On the Importance of Soybean Seed P for Shoot P Uptake before Anthesis
Round 1
Reviewer 1 Report
This manuscript reports on the results of two pot experiments in which different soybean cultivars with different seed weight and seed P content were grown in a low-P and a high-P soil and shoot and root characteristics were measured. The shoot P content relied to a large degree on seed P reserves during the vegetative growth period in case of the low-P soil and a close linear relationship between seed P and shoot P uptake was found. However, no substantial genotypic differences were observed in P use efficiency under P deficiency, apart from the effect of seed P reserves.
This is a useful study with useful results, with no surprising results. The experiments have been carried out carefully (standard errors of the treatments were low). The conclusions are supported by the results presented in the study. The manuscript is well-written.
I have two minor comments.
- There are 2 tables and 10 figures, which is much. Suggest that some of the supporting figures are transferred to the SI. Table 1 provides some background information about the soybean cultivars tested, but this is very meagre. Suggest authors to include information about the year of release of these cultivars, yield potential and the cultivated areas in the world.
- The context of the study is not well explained in the Introduction, and the implications of the results are also not well-elaborated. Suggest authors to frame the study in a wider context (see also below), and to better indicate the implications of the findings. For examples, readers may want to know the relationships between the seed characteristics and the yield potential of the cultivars. In the end, growers harvest the crop at maturity and not at anthesis.
Specific comments:
L30: A surprising start of the storyline about soybean cultivation here in the Introduction. The readers should be informed about the real story, not just about the introduction of soybean in Central Europe where hardly any soybean is grown currently. Suggest to present the full picture of soybean cultivation in the world and in Europe
L58: to inform readers outside Austria, it would be good to explain the CAL-method a bit further, and to indicate the equivalence with Olsen P, which is more common across the world
Author Response
We would like to express our gratitude to the reviewer for the time and efforts invested in reviewing our manuscript, the generally positive attitude and the very helpful suggestions for improvement.
Point 1: There are 2 tables and 10 figures, which is much. Suggest that some of the supporting figures are transferred to the SI.
In agreement also with the suggestion of Rev. 2, we moved Fig. 6 and 10 to supplementary files. Additionally we combined Fig. 2 + 3 and Fig. 5 + 8 + 9 in one Figure, respectively.
Point 2: Table 1 provides some background information about the soybean cultivars tested, but this is very meagre. Suggest authors to include information about the year of release of these cultivars, yield potential and the cultivated areas in the world.
We included the year of release, as far as known. More information about the genotypes with regard to yield potential of cultivation area is unfortunately not available. In addition, we added a sentence at the end of the first paragraph of the introduction on the strong dependence of grain yield and quality “on the genetic population investigated as well as on specific environmental conditions”.
Point 3: The context of the study is not well explained in the Introduction, and the implications of the results are also not well-elaborated. Suggest authors to frame the study in a wider context (see also below), and to better indicate the implications of the findings. For examples, readers may want to know the relationships between the seed characteristics and the yield potential of the cultivars. In the end, growers harvest the crop at maturity and not at anthesis.
Cf. Point 2 and Point 4. As we did not measure grain yield, we could only speculate about yield implications, which we prefer not to do. We also waive to mention the obvious assumption that a larger biomass before anthesis may presumably be favourable for yield formation.
Point 4: L30: A surprising start of the storyline about soybean cultivation here in the Introduction. The readers should be informed about the real story, not just about the introduction of soybean in Central Europe where hardly any soybean is grown currently. Suggest to present the full picture of soybean cultivation in the world and in Europe.
We start now the introduction with: “Soybean belongs to the five arable crops with the largest production area worldwide. It was cultivated in 2019 on 121 M ha in the world and on 908,000 ha in the European Union.”
Point 5: L58: to inform readers outside Austria, it would be good to explain the CAL-method a bit further, and to indicate the equivalence with Olsen P, which is more common across the world
We added a reference (Wuenscher et al. 2015), which (i) describes the CAL method among others in detail and (ii) shows the close correlation of the results with Olsen P. In addition, it proved especially suitable for estimating plant available P in soils with a pH below 7 as used in our experiments.
Reviewer 2 Report
Review of Manuscript agronomy - 1217656
On the importance of soybean seed P for shoot P uptake before anthesis By Kaul et al.
GENERAL COMMENTS: This study investigated the effects of soybean genotypes of different seed size and seed phosphorus (P) content on growth and P accumulation up to anthesis. The works also determined the correlations among seed dry matter, seed P content, shoot P content as well as root characteristics at low and high P concentrations. There is excellent work in this manuscript; however, in my view, the manuscript requires further work before it can be accepted for publication: i) too many figures in the manuscript, some of them can be combined into a figure, ii) It will enhance the overall quality of the work by having the discussion on what suggestions can be made based on the findings of low P and high P cases. Overall, the manuscript is generally well written and presented, and it is appropriate for Agronomy and will be of interest to its readership. I consider the manuscript acceptable for publication once the change and improvement suggested in the following are made. My specific comments are noted below:
- Materials and Methods section is clear for the most part. What is the main reason for choosing these 15 genotypes? How many replicates in experiments 1 & 2?
- 3.2. Experiment 2: I would separate the results into low P and high P subtitle to make it easier to follow.
- L339-341: I wonder if the authors can add some discussion regarding this statement (effects of other nutrients)
- Fig. 1: It’s hard to read your Fig 1 (d). I suggest changing the colors for different genotypes.
- Fig. 6: I my view, Fig. 6 doesn’t add much value in this manuscript. I suggest delete/ move it to SI.
- Figures: How many replicates do you use to calculate error bars? Are all the error bars from 4 seeds? Too many figure in the manuscript, I suggest combining Figs 2 & 3 as a figure and Figs 5, 8, 9 as a figure.
Author Response
We would like to express our gratitude to the reviewer for the time and efforts invested in reviewing our manuscript, the generally positive attitude and the very helpful suggestions for improvement.
Point 1: too many figures in the manuscript, some of them can be combined into a figure
We followed the suggestion of Rev. 1 and Point 8 and 10 of this review and moved Fig. 6 and 10 to supplementary files. Additionally we combined Fig. 2 + 3 and Fig. 5 + 8 + 9 in one Figure, respectively.
Point 2: It will enhance the overall quality of the work by having the discussion on what suggestions can be made based on the findings of low P and high P cases.
Our findings emphasize the importance of larg(er) seeds for better juvenile growth especially when the soil P supply is marginal. This is already stated in the conclusions by: “…seed size can be considered an important trait when screening genotypes for fast early P accumulation and growth. Apart from plant breeding, this finding is particularly relevant in seed production, as seed lots with larger seed size could be utilized to achieve rapid canopy development in stressful environments and for better weed competitiveness of soybean.” We added in the discussion a clarifying statement about the importance of large seeds on low soil P sites: “This indicates an advantage of large seeded genotypes or seed lots under low soil P supply.” As the positive correlation of seed P with shoot P uptake that we observed also at HP is presumably less important for crop growth, we continued in the discussion: “…, which suggests a minor role of seed P for plant growth at HP…”.
Point 3: What is the main reason for choosing these 15 genotypes?
As indicated in the M&M section, the genotypes were selected (from a larger number of germplasm available at one of the co-authors, JV, who works on soybean breeding) in order to have a substantial variation in seed size. To make the selection more transparent, we added two sentences in section 2.2.
Point 4: How many replicates in experiments 1 & 2?
As indicated in the M&M section, “The experiments were laid out in completely randomized design with 8 or 6 replicates in experiments 1 or 2, respectively.” These were pots, planted with 4 soybean each, which were pooled for sampling.
Point 5: 3.2. Experiment 2: I would separate the results into low P and high P subtitle to make it easier to follow.
As the experiment was a 2-factorial and the results we present are (in most cases) interaction effects, we want to emphasize the interaction aspect, i.e. the contrasting behaviour of genotypes at LP vs. HP. Thus we prefer to stay with the present sequence of results.
Point 6: L339-341: I wonder if the authors can add some discussion regarding this statement (effects of other nutrients)
As we did no analysis of other nutrients in the seeds that we used, we cannot discuss that further based on own results. However, the small differences between genotypes in P concentration that we found (cf. Fig. 1b) suggest that the concentrations of different mineral elements do not vary much between genotypes. We added that assumption to the text.
Point 7: Fig. 1: It’s hard to read your Fig 1 (d). I suggest changing the colors for different genotypes.
We agree that readability is not optimum for that figure. But it would need 15 different colours and a large legend. And the figure is not so much about identifying individual genotypes but to illustrate the close linear relationship. Thus we would like to stay with the present form of the figure.
Point 8: Fig. 6: I my view, Fig. 6 doesn’t add much value in this manuscript. I suggest delete/ move it to SI.
Done - cf. Point 1!
Point 9: Figures: How many replicates do you use to calculate error bars? Are all the error bars from 4 seeds?
The error bars are calculated based on the (8 or 6, cf. Point 4) replicated pots. Pot data were sums of 4 pooled plants per pot. We added in the M&M section: “aboveground biomass of four plants per pot” and included the number of individual data “n=…” in each Figure. With regard to the analysis of the seed material we added: “For seed analysis, 6 single seeds per genotype of the same size as those planted later were used as replicates.”
Point 10: Too many figure in the manuscript, I suggest combining Figs 2 & 3 as a figure and Figs 5, 8, 9 as a figure.
Done - cf. Point 1!
Round 2
Reviewer 2 Report
The authors have addressed my concerns. I recommend publication in the journal.
