To determine the optimum temperature mung beans germinate at
The mung beans placed at 27�C will germinate more efficiently (in terms of number of beans germinated after a set time frame) in comparison to beans placed at other temperatures.
In Asia, bean sprouts put in Chinese cuisine (which come from the mung beans) are usually grown at a warm temperature of 30-35� for longer, thicker sprouts, so although the beans would germinate at 40�, this temperature would probably start to denature the enzymes.
Cotton, Balance, Labels, Incubator, Distilled water, 25 ml Measuring cylinder, 5 Petri dishes
Variables:
Independent Variables: – Temperature
Dependent Variables: – Adequate partial pressure of oxygen
– Supply of light
– Amount of water
– Number of beans
– Mass of cotton
1. Used a balance to measure 1.5g of cotton
2. Spread cotton wool evenly around the base of the Petri dish
3. Carefully spread 8 mung beans in the centre of the Petri dish so that each was roughly 1cm apart
4. Measured 20 ml of tap water into the 25 ml measuring cylinder
5. Poured water onto the surface of the cotton and beans
6. Covered the Petri dish with its lid
7. Repeated steps 1-6 four more times
8. Without repeating, labeled each dish with one of the five temperatures: -4�, 18�, 25�, 40�, 60�
9. Placed each dish into its label’s respective incubator apart from the dish labeled at room temperature (25�)
10. Placed the room temperature dish on a counter away from the sun light
11. Observed germination of seeds everyday for a week
1. While we were conducting this experiment, the lab was not always open on certain days, which prevented us from observing our beans everyday.
So we altered Step 11 in the procedure, and made our observations at least once every three days.
Data & Observations:
Temperature
(in �C)
# Of Beans Germinated (/8)
Day 1
Day 2
Day 3
60
0
0
0
40
6
7
8
25
7
8
8
4
0
0
0
-18
0
0
0
We were able to obtain results from three different days. However, these observation days were not spread out at even intervals.
Day 1 of observations – 1 ‘day after experiment is set’
Day 2 – 2 ‘…’
Day 3 – 7 ‘…’
Day 1: The beans at 60� have a milky white substance covering the testa, that is producing a molding smell, and none of the beans have germinated. However, the beans that were in 40� have started to germinate reasonably well, with 6 beans that have short radicles. The beans at 25� have 7 beans with radicles, while its cotyledon expanded in size and the testa changed to a light green color. As for the beans at 4�, they bare similarities in appearance of the beans at 25� and 4�, with 0 beans germinated. Those that were placed in -18� didn’t have any growth at all either, and actually appeared to have shrank. The color of the testas were also a much darker shade of green in comparison to the beans in the original package, as well as the rest of the beans in other Petri dishes.
Day 2: White radicles have started to protrude the seed skin, no plumules are present in Petri dishes 40� and 25�, and one more bean has started to germinate in each. No germinating beans or other changes is present in the dishes that were in -18�, 4�, and 60�.
Day 3: All beans have sprouted in the 27� and 40� dishes, with hypocotyls, epicotyls, and roots growing rapidly. Seeds have become epigeal and photosynthetic, and have undergone photomorphogensis where they begin to make chlorophyll and turn green. The hypocotyl has elongated forming a hook, straightening and pulling the cotyledons and shoot tip into the air, and it appears that the cotyledon and apical hook have unfolded, revealing the epitcotyls and foliage leaves. In the 27� dish, the hypocotyls and epitcotyls are straight and long, with healthy light green foliage leaves and a tangle of main roots and side roots entwined in the cotton with no sign of the testa. A similar result can be observed in the 40� dish, however, hypocotyls are white and bent, and less side roots are present. Foilage leaves are light yellow, while the leave casings loosely cover the shoot tips. Beans that were placed in -18� still have not germinated at all, and maintained the same appearance. Likewise, none have germinated in 60� either, and the cotton surface has turned yellow. The beans have turned brown, and expanded, but they have a shriveled testa with a white milky solution covering it. In the Petri dish at 4�, there was no change from Day 2’s observations, no seeds have germinated, but all seeds have turned a light green color, while their hilums have all turned white from its original color, black.
The success of the germination in the 27� and 40� dishes was due to the right amount of energy the heat provided. As the temperature increased, more heat energy was provided which allowed for more collisions between the particles in the enzyme and substrate, resulting in a higher rate of reaction. However, when the temperature exceeded its optimum, the enzymes’ active site changed shape and became denatured which prevented it from holding the substrate molecule, slowing down the rate of reactions, thus explaining why the beans did not germinate at 60�. On the other hand, low temperatures like -18�, did not provide the enzyme with enough energy to collide with substrate molecules, so the rate of reaction decreased, or even ceased. Excessively high temperatures can cause dormancy, slow, erratic germination, poor development, and in some cases, death, while temperatures that are too cool can delay germination resulting in seed damage, and an uneven or inadequate seed emergence. Learn what is the optimum concentration of pectinase
However, there are other reasons why the seeds may not have germinated in other temperatures, for example, light could stimulate or inhibit the seed germination, but as the background of the seed was not known, all Petri dishes aside from the room temperature dish were place in an inhibitor (dark setting.) The differences in environment could have affected the results, as certain responses, such as the straightening of the hypocotyls are stimulated by light. And if germination were to be defined as the process where growth emerges from a period of dormancy, then the appearance and health of the sprout would be reflective of its germination process.
Some other reasons for the absence of germination could be a result of certain internal conditions. Physical, chemical, or physiological barriers may not have disappeared or been removed by the propagator before germination. Some embryos in the seeds may not have even been alive or capable of germination to be viable for the investigation at the start.
Conclusion & Discussion:
The results supported my hypothesis that mung beans would best germinate at room temperature. While no beans had germinated in the Petri dishes that were in 60�, 4�, and -18�, the number of beans that germinated in 27� was always higher than the rest. At observation Day 1 and Day 2, 7 and 8 beans had germinated respectively, while the only other germinating dish placed at 40� had one less seed during each observation. The way the mung beans had sprouted at 27� also support my hypothesis, as the sprouts were healthy, straight, long, and green in the 27� dish, while in the 40� dish, they were bent, yellow, and short.
If I were to repeat this experiment again, I would use distilled water instead of tap water. The tap water may have contained certain minerals and chemicals that could have increased or decreased the rate of germination. However, as the intervals of the tested temperatures were so far apart, the results would not have varied in terms of the order of the highest germinating dishes. But, if the testing temperatures were closer together, the optimum temperature that mung beans germinate at might not have been accurate. Furthermore, in the analysis of the results I mentioned that light might have altered the results, so to improve this experiment next time, I would put the room temperature Petri dish in a dark place to make this investigation more fair. I would also conduct another experiment, like this one, with closer intervals in the testing temperatures between room temperature and 40� to gather a more concise result for the optimum temperature mung beans will germinate at. Read mung bean experiment report
Another experiment I would conduct in conjunction with this investigation, is one that would analyze the effects light, water, oxygen concentration, chemicals, different soils, and the number of beans in a confined area has on the rates of germination.
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