Transpiration Lab

Question: Is the rate of transpiration in a plant, represented by the amount of water that escapes out through the stomata, affected by environmental factors? If so, which environmental factor will cause the greatest increase in the rate of transpiration? Will it be an increase in temperature, which will increase evaporation, an increase in light, which will increase photosynthesis, or an increase in wind, which will cause water to blow out of the leaves? This question is solvable through perfuming tests on a number of different plants. The environmental factors can be replicated through the use of a fan for the wind, a heater for the temperature increase, and a lamp for the light increase.

Hypothesis: If a number of plants are tested under different environmental factors, then the trials where heat is added will cause the greatest rate of transpiration for all of the plants, because if the temperature is raised, then more water will be evaporated out of the plant through the stomata, because the kinetic energy/molecular motion of the water molecules will increase, and the water molecules will vaporize. I also hypothesize that the tails with the fan will show the second highest transpiration rate in all the plants, because the wind will cause many of the water droplets hanging around the stomata to blow out of the plant, without the need of evaporation.

Plant Transpiration Data Table
	Normal	With Fan	With Heater	With Lamp
Arrowhead	3.6 mL	7.5 mL	6.6 mL	4.0 mL
Coleus	0.9 mL	6.0 mL	3.9 mL	3.0 mL
Devil’s Ivy	2.9 mL	4.6 mL	4.1 mL	3.0 mL
Dieffenbachia	4.1 mL	7.7 mL	6.0 mL	3.9 mL
English Ivy	1.8 mL	5.1 mL	3.2 mL	2.1 mL
Geranium	1.2 mL	4.7 mL	5.8 mL	2.4 mL
Rubber Plant	4.9 mL	8.4 mL	6.8 mL	4.3 mL
Weeping Fig	3.3 mL	6.1 mL	4.9 mL	2.5 mL
Zebra Plant	4.2 mL	7.6 mL	6.1 mL	3.2 mL

Question 1: Describe the process of transpiration in vascular plants.

Answer: Water is evaporated through the stomata in the leaves, which are usually on the underside of the leaves. Water in the plant is brought up from the roots to the leaves because water is pulled by the water molecules that are being evaporated (cohesion and adhesion). The water is let out when the stomata open to release oxygen and take in carbon dioxide.

Question 2: Describe any experimental controls used in the investigation.

Answer: The experimental control in this investigation is the normal experiment. It allows us to compare the environmental changes to normal environmental conditions. 

Question 3: What environmental factors that you tested increased the rate of transpiration? Was the rate of transpiration increased for all plants tested?

Answer: The introduction of wind, represented by the fan, and the introduction of heat, represented by the heater, both increased the rate of transpiration, with the fan causing the greatest increase. For those two factors, the rate of transpiration increased for all nine plants.

Question 4: Did any of the environmental factors (heat, light, or wind) increase the transpiration rate more than the others? Why?

Answer: The rate of transpiration was increased the most by introducing wind, with Geranium being the only plant who's rate of transpiration increase more with the introduction of heat than with the introduction of wind. This is because the wind causes the water molecules sitting at the stomata to be blown out of the leaves, without even evaporating. The reason the heat increased the rate of transpiration, though not as much as the wind, is because the increase in temperature meant that the molecular motion of the water molecules increased, and more were able to evaporate.

Question 5: Which species of plant that you tested had the highest transpiration rates? Why do you think different species of plants transpire at different rates?

Answer: The Rubber Plant had the highest rate of transpiration in all four tests. This is because the Rubber Plant, pictured below, has the large leaves and probably has more, and larger, stomata than other plants. Different species of plants probably have different rates of transpiration because they have to survive different environments. The Rubber Plant probably lives in a wetter environment than the Coleus, and therefore will not die if it loses a lot of water through transpiration. Also, Coleus looks like its texture may make it harder for water to escape, compared to the Rubber Plant, which looks like water can slide right off of it.

http://redfoxbb.com.au/indoor-plants-which-clean-toxins/

Question 6: Suppose you coated the leaves of the plant with petroleum jelly. How would the plant's rate of transpiration be affected?

Answer: The rate of transpiration would decrease because the stomata would be covered, and water would not be able to escape.

Question 7: Of what value to a plant is the ability to lose water through transpiration?

Answer: Just like people in sweating, plants use transpiration to cool themselves. As the water is evaporated, heat is lost with the water molecules. When evaporation occurs, water is pulled up to the leaves through cohesion and adhesion, carrying nutrients up to the leaves.

Plant Hormones

Ethylene

http://labs.bio.unc.edu/Kieber/ethylene.htm

Ethylene comes from the endoplasmic reticulum in a plant cell. It is not very soluble, and this causes it to diffuse out of the plant cell. So the concentration of ethylene in the plant depends upon the rate at which it is produced with comparison to the rate at which it diffuses out. It functions to inhibit growth and also for ripening. It is used by farmers to force ripening of fruits, since naturally there is a burst of ethylene production just before ripening. Ethylene converts starch and acid from unripe fruits to sugar in ripe fruit.

http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=998688536&topicorder=7&maxto=11

 It is a positive feedback loop, that stimulates its own production. When the first fruit begins to ripen, it emits ethylene, which is then absorbed by the surrounding fruit, causing all of them to ripen too. Ethylene suppresses auxin (and auxin suppresses ethylene).

http://www.pnas.org/content/103/36/13286/F6.expansion.html

http://www.hort.cornell.edu/mattson/leatherwood/

The flowers disappeared because they are too sensitive to the ethylene. The ethylene also causes the plant's leaves to become more curled. Ethylene is responsible for the aging process of plants

Auxin

http://www.nature.com/nrm/journal/v7/n11/fig_tab/nrm2020_F5.html

 Auxin is produced in immature parts of plants, such as the embryo, the young leaves, and buds, and it stimulates growth. It increases the activity of the protein pump, and causes the cell wall of the plant to become more acidic and become capable of elongating. It controls cell division and can regulate fruit development, helping the fruit grow bigger. Farmers inject auxin into fruits to make them bigger.

http://www.bio.miami.edu/dana/226/226F09_13.html

http://www.tutorvista.com/content/biology/biology-iv/plant-growth-movements/growth-regulators.php

Auxin is synthesized at the tip of the plant, and gets sent to the dark side of the plant. This causes cell division on the dark side, or stem elongation, and causes the plant to bend toward the light. Auxin is part of a process known as Positive Phototropism, where a plant moves toward light.


Abscisic Acid

http://www.pnas.org/content/105/11/4495.figures-only

Abscisic acid is responsible for the dormancy of plants, inhibiting plant growth. It is produced in the terminal buds. It reduces transpiration by closing the stomata, causing low levels of water to reach the leaves. It inhibits plant growth during stress to prevent the plant from dying.

Flowers

All of the flowers smelt good. This is most likely to attract insects to pollinate them.

     The flowers are not open very much, but enough for a bee to be able to go in and pollinate it. The reason that it is not open much may be that it is better protected than it would be if it completely opened up.

      The flower is pink and has many pedals. The plant that it is attached to has thorns, which are designed to protect the flower.

     You can see it very well in any of these pictures, but there is a moldy fungi on some of the flowers.   The fungi is living of the plant, and the plant may also be benefiting from this situation.

     You can see that the pedals are white in the middle, then become pinker and pinker the farther from the center they are.

      There are small pieces of pollen, the males, surrounding a thicker stem, which is the female.

      Above is some pollen that came off of the flower when I gave it a gentle shake. The pollen for this flower is yellow.

I found the Pincher Bug above inside of the flower. These, along with tiny beetles, pollinate the flowers by transferring the male pollen to the female part of the flower. 

     Though I did not see any insects, I would guess that small flies might pollinate these. The opening of the flower is too small for a bee, and its position on the tree would make it hard for beetles to climb up to pollinate it.

If i had to compare the smell of the flower to something, I would say it is a similar smell to shampoo.

     The little purple things on the right are male pollen, and the white stem on the left is the female part of the flower.