seed germination Flashcards
is the process of seeds developing into new plants.
germination
must trigger the seed to grow. Usually, this is determined by how deep the seed is planted, water availability, and temperature.
environmental conditions
The uptake of water by dry seed is called
imbibition
is the process by which cells irreversibly stop
dividing and enter a state of permanent growth arrest without undergoing cell death.
Senescence
can be induced by unrepaired DNA damage or other cellular stresses.
senescence
hormone that accelerate senescence
aba and ethylene
hormone retard senescence
auxin and cytokinin
nitrogen increases senescence
nitrogen deficiency
nitrogen retards senescence
nitrogen supply
accelerates senescence
high temp
retards senescence
low temp
is rapid in dark than in light
senescence
Water stress leads to accumulation of ABA leading to
senescence
Senescence is controlled by plants own genetic programme and death of the plant or plant part consequent to senescence is called
programmed cell death
The nutrients and other substrates from senescing cells and tissues are remobilized and reallocated to other parts of the plant that survives.
programmed cell death
The protoplasts of developing xylem vessels and tracheids die and disappear at maturity to make them functionally efficient to conduct water for transport.
programmed cell death
is a physiological process of shedding of organs like leaves, flowers, fruits and seeds from the parent plant body.
abscission
• When these parts are removed the plant seals off its vascular system to prevent loss of water and nutrients.
• Final stage of senescence
abscission
retard abscission
auxin and cytokinin
induce abscission
aba and ethylene
separates dead parts of the plant, like old leaves and ripe fruits.
• 2.It helps in dispersal of fruits and continuing the life cycle of the plant.
• 3. BLANK of leaves in deciduous plants helps in water conservation during summer.
• 4. In lower plants, shedding of vegetative parts like gemmae or plantlets help in vegetative reproduction.
abscission
occurs in annuals where whole of the plant is affected and dies
overall senescence
this is represented by perennial herbs where senescence occurs only in the above ground parts, the root system and underground system remaining viable
top senescence
less drastic and takes place in woody deciduous plants.
occurs in all the leaves simultaneously but the bulk of the stem and root remins alive
deciduous senescence
characterized by gradual progression of senescence and death of leaves from the base upwards as the plant grows.
the senescence of the entire plant after a single reproductive cycle is also known as monocarpic senescence
progressive senescence