the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 19 Sep 2024
Foliar nutrient uptake from dust sustains plant nutrition
Abstract. Mineral nutrient uptake from soil through the roots is considered the exclusive nutrition pathway for vascular terrestrial plants. Recently, desert dust was discovered as an alternative nutrient source to plants, through direct uptake from dust deposited on their foliage. Here we studied the uptake of nutrients from freshly deposited desert and volcanic dusts by chickpea plants under ambient and future elevated levels of atmospheric CO2, through the roots and directly through the foliage. We found that within weeks, chickpea plants acquired phosphorus (P) from dust only through foliar uptake under ambient conditions, and P, Iron (Fe) and Nickel (Ni) under elevated CO2 conditions, significantly increasing their growth. Using additional chickpea variety with contrasting leaf properties we have shown that the foliar nutrient uptake pathway from dust is facilitated by leaf surface chemical and physiological traits such as low pH and trichome densities. We analyzed Nd radiogenic isotopes extracted from plant tissues after dust application to assess the contribution of mineral nutrients that were acquired through the foliage. Our results suggest that foliar mineral nutrient uptake from dust is an important pathway, that may play an even bigger role in an elevated CO2 world.
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RC1: 'Comment on egusphere-2024-2531', Anonymous Referee #1, 13 Nov 2024
Lokshin et al. show significant foliar nutrient uptake from desert dust and volcanic ash in chickpeas grown under elevated CO2 levels. Using neodymium isotope tracers, they quantified major acquisition of P, Fe, and Ni through leaves rather than roots. This study addresses an important knowledge gap in plant nutrition mechanisms under rising CO2 scenarios.
The experimental design used controlled greenhouse conditions with continuous CO2 fumigation, providing more stable CO2 concentrations compared to traditional Free-Air CO2 Enrichment (FACE) studies, which suffer from fluctuating daytime CO2 levels and nighttime CO2 shutoffs. Furthermore, FACE studies usually have low replication (n = 3) to save on CO2 costs. In contrast, the authors had 12 replicates, if I am not mistaken.
The authors' findings are important for understanding plant nutrition in a high-CO2 world, especially given concerns about declining nutrient content in crops. The research is informative about foliar supplementation as a method to maintain crop nutritional quality under elevated CO2 conditions.
The study has limitations, some of which can be addressed:
- The shading effect of dust particles on photosynthesis was not fully controlled for, as no inert dust treatment was included to equalize light intensity between groups. While the authors mention this limitation in their discussion, they do not measure the size of potential shading impacts.
- Statistical analysis is very limited. No statistical power for any of the tests is provided. The number of replicates is not even mentioned in Fig 5 legends for its error bars. The authors should clearly state the number of replicates in the text and all figures that use replicate numbers.
3) a few typos and errors easily fixable:
L64 “hidden hunger” is among key words and is relevant for this paper but the authors do not discuss the issue of hidden hunger and CO2 anywhere in the paper. Adding some discussion can be beneficial.L 219 Formula has missing subscripts
L232 should be X-ray, not X rayL281 Table 1 should be foliar-treated not foliar-trated
L343 and many other places references repeated twice such as (Hinsinger, 2001)(Hinsinger, 2001)
L378 Delete this phrase “Click or tap here to enter text.Click or tap here to enter text.L409 messed up font sizes with text in subscripts
Figures have text boxes that are barely readable due to tiny fonts
Citation: https://doi.org/10.5194/egusphere-2024-2531-RC1 -
RC2: 'Comment on egusphere-2024-2531', Anonymous Referee #2, 15 Nov 2024
The paper shows that plants can absorb nutrients from deposited dust resulting in increased growth and that the relative benefit can be higher under elevated atmospheric CO2 concentrations. Using Nd isotopes as tracers the authors were able to estimate the contribution of leaf uptake of individual nutrients. The paper thus delivers important and relevant data contributing to our understanding of the importance of dust deposition to plant nutrition, especially under increasing CO2 levels.
However, I think that the paper needs improvement in several aspects, both in general terms and some specific aspects.
The following general aspects need clarification / improvement / discussion:
- The authors follow a rather teleological approach when interpreting their results. This means they imply that plants induce changes in specific traits on purpose. Examples can be found throughout the paper, especially in the sections with the following headers: “Physiological adaptions toward foliar uptake” (l. 290), “Plant strategies for foliar mineral nutrient uptake” (l.337). I have some doubts about such postulates. First, evolution doesn’t follow a plan, and plants are unable to directly, deliberately “adapt” to their environment. They don’t have a “strategy”. Rather, certain plant traits happen to offer some advantages under specific conditions and are therefore selected during evolution. Second, in the present case, the cultivar showing improved nutrient uptake is the product of plant breeding, i.e. human intervention. This excludes that the plants themselves “adapted” or developed “strategies” to benefit from dust deposition. This obviously was the result of coincidence.
- The plants were treated with rather high dust doses. The amount of dust was higher than the final dry mass of plants, and the image in Fig. 1 illustrates that dust coverage was extreme. The authors mention that the dust coverage represents the average natural dust deposition in southern Israel during the entire growth period (l. 158/159). It is furthermore not clear whether the entire average deposition per m2 was applied to a single plant or planting density was considered and values were corrected for the area covered by an individual plant. In any case, the relevance of this approach needs more attention and should be further discussed in the paper. Shading effects should also be discussed in more detail. The authors briefly refer to effects on photosynthesis. Light stress due to high light intensities, which can be expected in this region, may negatively affect plants and dust coverage could thus be beneficial. In this context: the conditions in the greenhouse (temperature and humidity regimes, light) should be given.
- Some conclusions are too general and not justified by the presented results. In l.440/441 it is stated that “[…] we showed here that dust nutrient uptake via the foliar pathway in chickpea plants plays a major role in their nutrition”. This implies that this is the case for all chickpea plants, wherever they grow worldwide. Please keep in mind that you conducted (i) only one experiment (ii) under rather artificial conditions (pot experiment, greenhouse, rather (unnaturally?) high dust doses) and (iii) foliar uptake was only relevant for one specific cultivar. Later (l. 452/453) you conclude that “[…] foliar nutrient uptake from natural dust will play a central role in eCO2 earth […]. Again, I think that is a strong overinterpretation of your results for the above reasons.
- Please separate the (objective) presentation of results from (subjective) conclusions. Conclusions and interpretations should be restricted to the section “Discussion”. In Figs. 1-3 the headings not only explain the results but contain your conclusions: Fig. 1 (l. 266-267) and Fig. 2 (l.275-276): “This implies that […], Fig. 3: “[…] rendering it as more fit to extract nutrients from dust particles”.
Specific remarks (from l.1 – 659):
l.34: Root uptake is for a long time no longer considered the “exclusive nutrition pathway” for plants (as also mentioned in the introduction). Please modify sentence accordingly.
l.82: “has bever been quantified before”. I don’t agree. A quick search in any database will deliver a whole bunch of respective papers.
l.82-84: The cited literature on foliar uptake is outdated, and the citations are furthermore missing in the literature list. Please refer to more recent papers (latest edition of Marschner’s textbook and references cited therein). You should also mention, at least briefly, the known pathways of foliar uptake and how nutrients bound in solid particles can be absorbed by leaves at all (nutrients in solid form are not available for uptake). In the discussion you explain how acids and sugar may increase availability, but the mechanisms proposed are rather vague and avoid direct explanations.
l.86: Please use more precise wording. Accumulation of C always exceeds the that of mineral nutrients.
l.88: “These changes will drive plants to adapt and search for other nutrient uptake”. See my general comment #1 above. Plant’s IQ is rather low 😊
l.90: typo. “…of macro…”
l.92: “…and for their dependent human and livestock nutrition”. Weird sentence, please rephrase.
l.93: New paragraph starting with “In this experiment…”
- 103: “...a non-responsive genotype”: The meaning of this phrase is unclear at this point (later it becomes clear). Responsive to what?
l.114-116: Both sentences are grammatically incomplete, please rephrase. Again: the meaning of responsive is unclear at this stage.
l.118: Please specify the climatic conditions in the greenhouses (see comment #2 above).
l.122: Typo: liter or litre
l.126: Give composition of the nutrient solution and mode of application (intervals, how was it given, from above or below?)
l.128: “responsiveness”. Again: what does it mean?
l.133-137: Please give more details: how did you make sure that all plants uniformly received the same dose (3 g)?
- 139/140: “…harvested 10 days after the last dust application”. You didn’t mention so far that dust was applied twice and when the first application took place. This information is given later under the caption “Mineral dust material” (l.145). Please move the information given in l.157-163 to the general description of experimental design (l.133-136).
- 125-142: The description of treatments is quite confusing. While reading I permanently had to do the math. Why don’t you describe your experiment as a 2-factorial design with additional controls plants, n reps each. Think of presenting your design in a table.
l.152: Typo: monthS
- 157-163: The information given here is not about the materials themselves (as indicated by the heading) but about the mode of application. Move and merge, see comment above.
- 166-167: Washing plants without using detergents and/or organic solvents may leave unabsorbed residues on the surface, even if the plain leaf surfaces appear clean. Scanning some random samples by SEM will not safely exclude contamination. Think of particles left in leaf axils or between trichomes. This will lead to a massive overestimation of nutrient uptake. Please consider this when discussing your results.
- 211-215: Not all readers will be familiar with the abbreviations in this section. Please give explanations (TRU, LN-spec, JNdi, BRC-2)
l.219: missing subscripts
l.281, Table 1: Please give data as means and standard deviation (or similar). Showing individual plant data makes this table rather confusing. Show macro element concentrations in % or mg/g rather than ppm. The value of 713 ppm P is very little for a P-fertilizer. I conclude that the data show the composition of the nutrient solutions, which should be indicated in the table.
l.301, Caption Fig.3. Panel b: There are no cases of one or two asterisks, please remove. Panel e: “rendering it more fit to extract nutrients”. If consider this an unjustified speculation and not a direct conclusion from the shown results! Trichome density will probably affect retention of dust on leaf surfaces any may be involved in exudation. Both was not in focus of your study and therefore not shown. Furthermore, "extraction" of nutrients again implies a deliberate action of plants (see above). BTW: The only purpose of figures/tables in the section "results" is to transport pure information, not interpretations! Panel f, y-axis: units are missing.
L.377/378: remove text.
L.428: “…of the seed”. The value is also affected by root uptake of the seedling
l.477: remove double citations throughout the paper (also in the list of references)
Citation: https://doi.org/10.5194/egusphere-2024-2531-RC2
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- 1
Anton Lokshin
Daniel Palchan
Elnatan Golan
Ran Erel
Daniele Andronico
Avner Gross
Our research explores how chickpea plants can absorb essential nutrients like phosphorus, iron, and nickel directly from dust deposited on their leaves, in addition to uptake through their roots. This process was particularly effective under higher levels of atmospheric CO2, leading to increased plant growth. By using Nd isotopic tools, we traced the nutrients from dust and found that certain leaf traits enhance this uptake. This discovery may become increasingly important as CO2 levels rise.
Our research explores how chickpea plants can absorb essential nutrients like...