Introduction: The environmental conditions in which an organism is exposed to plays a huge role in the success of that organism. For example, there are several environmental factors that could potentially have detrimental effects on the overall growth and development of many types of plant species (Rahdari et al. 2012). High salinity in water and soil has been a major problem in the agriculture industry for several years now because these high levels of salinity limit crop growth and development (Singh et al. 2017).
For many plants, successful water uptake is essential for optimal growth and overall development (Läuchli and Gratton 2007). Soil and water that have high salinity concentrations hinder the growth and development of many plants primarily due to reducing osmotic potential, which limits the amount of water that these plants can take up (Singh et al. 2017).
The goal of this experiment was to examine the effects that different salinity concentrations have on the germination rate and root length of Lens culinaris seedlings. Lens culinaris seeds were a good model to use in this experiment because they are affordable, easily accessible, fast growing, and sensitive to salinity. For this experiment, the conducted hypothesis is that if the L. culinaris seedlings are exposed to an environment that is higher in salinity, then the germination rate and root length of the seedlings will be negatively affected. The higher salinity concentrations should inhibit the germination rate and root length of the seedlings because the excessive amount of salinity will reduce the amount of water uptake by the the seedlings (Singh et al. 2017).
Methods: 50 L. culinaris seeds were obtained and then placed into a tea ball. The tea ball containing the seedlings was then placed in a 10% bleach solution for 10 minutes. Following this, the L. culinaris seeds were rinsed under running water for another 10 minutes. After this, five petri dishes were obtained, and 5% solution of NaCl was used to make 10 mL of a 0, 0.5, 1, 2, and 3.5% NaCl solution. Pieces of paper towels were folded into thirds, traced with a petri dish, and were then cut out. This was done a total of five times, and the pieces of cut paper towels, each consisting of three layers, were then placed into five different petri dishes. A pipette was then used to collect 8 mL of saline solution, and this was placed into a petri dish. This was repeated for all of the other petri dishes, and each dish was labeled with the concentration that it had in it. After 60 seconds, any excess liquid was poured out of each dish. When this was completed, 10 L. culinaris seeds were placed into each of the five petri dishes. The five dishes were then stacked on top of each other and placed into a ziplock bag, and then the bag was placed in the incubator. The L. culinaris seeds were incubated at 23.5℃ for one week. After one week of incubation, the seeds were removed from the petri dishes, and each seedlings root length was measured in millimeters and recorded.
Results: It is evident that the data followed a trend in which the L. culinaris seeds that were placed in petri dishes with a lower NaCl concentration had more root growth compared to the seeds that were placed in the petri dishes with higher concentrations (Figure 1). The average root lengths were 19.5 mm for 0% NaCl concentration, 16.2 mm for 0.5%, 9.1 mm for 1%, 8.8 mm for 2%, and 1.1 mm for 3.5%. To compare all of the treatments, an ANOVA analysis was used and a p-value of 2.42E-6 was calculated. Following this, a Tukey-Kramer test was ran, and it found that there was a significant difference between the L. culinaris seeds that were placed in the 0% concentration petri dish, and the L. culinaris seeds that were placed in the 1%, 2%, and 3.5% concentrations. The seeds that were placed in the 0.5% concentration were also significantly different than the seeds that were placed in the 3.5% concentration. The L. culinaris seeds that were in the 0% and 0.5% NaCl concentrations had noticeably longer roots compared to the seeds that were in the 1%, 2%, and 3.5% NaCl concentrations. It was also observed that there was mold present on some of the seeds.
Fig. 1 Effects of varying concentrations of NaCl solutions on L. culinaris root growth. The average growth rate of the L. culinaris seeds that were in the 0% NaCl concentration was significantly different than the average growth rates for the L. culinaris seeds that were in the 1%, 2%, and 3.5% NaCl concentrations (p-value<0.05). There was also a significant difference between the seedlings that were in the 0.5% concentration and the seedlings that were in the 3.5% concentration (mean±SE, n=10 for each concentration).
Discussion and Conclusion: The hypothesis that if the L. culinaris seeds are exposed to an environment that is higher in salinity, then the germination rate and root length of the seedlings will be negatively affected was supported by the data. The L. culinaris seeds that were placed in the petri dishes that had a higher NaCl concentration had less root growth on average because the excess amount of salinity created an osmotic potential that resulted in a reduced ability to obtain the amount of water that was needed for optimal germination and root length growth (Singh et al. 2017). For many plant species, like the L. culinaris that were used in this experiment, the ability to absorb the necessary amount of water is essential for optimal growth and overall development (Läuchli and Gratton 2007). This explains why the seeds that were placed in the 0% NaCl concentration petri dish were the most successful when it came to root length growth.
Although this experiment tested the effects of salinification on the germination and root length of L. culinaris that were placed in a petri dish, the findings of this experiment are consistent with similar studies that have been tested in field research. For example, several studies show that water and soil that have high concentrations of salinity have negatively impacted agricultural crops all over the world over the last several years (Singh et al. 2017).
In conclusion, the results of this experiment show how much of an impact environmental conditions can have on an organism. The seedlings that were placed in more favorable environmental conditions exhibited much greater developmental success compared to the seedlings that were placed in the unfavorable, high NaCl concentrations. A future research experiment that could be conducted that relates to this topic is determining several other environmental factors that could potentially have detrimental effects on germination rates and root length growth of plants that are native to Arkansas.
Literature Cited:
Läuchli A., & Grattan S. (2007). Plant growth and development under salinity stress. Advances in Molecular Breeding Toward Drought and Salt Tolerant Crops, 1-32. https://doi.org/10.1007/978-1-4020-5578-2_1
Rahdari, P., Tavakoli, S., Hosseini, S.M. (2012). Studying of salinity stress effect on germination, proline, sugar, protein, lipid and chlorophyll content in Purslane (Portulaca oleracea L.) leaves. Journal of Stress Physiology & Biochemistry, 8(1), 182-193.
Singh, D., Singh, C.K., Kumari, S., Tomar, R.S., Karwa, S., Singh, R., Singh, R.B., Sarkar, S.K., Pal, M. (2017). Discerning morpho-anatomical, physiological and molecular multiformity in cultivated and wild genotypes of lentil with reconciliation to salinity stress. PLoS ONE 12(5).