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Transpiration of A Pine Needle Lab

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How Different Conditions Affect the Transpiration Rates of Pines By Steven Chen, Patrick Huang, Andy Zhang, and Jerry Zhang AP Biology Period 1-2 Mr. Resch September 30th, 2009 Abstract We attempted to find the effect of different conditions on the transpiration rate of pines. We measured the amount of water transpired per gram of pine needle under windy, humid, constant light and dark conditions by placing a pine in a sealed Ziploc bag under each condition for a day. The transpiration rates for darkness, control, constant light, humidity and wind were 17.78, 6.91, 2.92, 0.382, 1.92 grams of water transpired per gram of needle respectively. We concluded that plants transpire the most under dark and normal conditions and that wind, humidity and daylight inhibit the transpiration rates of plants. Introduction [Transpiration is] in botany, the loss of water by evaporation in terrestrial plants. Some evaporation occurs directly through the exposed walls of surface cells, but the greatest amount takes place through the stomata, or intercellular spaces (Columbia Universtiy Press, 2004). The amount of water that plants transpire varies greatly geographically and over time. Because of that, there are a number of factors that determine transpiration rates (Burba and Pidwirny, 2007). Some conditions that affect the rate of transpiration include light intensity, humidity, temperature and wind (Transpiration Article). ...read more.


The daylight environment consisted of placing the plant underneath an artificial light. The humidity environment was located in a humid tank in the green house. The control environment was placed underneath the window where it would be affected by the changes in daylight. The following day we removed the pines from their respective bags making sure no water escaped and then we removed the elastic bands. Next we massed the bags with the water and then we massed the pine needles of the corresponding plant at our lab bench where we originally massed the bags and water. Results Table 1. Rate of transpiration of pine twigs. Pine twigs were placed in different environments and the amount of grams of water transpired per gram of needles was measured. Condition Rate of transpiration (grams of water loss/ gram of needles) Control 6.91 Daylight 1.92 Darkness 17.78 Humidity 0.382 Wind 2.92 Figure 1. Rate of transpiration of pine twigs in different environments. Pine twigs were placed in constant daylight, constant night, windy, humid, and normal (constant) environments. Discussion Our experiment was designed to discover the effect different conditions such as daylight, wind, humidity, and darkness have on the transpiration rate of pines. Our hypothesis stated that the groups under the daylight and wind conditions would experience the highest transpiration rates while the groups under the darkness and humidity groups would experience the lowest transpiration rates. ...read more.


Our results supported the idea that when the pine is placed under the condition of darkness, its transpiration would increase the most. If the transpiration rate in dark conditions is high, then the plant placed in humid conditions should have also had a very high transpiration rate instead of the low transpiration rate indicated by our results. Darkness and humidity have similar effects on the pine as they both cause the closing of the stomata, so if darkness has the highest transpiration rate, then humidity should also have a high transpiration rate. However, we know that our bag under the humidity condition did not have a hole so it can be stated that the bag affected by darkness did not really have that high of a transpiration rate, but was indeed affected by a leak. We only had one pine for each condition and therefore we did not have enough samples to have confidence in our conclusion. Considering we only tested pines, we cannot conclude that these conditions apply to all plants as well. Conclusion The control twig that was subjected to normal condition transpired more grams of water per gram of needle than all the other twigs except the darkness twig. This means constant daylight, high humidity, and wind decrease the transpiration rate of a plant while darkness increases it, disproving our hypothesis. This information is most likely incorrect because some of our bags leaked water, making our results invalid. ...read more.

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