embryo growth and development Flashcards
what are the first two things to emerge
radicle(first) and the plumule
what makes up the embryo of a seed
the plumule and radicle
what does the radicle grow into
the root system
what is the plumule protected by
a structure called the coleoptile
what is epigeal germination
above ground germination
what is hypogeal germination
below ground germination
what is the epicotyl
the stem above the cotyledons
in hypogeal germination what does the epicotyl do
pulls the plumule out of the soil
what conditions promote good germination
- seed viability
- seedling depth
- seedling vigour (do seeds have enough strength to grow to a healthy plant)
generally, it’s safer to plant ___ seeds deeper then ____
larger, smaller
what is successful germination dependent on
weather or not the seedling can become self-sustaining before the food in the seed is used up
what does dormancy in seeds mean
seeds are viable but fail to germinate when conditions are favorable
a period in which a plant does not grow, awaiting necessary environmental conditions such as temperature, moisture, nutrient availability
what are some benefits of dormancy
survival mechanism which prevents germination until favorable times
also allows for staggered germination
what are the two types of dormancy
exogenous
endogenous
combination of both is called double dormancy
what is exogenous dormancy
dormancy due to physical restraints. germination is prevented due to physical, mechanical, or seed coat dormancy. the hard seed coat prevents the entry of oxygen or water for germination to begin
how is exogenous dormancy overcome
weathering of the seed or passing through an animal’s digestive tract or microorganism action is needed
scarification
heat treatment
deprivation of oxygen
what is scarification
is mechanical scratching or rupturing of the seed coat to enables germination
what seed family often needs to be scarified
the legume family as often have very hard seeds
what are some other terms for endogenous dormancy
embryonic or physiological dormancy
what are some strategies used to overcome endogenous dormancy
stratification,
chemical block
what is stratification
many seeds won’t germinate until they have been exposed to (weeks-months) to cool temperatures with oxygen and moisture present
how is stratification used as a survival mechanism
prevents seeds from being germinated in the fall when they may be killed over the winter. it forces them to wait till spring when conditions are good
what is chemical blocks in germination
some seeds contain chemicals that prevent germination.
chemicals may include salt, cyanide, or ammonia releasing compounds
how are chemical blocks overcome
with adequate moisture, the chemicals will leach out of the seed and allow for germination.
this will ensure that seeds will begin germination when there is an adequate amount of moisture to support growing
do our cultivated crops still have dormancy
no many of our crops have lost their dormancy or been selected against them
why is no dormancy in cultivated crops beneficial
dormancy can interfere with the production of the crop or the further use of the seed. it allows for rapid even germination.
what is viability in a seed
the ability to germanate if suitable conditions are present
what is longevity
the length of time a seed can remain dormant and still be viable
what factors depends on the longevity
plant species
growing conditions
storage conditions
what is the longevity of wheat
6 to 32 years
what is the longevity of barley
2 to 10 years
what is the longevity of oats
6 to 29 years
what is the longevity of wild mustard
up to 60 years
what is the longevity of vegetable seeds
1 to 5 years
what are some factors the contribute to a lower longevity
immature sees
low food reserves in food
diseased
physically damaged
