germination Flashcards
what happens to a plant during senescence
the plant naturally deteriorates and dies
what is a zygote
the beginning of a new plant formed by the fertilization of the ovule by the pollen
what is germination
the sequence of events which begins with the absorption of water and leads to the growth and development of the seedling
what is needed for germination
suitable moisture
suitable temperature
adequate oxygen
the first step of germination is the absorption of water what is this process called
imbibition
what effects does water have on a seed
- causes the seed to swell and may cause the seed coat (testa) to rupture
- activates enzymes
what do the enzymes do
- breaks down stored food
- increases respiration
- activates cell division at the meristem
- breakdown stored food in simpler compounds which are transported and used for growth
what hormone does the embryo produce
gibberellin
what does gibberellin do
it triggers the enzymes in the lurome layer (layer of cells around the endosperm)
what what does alpha-amylase do
it is in the aleurone layer and it covers starch to sugar that is used by the embryo for growth
what two factors influence water imbibition
soil firmness
soil water
how does soil firmness contribute to germination
if the soil is firm the moisture will be able to be in close contact with the seed and easier for the seed to take up
if there are large pockets of air the soil moisture will evaporate into the air and be lost to the atmosphere instead of being taken up by the seed
how does soil water content affect germination
too much of too little water will inhibit germination
too little water germination may begin but not complete
waterlogged soils have insufficient O2 for germination
what does the rate of imbibition depend on
- composition of the seed ( proteins absorb more water than starch therefore the embryo absorbs more than the endosperm)
- seed coat (testa) some seeds have coats that are initially impermeable to water
