embryo growth and development Flashcards
(35 cards)
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
