transpiration lab write up - Measuring transpiration and vapor pressure of Helianthus Annuus in different environmental conditions to determine the

transpiration lab write up - Measuring transpiration and...

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Measuring transpiration and vapor pressure of Helianthus Annuus in different environmental conditions to determine the conductance of the leaves. Megan Ganzenmuller October 5, 2010 Section 002
TITLE: Measuring transpiration and vapor pressure of Helianthus Annuus in different environmental conditions to determine the conductance of the leaves. INTRODUCTION: By measuring water uptake of the sunflower shoot, as well as other environmental factors including temperature and humidity, we wish to determine transpiration rate for three different environmental conditions (control, wind, and shade). And, using this information, calculate the conductance and mole fraction gradient as other sources for comparison between the different environmental conditions to determine which environmental conditions yields the highest transpiration rate. Several other experiments have been done to test transpiration rate. The ones I felt related best were those that tested the same environmental conditions. One experiment done by M. Furuya and O. Van Auken tested “Gas exchange rates of sun and shade leaves of Sephora Secundiflora (Leguminosae. Texas Mountain Laurel)” (Furuya 2009) In this experiment they tested the difference between leaves exposed to the sun with those in the shade, and how thir gas exchange rates compare. Results of his study showed a decrease in transpiration rate in shade leaves when compared to sun leaves (sun leaves correspond to control group in our experiment). Another experiment conducted by P. Thongbai “CO2 and air circulation effects on Photosynthesis and transpiration of tomato seedlings” tested the affects of CO 2 concentration as well as air circulation, comparable to wind in our experiment, on
transpiration rate of the plant. The results for this experiment show that “transpiration rate increase significantly as the air circulation increased”. (Thongbai 2010) And, this experiment was also significant because it measured the humidity inside and out, comparable to the vp in and vp out to be measured in our experiment. However, for our experimental set up I believe that if shade or wind are applied to the plant the amount of transpiration will decrease because both factors reduce the heat and therefore the surrounding air requires less water, and can hold less water than the previously warmer air. MATERIALS and METHODS: In this lab we used a Potometer to measure rate of water intake in a sunflower shoot, in average room conditions as well as in the shade or in wind stimulated with a fan. To complete the lab we followed directions as specified in Biology 1108 Laboratory Manual fall 2010 edition. RESULTS: Text There were many different results measured in this experiment. First were the overall environmental conditions. For this, both air temperature and relative humidity were taken. The measurements of environmental factors can be seen in Table 1. First, the temperature changed from 23.1C at the beginning to 19.7 C at the end of the experiment. Relative Humidity however, remained relatively constant rising only 1%
from 34% to 35%. These changes caused a drop in vp

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