seeds Flashcards
what is the dormancy cycle of a seed
- Starts at primary dormancy. As the seed is actively growing one or more dormancy mechanisms may be initiated within the seed and take effect to stop the seed germinating on the parent plant
- Quiescence is the second stage and is a gradual release from primary dormancy. It’s a non-dormant state where growth is not occurring simply because one or more of the basic environmental factors are absent. The seed will germinate if water, oxygen, and suitable temperature are present.
- secondary dormancy is induced in seeds by environmental factors other than those experienced on the mother plant.
what is and apart of imposed dormancy
the seed is dormant because of some constraint imposed on the embryo by the tissue around it
- hardseededness. The coat is impermeable to water, will only become permeable to water if seed coat is scratched
- after ripening. seeds that don’t require environmental stimuli to break dormancy but a period of storage to complete development.
what is and involved in true dormancy
dormancy is a function of the embryo. a specific environmental stimulus is needed for germination the two types are
light
or temperature is also known as stratification requirement
what is the role of phytochrome in seeds
phytochrome exists in two forms
it causes a series of events that result in dormancy breaking
Pr and Pfr go round in circles
what are the dormancy mechanisms
Imposed dormancy is the inhibition of germination due to factors outside the embryo
true dormancy situation where embryo itself is metabolically incapable
what is after ripening
seeds require a period of storage before germination rather than any environmental factor.
what is a germination inhibitor
chemical or other inhibitors within the embryo the inhibit germination
what is impermeability to oxygen
a seed coat can be impermeable to gasses such as oxygen
usually due to a chemical inhibitor
what is physical constraint of embryo growth
The seed coat or surrounding tissues may also prevent germination by physically constraining the growing embryo
what is Primary dormancy
the sum effect of dormancy mechanisms established in the mature seed during development on the plant
what is quiescence
gradual release from primary dormancy. It’s a non-dormant state where growth is not occurring simply because one or more of the basic environmental factors are absent. The seed will germinate if water, oxygen, and suitable temperature are present.
what is relative dormancy
Dormancy relative to the dormancy mechanisims experienced
what is secoundary dormancy
dormancy induced by environmental factors
what is stratification
seeds that require exposure to low temperatures to break dormancy
what is temporal dispersal
provides means of preventing germination until after winter has past
what is the seed bank
the sum total of all viable seed is called the seed bank
what is seed pelleting
Palleting alters the shape of the seed. it can add volume and increase precision
what is film coating
pesticide or beneficial organism is added as a thin polymer-coating.
coating doesn’t rub off
seed coating should deliver any of the required
pesticides,
mineral nutrients
plant growth regulators
beneficial microorganisms
what is encrusted coating
doesn’t obscure shape of seed contains micronutrients, fungicides, and insecticides
what does Trichoderma spp do
help control disease when added to a seed coat
helps with damping off
what are the types of seed coating available
encrusting
palleting
film coating
what is the key factor that distinguishes a palleted seed from a seed that is film-coated
film-coated keeps the shape of the original seed
the palleted seed will be round and uniform
why chose palleted seed rather than film coat it
facilitate precision sowing of seeds
protection of seed
what are biocontrol agents and how do they relate to seed coating
seed treatment used to control pests
includes fungal strains such as Trichoderma which helps with damping off
why is production location important for a seed crop
the choice of production ares is dependant on climate, vernalisation and photoperiod requirements.
a crop may have specific requirements, vernalisation or day length (photoperiod)
a seed producer can manipulate the production system through sowing dates and can have flowering and seed filling at the most favourable time of year
important factors of field selection and preparation
cropping history is important
the area must be clean from weed seeds
and distance from other crops
field prep should remove weed species by chems or tillage
deficiencies in soil need to be remedied
important factors of seed and variety selection
seed should be of high quality so establishment is good
demand selects variety however where possible grow varieties that have an advantage for production in that area
important factors of sowing and establishment
date sowing as early as possible
sown direct or transplant may need staggered planting for m/f
plant density: need air movement to reduce disease and flower development
important factors of irrigation
avoid moisture stress during establishment and early seed development
dry is needed when the crop is maturing
important factors of pollination for vege seed production
pollinators required
reduce cross-pollination via isolation distance
cages to keep wind but stop insects
remove weeds that can cross-pollinate
problems with weeds in seed production
compete with seed crop for water, light and nutrients
interfere with cultivation and harvesting
may harbour pests and diseases
may produce seed that is similar to size and shape to crop seed.
important factors of disease control in seed production
low relative humidity
away from fresh market production
crop-rotation
foliar sprays
important factors of insect control when producing crops
insecticides if needed
important factors for harvest in seed crops
harvest at right time to early, immature seed too high moisture = lower storage capabilities and quality
delayed harvest can lose yield to crops which disperse their seeds and or birds
avoid contaminating seed lot
important factors of cleaning and storage with seed prod
cleaned to remove contaminants
some seeds need to have appendages
should not be used as a substitute for good seed production
stored at conditions to maintain seed quality and keep dormancy
important factors with quality assessment when producing seed crop
the final step is to verify seed has met quality standards
done my seed lab
what are the key steps that have potential for limiting yield or quality in a seed crop
- production site selection
- establishing the crop
- getting the crop to flower
- getting seed set
- getting the seed from fertilisation to harvest
- harvesting, processing and storing
