What Makes Plants Grow?
What makes plants grow? Several people have puzzled over this question.
There is no one single answer to this. Several factors contribute: Tropisms,
environment, hormones, biological clocks, and even humans. We are trying to
determine the effects of music on plants. It takes all these combined to have a
plant that actually grows and a plant that is healthy and happy in its
habitat.
Hormones
Hormones contribute greatly to the growth of
plants. Hormones such as auxins, gibberellins, cytokinins, and inhibitors make
plants start growing through stimulation, have protein synthesis, maintain
growth, and also inhibit plant growth, respectively. Hormones, very simply,
control the plant’s instincts to grow.
Auxins accumulate in certain parts
of the plant, for example the
(1)
stems grow toward the light. Auxins also
make roots grow and make the veins in leaves grow. Tropisms, which are discussed
later, in conjunction with auxins, make the plant grow in the proper
direction.
Gibberellins are the leaves and roots that form in the baby
plant seed. Gibberellins are also responsible for protein synthesis, which is
the building of protein for basic life purposes. Gibberellins are used
commercially to promote flowering and fruit development because of their growth
stimulation.
Cytokinins are a group of natural plant chemicals found in
endosperms, the nutritive tissue of embryonic seeds, and in the development of
fruit. The cytokinin zeatin, in conjunction with auxins, stimulates cell
division, particularly for shoot growth. Cytokinins also maintain cell growth,
differentiation, and division.
Inhibitors are hormones that inhibit plant
growth. Some inhibitors make the plant leaves fall off in the Autumn. Other
inhibitors prevent the formation of buds in cold seasons. Ethylene makes fruit
ripen which inhibits certain plants from maturing fully.
The
Environment
All plants need a fitting place to call home. This place is
called its environment. Everyone knows that plants need suitable climate, water,
and sunlight for photosynthesis in their environment.
In certain
plants, shade is needed for proper growth but some light
(2)
is still
needed. The length of the periods of light a plant receives also affects its
growth and flourishment. Photosynthesis occurs using the suns energy to create
the plants own energy. Long-day plants blossom only during the long periods of
sunlight. Short-day plants bloom when the dark period is long. There are other
types called day-neutral which are not affected by the duration of
light.
All plants need different amounts of water. Some plants need lots
of water, like the and when they grow in the wild they grow in the tropical
regions of the Earth where there is an abundance of rain water. Plants like the
Cacti grow only in the desert regions of the Earth where there is little rain.
The pathos ivy requires only a medium amount of water.
The other factor
is the climate. Again, the cacti needs a warm climate like the desert. The
evergreen plant like firs normally grow in the tiaga regions of the Earth. The
pathos ivy grows in temperate regions of the Earth. Climate is an important
factor when determining plant growth.
Tropisms
In botany the
orientation or directed movement of plants in response to an external stimulus
is called a tropism. Tropisms are classified according to the nature of the
stimulus: a response to light is called phototropism; a response to gravity is
called a gravitropism which used to be called a geotropism.
A
phototropism is a response to light so there must be a pigment
(3)
present
to absorb the light. The effective light is normally from the blue region of the
spectrum. The significance of phototropism to the plant is to assist in making
the plant grow toward the light that it requires.
Growth movements in
response to gravity are called gravitropism. Roots are gravitropic, growing in
the direction of the Earth's gravitational field. Primary roots are more
positively gravitropic than secondary roots. Shoots are negatively gravitropic,
growing away from the gravitational field.
Gravitropisms are caused by
different auxin concentrations, with more auxins collecting on the lower side of
the shoots or roots. How higher concentrations on the lower sides of both shoots
and roots produce opposite effects are not clear.
Biological
Clocks
Biological clocks, physiological systems that enables organisms to
live in harmony with the rhythms of nature, trigger certain cells and hormones
that are crucial in the growth and development if plants. These clocks aren't
perfect though they are necessary to all plants. Biological clocks help plants
to maintain a steady and constant growth progression.
Biological clocks
can exist in different parts of the cell in countless cells. This means
different parts of the plant can grow and blossom at different rates instead of
at the same time. For instance, a flowering plant, a sunflower, might grow to be
very tall. If its blossom grew at the
(4)
same rate it would be
gargantuanly enormous.
When outside factors inter in to this equation
things start to happen. For example, a flash of light signifies dawn for some
plants like the morning glory. This makes the flower blossom. The problem is
that any flash of light might trigger this, possibly a headlight or a strand of
Christmas lights. If this happens the flower could be
injured.
Humans
Humans have affected plants in very good ways. We
have affected plants by breeding them as food sources. Human intervention isn’t
necessarily a good thing. It can affect plants in certain ways that aren't
beneficial to the plant.
Take wheat for example early humans cultivated
it for food sources. They didn’t know what they did but they domesticated the
first plants. There was plenty of food for all humans and then some. This
created a running food source for later humans.
The human relationship to
plants is now almost reversed. Human intervention is still helpful and
beneficial. The problem is there is a much greater demand for food and so humans
have been forced to use fertilizers and other possibly harmful product on
plants. Some plants are now dependent on certain fertilizers to sustain proper
growth. Humans are not helping plants as much as we are hindering
them.
(5)
Music
Does music affect plant growth? That is what
our experimental design is supposed to do (see p 8). We know music affects
humans in different ways. Even certain types of music evoke different
actions.
Ever noticed that at Kroger the music is always 60’s and 70’s
hits. This triggers the Kroger target buyers, 30-60 year old persons, memories
and makes them slow down to enjoy the music. This in turn makes the shopper walk
slower and purchase more.
When two people that are the same age, sex,
weight, ect. and they listen to different music they are act differently. It is
known that people who listens to violent music and people that listen to violin
music are normally different. The violent person acts more hostile that the
others. This isn’t always true but it’s the way it normally occurs.
We
are trying to determine is music has any effect on the growth of plants. We
think that from past research on humans that music will have an affect on plants
as well. We are not sure what effect that will be however.
What makes
plants grow? Hopefully this is understood a little bit better now. Although
there is no one single answer to this question, There are several factors that
contribute: Tropisms, environment,
(6)
hormones, biological clocks, and
even humans. We are trying to determine
the effects of music on plants in our
experiment (see p 8). Plants take lots of things to make them grow and now you
know just a few of the many factors contributing.