Techniques of Seed Propagation
Cards (27)
- dormancy: a condition in which seeds will not germinate even when the environmental conditions are permissive for germination
- advantages of dormancy:
- allows storage, transport, and handling of seed
- seedling survival
- creates a "seed bank"
- seed dispersal
- quiescent seeds: no dormancy
- primary dormancy: a condition that exists in the seed as it is shed from the plant
- secondary germination: induced under unfavorable environmental conditions
- primary dormancy
- exogenous
- endogenous
- combinational
- secondary dormancy
- thermodormancy
- conditional
- exogenous dormancy: imposed by factors outside the embryo
- exogenous dormancy
- physical
- impermeable seed coat
- inhibits water uptake, physical restriction on embryo expansion or radicle emergence, inhibition of gaseous exchange
- scarification
- chemical
- inhibitors in seed coverings
- fleshy fruits
- removal of seed covering
- scarification: any treatment that weakens or removes the seed coat
- endogenous dormancy: imposed by factors within the embryo
- stratification: imbibed seeds are subjected to a period of warm or chilling temperatures to alleviate dormancy conditions to stimulate natural conditions that seed must experience before germination
- photodormancy: seeds require either light or dark conditions to germinate
- light sensitivity involves a photochemically reactive pigment "phytochrome"
- endogenous dormancy
- physiological
- factors within embryo inhibit germination
- non-deep
- embryo growth potential inadequate to escape seed covering, short periods of moist chilling or dry storage after ripening, can be light sensitive
- intermediate
- embryo growth potential inadequate to escape seed covering, embryo will germinate if separated from seed coat, moderate periods of chilling
- deep
- embryo will not germinate when removed from seed coat or will form a physiological dwarf, long period of chilling
- endogenous dormancy
- morphological
- the embryo is not fully developed at the time seed sheds from plant, warm or cold stratification
- endogenous dormancy
- morphophysiological
- combination of an underdeveloped embryo and physiological dormancy, cycles warm and cold stratification
- combinational dormancy: combinations of exogenous and endogenous dormancy conditions
- thermodormancy
- high temperatures induce dormancy
- once exposed to high temperatures, will not germinate when temperatures return to optimal germination range
- growth regulators, cold stratification
- conditional dormancy
- change in ability to germinate related to time of the year
- chilling stratification
- techniques of propagation by seed
- field seeding
- field nursery production
- nursery production under controlled conditions
- field seeding
- in the location where the plant is to remain during production cycle
- common method for agronomic, lawn grasses, forestry, and vegetable crops
- less expensive
- can grow continuously without delay in growth
- factors to maximize seeding success
- good site selection and seed bed preparation
- high quality seed
- plant at correct time
- seed treatments to facilitate sowing or to relieve dormancy
- select appropriate mechanical seeder
- use correct sowing depth
- sow seed at appropriate rate
- proper post-sowing care
- low sowing rate: high quality seeds that produce high germination percentages, vigorous, uniform, healthy seedlings
- field nurseries for transplant production
- outdoor nurseries
- produce seeliseedlingsngs at closer spacing
- less expensive than producing seedlings in a greenhouse
- advantages of plug production
- optimization of the number of plants produced per unit of GH space
- allows growers to invest in equipment to control environmental conditions
- fast production
- permits accurate crop scheduling
- easier to ship
- easier transplanting
- plug growth stages:
- sowing to germination
- germination to full cotyledon spread and root system establishment
- seedling plug growth
- seedling plug getting ready to transplant or ship