Essential and Beneficial Elements: What Do Plants Actually Need?

Plants need 17 essential elements to grow and complete their life cycle. But plant nutrition does not end with that list. Silicon can accumulate in structural tissues and influence stress responses, while iodine has been linked to flowering, growth and proteins involved in photosynthesis. Neither has to be a universally essential nutrient to be relevant to cultivation.

For growers, the useful distinction is between an element a plant must have and one that can improve performance under particular conditions.

The 17 essential elements

Three essentials—carbon, hydrogen and oxygen—come primarily from air and water. The other 14 are mineral nutrients that plants obtain largely from their root environment. The table groups them by source and by the amount required.

Macronutrients and micronutrients differ in the quantities plants need, not their importance. Nitrogen and potassium are required in much larger amounts than nickel or molybdenum, yet a shortage of any essential element can interfere with normal growth or reproduction. Required amounts, tissue concentrations and nutrient balances depend on the species, growing stage and conditions.

What makes an element essential—or beneficial?

The classical test of essentiality asks whether a plant can complete its life cycle without an element, whether another element can replace its role, and whether it has a direct function in plant metabolism. This is more demanding than detecting an element in plant tissue. Trace contamination in water or growth media can also complicate experiments intended to exclude an element completely.

Nickel is a useful example. In barley cultivar ‘Onda’, Brown, Welch and Cary (1987) showed that severe nickel shortage impaired the production of viable grain. Supplying nickel corrected the deficiency. The reproductive response helped establish nickel as an essential micronutrient, even though plants need very little of it.

The distinction matters because plants absorb far more than the 17 essentials. Coker et al. (2026) assembled a global dataset reporting tissue concentrations across 52 elements, using 5,474 samples from 73 countries. That is a picture of plant elemental composition, not a list of 52 nutritional requirements. Gerendás et al. (2026) propose the term conditionally beneficial elements for elements that improve plant performance in specified species or environments. Silicon is a well-studied example, while iodine is an emerging case with intriguing experimental results.

Silicon: uptake and plant resilience

Silicon is taken up mainly as orthosilicic acid (H₄SiO₄) and can accumulate as silica in plant tissues. In Cannabis sativa, researchers have identified silica deposits in bast-fibre cells and at the base of leaf trichomes (Guerriero et al., 2019).

Silicon can also help plants cope with stress. In a hemp study, silicon treatment reduced salt-stress symptoms in older leaves (Berni et al., 2021). That makes silicon relevant to growers interested in plant resilience as well as tissue structure. The mechanisms, research findings and different silicon sources are explained in Silicon in Plants: Food, Biostimulant or Structural Tool?.

Iodine and photosynthesis-related proteins

Kiferle et al. (2021) identified 42 iodinated proteins in the above-ground tissues of Arabidopsis thaliana. Of 40 proteins forming an interaction network, 31 were involved in photosynthesis. Iodine was thus found in proteins associated with the machinery plants use to capture light and fix carbon.

For growers using artificial lighting, this connection is particularly interesting because photosynthesis underpins how light contributes to crop growth. In lettuce, low iodine concentrations increased biomass, photosynthetic pigment content and protein content (Sun et al., 2025). The role of iodine incorporation in the activity of individual proteins is still being studied.

Other trials add a growth and crop-production perspective: Kiferle et al. (2021) observed earlier flowering and greater biomass in Arabidopsis, while Kiferle et al. (2022) found higher tomato fruit fresh-weight yields under specific iodine treatments. Researchers also observed changes in defence-related gene expression in Arabidopsis (Kiferle et al., 2021), linking iodine research to both growth and plant responses to stress. For the research details and wider context, see Do Plants Need Iodine Too?.

From essential nutrition to beneficial additions

The 17 essential elements provide the foundation of plant nutrition. Silicon and iodine offer a way to think more broadly about what an element can contribute to plant structure, physiology and stress responses.

Before changing a feeding programme, it helps to know what the fertiliser and root environment already supply. More Fertilizer, Less Uptake? The Roots Decide explains the relationship between availability and uptake. For a practical assessment of plant health and growing conditions, see Before You Add Anything, Learn to Read the Plant.

Explore silicon and iodine with PlantPotential

Ortho Origin provides orthosilicic acid (H₄SiO₄), the form of silicon plants can absorb. For growers looking to include silicon in a cultivation programme focused on plant structure and resilience, it offers a targeted source of plant-available silicon.

Iodine Insight puts iodine at the centre of its approach to plant nutrition. Research connecting iodine with photosynthesis-related proteins and positive growth responses in several crops makes this element worth exploring. Iodine Insight also contains other naturally occurring elements and constituents; its product page provides more detail about the composition and application.

References

Brown, P. H., Welch, R. M., & Cary, E. E. (1987). Nickel: A Micronutrient Essential for Higher Plants. Plant Physiology, 85(3), 801–803. https://doi.org/10.1104/pp.85.3.801

Coker, H. R., et al. (2026). The Elemental Composition of Land Plants: A Global Database and Meta-analysis. ACS Environmental Au, 6(5), 814–828. https://doi.org/10.1021/acsenvironau.6c00028

Gerendás, J., et al. (2026). Plant nutrient elements defined from the plant’s perspective. Plant and Soil, 526(2), 1049–1060. https://doi.org/10.1007/s11104-026-08946-1

Kiferle, C., Martinelli, M., Salzano, A. M., Gonzali, S., Beltrami, S., Salvadori, P. A., Hora, K., Holwerda, H. T., Scaloni, A., & Perata, P. (2021). Evidences for a Nutritional Role of Iodine in Plants. Frontiers in Plant Science, 12, 616868. https://doi.org/10.3389/fpls.2021.616868

Nascimento, V. L., Souza, B. C. O. Q., Lopes, G., & Guilherme, L. R. G. (2022). On the Role of Iodine in Plants: A Commentary on Benefits of This Element. Frontiers in Plant Science, 13, 836835. https://doi.org/10.3389/fpls.2022.836835

Wise, K., Simovich, T., Gill, H., & Selby-Pham, J. (2025; first published online 2024). Bioaccumulation of silicon and enhancement of cannabis inflorescence yield from fertiliser supplementation with the biostimulants silicate and phosphite. New Zealand Journal of Crop and Horticultural Science, 53(4), 1261–1273. https://doi.org/10.1080/01140671.2024.2339494

Montana State University Extension. Module 2: Plant Nutrition and Soil Fertility. https://landresources.montana.edu/soilfertility/html/modules/4449-2/index.html

Washington State University Extension. Chapter 4: Plant Mineral Nutrition and Fertilizers. The Pacific Northwest Gardener’s Handbook: Growing for the Future. https://extension.wsu.edu/pnw-gardeners-handbook/chapter-4-plant-mineral-nutrition-and-fertilizers/

Guerriero, G., et al. (2019). Identification of the aquaporin gene family in Cannabis sativa and evidence for the accumulation of silicon in its tissues. Plant Science, 287, 110167. https://doi.org/10.1016/j.plantsci.2019.110167

Berni, R., Mandlik, R., Hausman, J.-F., & Guerriero, G. (2021). Silicon-induced mitigatory effects in salt-stressed hemp leaves. Physiologia Plantarum, 171(4), 476–482. https://doi.org/10.1111/ppl.13097

Kiferle, C., Gonzali, S., Beltrami, S., Martinelli, M., Hora, K., Holwerda, H. T., & Perata, P. (2022). Improvement in fruit yield and tolerance to salinity of tomato plants fertigated with micronutrient amounts of iodine. Scientific Reports, 12, 14655. https://doi.org/10.1038/s41598-022-18301-w

Sun, J., Jin, J., Xia, J., Yu, R., Zhang, Y., Hou, J., Gao, C., & Wang, M. (2025). Integration of Phenotypic, Accumulative, Physiological–Biochemical, and Transcriptomic Analyses Reveals New Insights in Lettuce Response to Iodine: Enhancement or Toxic Effects. Journal of Agricultural and Food Chemistry, 73(23), 14533–14547. https://doi.org/10.1021/acs.jafc.4c10919