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Which environmental conditions most influence the success of seed…
Which
environmental condition
s most
influence
the
success
of
seed germination
?
Seed Germination
How does seed germination work?
The process is a folllows.
The seed coat, or testa, breaks and the first root, or the radicle, grows into the ground to extract nutrients and minerals
The cotyledon emerges and produces the growing shoot’s first leaves
The growing plant then can be divided into the embryonic shoot (epicotyl), the embryonic stem (hypocotyl) and the developing roots
What types of seeds are there?
Monocots
Seeds with 1 cotyledon
Flowers that part in 3s
Leaves that have parallel primary veins
Eg. corn, grasses, orchids, wheat and palms
Dicots
Seeds with 2 cotyledons
Flowers that part in 4s or 5s
Leaves with a distinct vein network
Eg. magnolias, roses and daisies
Environmental Factors that affect seed germination
Specific - some seeds
Fire/smoke
some seeds only sprout after exposure to intense heat or to smoke
Digestion
some seeds require prior animal digestion to erode the seed coat so they are able to sprout
Freezing
some seeds only sprout after periods of intense cold
Washing
some seeds may be covered by inhibitors and will only sprout after their removal
Scarification
some seeds are more likely to germinate if the seed coat is weakened from physical damage
Standard - all seeds
Oxygen
Needed for respiration to create ATP
ATP is needed for the seed to develop
Without oxygen, seeds fail to germinate because they cannot create energy meaning they cannot sprout
Water
needed to metabolically activate the seed
without it the seed can't germinate
Temperature
Seeds require certain temperature conditions to sprout
The temperature determines how well the enzymes function
Seeds won't germinate until they have their needed temperature
Light
Seeds require light to 'tell them' when to germinate. Light will indicate they are close enough to the surface to emerge and photosynthesize
Though seeds don't require light to sprout, if they sprout without it they will quickly become weak, pale and stretched out.
Soil's pH level
In order for the seed's enzymes to function optimally, they require a suitable soil pH leve to sprout
If the seed doesn't have a suitable pH level the resulting seedling often suffers from stunted growth or nutrient deficiencies
Seed Age
Fresh (younger) seeds almost always germinate better, they sprout faster and produce more successful seedlings as well as creating stronger plants
If seeds are older, they struggle to germinate because as they age they naturally deteriorate. This means old seeds generally experience delayed germination and produce weaker plants. They also have a lower success rate.
What factors can't be controlled by us?
Oxygen levels in the lab
Whether the seeds we use have been digested by animals
What's does successful seed germination look like?
Visual Success
The seed will swell due the intake of water and oxygen
The seed coat will split
The first sign of growth (success) is the first root (the radicle) emerging
Following the emerging of the root, the first shoot will emerge
Depending on the plant, the first leaves (cotyledons) will grow too
Method Dependent
If in soil, success is visible when there is a healthy, green, upright seedling peeking through the soil surface
If in a paper towel, success is visible when there are swollen seeds with small root tails
Unsuccessful/unhealthy sprouting
Pale, thin and tall stretching seedlings - they are stretching to try and reach the light
Sprout emerges but shrivels, bends or rots
Stunted growth or deformed leaves
How do these factors influence germination?
Seed germination relies entirely on water, oxygen, and temperature, with other factors supporting this process
Without some of these factors, the seeds cannot germinate
Environmental factors dictate whether a seed breaks dormancy and sprouts
The factors have to have a perfect balance to help germination
Examples:
Temperature - if the temperature is too low, germination is delayed or halted, if the temperature is too high it can cause it to become dormant again or kill it
Oxygen - compacted or waterlogged soil prevents oxygen from reaching the seed, stopping the germination process
Light - some seeds need light to germinate, other's don't while some neither do or do not
Water - with not enough water, the seeds stay dormant. with too much water, the seeds cannot get oxygen, resulting in it rotting or choking.
What is seed germination?
The process that dormant seeds go through to “wake up” as they begin to grow into a new plant. This process is triggered by specific environmental factors and ends when the first leaves emerge, and the plant begins to create its own energy.