Transpiration Lab Report

Transpiration: The Effects of Wind and Light on Solanum lycopersicum Katelyn Stapler Biology 156 March 9, 2011

Lab Partners: Magan Domingue Mary Lee Amanda Parham

Abstract Wind and light were used to test the rate of transpiration of Solanum lycopersicum, a tomato plant. Transpiration is the loss of water from the stomata of a plant’s leaves. The hypothesis for the experiment is that direct light on the plant will make transpiration occur more rapidly. Results from the experiment prove that light, not wind, make transpiration rates faster. Transpiration occurred more rapidly in the controled experiment instead of the lighted experiment.

Introduction

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Transpiration is the loss of water from the Stomata of plant leaves (Vodopich and Moore 2010). Environmental conditions such as Carbon dioxide levels, light, wind, and humidity can affect transpiration. In higher temperatures transpiration increases due to the rate of change of saturation pressure within the plant (Jarvis and Morrison 1981). In the presence of wind, transpiration increases at first and after signs of water loss from the stomata transpiration rate slowly decreases. The rate of transpiration decreases only when satruation pressure decreases (Raven and Singer 2010). The purpose of the experiment is to find out how quickly transpiration would occur with and without light or wind. The hypothesis for the experiment was that the tomato plant or Solanum lycopersicum would absorb more water with light instead of wind since light causes photosynthesis to occur more rapidly. Materials and Methods A transpirometer apparatus, a tomato plant stem, a fan and a lamp were needed for the experiment. Obtain a stem from a tomato plant (Sloanum lycopersicum). Then set up the transpirometer apparatus by opening the screw valve below the reservoir and flushing out the system. Clamp off the micropipet using a spring clamp. Submerge the stem in water and attach it to a water-filled tube connected to a pipet (Vodopich and Moore 2010). Unsubmerge the stem and tubing and wrap in a papertowel and place the stem into open clamp. Lightly clamp the stem to keep from stopping transpiration from occuring. Make sure there are no air bubbles within rubbr tubing and that there is no water on the leaves before starting. Open the clamp that is on the line leading to the pipet and

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open the screw valve on the reservoir only enough to let water drop from the tip of the pipet, then close the screw valve. As transpiration occurs water will slowly be drained from the pipet. Record the data every five minutes for fifteen minutes. Then repeat the experiment with a fan that is placed 200mm away from the plant or with a lamp that is placed 200mm away from the plant. Record data, and tempurature for the light experiment, every five minutes for fifteen minutes. Results In Table 1 the overall class results are shown for wind and light; the transpiration of light was 9. 45x10-5 and the transpiration rate for wind was 8.61x10-6. Table 2 and Figure 1 show the results of an individual group instead of the overall class. Table1. Overall Class Final Results for the Light and Wind Experiments Trial Light Wind

Class Transpiration Rate Average 9.45x10-5 8.61x10-6

Table 2. Control vs. Light Transpiration rates according to temperature differences Experiment Control (avg. temp: 21C) Light (avg. temp: 22C)

Time (min) 0 5 10 15 0 5 10 15

Distance (mm) 2.9mm 4.1mm 5.5mm 6.1mm .3mm 1.4mm 2.1mm 3.4mm

Transpiration Rates of the Control Experiment and the Light Experiment 7 6 5 4

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Distance In Milimeters

Time in Minutes

Figure 1. Control vs. Light Transpiration Rate Discussion The experimental data collected by the group proves that the hypothesis is wrong in that light does not make transpiration occur more rapidly. Yet, the experimental data collected by the class proves this hypothesis to be correct. Compared with the class data, the experimental data that the group collected was off. The reason behind this was believed to be that during the controlled experiment the group did not start measuring and keeping track of time as soon as the experiment started. Thus, transpiration was already well underway when the first measurements were being recorded. The hypothesis that light makes transpiration occur more rapidly is infact correct. The class experimental data proves that transpiration occurs more rapidly when there is direct light to stimulate the plant.

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Literature Cited Jarvis, P. and Morrison, J. "The Control of Transpiration and Photosynthesis by the Stomata." Stomatal Physiology. Cambridge, NY: Cambridge UP, 1981. 247-56. Print.

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Raven, Peter H., George B. Johnson, Kenneth A. Mason, Jonathan B. Losos, and Susan R. Singer. Biology. 9th ed. Dubuque, IA: McGraw-Hill, 2010. Print. Vodopich, Darrell S., and Randy Moore. Biology Laboratory Manual. 9th ed. William C Brown Pub, 2010. Print.

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