Plants vs. Chemicals
By
Toluwanimi Obiwole
Abstract:
I conducted this experiment to observe the effects of nitrates on plant cellular behavior and to,
in the process, learn more about cells. I began by reading text books and gathering general information
about cells ( i.e. life cycle, structure, reproduction). I went on to look for experiments to fit my
investigation, and I ended up with studying the effects of chemicals (pollutants) on plant growth. My
hypothesis stated that the plant treated with the most concentrated amount of Ammonia will act the
most abnormally because the Ammonia will weaken the plant, just as chemical pollutants do in nature. I
planted four oat grass plants and allowed them to sprout. I chose Ammonia for my chemical and dosed
each plant, save for my control, with different dilutions of Ammonia. After three days, each of the
treated plants showed damaged cells in the root; however, the plant with the heaviest concentration of
Ammonia showed the most damaged cells in both the leaf and the root. My hypothesis was proved
correct. The Ammonia demonstrated how pollution damages plants.
Intro:
I began this experimental investigation by asking the question, “How do pollutants and/or
herbicides affect plant cellular behavior?” We learn about plant cells and some of us have seen them in
a microscope, but how do they function when they are under attack from chemical pollutants? Plants
are exposed constantly in today’s world from pollutants ranging from carbon dioxide (CO2) to acid rain
(rain heavy in nitrate gas (NO3)). These pollutants weaken the plants’ defense mechanisms, causing
them to die out from diseases that they would otherwise be immune to. I wanted to see specifically how
this affects plant cellular behavior, so I chose to test the plants with Ammonia, a common base, to see
whether the same pollution effects (weakening and death) would happen.
Plant cells, like any other cells, are the smallest living units in an organism. They have all of the
vital components such as: a brain (nucleus), food makers (chloroplasts), mechanisms that turn that food
into energy (mitochondrion), organelles that keep the shape and structure of the cells (vacuoles), waste
cleaners (lysosomes), and skin (cell wall).
Plants contain specialized cells (cells that exist to serve a specific purpose) such as: parenchyma,
collenchyma, and sclerenchyma. Parenchyma function in photosynthesis, the storage of water and
nutrients, and in healing. Collenchyma are the thick cells that support regions of the plants that are still
lengthening. Sclerenchyma strengthen the plant in areas where it is no longer growing, and after
reaching maturity, they support the frame of the plant.
Pollutants primarily damage the parenchyma, hindering them from doing their jobs. One type of
chemical pollution, acid rain pollution which is heavy in nitrate (NO3), wears down the frame supporting
cells and then damages the parenchyma so the plant is unable to heal properly. Ammonia has a pH of
about 11.6 in water, making it a base. Although it is a base, is a very strong base and can still burn
through the defense organelles pretty quickly.
Materials + Procedure
List of Materials used:

16 oat grass seeds

3 ml of Ammonia (household cleaner)

4 plastic growing pots

3 graduated cylinders measuring up to 100 ml

Water
Procedure:

Lay out the growing pots and fill them up with the same amount of dirt

Plant four seeds in each pot, about an inch deep

Moisten the soil and allow the plants to sprout

Fill the graduated cylinders with 59ml, 39ml, and 29ml, of water respectively

Apply 1ml of Ammonia to each cylinder

Water three of plants: one with 59ml, one with 39ml, and the last one with 29ml. Be sure to
label the pots after watering them.
After I had watered the plants with the Ammonia, I waited about three days before checking in
on them. I did not water them during these three days. I then took a sample of one leaf and one root
from each of the plants, including the control. I observed them under the microscope. But, before
examining the roots, I shaved them down with a razor blade in order to see the cells better and I applied
a drop of iodine so that the cells would be visible under the microscope.
Results:
Individual Results:
Control:
The cells in the leaf were green, thick, and looked very healthy. The leaf itself felt thicker and sturdier
than the others. The root was clear with healthy-looking cells.
59ml:
The leaf was softer than the control, but the cells still looked green and healthy. The root was brown
and weak and the cells looked infected.
39ml:
The cells in the leaf looked a little withered and the leaf was a little browner at the edge and very soft.
The root cells looked even worse than the 59ml cells. They looked really sick.
29ml:
The leaf looked really brown and withered. The cells in the leaf looked really withered and dry. The root
was really thin and the cells were very dried out and damaged.
Discussion:
My results lined up exactly with what I was expecting. The chemical, when really concentrated,
can cause a lot of damage in a short amount of time. The plant with the highest concentration of
Ammonia (29ml) was the weakest. However, I was expecting the leaves to show more signs of being
poisoned. The only difference in the leaves was the softness. I suppose this occurred because of the
Ammonia disrupting the sclerenchyma from properly supporting the frame. The roots turned out to be
the most useful indicators of the Ammonia taking effect.
My results were similar to what happens in nature when chemical pollutants invade. This is
becoming an ever increasing issue in this day and age as we are becoming more and more industrialized.
We give off more carbon dioxide and hydrocarbon pollutants than nature can clean up. The plants get
weaker and die faster which not only creates consequences for our ecosystem, but for human health as
well. Plants absorb carbon dioxide and give off oxygen, but if we are giving them too much carbon
dioxide and other pollutants, then they basically get choked and they cannot function properly.
References:
1. Alcamo, Edward, et al. Modern Biology. Austin, Texas: Holt, Rinehart, and Winston. Print