Introduction
The topic of salt’s influence on agriculture and plant growth has been explored in controlled and natural agricultural environments. In the context of agricultural explorations, it has been noted that soil salinity causes biotic and abiotic stresses (Lauchli and Epstein, 1990). According to Audesirk et al. (2008), salinity has been a major environmental stress to agriculture and plant growth for over 3000 years. Lauchli and Grattan (2002) further contend that at least 20% of plant growth is affected by salinity, especially in irrigated lands. Quantitative studies in grass species have also depicted salt stress’ reduction of growth by 20% and inhibition of maximal relative elemental growth rate (Lauchli and Epstein, 1990). This experimental paper explores the influence of salt (salinity) on grass growth.
Hypothesis: Increased salinity, as a result of spreading salt on the drive way, inhibits growth of grass.
Prediction: It was predicted that if salinity was increased in certain regions of the growth medium, then growth rate in such regions was likely to be low, and vice versa.
Method
The experiment was carried out at Biology Laboratory B-13 in the University of California. The list of requirements included salinized water, 2 irrigation cans, germination paper, unsalinized (pure) water, 2 Petri dish-like containers of 1 meter diameter and grass seeds. In the first set up (test experiment), the growth medium (germination paper) was put in the container. 25 Grass seeds were evenly placed in each of the ten concentric regions which were ten centimeters apart, starting from the center of the container. Unsalinized water was irrigated daily (at the center of the container), till the germination paper soaked. In the second set up (control experiment), unsalinized water was used daily to irrigate the center [Note that in the two experiments above, all requirements for seed germination was provided]. After two weeks, the number of plants which germinated in each concentric region was counted. The growth rate was determined as a percentage of total number of seeds in each concentric region.
Results
Test Experiment: Salinized Growth Medium
Control Experiment: Unsalinized Growth Medium
Discussion and Conclusion
Following the results and prediction, the control experiment depicted that salinity inhibited growth, as the uncolonized container had higher growth rate in all regions unlike the salinized container. In the test experiment, growth rate decreased towards the centre implying that increased salinity at the centre inhibited growth. Areas of low salinity at the periphery showed marked growth.
Although the majority of germination studies have been simplified by laboratories, Audesirk et al. (2008) contends that artificial laboratory environments are uncharacteristic of field conditions and lead to assumptions, which was (likely) a limitation for this experiment. In addition, there was no account for extraneous variables/stresses which affect plant growth, like water-stress, fluctuating salinities due to capillary rise and evaporation, and diurnal changes in temperature. Therefore, additional research has to be done to determine effects of other stresses on growth (Lauchli and Epstein, 1990).
References
Audesirk, T., Audesirk, G., & Byers, B.E. (2008). Biology: Life on earth with Physiology (9th ed.). Pearson Publishers.
Lauchli, A., & Epstein, E. (Eds.). (1990). Plant responses to saline and sodic conditions. In Agricultural salinity assessment and management: ASCE manuals and reports on engineering practice. New York: Oxford University Press.
Lauchli, A., & Grattan, S.R. (2002). Plant growth and development under salinity stress. California: University of California Press.