Science Buddies: "Ask an Expert"

I am doing a science fair project, where I am testing the effect of car exhaust on the health and growth of plants.
Are the stomata in plants able to clog? If so, Which chemicals that run through the stomata might clog them?

Hi,

A Google search came up with this answer

) antitranspirants - chemicals that close or clog stomata.
Two Types
a) physiologically cause stomatal closure
b) wax, resin or latex that clogs stomata

This is located at the bottom of page 65 on this site

http://generalhorticulture.tamu.edu/lec ... water.html

This site claims dust can clog stomata:

http://howsitgoineh.com/growguide/watering.htm

This site claims cigarette smoke can clog stomata:

http://www.ehow.com/about_5090744_effec ... plant.html

This is another answer:

Oiling leaves to make them shine
This clogs the stomata (breathing pores) and is especially injurious if the oil is applied to the underside of the leaf where most of the breathing pores are situated.

From rhis site:

http://www.homerenotips.com/tutorials/g ... use_plants

And then these is this explanation of the damage aphids do:

http://www.bio-bee.com/site/pests.asp?p ... age_id=280

So the answer seems to be that many things can clog stomata, and this answere is only a partial list.

I hope this helps.

Best wishes,


Barrett L. Tomlinson

I am currently doing a Science Fair Project on plants, and their response to the chemicals and toxins that are released in car exhaust. My plants need to be in a sustainable environment. I am aware that most plants are comfortable with a neutral to slightly acidic soil (pH 6-7), Do I need to monitor the pH in the soil, or will my plants take root naturally by themselves?


Please help me by assisting me in understanding this content
Cordelia Peters

Thank you
The information you gave was very useful, and answered my question. However, for me, it brought up another one. In my project, I am running Car exhaust into the living environments of plants. The main chemical or gas that will be inflicting upon the plant will be CO2. I am aware that CO2 is beneficial for the plant, however I was curious to if plants can have an overload of it, or if there is a mechanism in the plant, which stops the intake of the gas, once the plant has gathered all it needs.

Can plants have an overload of CO2?
And, do plants have a mechanism that will stop the intake of gasses, once the plant has received all that is necessary?

Thank you for your help,
Cordelia Peters

In my project, I am running Car exhaust into the living environments of plants. The main chemical or gas that will be inflicting upon the plant will be CO2. I am aware that CO2 is beneficial for the plant, however I was curious to if plants can have an overload of it, or if there is a mechanism in the plant, which stops the intake of the gas, once the plant has gathered all it needs.

Can plants have an overload of CO2?
And, do plants have a mechanism that will stop the intake of gasses, once the plant has received all that is necessary? How do they react to an increase of this gas?

Thank you for your help,
Cordelia Peters

Hi,

I have merged all of your questions into a single thread so that experts can better understand what you are trying to do and therefore better help you. Please keep all your future posts about this experiment in this topic.

To answer your questions, no, you do not need to monitor pH. However, since CO2 is weakly acidic (if I remember my chemistry correctly), you might consider measuring it anyway because it may change over the course of the experiment.

Secondly, yes, plants can get too much CO2--but to my understanding it does not hurt them; they simply cannot use any more to grow any faster because other things are limiting their growth.

Stomata usually open and close based on water pressure, so water vapor is the one gas that plants really actively try to include/exclude. However, plants with different types of photosynthesis do use various 'tricks' to maximize CO2 gain while minimizing H2O loss. See this article for more details: http://en.wikipedia.org/wiki/Photosynthesis.

Keep in mind that car exhaust has a lot more in it than CO2--not only are there gases, but there is particulate matter as well (the particulate matter that contributes to smog, for example). So, the plants may actually react badly even though you are giving them 'more' CO2, which you might otherwise think is good.

Thank you,
While running the car exhaust into the living environments of the plants, do you think that the heat created in the engine, that is put out in the exhaust will have and effect on the plant? Should that be a factor I consider apart from just the chemicals and toxins in the exhaust?

Also, does injecting oxygen reduce the oxygen content?

Thank you,
Cordelia Peters

Also, I am aware of the carbon monoxide and CO2 in the exhaust, are there any other especially important chemicals, or toxins that could positive or negative effects on the plants? What are these chemicals, and what are their effects?

Thank you for our help,
Cordelia Peters

Yes, heat could definitely affect your experiment, and I would suggest keeping it constant if you can.

I'm not sure I understand your second question. What would you inject oxygen into, and the oxygen content of what? Plants? If you can clarify this, I will try to answer.

Here's a couple of websites to get you started answering your final question: http://www.greenlivingtips.com/articles ... icals.html , http://www.nutramed.com/environment/carschemicals.htm

Good luck!

Sorry, Let me see If I can clarify.
For example, if I injected CO2 into a "bucket" full of oxygen, how would they mix? would the CO2 puch the oxygen out? would the Oxygen stay in, and the CO2 just not be able to enter? or do you think that the CO2 would flow in, mix with the oxygen, and then a portion of both would exit the bucket?

Sorry for the mixup,
Also is there a way to rid plants of bugs and insects without using pesticides?
Thank you,
Cordelia peters

Okay, now I understand the question. Unfortunately, the answer is that it depends on how slowly you let the CO2 in and the size and shape of the bucket. If you put it in very quickly so that the gases do not have time to mix, then it would push most of the O2 out--temporarily, of course, because unless the bucket is closed, it would mix with the outside atmosphere. Remember, gases diffuse into areas where they are less concentrated until the concentration is equal in both places, as long as there is some connection between the two places.

As for pesticides, there are two ways to do it: genetically engineer plants to be resistant to/toxic to certain insects, or bring in some sort of biological control (bird, other insect, disease) that will eat/kill them.

Thank you for your response,
Also apart from pH levels, and other aspects that need to be present in plant survival, I was curious about iron levels.How much Iron do plants need? And can this be found in the soil? or do I have to supply it for the plants?

Going back to the temperature of the exhaust. How do you think the temperature will affect the plants? will it be a positive component? or do you think that it will decrease the growth? are there reasons behind the effects it might have?

Thank you,
Cordelia Peters

Again, it depends on the plants. Plants do need trace amounts of iron because iron is an important part of chlorophyll. As long as you have the same soil in the pots you are exposing to car exhaust and not exposing to car exhaust, this should be fine--iron leaching may occur in one of the pots if the pH changes, but this would be more important over the course of months or years than the few weeks typical of science experiments.

Temperature will increase growth up to a point, and then it will level off and eventually have a negative effect. I doubt the temperature of the exhaust will be high enough that you will see a negative effect, BUT the problem here is that if you are blowing car exhaust onto plants and not blowing it onto other plants and measuring the effects, you are measuring the effects of several variables (CO2, temperature, particulate matter, etc.). Either you need to figure out a way to measure the effects of these things separately, or you need to say that you are looking at the overall effects of car exhaust.

For example, if you wanted to control for the effects of temperature, you could have one control group of plants at 'normal' temperature, one group at the same temperature as car exhaust, and then the group in the car exhaust. The difference between the first two treatments will give you the effect of temperature, and then you can subtract this from the effects of the car exhaust. (But be careful--only keep the high-temperature group at high temperatures for the same amount of time you blow car exhaust on the plants--I assume you will not do this 24 hours a day!)

Hi Melissa,

I am trying to find information about why dark green vegetables have a higher iron content. I understand that chlorophyll has traces of iron, but am not able to find any more details on the subject. Can you please help me? I will be happy to be pointed to relevant sources of information as well. Thank you for your help.