Small amounts of salicylic acid are known to be present in plants. Originally salicylic acid was extracted from the willow bark to make the well known pain relief medication Aspirin. Salicylic acid is thought to promote disease resistance, increase flower life, inhibit seed germination, and promote ethylene synthesis. My initial research indicated that large concentrations of salicylic acid actually killed plants so this study deals with plant growth attributed to the addition of low concentrations of salicylic acid. The latest research into plant growth is explained and experimental evidence is provided that shows whether salicylic acid has an affect on plant growth.
is a lot of information about growing plants and about plant life
("botany"). One substance
acid, which is found in “pain relief” medication
like Aspirin tablets. Researchers
think that this might be a new plant growth hormone but no evidence is given to
prove it. I was curious to see if
there was a relationship between plant growth and the amount of aspirin fed to plants. After my experiment
I could show that some amount of Aspirin might actually increase plant growth
compared to no Aspirin at all, while a lot of Aspirin harms the plant.
This research gives some background about plants, the plant growth
process, plant growth hormones and Salicylic Acid.
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The plant kingdom (plantae)
is divided into 12 divisions called phyla and there are at least 4
classification systems that experts use to classify plants: by reproduction, by
tissue-structure, by seed structure and by stature.
bean plant is a member of the pea family (Fabaceae) and is a dicot which means
it has two seed leaves. Most trees,
shrubs, vines, and flowers belong to this group of around 200,000 species. Most
fruits, vegetables come from this class.
Bean Plants and How Beans Grow
is the sprouting of a seed. When germination begins the seed needs a lot of water.
The water makes a chemical change that enables the embryo to store food
and energy for growth. The water
also causes the baby seed (“embryo”) to enlarge and split the seed coat.
Germinating seeds require a large amount of oxygen and give off carbon
dioxide. One part of the embryo,
called the radicle,
comes out and grows making the roots. Another
part, called the plumule, turns into the shoot of the plant.
The endosperm is the food store that surrounds the baby plant.
the shoot and roots become visible the first plant part you see is called the
cotyledons. They help feed the new
seedling until it can make its own food.
plants require food. The food is
also call nutrients. Macronutrients
are needed in large quantities (such as carbon, oxygen, nitrogen and
phosphorus). Micronutrients like
iron, copper, manganese, boron and zinc are needed in small amounts.
Three important nutrients are nitrogen, phosphorus, and potassium.
is very important and has to be converted to nitrate by the bacteria that live
on roots and in the soils.
The Nitrogen Cycle is very
important to plants. Nitrogen is a major component of amino acids, proteins, and
chlorophyll present in plants and is needed for plants to live.
were made to supply plants with any nutrients that they are short of to
stimulate growth and are made of nitrogen, phosphorus and potassium.
How to Grow Plants
Allow room to grow so pick the right sized pot.
Don't put too many plants in it.
Keep them warm. Plants grow
best if the temperature does not go below 12°C
or above 24°C.
Plants can grow in lots of different kinds of light.
Some need shade but most love sunlight the best.
Give those plants 7 to 12 hours of strong light each day.
Plants make their own food because they have chlorophyll.
Photosynthesis is the chemical change that produces food for the plant.
In photosynthesis, carbon dioxide, gas and water are mixed to make sugar
and oxygen. Sunlight is the energy
it needs to make the chemical reaction.
Water your plants only when they need it.
If roots are not given enough water, the plants will wilt and die.
If the roots are given too much water they will rot and the plant will
Plants don't breathe like people, but they do take up air through their
leaves and roots.
Plants take up food from the soil (called nutrients) to help them grow
Care for your plants and be patient, plants need time to grow.
pH or soil reaction is an indication of the acidity or alkalinity of soil and is
measured in pH units. The pH scale
goes from 0 to 14 with pH 7 as the neutral point.
From pH 7 to 0 the soil is increasingly more acidic (eg. soda = 2 – 4)
and from pH 7 to 14 the soil is increasingly more alkaline (eg. borax = 9).
Most minerals and nutrients are more soluble in acid soils than in
slightly alkaline soils.
Plant Cell Types
cells help the plant grow. Parenchyma
tissue is made up of thin-walled cells that store water and salt.
Xylem tissue is made up of thick-walled cells that transport water and
dissolved minerals from the roots up through the stem to the different parts of
a plant. Phloem tissue contains
living cells that transport food produced throughout the plant.
Collenchyma tissue has thick walls for added strength and support.
Meristematic cells give rise to all three fundamental mature cell types.
Their major function is cell division.
Plant growth is controlled by growth hormones such as auxins,
cytokinins, gibberellins (GA), and abscisic acid (ABA).
Water stress, the lack of water, decreases auxin and increases abscisic
acid. Auxins are involved in the
growth of all parts of the plant, and abscisic acid is an inhibitor that may be
involved in inducing dormancy. Pruning
is a stress because hormones made by buds are not present.
The result is the cytokinin to auxin ratio is high which produces unusual
growth. Sometimes plants grow
better because of this. Sometimes
stress is helpful. For example, at
the end of summer, the changes in temperature, light and moisture change the
hormone balance in plants causing the plant to enter dormancy long before the
frost comes protecting plants from frost. Sometimes
stress is harmful and the plant does not thrive.
The stimulating hormones (auxin,
brassinosteroid) generally suppress the effect and production of the
inhibiting hormones (ABA,
GA) and vice versa.
Salicylic Acid (SA)
Salicylic Acid naturally occurs in plants in very low amounts. It is also manufactured and used to make Aspirin tablets. Evidence has been found that shows Salicylic Acid can stimulate flowering. Also, Salicylic Acid has been found to cause temperature increases of as much as 14ºC above the ambient temperature in the Arum group of plants (eg. duckweed, Skunk Cabbage). Salicylic Acid is thought by some people to be a new plant growth hormone. Also, some people use Aspirin in cut flowers to make the flowers last longer.
Phyllis J. Perry, Science Fair Success with Plants, Enslow 1999
Robert W. Wood, Science for Kids, Tab 1991
(3) Biological Sciences in Middle East Technical University
MadSci Network: Agricultural Sciences
Botany online University of Hamburg
(7) Cornell University College of Agriculture and Life Sciences
(8) Ellen Silva, Originally published as "Plant Stress Management,"
Extension Technician, Department of Horticulture, in
Virginia Gardener Newsletter, Volume 10, Number 4.
(10) Santiago Ortiz - FLASH 5 - my modifications and use in Virtual Garden
(11) Prof R. Koning, PhD Botany
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