Arora, N. K. 113389821
Woelfel-Monsivais
Observing How Environmental Changes Can Affect Transpiration Rates in Different Plants
Introduction
The purpose of this lab is to test the effects different environmental conditions can have on transpiration rates for both C3 and C4 plants. Transpiration is a process that begins with a plant absorbing water in its root hairs and finishes with that water evaporating out its stomata (Gibson 2017). This movement of water ends up benefiting plants, as it also moves nutrients up a plant’s stoma, cools the plant, and provides turgor pressure for the plant (Gibson 2017).
Not only does transpiration benefit plants, but its effects also greatly affect our daily lives. The food humans eat every day either comes directly from plants or the animals that eat the them, making maximizing the efficiency of growing such plants such an important task. The farmers who grow the crops that are important for our food have to take into account multiple factors when growing their plants. These factors include the amount of water available for the crops, the amount of light they can receive, and other factors like the temperature and amount of wind present in the environment ( De Wit 1958) . These factors influence how well plants transpire, which positively correlates to the growth and development of such plants ( De Wit 1958). As a result, farmers have to carefully choose what kind of plants to plant and when, depending on how successful they will transpire and successfully grow in different conditions.
The objective of the lab is to observe the transpiration rates for different plants when we place them in dark conditions. We hypothesized that if we placed corn plants in complete darkness for 90 minutes, then they would transpire less than sunflower plants in the same environmental conditions. We predicted that this will occur because corn plants are C4 plants and sunflower plants are C3 plants, which in itself affects and should differentiate their transpiration rates. By placing the plants in darkness, we could calculate their transpiration rates by observing their weight change over a fixed interval of time, using an electronic balance. This weight change should indicate how much water either evaporates out of the stomata of the plant into the atmosphere, giving us the transpiration rate.
METHODS
Our group began the lab by obtaining three corn plants. We then wrapped the stem of each of our plants using twist ties and plastic bags, so that only the part of the plants above the soil would be exposed to the experimental conditions. After then using an electronic scale to measure the initial weight of each of our corn plants, we placed two of the plants in cabinets underneath our table and closed the cabinet doors so that we could simulate the plants being in complete darkness. We placed our third and now control plant out in the open of the class, exposing it to light and standard conditions. After waiting 15 minutes, we took each plant out of their experimental conditions to weigh them on the same electronic balance. We then placed the plants back in their same experimental condition for another 15 minutes, and then after that time, repeated the process of measuring the weight of each of the plants. After then placing each of the plants back in their experimental conditions, we repeated the process of weighing them every 15 minutes until we had done it for 90 minutes in total. After finishing obtaining all of the raw data from the plants, we converted the change of each of our plants weight’s to the amount of water each transpired, which was 1 mL per 1g of H 2O . We then used these numbers to find the cumulative % change for the weight of each of our plants, using the equation Cumulative % Change = ((Weight at t 0– Weight at time t n) /weight at t 0) . I then used these numbers to calculate the average cumulative percent change from each of the six time intervals per group. The other group at our table conducted the same experiment as us, with the key difference being that they used the C3 sunflower plant for their tests instead of corn (Gibson 2017).
RESULTS
The overall results concluded that the corn plants transpire less than the sunflower plants in the same, completely dark conditions. This can be seen in table 1, where the average cumulative percent change in transpiration rates for both corn experimental groups was less than both that of both sunflower experimental groups. However, the transpiration rates for both experimental groups were both less than the same plants in standard, control conditions, which can be seen in table 2.
DISCUSSION
Based from the findings in our results, our hypothesis was supported. We hypothesized that if we placed corn plants in complete darkness for 90 minutes, then they would transpire less than sunflower plants in the same environmental conditions. Our experimental results show that both experimental groups for the sunflower plants had higher average cumulative percent changes in transpiration than both experimental corn plants. One possible explanation for these results is the fact that because corn and sunflower plants are C4 and C3 plants, respectively, then they will not transpire at the same rate if placed in similar conditions. Most plants close their stomata in the dark, preventing water from evaporating out of the plant and therefore slowing respiration rates ( Margareth et al. 2007). This is one possible reason why the percent changes in transpiration rates for both plant’s experimental groups was lower than their control group’s transpiration rates, seen in table 2. C4 plants, like corn, are more efficient at using water in the soil than C3 plants, so they are able take in less water are therefore able to successfully grow in warmer climates (Mason 2018).This means they will transpire less. This can be seen in the experimental results in table 1. C3 plants like sunflower, however, grow better in cooler climates, and need more water to do so, meaning they will transpire more (Mason 2018). This can also be seen in the experimental results in table 1.
This experiment informed us of the differences plants have in the way that they transpire and therefore grow. The transpiration rates for both the corn and sunflower plants were likely affected by their classification as a C4 and C3 plant. However, they may have also been affected by issues in the lab. These issues could have been not measuring the weight of each of the plants exactly every 15 minutes, or also a misread of of the plant’s weights on the electronic balance. Any of these issues could have interfered with the results of the lab.
REFERENCES
Gibson, JP. 2017. Transpiration Lab Report Procedure. BIOL 1134. Department of Biology, University of Oklahoma.
De Wit, C. T. 1958. Transpiration and crop yields [Internet].[cited 2017 Nov 14] No. 64.6, p. 88 Available from:http://library.wur.nl.ezproxy.lib.ou.edu/WebQuery/wurpubs/fulltext/186445
Mairgareth C, Richards J, Donovan L. 2007. Nighttime stomatal conductance and transpiration in C3 and C4 plants. Plant Physiology [Internet].[cited 2017 Nov 14] 143.1 4-10. Available from: http://www.plantphysiol.org/content/143/1/4.full
Mason, Kenneth A. Understanding Biology. 2nd ed., McGraw-Hill Education, 2018.
FIGURES AND TABLES
Table 1: Percent Changes in Transpiration Rates for the Plants Placed in Experimental
Conditions
Experimental Group’s Placed in Complete Darkness
Average Cumulative Percent Change in Transpiration
Sunflower C3 Plant Group 1
0.00462%
Sunflower C3 Plant Group 2
0.00372%
Corn C4 Plant Group 1
0.003079%
Corn C4 Plant Group 2
0.00140%
Table 2: Percent Changes in Transpiration Rates for the Control Plants not Placed in Experimental Conditions
Control Group’s Placed in Standard Conditions in Classroom
Average Cumulative Percent Change in Transpiration
Sunflower C3 Plant Control
0.006745%
Corn C4 Plant Control