Although plants naturally take up Li even in uncontaminated soils (Bolan et al., 2021), excess intake is harmful to plants. Li concentration in soil naturally is extremely low, and small amounts of Li can improve and benefit the growth of organisms (Chow, 2022). However, the concentration of Li in soil has increased drastically along with the exponential growth in demand for renewable energy and the lack of regulations for the disposal of Li products (Bolan et al., 2021; Hayyat et al., 2021) (Figure 1). Furthermore, as plants absorb this Li, it enters the food chain when humans consume contaminated edible crops (Hayyat et al., 2021). 

Figure 1: (Bolan et al., 2021)

While Li is toxic to all plants at high concentrations (Hayyat et al., 2021), different Li sources have varying impacts on plants and different plants react to Li differently (Shakoor et al., 2022). By and large, plants in soil with a lower pH absorb more Li (Hayyat et al., 2021). The three main physiological parameters that are studied and affected by Li concentrations are germination, root biomass and shoot biomass (Shakoor et al., 2022). Shakoor et al. (2022) studied four main sources of Li namely LiNO3, Li2SO4, LiOH and LiCl and generally, an increased concentration of Li reduces the germination, root biomass and shoot biomass of plants with some exceptions such as soybean when LiOH is the Li source (Shakoor et al., 2022). Among the four sources, Li uptake is highest with LiCl (Figure 2). 

Figure 2: (Shakoor et al., 2022)

Furthermore, Shakoor et al. (2022) observed a decrease in chlorophyll content as Li concentrations increased. Chlorophyll a, the primary photosynthetic pigment experienced a higher fall in percentage compared to chlorophyll b (Shakoor et al., 2022). 

Chlorophyll a and b decreased by 17% and 5% at <50 ppm 234 concentration with exposure at ≥50 ppm concentrations declined chlorophyll a and b by 34% and 235 10% respectively. – Shakoor et al. (2022)

Compared to most elements, Li is very mobile and can easily travel through soil and within the plant (Hayyat et al., 2021; Shakoor et al., 2022). Therefore, the part of the plant where Li is mainly accumulated in varies between plants and the exogenous level of Li (Shakoor et al., 2022).  

Besides limiting crop development, Hayyat et al. (2021) also found that an increase in Li concentrations in soil reduced other essential nutrients such as Na, N and K that are crucial to the growth of plants. Li also increased the average pH of the soil which will threaten the survival of plants that grow primarily in soils with low pH (Hayyat et al., 2021). With the potential to threaten the survival of plant species and disrupt food supply, Li pollution must not be taken lightly just because its effects are yet to be observed on a global scale.  

 

Reference List

Bolan, N., Hoang, S. A., Tanveer, M., Wang, L., Bolan, S., Sooriyakumar, P., Robinson, B., Wijesekara, H., Wijesooriya, M., Keerthanan, S., Vithanage, M., Markert, B., Fränzle, S., Wünschmann, S., Sarkar, B., Vinu, A., Kirkham, M., Siddique, K. H., & Rinklebe, J. (2021). From mine to mind and mobiles – Lithium contamination and its risk management. Environmental Pollution, 290, 118067. https://doi.org/10.1016/j.envpol.2021.118067 

Chow, A. T. (2022). Proactive approach to minimize lithium pollution. Journal of Environmental Quality, 51(5), 872–876. https://doi.org/10.1002/jeq2.20405 

Hayyat, M. U., Nawaz, R., Siddiq, Z., Shakoor, M. B., Mushtaq, M., Ahmad, S. R., Ali, S., Hussain, A., Irshad, M. A., Alsahli, A. A., & Alyemeni, M. N. (2021). Investigation of Lithium Application and Effect of Organic Matter on Soil Health. Sustainability, 13(4), 1705. https://doi.org/10.3390/su13041705 

Martin, L. (2019, June 10). What Are the Roles of Chlorophyll A & B? Sciencing. https://sciencing.com/what-are-the-roles-of-chlorophyll-a-b-12526386.html 

Shakoor, N., Adeel, M., Azeem, I., Ahmad, M. A., Zain, M., Abbas, A., Zhou, P., Li, Y., Ming, X., & Rui, Y. (2022). Responses of Agricultural plants to Lithium pollution: Trends, Meta-Analysis, and Perspectives. BioRxiv. https://doi.org/10.1101/2022.05.07.491047