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8/8/2019 Seedling Establishment
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Seed germination andseedling establishment
Objectives of today·s lecture
Learn about horticultural practices that are
used to promote seed germination andseedling growth
Prenatal and postpartum care of plants
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Seed germination and seedlingestablishment
2 major uses of seeds inagriculture
Plant part that is harvestedfor food, either directly or after processing
Used for propagating plants a $23 billion market for seeds
worldwide
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Why are seeds used for plant propagation?
Advantages
relatively inexpensive
many seeds produced from a singleplant
convenient for storage
naturally dormant in many cases long shelf life
disease free propagation
few pathogens carried by seeds
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Why are seeds used for plant propagation?
Disadvantages
Genetic segregation of traits - plants grown
from seed may not be genetically identical tothe parent plant; examples include:
Seed produced from plants that are self-
incompatible, e.g. apples Seed produced from F1 hybrids, e.g. onions, sweetcorn
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Why are seeds used for plant propagation?
Disadvantages
Time to maturity
Apple trees grown from seed may grow for 10years before bearing fruit
Potatoes grown from seed take 2 years to produce
tubers
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Important criteria for seeds used in propagation
Viability and vigor
percent seed germination
rate of germination
rate of seedling growth
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Important criteria for seeds used in propagation
For most horticultural crops viability and vigor are maintained when seed are stored at:
low temperatures
low humidity
Note that these are the opposite of the
conditions that promote germination
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Long term storage of seeds
Seeds of many species are kept under refrigeration for long term storage
National Seed Storage Lab in Colorado
repository for many species
important for preservation of germplasm, a gene
bank stored in liquid nitrogen
seed are regrown every few years
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Seed quality
Seed quality is important in commercial sales
Federal and state regulations
Indiana requires all seed to be tested (by the StateChemist·s Office) and labeled
percent pure seed
percent weed seed
percent germination date of testing
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Conditions for seedgermination
Successful seed germination requires
Viable, vigorous seed
Adequate moisture
Supply of oxygen
Appropriate temperature
Protection from pathogens and pests
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Seed dormancy
Some seed will NOT germinate under standardconditions; seed are dormant
require specific treatments (temperature, abrasion,light) to break seed dormancy and before seed willgerminate
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Breaking seed dormancy
Stratification
Scarification
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Methods of seeding
Direct seeding
Seeds are planted where the plants will
grow to maturity or harvest Convenient to use
Adaptable to mechanization
Not well suited for very small seed Obtaining a good stand of plants requires
soil preparation
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Methods of seeding
Indirect seeding Two stage process with seeds germinated in a
nursery before being transplanted to field Ensures good stand establishment
Crop matures earlier
Increased costs More difficult to mechanize
Higher level of crop management
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Conditions for seedgermination
Successful seed germination requires
Viable, vigorous seed
Adequate moisture
Supply of oxygen
Appropriate temperature
Protection from pathogens and pests
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Moisture is required for seed germination
Seed survive at very low moisture
Germination starts with imbibition,uptake of
water into the seed Once seed are imbibed and development is
initiated, the seedling is very sensitive todehydration
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Moisture for germination
Maintaining an adequate supply of water is essentialfor good germination
In greenhouse (indirect seeding) thorough watering after seeding
monitoring of soil moisture and regular watering or
misting using plastic wrap to retain water
Beware! Many pathogens thrive under high humidity
conditions
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Moisture for germination
Direct seeding
preparation of seed bed
good contact between soil particles and seedsfacilitates uptake of water into seed
planting at appropriate depth
deep enough so the soil doesn·t dry out shallow enough that the seed will emerge before its
reserves are exhausted
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Oxygen is readily available if seed isplanted in a well drained, porous medium
- soil or greenhouse mix
Oxygen deprivation results fromwaterlogging, flooding or other soil
drainage problems
Germination requires oxygen
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Temperature
Requirement varies betweenspecies
Temperature can be adjusted ingreenhouse
use of ´bottom heatµ
In the field, planting depends onenvironmental conditions andweather, not necessarily thecalendar
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Protection from pathogens
Developing seedlings are a rich source of food for microbes
Seedlings are relatively unprotected cuticle and other defenses are not fully
developed in young seedlings
Many fungal pathogens cause ´dampingoffµ of seedlings
Phytophthora, Pythium, Rhizoctonia
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Protection from pathogens
Preventive measures include:
soil pasteurization (180ÜF, 30 min)
using purchased sterilized soil mix
clean containers
controlling moisture
using clean seed
use of fungicides, seed treatments
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Seed coatings
Seeds can be coated with a variety of
compounds to enhance germination and
seedling growth Fertilizer - to stimulate growth
Insecticide - to prevent insect damage
Fungicide - to inhibit growth of fungalpathogens
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Specialized seeding methods
Hydroseeding
Spray application of primed seed in a mix
containing mulch and fertilizer
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Other seeding methods
Liquid drilling
Seeds are germinated under controlled conditions,
until the radicle emerges Germinated seeds are mixed into a gel that contains
fertilizer
Mixture is sown in prepared field
Pre-germinated seed promotes rapid growth of seedling
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Conclusions
Seeds are living organisms, handle with care
Successful establishment of seedlings requires
a rapid transition from dry seed to autotrophicplant
A variety of horticultural practices are used to
promote seedling establishment