Effect of moisture on lentil seed germination and growth

Transcription

1 Effect of moisture on lentil seed germination and growth By Francisco Javier Hidalgo Zamora, 7º A (This experiment was carried out in collaboration with Robert Henshaw Amado) Objective/Hypothesis The objective of this experiment is to determine the effect of moisture on the germination and growth of lentil seeds. Therefore, I will change the moisture of the sand where I am going to germinate and grow the seeds (independent variable) and I will see if the seeds germinate or not, and how much they grow (dependent variable). My hypothesis is that lentil seeds will only germinate and grow at a specific moisture range. Out of this range lentils will not germinate and grow because they either will not have enough water or they will have too much water. Relative humidity in seed germination chambers is between 40 and 90%. 1 I suppose that this is the most appropriate range for seed germination. A seed is a small embryonic plant. It is the result of the fertilization of the plant ovule. When proper environmental conditions exist, seed embryo develops into a seedling, which is a new phase of plant growth. Environmental conditions that influence seed germination and growth are: water, oxygen, temperature, and light. Proper environmental conditions are needed by the plant to growth. If these conditions are not obtained, the metabolism of the seed will not resume and the plant will not germinate. Variables: Independent: The concentration of water in the sand. I will assay different quantities of water to be sure that the hypothesis is correct. The quantities of water that I will assay will be: 0, 5, 7.5, 10, 17.5, 5, and 50 ml water in 50 g of sand. Dependent: I will observe the seeds that germinate and I will measure the size of the stem after a period. I will count the number of seedlings every day for three weeks. I will measure the length of the stem at the end of the experiment (1 days). Controlled: Temperature, oxygen content, air humidity, and light. Although they might also be independent variables in other experiments, I will fix them so that I can investigate the effect of moisture. If I can employ a seed germination chamber, I will fix these variables. If the chamber is not available, I will not fix the variables. However, all samples will be studied under the same temperature, oxygen content, air humidity, and light conditions. The only variable that I will change from one sample to other will be humidity. Therefore, although other variables are not fixed, the differences observed in the dependent variable between one and other sample will be a consequence of the independent variable. Materials: 1 Geneva Scientific LLC (00). Germination Chambers Germination Incubator Model GR 3L Percival Chamber. [online] Retrieved from: scientific.com/models/seedgermination/gr 3L.php [Accessed: May 013]. 1

2 100 ml beaker (8) Lentil seeds (70) Soil Water (tap water) Measuring pipette and measuring cylinders Scale Permanent marker Ruler Procedure: 1. Mark the beakers with the permanent marker making sure that you take the following codes: 1) Soil with no water ) Soil with 5 ml of water 3) Soil with 7.5 ml of water 4) Soil with 10 ml of water 5) Soil with 17.5 ml of water ) Soil with 5 ml of water 7) Soil with 50 ml of water. Put 50 g of soil in all beakers. 3. Add the corresponding amount of water to each beaker according to its number. 4. Mix soil and water so that the moisture is uniform in all the soil. 5. Put 10 seeds in each beaker. The seeds should be distributed uniformly and they should be about one cm below the surface of the soil.. Put all beakers under a controlled temperature, light, oxygen content, and air humidity. If this is not possible, be sure that at least all of them have the same temperature, light, oxygen content, and air humidity. To provide adequate environmental conditions for seed germination, at least 1 h of light, a temperature of 0 C, and air should be present. 7. Maintain the humidity in the beakers by replacing every day the water lost. Therefore, every day each beaker should be weighed, and the water needed to maintain the original weight added. 8. Everyday count the number of seeds that have germinated (you should see the seedling outside of the sand surface). In addition, measure a gross mean height of the plants so you have an idea of the growth rate. The number of germinated seeds and the mean height should be written in the following table, this table also includes the room temperature:

3 beaker 1 0 ml beaker 5 ml beaker ml beaker 4 10 ml beaker ml beaker 5 ml beaker 7 50 ml day no. cm no. cm no. cm no. cm no. cm no. cm no. cm T( C) At the end of experiment (three weeks) remove the seeds and measure the length of the stem of each seed. Write the length of each stem (in mm) in the following table. Beaker no Mean 10. The study of the data in the first table will confirm or not the hypothesis. I think that no seeds will germinate in beaker 1 (I do not think that there is enough water in these beakers). In addition, I do not think that seeds will germinate in beaker 7 (too much 3

4 water). On the other hand, I hope that seeds germinate in the intermediate beakers. The beaker where a higher number of seeds germinate will indicate the optimum moisture level of the soil for lentil seed germination at the fixed temperature, oxygen, air humidity, and light of the experiment. It may also occur that all seeds germinate in several beakers but germination is produced faster with one moisture level than with other. This will also be answered with the results in the first table. 11. The study of the data in the second table will indicate the role of moisture in the growth of the seedlings. It may be interesting to know if the same moisture conditions that produce higher seed germination also produce taller seedlings. References: I have consulted the following web pages to prepare this experiment: Doneen, L., and MacGgillivray, J. (1943). Germination (emergence) of vegetable seed as affected by different soil moisture conditions. Plant Physiology, 18 (3), pp Retrieved from: pdf [Accessed: May 013]. This is a scientific paper studying the role of moisture in seed germination. En.wikipedia.org (013). Germination Wikipedia, the free encyclopedia. [online] Retrieved from: [Accessed: May 013]. This article explains the factors that affect seed germination. Loupassaki, M., and Vasilakakis, M. (1995). "The effect of temperature and relative humidity on the in vitro germination of the pollen of avocado ", Proceedings of The World Avocado Congress III, pp Retrieved from: [Accessed: May 013]. This is a scientific paper on the role of temperature and humidity in the germination of the pollen of avocado. Successwithseed.org (009). What Do My Need for Good Germination?. [online] Retrieved from: started/38 what do my seedneed for good germination [Accessed: May 013]. Very good page to know what seeds need to germinate and growth. Results The experiment was carried out as described in the procedure. Every day I weighed the beakers and replaced the lost water. I also counted the germinated seeds and measured a gross mean height of the plants so I had an idea of the growth rate. 4

5 The number of the seedlings (no.) and the height of them (cm) are indicated in the following table. This table also indicates the temperature of the room ( C). Table 1. Growth of the plants beaker 1 0 ml beaker 5 ml beaker ml beaker 4 10 ml beaker ml beaker 5 ml beaker 7 50 ml day no. cm no. cm no. cm no. Cm no. cm no. cm no. cm T( C) <1 1 <1 3 <1 1 <1 3 < <

6 According to the recorded data, the temperature was quite constant (it increased slightly throughout the experiment) and was close to 0 C, a good temperature for germination. I have plotted the number of seedlings as a function of time. The plot is the following: No. of seedlings Beaker 1 Beaker Beaker 3 Beaker 4 Beaker 5 Beaker Beaker Number of days As can be observed, seeds germinated in beakers 1. Only beaker 7 contained too much water and seeds were unable to germinate. According to the number of germinated seeds (90%), the optimum conditions were achieved in beakers Humidity in beaker 1 was too low 8 and only 80% of seeds germinated. Humidity in beaker was too high and only 0% of 4 the seeds germinated. If we plot the number of germinated seeds No. of seedlings Water amount (ml)

7 against the number of ml of water in the beaker we obtain the plot on the right: The maximum number of seedlings was obtained when adding between 5 ml and 15 ml of water to 50 g of soil. Independently of the amount of water, seedlings appeared more or less at the same time: between days 3 and. Only, seeds in beaker 4 seemed to appear slightly earlier (the 9 seedlings appeared by day 5). Curiously, this beaker 4 contained an amount of water that was in the centre of the parabola obtained in Fig.. Was this amount of water the best for our conditions? Humidity in beaker 4 was about 17% (taking into account only the water that I added). The effect of humidity on seed germination depends on the involved seed. However, Doneen and MacGgillivray found that most of the studied seeds germinated best between 10 and 18% of humidity. Although they did not study lentil seed germination, it is reasonable to suppose that optimum humidity for lentil seed germination will also be within that range (I could not find the optimum humidity for lentil seed germination). Therefore, our conclusion that humidity if beaker 4 was the optimum under our conditions, may be correct. If we the plot ling length (cm) Beaker 1 Beaker Beaker 3 Beaker 4 Beaker 5 Beaker Beaker Number of days length of the seedlings against the time, we obtain the following plot: Doneen, L., and MacGillivray, J. (1943). Germination (emergence) of vegetable seed as affected by different soil moisture conditions. Plant Physiology, 18 (3), pp Retrieved from: pdf [Accessed: May 013]. 7

8 The figure shows that the seedlings grew very similarly. The growth was produced between days 4 and 17, and was produced very similarly in all the beakers. These measures are only approximate because the length of the plant were measured in the beakers and were a gross mean value for the different seedlings in each beaker. The real length achieved by the plants is collected in the following table. These values were obtained at the end of the experiment. Table. Length (cm) of the seedlings at the end of the experiment (1 days) Beaker Mean no * * * 14 15* 11* The numbers with an asterisk (*) indicates that the plant was dead at the end of the experiment. 8

9 The mean lengths of the seedlings were very similar in the seven beakers. The beaker that had the tallest plants was beaker 5. However, this beaker was where a higher number of plants died before the end of the experiment. Is higher water content good to obtain taller plants but plants live shorter? I have trying to look for information to answer this question, but I have not been able to find out the answer. I do not know whether such study has not been carried out previously. Nevertheless, beaker, where only seeds germinated, had a higher height mean than beaker 5. These results suggest that, once seeds have germinated, a higher humidity will produce taller plants than the maintenance of the humidity needed for seed germination. I think that this would be an interesting topic for a further study: to germinated all the seeds with the same humidity and then study the effect of increasing humidity on the size and the mortality of the plants. My hypothesis is that a higher humidity will produce taller plants (analogously to the taller plants found in tropical forests). Conclusion germination was produced over a wide range of humidity, and the humidity present originally in the soil was enough to produce the germination of the assayed lentil seeds. Using our conditions, seeds germinated (at least an 80% of success was obtained) from 0 to 17.5 ml of water in 50 g of the employed soil. The determination of the humidity in the original soil is needed to know the exact amount of water needed for seeds to germinate. Within this humidity range, all seeds seemed to develop similarly and the obtained plants had very similar heights. The increased height and mortality observed in beaker 5 should be confirmed to determine if this humidity is the optimum for obtaining the tallest plants but it also produces an earlier plant death. Revision of the method The main problem with the experiment has been the amount of water initially present in the employed soil. I think that this soil should be dried before starting with the experiment. This is the only way to determine the exact humidity range in which germination is produced. The rest of the experiment can be followed as indicated including the maintaining of the humidity each day by replacing the evaporated water. 9

10 10