Communicating With Plants
Photobiology in Plants
Plants depend on many environmental factors for survival. A plant's survival
is, among other things, directly dependent upon light. In addition to using
light for photosynthesis, plants determine information about their surroundings
by the quantity and color of light that they receive.
How does a plant "know" what season it is?
Plants know what season it is according to the day length. They have a
chemical called phytochrome that helps them measure the periods of light
and darkness. Plants know when to flower and when to produce fruit according
to the length of day. Some plants, such as clover plants, attempt to survive
the winters and some do not. In order to survive the cold winter, clover
plants store their energy in their roots instead of trying to grow taller
and produce leaves. As the days get shorter in length, the clover plant
will begin to store energy in the root to be used for early shoot growth
the following spring. In this way, the amount of light they receive in
a day tells them what they need to be doing to survive.
How does a plant "know" there are other plants around?
Plants compete with one another for light, so they need to know when other
plants are around them. Although plants do not have eyes, they are able
to sense that other plants are nearby. They do this through the light that
they receive. When light hits the plant's leaves, some of the light is
absorbed and some of it is reflected. The reflected light is different
and is sensed by the other plants. As the light is sensed by the neighboring
plants, they begin to try to outgrow each other.
How does a seed "know" when to germinate?
In order for a seed to sprout, there are certain environmental conditions
that have to be right. Two factors that are very important for seed germination
are proper temperature and water. For some very small seeds, light is a
requirement for germination. By germinating only when there is light present,
the seed is ensuring that it is near the surface of the soil. This is important
for smaller seeds because they lack the energy that larger seeds have to
push through a deep layer of soil.
These are a few examples of how light regulates the behavior and actions
of plants in their different environments. In a sense, plants "know" what
is going on around them. Humans can communicate with plants through light.
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