Give two reasons why plant hormones may be released

During times of stress such as dryness and lack of water(ABA is released which causes the stomata to close)

During seed germination(mainly gibberellins)

During phototropism and geotropism(auxins)

Hope this helps:))

substitution is the answer in this case

the circled areas are referred to   as sunspots.   the sunspots are cooler than the   surrounding area.

sunspots are temporary phenomena on the photosphere of the sun that appear visibly as dark spots compared to surrounding regions. they correspond to concentrations of magnetic field flux that inhibit convection and result in reduced surface temperature compared to the surrounding photosphere.