Olericulture…vegetable production, harvesting, storage, processing, and marketing
Olericulture is very complex and competitive.
Pomology…growing, harvesting, storing, processing, and marketing of fruits and nuts
Post-harvest preservation is a major aspect of pomology
Many jobs are available within horticulture including:
Florist
Golf course superintendent
Cooperative extension specialist
Crop consultant
Teaching
Research
Botanical gardens and arboreta
Landscape architect
Theophrastus was the first person to classify plants
Carolus Linnaeus was the creator of the current classification system that is now regulated by the International Code of Botanical Nomenclature
The classification system assigns organisms into kingdom, phylum, class, order, family, genus, and species (King Phillip Came Over From Germany Stoned)
Scientific names are typically preferred over common names as common names can be misleading and refer to a number of different species.
There are many different ways to group horticultural plants together
Dicots vs. monocots
Kinds of stems
Stem types are described as physical hardness
Herbaceous…stems that are not woody and are short lived
Vines…herbaceous plants that twine
Woody plants…dense, sturdy, long lived plants
Liana…woody plants that twine
Climate
Warm season and cool season are often categories used for grass and vegetables that define optimal conditions for growth and survival
Plants can be cold hardy or tender
Soil moisture
Hydrophytes…aquatic plants such as water lilies
Xerophytes…drought tolerant plants such as cacti
Mesophytes…plants that prefer intermediate soil moisture, a group including most plants
Unique characteristics
Halophytes…plants that thrive in high salt soils
Basophilic…plants that prefer basic soils
Acisophilic…plants that prefer acidic soils
Life Cycle
Annuals…plants which go from seed to seed in one season
Biannuals…plants that have a two season life cycle
Winter annuals…plants that germinate in the fall, overwiner, and flower in the spring
Perennials…plants that live two or more seasons
Foliage
Deciduous…plants that drop their leaves
Evergreen…plants that hold leaves all year long
Usage
Edible…plants whose primary usage is consumption
Amenity…plants that provide aesthetic primarily
Forma…subdivision of a species differing only slightly
Variety…subclassifications of the traditional species
Plant verists are listed as the genus and species name followed by their variety, such as Scilla sibirica var. alba.
Cultivar…a group of plants within a species often distinguished by flower, fruit, or vegetative characteristics that can be patented
Cultivars can be listed of ‘Hidcote’ or cv. Hidcote, but should be kept separate.
Hybrid plants names should be preceded by a capital X (Petunia X hybrida)
Cultigen…plant or group of plants originated in domestication with no native form
Cultigens include brussels sprouts, cabbage, and corn
Line…sexually reproduced cultivar
Clone…population of plants derived asexually from one individual
Horticulture is the manipulation of plants and their environment
Plants are bred for particular characteristics and growth
A plant’s environment includes both abiotic and biotic factors
Atmospheric environment includes wind, light, temperature, and rainfall
Edaphic environment refers to underground conditions
Plants are influenced by genetics primarily and their environment secondarily. Their environment impacts growth and development.
Wind is an abiotic facor that impacts aboveground plant growth
Higher winds lead to plants that are smaller, more compact, and with a tougher cuticle.
Wind cools a plant, reduces moisture, and reduces disease by making plants more resistant to mechanical stress, pathogens, and pests
Wind can cause destruction of plants, spread spores, pests, and seeds, and cause salt spray.
Light is majorly important to plant growth
Light can be defined by its itensity (quantity), color (quality), and the length of the dark period (photoperiod).
Light quantity…the amount of light within particular wavelengths
The main source of light for plants is the sun and the highest amount of light is at noon.
Light can be absorbed or reflected off of a leaf; only a small amount is used in photosynthesis
Photon…discrete particle of energy
Light compensation point…where carbon dioxide ficed by photosynthesis is equal to that lost by respiration. At this point a plant maintains tissue but does not grow.
Light saturation point…the point where light is no longer the limiting factor. Varies by species and number of leaves per individual.
Light quality refers to its wavelength
Plants absorb light from the visible spectrum. Chlorophylls, carotenoids, and phycobilin absorb light from specific wavelength
Leaves absorb blue and red light and reflect green light.
Photosynthesis takes place in the chloroplasts.
Light reactions are driven by light energy and occur in the grana.
Photosynthesis required carbon dioxide, water, and light, and yields glucose and oxygen as a waste product.
Stomatal opening is regulate by guard cells and facilitates carbon dioxide entering the leaves as well as water exiting.
Field plants need to be spaced ideally for maturity. This leads to wasted space when plants are young.
As a rule of thumb, bigger plants should be placed in the back or to the north and smaller plants should be in the front or to the south.
Horticultural crops are often pruned for enhanced light interception, particularly for more light to hit the middle of the tree.
Pruning properly allows for more photosynthesis, more sugars, higher yields, and more fruit color.
Ornamental hedges are pruned for aesthetic, but also light capture. Keeping bottoms wider ensures that the tops don’t shade lower leaves.
Etiolation…exaggerated plant stem growth in the absence of light
Etiolatoin results in visible internode elongation and yellow tissues
Etiolation does not occur in monocots, rather leaves just get bigger
Cuttings from etiolated leaves root easier
Blanching…when plants or plant parts are covered to be devoid of light.
Cauliflower heads are covered with leaves to keep the head white in an example of blanching.
Plants can etiolate in response to blanching treatment
An excess of red and far red light can lead to phytochrome responses in plants. This is a light quality issue.
Phytochrome resonses are essentially etiolation, but due to lower quality light rather than lower quality.
This occurs in plants so that they can outcompete surrounding competitors that may be shading them.
Light can stimulate anthocyanin production, making fall leaves more colorful and fruits more red.
Photoperiodism…a plant’s response to daylength where darkness is the critical portion
Day neutral plants…plants that flower across a wide range of day lengths
Some day neutral plants flower more or less in response to day length, called quantitative long or short plants.
Long day plants…plants that flower when nights do not meet a critical length
Short day plants…plants that flower when nights are more than a certain critical length
Alternating day length plants…plants that need short days followed by long days or vice versa
Understanding photoperiodism allows plants to be produced in any hemisphere at any time.
Critical night length aries by species and by cultivar of a species.
Storage organ development can also depend on photoperiodism, such as in onion and garlic, which depend on a long day (short night)
Plants can be very sensitive to light when it comes to photoperiodism, with some being able to be reset by a flashlight.
Many horticultural crops need full sun
Rapidly shifting an individual from shade to sun or vice versa can cause issues with scorching and mortality
A variety of supplemental lighting can be used to improve plant growth
High intensity discharge lamps are very expensive, but can last up to 24,000 hours, be used in windowless warehouses, and increased rose production by 240%
Fluorescent lamps are used in seed germination and tissue culture. They are less intense but can be used to lengthen the day
Incandescent lamps are too hot and have improper wavelengths, so they are primarily used to control the photoperiod
LED lights are expensive, but last longer, use less energy are harder to break, and can be put closer to plants than other light options.
Temperature is the most important factor in plant distribution. It also plays a major role in plant physiology, impacting growth, development, flowering, dormancy, yield, and color.
Hardy plants are less sensitive to temperature.
Tender plants cannot tolerate cold temperatures.
Many horticultural crops are divided into cool season, intermediated season, and warm season.
Most plants can survive from 0 to 50 degrees celsius, but 10 to 30 degrees celsius is optimal.
The USDA breaks the country into zones 1-11 based on annual minimum temperatures. Zones do not factor in maximum or mean temperatures.
Plants can be grown outside of their zones by using protection, placing them in sheltered areas, and burying them with soil and snow.
Soil temperature impacts seed germination, root growth, water uptake, and disease.
Plant roots stop growing when soil temperature is below 41 degrees Fahrenheit.
Sandy soils warm more quickly than clay soils due to differences in water content. Soil temperature is also impacted by air temperature, wind, and solar radiation.
Optimum soil temperature is 59-86 degreed Fahrenheit
Soil temperature can be modified by applying plastic mulch in light or dark colors to achieve the desired effect, altering soil moisture, heating irrigation water, or using heating pads.
Thermoperiodicity…When plants grow better with alternating day and night temperatures
In 1944 it was discovered that tomatoes grow much less when they are constantly at 80 degrees Fahrenheit than when the day was 80 degrees Fahrenheit and the night was 68 degrees Fahrenheit.
Thermoperiodicity is especially important to plant height
Recommendations regarding thermoperiodicity vary based on species, market, and sunny vs. cloudy.
Lilies, poinsettias, and chrysanthemums grow taller if night temperatures are constant and day temperatures are increased, but shorter if the night is increased and the day is constant.
The difference between night and day is DIFF, calculated by subtracting the night temperature from the day temperature.
Growing degree days relate to development and reproduction of plants and insects. They are also known as heat units.
Growing degree days are used for organisms that cannot maintain their own temperature, where their development is predicted by temperature and time.
Growing degree days help people know when to scout for pests or market crops.
Minimum development threshold…minimum temperature at which growth occurs
Maximum development threshold…maximum temperature at which growth occurs
A growing degree day is 24 hours at 1 degree above the minimum development threshold
Biofix date…date at which you being calculations, including seedling emergency, calendar date, first trapping, etc.
Degree days= ((daily maximum temperature + daily minimum
temperature)/2)-minimum threshold temperature
A plant needs a certain number of degree days to exist.
Buds of woody plants go to pre-dormancy in the summer, which is broken if the plant needs more growth. By winter the buds are dormant. If a plant is placed in a greenhouse after this, buds will not grow unless overcome by a chilling period.
There is a minimum number of hours that a temperature must be below a certain threshold for buds to break dormancy.
Chilling period varies by species and cultivar.
Endodormancy…imposed by internal blocks in seeds and buds, regulated by hormones and removed by winter chilling (rest)
Ectodormancy…plants refrain from growing until external conditions are satisfied (quiescence)
Both endodormancy and ectodormancy work together to prevent bud break during the wrong time of year.
We can overcome dormancy by calculating chilling hours and the heat units required for buds to break once chilling hours are reached.
Chilling injury can occur to tropical plants at temperatures as warm at 59 degrees Fahrenheit (non-freezing temperatures).
While tropical plants are susceptible to cold at any time, temperate plants have different tolerances depending on whether they are growing or dormant.
Two main freeze events can threaten plants that grow in temperate regions.
Advective freeze…mass of cold air moved in by strong winds often leading to temperatures below freezing for a full day or more.
It is difficult to protect plants from advective freezes as they are very windy and have long durations.
Radiational cooling…clear nights and calm winds that last a few hours.
Protection
There are multiple ways to protect from radiational cold events as they typically only last a few hours on either side of the sunrise.
Row covers…protection from radiational cooling that can offer 1-3 degrees C of protection. Woven materials protect more than paper or plastic
Torches…a method of protection from cooling events that uses open flames throughout plantings, used widely in European vineyards
Helicopters…can be used to protect crops from cooling by mixing the air
Irrigation may be used to protect plants. Overhead irrigation begins at a very specific time using low volume sprinklers. As the water freezes, it gives off heat that warms plant tissues. Irrigation must continue until the ice is melted. This method is only effective for short periods within a few degrees of freezing.
Sunscald…damage of thin market trees which occurs when temperatures are below freezing, sun hits the bark and raises the temperature, thawing the tissues, and freezing conditions return as soon as the sun is no longer on the tissues. The cells die and the bark splits.
Frost cracking…splitting of turns due to extremely cold temperatures
Very high temperatures can kill plants
High head with direct sunlight can cause sunburn or sunscald.
Rapid changes in temperature can cause injury to plants, sometimes even including cold water falling on leaves.
Temperatures are important to consider when selecting a site, with many factors impacting it such as air, slope, altitude, bodies of water, and latitude.
Frost pockets…low areas where cold air settles
Cool air is more dense than warm air and thus will flow downhill. Fruit orchards are usually planted on slopes to avoid cool air.
Altitude…the elevation of the site
For every 300m increase in altitude, the air temperature can drop by 5 degrees celsius, and higher altitudes have higher thermoperiodicity.
Variables at particular latitudes make prime locations for fruit production.
Large bodies of water can be useful for crop production due to the temperature moderation provided by the heat capacity. Warm water in the fall protects from early frosts, cool water in spring prevents buds bursting before a cold snap, and summer and winter temperatures are much less extreme.
70% of the Earth’s surface is water and many ancient civilizations were built near water.
Water is important for plants so that they can perform photosynthesis. Requirements vary by crop, region, and development state. Herbaceous plants are 80-90% water by weight, woody plants are 50% water by weight, and tomatoes are 95% water.
200 to 1000 grams of water can be needed to produce 1 gram of dry matter.
Water has unique properties that make it even more useful for plants.
High specific heat stabilizes extreme temperatures
Water is a universal solvent, helping transport nutrients, fertilizers, sugars, and hormones
Surface tension
Turgor pressure keeps plants erect
Water in guard cells open stomata
Transpiration…loss of water from a plant as vapor. Loss occurs through stomatal openings
Evapotranspiration…evaporation loss of water from plants and soil influenced by humidity
When soil is saturated, all pores are full of water moving along gravitational potential
When soil is not saturated, water moves by metric potential
Water enters plants through root tips.
Field capacity…when water is only held in small pores, reached when large pores are drained by gravity
Permanent wilting point…the point when water will not longer be able to be absorbed
Incipient wilting…occurs when plants temporarily wilt and then recover without additional water
Water penetration of soil is important in irrigation as runoff is not desired and standing water reduces oxygen to plants
Irrigation…supplemental meeting of water needs of a crop
There are many different ways to irrigate plants
Hand watering is simple and low cost, but has variable success and requires a lot of labor.
Furrow irrigation…irrigation where ditches are placed between crop rows and gates are open to release water
Requires ground to have slope, not suitable for well draining soils, and does not wet foliage
Flood irrigation…irrigation that covers most of a field
Most inefficient form of irrigation
High volume irrigation
Overhead irrigation using sprinklers
Circular pivot sprays in a circular pattern
Lateral system walks through a field
Common in fields as good airflow is needed if it is used in a greenhouse
Wind can distort patterns
Evaporation loss is high, equipment is expensive, and salt can build up in soils
Low volume irrigation
Trickle or drip systems
Conserves water, limits weeds, reduces disease issues, more uniform, and fertilizers can be added
Clogging can be problematic, coyotes may destroy systems, and they are expensive
Subirrigation…applying water below the root zone
Floor flood
Plants are on a floor or bench and flooded for 15 minutes at a time
Efficient for water and fertilizer, low labor and cost
Pathogens become problematic very quickly
Open irrigation system…water is not reused
Closed irrigation system…water is recycled repeatedly
Nursery crops mostly involve the sale of woody ornamental plants in one of the fastest growing segments of agriculture
In the USA there are both wholesale and retail nurseries
Wholesale nurseries have fewer crops on a larger scale and sell to other nurseries whereas retail nurseries often sell these plants.
Product mix…type of plants to be grown
Container production and field production are used, but the trend is leaning towards container stock.
Less labor required
More control
High density of crop
Quicker recovery
More marketable
Plants are grown in pots
Very valuable in the market
Pots need to last a long time
Ground needs to be level
Issues with root binding
Pots are expensive
Roots are not are protected in the winter
Plants should be grouped together or border pots can be placed
Alternatively, pots can be buried in the ground
Fields need tilled before planting
Cover crops may be used to make soil more fertile
Plants must be spaced for maximum size because they cannot be moved
Space for equipment must be considered as well
Plants may be sold “balled and burlapped” with a ball of soil dug up and wrapped or bare root, which risks transplant shock
Greenhouses may be used to control the environment
Cold frames have no heat
Shadehouses only protect from the elements
The first use of flowers is documented in 2800 B.C.E. Egypt
Flower petals are used during ceremonies in Greece in 600 B.C.E.
Flowers are used in India, China, and Japan for religious ceremonies
In the 1920s corsages began to be used
Flowers are detached and used in arrangements
Cut flowers have very short lifespans
Both woody and herbaceous plants are used
Vase life…how long a cut flower will last
There are different stages or development that are optimal for harvesting in different plants and all species have their own vase life
Once cut one should minimize a flower’s exposure to heat and ethylene and should recut stems and place in warm, high quality water
Interiorscaping…ornamental plants for functional and aesthetic purposes
Interior plants filter the air, reduce noise, and look nice.
Lighting is key in interiorscaping.