Chloride is a plant micro-nutrient and dominant anion in the soil; however, chloride is toxic at high concentrations. Chloride is ubiquitous in soils and underlying bedrock material, mostly due to the deposition through irrigation water and fertilization. The process of chloride uptake from soil to plant is an active process that expends the plant energy. Chloride is also required for the plant to undergo photosynthesis. Plant photosynthesis also requires carbon dioxide and water to create oxygen as a by-product. That said, the availability of chloride to plants will increase the overall productivity of photosynthesis, thereby significantly intensifying the overall production of growth and biomass. The increase in growth due to extracellular accumulation of chloride leads to larger epidermal cell size, larger stomata, and increased surface area. All that together potentiates plants’ ability to conduct photosynthesis. Chloride plays an important role in the production and modification of stomatal activity and abundance. According to Wege et al., 2017, chloride anion fluctuations can alter the osmotic gradient within the plant, which will increase or decrease water uptake in the plant. Since chloride is a weak anion, it requires positively charged surfaces to be adsorbed by the soil. The process of soil adsorption is pH-dependent and occurs when the soil constituent binds to the surface of soil particles via electrostatic forces. According to Smith, 1972, soil leaching causes anions to move through the soil faster than the water molecules. This rapid anion movement through the soil results from exclusion from negatively charged soil particles. Therefore, chloride moves from the upper soil surface to lower depths faster, where they accumulate with the soil water.
Chloride
How Chloride is a Plant Micronutrient and Dominant Anion
Source: Geilfus, 2018
Figure 1. The symplastic pathway is the main route for Cl− uptake. Under non-Cl-stress conditions, most Cl- taken from the soil solution moves via the symplastic pathway toward the xylem. When plants are under Cl-stress, this route is not as efficient, and more Cl− is transported via apoplastic pathways, which is an alternate pathway for absorbing nutrients. The apoplastic pathway transports Cl- through the cell walls of plant tissues. This route is much less efficient than the symplastic route, but it allows plants to absorb nutrients in a stressful environment.
Further Reading
Agriculture, U. S. D. of. (n.d.). Relative rate of chloride movement in leaching of surface: Soil science. LWW. Retrieved August 22, 2022, from https://journals.lww.com/soilsci/Citation/1972/10000/Relative_Rate_of_Chloride_Movement_in_Leaching_of.4.aspx
Broyer, T. C., Carlton, A. B., Johnson, C. M., & Stout, P. R. (1954). Chlorine—a micronutrient element for higher plants. Plant Physiology, 29(6), 526–532. https://doi.org/10.1104/pp.29.6.526
Brumos, J., Colmenero-Flores, J.M., Conesa, A., Izquierdo, P., Sánchez, G., Iglesias, D.J., López-Climent, M.F., Gómez-Cadenas, A., Talón, M., 2009. Membrane transporters and carbon metabolism implicated in chloride homeostasis differentiate salt stress responses in tolerant and sensitive Citrus rootstocks. Funct. Integr. Genomics 9, 293–309. https://doi.org/10.1007/s10142-008-0107-6.
Colmenero-Flores, J. M., Franco-Navarro, J. D., Cubero-Font, P., Peinado-Torrubia, P., & Rosales, M. A. (2019). Chloride as a beneficial macronutrient in higher plants: New roles and regulation. International Journal of Molecular Sciences, 20(19), 4686. https://doi.org/10.3390/ijms20194686
Dowling, K.C., Costella, R.G., Lemley, A.T., 2018. Modeling the Movement of a Rapidly Degrading Solute, Methomyl, in Dynamic Soil-Water Systems. Mechanisms Of Pesticide Movement Into Ground Water. pp. 101. https://doi.org/10.1111/gwat.
Franco-Navarro, J. D., Brumós, J., Rosales, M. A., Cubero-Font, P., Talón, M., & Colmenero-Flores, J. M. (2015). Chloride regulates leaf cell size and water relations in tobacco plants. Journal of Experimental Botany, 67(3), 873–891. https://doi.org/10.1093/jxb/erv502
Geilfus, C.-M. (2019). Chloride in soil: From nutrient to soil pollutant. Environmental and Experimental Botany, 157, 299–309. https://doi.org/10.1016/j.envexpbot.2018.10.035
Gong, H., Blackmore, D., Clingeleffer, P., Sykes, S., Jha, D., Tester, M., Walker, R., 2011. Contrast in chloride exclusion between two grapevine genotypes and its variation in their hybrid progeny. J. Exp. Bot. 62, 989–999. https://doi.org/10.1093/jxb/erq326
Hooks, T. N., Picchioni, G. A., Schutte, B. J., Shukla, M. K., & Daniel, D. L. (2018). Sodium chloride effects on seed germination, growth, and water use of Lepidium alyssoides, L. Draba, and L. Latifolium: Traits of resistance and implications for invasiveness on Saline Soils. Rangeland Ecology & Management, 71(4), 433–442. https://doi.org/10.1016/j.rama.2018.04.001
Smith GS, Clark CJ, Holland PT. 1987. Chlorine requirement of kiwifruit (Actinida deliciosa). New Phytologist 106, 71–80
Terry N. 1977. Photosynthesis, growth, and the role of chloride. Plant Physiology 60, 69–75.
Wege, S., Gilliham, M., & Henderson, S. W. (2017). Chloride: Not simply a ‘cheap osmoticum’, but a beneficial plant macronutrient. Journal of Experimental Botany, 68(12), 3057–3069. https://doi.org/10.1093/jxb/erx050
White, P. (2001). Chloride in soils and its uptake and movement within the plant: A Review. Annals of Botany, 88(6), 967–988. https://doi.org/10.1006/anbo.2001.1540
