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Isotonic Concentration of Lettuce and Chinese Cabbage

Determination of the Isotonic Concentration of Sodium Chloride Solution to Lettuce (Lactuca Sativa) and Chinese Cabbage (Brassica rapa)1
Josua Alvarez
Ann Justine Marzo
Patrick Ocampo
Paula Tiongson
The isotonic concentration of lettuce and Chinese cabbage to sodium chloride was determined by obtaining a thin layer from the midrib of each of the freshly harvested leaves and then was cut to four. Each cut for each vegetable was then distributed to four glass slides and then labeled A, B, C, D respectively with NaCl solutions of 0.05 M, 0.15M, 0.30 M, and distilled water as control. After each was compared under the microscope, results showed that isotonic concentration was observed in both set-up B with 0.15 M of NaCl solution in both the Chinese cabbage and lettuce because the cells were alike with the control group. Both also observed hypotonic concentration in set-up A with 0.05 M and hypertonic concentration in set-up C with 0.30 M of NaCl solution because the cells showed an increased and decreased in size respectively. Therefore, the isotonic concentration of both Chinese cabbage and lettuce were observed in 0.15 M of NaCl solution.
INTRODUCTION Vegetables are edible parts of plants or the whole plant itself that is intended for human cooking or eating raw (Vainio and Bianchini, 2003). Vegetables have a particular role in the diet of humans because they contain different vitamins and minerals necessary for the wellness of the human body. In order to prolong the life of vegetables, which are living tissues, techniques for increasing the shelf life of vegetables such as rapid post-harvest cooling is being done since it minimizes respiratory rates and inhibits the growth of decaying microorganism (Kohli, 2008).
Lettuce (Lactuca sativa) and Chinese cabbage (Brassica rapa) are leafy types of vegetables. Lettuce contains different vitamins and minerals such as calcium, phosphorus, iron and vitamin C. It is mostly and easily produced on regions under relatively cool and mild temperatures (Ryder, 1999). Chines cabbage locally known as Pechay Wambok on the other hand, is the most important vegetable being grown in China. However, due to trade and exchanges, it has been also being grown in different parts of the world. This vegetable is also known to contain different vitamins and minerals like calcium, potassium, and vitamins C and A (Tatekar and Griggs, 1981).
Osmosis is defined to be as the cellular or artificial diffusion of free water across a selectively permeable membrane like the cell. In studying this, it is necessary to know the solute concentration and membrane permeability thus leading to tonicity, the ability of the cell membrane to gain or lose water. The medium at which the cell is exposed can be classified as isotonic, hypertonic and hypotonic. Hypertonic means the cell has a lower concentration than the medium while hypotonic refers to the higher concentration of the cell than that of its medium. Isotonic concentration on the other hand, means equal concentration of both cell and the medium (Campbell 2011).
In this paper, lettuce and Chinese cabbage w exposed to sodium chloride of different concentrations. Thus this study aimed to determine the isotonic concentration of sodium chloride to lettuce and Chinese cabbage. The specific objectives were:
to compare all the media whether they are hypotonic, hypotonic or isotonic to lettuce and Chinese cabbage and;
to differentiate the isotonic concentrations of lettuce and Chinese cabbage.
This study was conducted on November 17, 2014 at Room C-117 of the Institute of Biological Sciences, University of the Philippines, Los Baños.
MATERIALS AND METHODS Thin layer from the midrib of the freshly harvested Chinese cabbage (Brassica rapa) was obtained. The layers were cut into four and were placed in four different glass slide and label as PA (Pechay A), PB (Pechay B), PC (Pechay C) and PD (Pechay D).

Figure 1. Chinese cabbage specimens.
Few drops of 0.05 M NaCl solution was added to the glass slide labeled Pechay A and place a coverslip to the slide while 0.15 M NaCl solution was used on the glass slide labelled Pechay B. On the glass slide labelled Pechay C, 0.30 M NaCl solution was added. Distilled water was dropped on the glass slide labelled Pechay D to serve as control. To prevent the specimen from drying, few more drops of each solution and the control were added to their respective glass slides to avoid extraneous results.
The glass slides were placed and examined under a microscope using the low power objective (LPO). The appearance of the cells in slides A-C were compared to the appearance of the cells on slide D. Using the comparison of the appearance of the cells, the isotonic, hypotonic and hypertonic concentration of sodium chloride solution to Chinese cabbage was determined.
The steps were repeated using the Lettuce (Lactuca sativa) leaf.
RESULTS AND DISCUSSION The slides labeled with A, B, and C, contained 0.05, 0.15, 0.30 M NaCl, respectively. The slides labeled with D contained distilled water and is therefore the controlled set up. The slides labeled with P and C contained cabbage and lettuce, respectively.
The cell in the slide labeled P.A. was hypotonic with the slide labeled P.D. since the former was larger than the latter which can only mean that the cell was filled with water. An isotonic osmotic concentration was observed in the slide labeled P.B. since there was no change in appearance compared to the controlled experiment. A shrink in appearance was observed in the slide labeled P.C. in comparison to the slide with just distilled water and cabbage since the cell undergone plasmolysis. This is therefore hypertonic. As seen in table 1
In the next experiment, a hypotonic osmotic concentration was observed in the slide labeled C.A. since the cell had an increase in size compared to the controlled experiment since water was absorbed. The cell in the slide labeled C.B. was isotonic since it was identical to the cell in the slide labeled C.D. A decrease in size was observed with the slide that contained 0.30 M NaCl and lettuce in comparison to the slide that contained distilled water and the same substance. Thus, it is hypertonic (refer to table below).
Cabbage (Pechay)
0.05 M NaCl

0.15 M NaCl

0.30 M NaCl

Distilled Water

Table 1. Figures of cells of lettuce and cabbage exposed in different media.
SUMMARY AND CONCLUSION The isotonic concentration of sodium chloride to lettuce and Chinese cabbage was determined. Thin layer from the midrib of each of the freshly harvested leaves was obtained and cut into four. Per vegetable, the divided leaf was distributed to four glass slides and the slides were differentiated by labeling A, B, C, and D respectively. NaCl solutions of 0.05 M, 0.15 M, and 0.30 M were added to slides A, B, and C respectively while distilled water was added to slide D that served as the control group. The appearance of the cells in slides A, B, and C was compared in slide D.
Results showed that Chinese cabbage in 0.05 M NaCl solution was hypotonic because enlargement of the cells was observed when compared to the control. NaCl solution of 0.15 M was isotonic because the cells were alike to the control set up. Lastly, 0.30 M NaCl solution was hypertonic to Chinese cabbage because the cells were smaller compared to the control set up. As for the lettuce, 0.05 M NaCl was also hypotonic because there was an increase in the size of the cells. Sodium chloride solution of 0.15 M was isotonic to Lettuce because the cells were identical to the control set up. Lastly, 0.30 M NaCl solution was hypertonic because of a decrease in the size of the cells.
Therefore, the isotonic condition of both lettuce and Chinese cabbage to salt solution is 0.15 M.
However, due to lack of equipment, it is recommended to do this experiment again in a proper laboratory. Furthermore, the specimens shall be observed under an electron microscope to get quantitative results.
LITERATURE CITED Campbell, N.A., J.B. Reece, 2011. Campbell Biology. 9th ed. USA: Pearson. p. 133.
Tatekar, N.S. and T.D. Griggs. 1981. Chinese Cabbage: Proceedings of the First International Symposium. Taiwan, China: Hong Wen Printing Works. p. 1-9.
Ryder, E.J. 1999. Lettuce, Endive and Chicory. New York, USA: CABI Publishing. p. 1-13.
Vainio, H. and F. Bianchini. 2003. Fruits and Vegetables. IARC. p. 2.
Kohli, P. 2008. Fruits and Vegetables Post Harvest Care: The Basics. Crosstree Techno-visors. p. 3-5.

Stereopsis Experiment Design

INTRODUCTION Stereopsis is the capability of assessing the depth of objects in the visual field, using the relative positions of the objects visualized by each eye.1 The difference in the right eye’s and left eye’s views in terms of the location of an object is defined as binocular disparity.2 The acquirement of the depth concept is a direct consequence of having laterally placed binocular visual system.1

Figure 1: Binocular disparity shown in detail2
Stereograms, also called Single Image Random Dot Stereograms (SIRDS) are visual illusions that make it possible to get three dimensional images from two dimensional figures via looking at different parts of the image with each eye and copying the acquired images on top of each other.3
As perception of the vision is a phenomenon in which eye and brain work in harmony where eye is to see and brain is to process and correlate the incoming information. As it is light that makes the vision possible via being absorbed and converted into electrical impulses by photoreceptor cells, the quality and also the quantity of light coming to the eye play determinative roles in visual perception.4
Pulfrich effect is one illustration of the significant role of acquired light for visual perception. In this specific phenomenon, a low contrast object is perceived as slower whereas a higher contrast object is perceived as faster comparing the two objects moving with the same speed. The contrast difference is provided via attenuating one eye’s light acquiration using filter glasses. Pulfrich’s pendulum is constructed to express this effect in quantitative terms via calculating the pendulum’s period. It has been assumed that the subjective slower perception of the filtered eye contributes to the depth perception and the binocular disparity in a way, creating a so thought elliptical movement perception.5,6

Figure 2: The diagram of the Pulfrich pendulum5
Another example of the depth concept in light of data known about visual perception is Ames room. In this particular illusion,if two person stands in the opposite edges of the room, one is perceived as gigantic compared to the other. The reason is that the walls and the windows or any other decorative elements are located in a trapezoidal way with one end of the room is far away located compared to the other with respect to the eyes. In the end, the cues on which the binocular vision depends to interpret relative features of visualized objects were mislead.7

Figure 3: Ames room7
Pulfrich’s pendulum
Filtered sunglasses
SIRDS images
Cube with three rods inserted
METHODS: Lateral Component of Depth Perception
A small cube with three rods inserted in was observed by experimenters and the position when the relative distance between the rods could be perceived was discussed.
Qualitative Evaluation of the Pulfrich Phenomenon
Using the website “”, the Pulfrich effect was observed and the perception changes along with the adjusted parameters was determined.
Quantitative Evaluation of the Pulfrich Phenomenon
We were provided with a Pulfrich pendulum and filtered sunglasses. By filtering one eye each time, experimenters were asked when they could no longer observe the elliptical movement while a pointer was driven towards them under the pendulum. Then the distance moved by the pointer relative to the pendulum axis was measured. The process was repeated after changing the eye filtered, changing the amplitude of the pendulum and also changing the distance of the eye to the pendulum set up.The results were recorded along with each experimenter’s distance between two pupil of their eyes. Using these data, the period was calculated.
RESULTS Experiment 1
A cube with 3 differently sized rods are given. It is observed that when the cube is hold horizontally all three rods are seen in the same depth while when it is hold vertically it was clearly seen that one of the rods are not on the same axis with the other two.
Experiment 2
From a website, movement of black dots is observed with using filtered glasses. It is observed that looking with a filter adds a depth of the movement, which is actually happening in two dimensions. The darker the filter is the more deep the circulation occurred; an elliptical path is observed. When the left eye is closed, the dots appear to come close to observer. The dots looks bigger when the degree of filter increased too.
Experiment 3
A pendulum is fixed and set in motion, while eye of the observers is closed with a filter. Pendulum appeared in an elliptical path with a diameter. The results are shown in Table 1. P is the distance between right eye and left eye. When the left eye is closed, clockwise motion is observed while when the right eye is closed counter clockwise motion is observed. The object looks smaller when it seems to get closer to observer.
Table 1. Elliptical pathway observations
2 m
3 m
3 m
0.5 m
1 m
1 m

It is observed that Fatma and Esra’s results are not very consistent with the expected result but Ekin’s values were consistent except the last part of the experiment. The calculations will be made on Ekin’s results.
The period of the pendulum is found with .
For Amplitude A=0.5 and 1 m T= 2. The angle is so small that amplitude doesn’t make a change.
ω=2 π/T so ω=3.
Δt = Δx / A sin ω
Δx / b = p / (a-b)
The calculations are shown in Table 2. The final part of the experiment is excluded because Ekin didn’t see the pendulum in that one.
Table 2. Calculations
2 m
3 m
3 m
0.5 m
1 m
Δx= p*b / (a-b)
Δt = Δx / A sin ω
DISCUSSION In this experiment, the purpose is to examine and understand the working principle of eye according to the light coming to eyes and to understand the perception of the depth according to the orientation of the object.
In first experiment, it is understood that orientation of objects affects the depth of the object in the brain. When rods are vertical, it was seem deeper than rods are horizontally orientated.
In second experiment, Pulfrich Effect is observed. the light coming to our one of the eye was delayed somehow relative to the other one, we saw moving objects in 2-Dimension as if they were moving in three dimensional.
In third experiment, the classical demonstration of the Pulfrich Effect by a swinging pendulum was examined in order to learn the relationship between retina position of corresponding object and depth perception .The pendulum is swung back and forth,when viewed normally with both eyes, it seemed swinging back and forth. When a filter is placed in front of one eye, the pendulum suddenly seemed as swinging in an ellipse parallel to the floor. The background information of this depth perception relies on a reduction in retinal illumination which results a corresponding delay in signal transmission, imparting instantaneous spatial disparity in moving objects. This seems to occur because visual system latencies are generally shorter for bright targets as compared to dim targets. This motion with depth is the visual system’s solution to a moving target when a difference in retinal illuminance, and hence a difference in signal latencies, exists between the two eyes.
As it can be seen from the results part, changes in amplitude ,number of filters,distance from the objects leads to the differences in time delay results.For example, when we increase the size of amplitude, the time also increases because the more amplitude means the more in size of the eliptical pathway.Also, the increase in the distance from a real object results in an increase in the deviation of time. In Ekin’s result, the relationship amplitude and pendulum is the most close one to expected result. In Esra’s and Betül’s result, it was expected to increase the pendulum with the amplitude but it did not so. And also, time differences increases when the number of filters increase and with double filters ,higher optical density leads to more eliptical observation of pendulum.
Moreoever, it could also be noted that when the object is far away from observer, it looks larger than the normal and when it is closer to observer it looks smaller than the normal.
REFERENCES: Kalloniatis, M. (2007). Perception of Depth. Retrieved 05 24, 2013, from Webvision, The Organization of the Retina and Visual System:
Heeger, D. (2006). Perception Lecture Notes: Depth, Size, and Shape. Retrieved 05 24, 2013, from Department of Psychology, New York University:
Stereograms. (n.d.). Retrieved 05 24, 2013, from
The Eye and The Visual World. (n.d.). Retrieved 05 24, 2013, from Macalester College:
Pulfrich Phenomenon. (n.d.). Retrieved 05 24, 2013, from Medical Dictionary: stereophenomenon
Phenomenology of Motion. (n.d.). Retrieved 05 24, 2013, from Rochester Institute of Technology.:
DorwardF M C, DayR H, 1997, “Loss of 3-D shape constancy in interior spaces: The basis of the Ames-room illusion”Perception26(6) 707–718