Another student asked me a similar question
recently about the color of light. Maybe you are
in the same class. As you know, the phenotype is
what the plant is like. For example, is it tall,
does it have a lot of leaves, what is its shape,
and what color is it?
More intense light—which is another way of saying
more light—provides more energy for
photosynthesis. More photosynthesis means more
building of molecules that the plant is made
of—more growth and a bigger plant. Of course,
there’s a limit where too much light is a problem
high-energy light can actually damage the
chlorophyll, which is the pigment that plants use
to do photosynthesis.
Another problem is that with light, you get
heat. This usually means that the plant will dry
out too fast. To protect itself from drying out,
the leaves will close their tiny holes (stomata or
stomates). Unfortunately, this also means that
they can’t get rid of the oxygen that they produce
as a waste in photosynthesis. They also can’t
bring in the carbon dioxide that they need for
Can you just water the plant more? That will
help if the light isn’t too intense.
Photosynthesis only works because there are
many enzymes that speed up all of the chemical
reactions. If the temperature gets too high,
these enzymes can be destroyed. Then the plant
will probably die.
You can test your ideas about plants for yourself
by putting plants at different distances from a
light source. According to the inverse-square
law, the plants that are 10 cm away from the bulb
will get four times the energy of the plants 20 cm
away. Put soil in small cups and put 2 or 3 seeds
in each. Be sure to design a good experiment.
Have at least a few cups at each distance. Make
sure that the cups are alike in every other way
(don’t have some closer to the heater or the
window, for example). Make careful measurements
and write everything down.
If you are interested in questions like these,
you may be interested in a career in botany or
Thanks for asking,
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