Name: Rick M.
I may not be a student K-12, but I am the parent of two
who are. Now that we have had our first frost here in Alaska, the kids
and I have been watching our home-grown tomatoes ripen on the kitchen
window sill. As we observe, the following questions came to mind (a
literature search got us nowhere):
What is the adaptive advantage for fruit to turn color as they ripen?
Specifically, why do tomatoes turn from a nice native green to a bright
red (or yellow)? Presumably this change must create some reproductive
advantage. How does the color (or change in color) contribute to the
successful germination of the seeds inside the fruit? Is it a necessary
change in chemistry of the surrounding meat required to nourish the seeds?
Or does the bright contrasting color attract a symbiotic host (eg. bear)
to transport the seeds away from the parent plant? Generally, is there
always a functional/reproductive/adaptive reason why fruit changes color
as they ripen?
The changes in color as a fruit ripens is considered to be a signal to
potential eaters of the fruit that it is ripe. This is important for
plants that rely on their fruit being eaten and the seeds transported by
the predator to a different place. Often a developing fruit will be
toxic to stop predators from eating fruit with undeveloped seeds.
Dr. Jim Tokuhisa
Think about how fruits usually are hard and bitter or sour when the AREN'T
ripe. Any animal who eats a fruit that is unripe learns not to eat them
again. When a fruit's seeds are ready for germination, they need to be dispersed
away from the parent plant. A color change could signal animals that the
fruit is ready to be eaten, which will help in dispersion.
The bright colors of mature fruits attract animals that eat the fruits, and
disperse the seeds
Anthony Brach Ph.D.
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Update: June 2012