Water Stress Permanently Alters Shoot Architecture in Common Bean Plants

BROAD COMMENT

The Introduction section is well done. I   appreciate the fact that the methodology section is detailed and well   explained. Also, the results are well presented, and an in-depth discussion   is provided. However, the study has some shortcomings. Just one season was   analysed. Thus, not enough information is provided to establish a strong   conclusion to support findings of the effects of water stress on bean yield   through modifications of plant architecture. This limitation should be   mentioned explicitly in the outlook section.

We included an observation about the   mentioned limitation in the end of the Outlook section, combined with an   observation of the Reviewer 3:

“Two limitations of our study can be   addressed and better explored in a future work. First, only one growing   season was analyzed (2015). Data is not enough or representative to establish   a strong conclusion to support findings of the effects of water shortage on   common bean yield through modifications of plant shoot architecture.   Moreover, only one cultivar was used (cv. Berna). A comparison between   different common bean cultivars taking into account their water shortage   tolerance or sensitivity conducted in broader environmental conditions   expressed in different growing seasons can support and clarify the results of   our study.”

SPECIFIC COMMENTS

-Lines 192-194: Please did you conduct a   normality test on your dataset before you proceed with ANOVA? Because ANOVA   is a parametric test, thus if a dataset is not normally distributed, ANOVA   cannot be performed on it. In that case, the transformation of the data is   needed or one can use non-parametric tests. Please do check the normality.

A normality test by Shapiro-Wilk’s test was   conducted to the variables evapotranspiration, grain yield, shoot biomass,   harvest index, number of pods per plant, length of pods, phyllochron, final   number of phytomers and leaflet blades, and the angle between the petiolules   and top leaflet blades. The factor used was the irrigation treatments. All of   them followed a normal distribution. It was not necessary to transform any of   these variables. This information was not given in the original manuscript   but is now included in the revised version.

Abstract:

L21: Variables measured should be   specified, since “sizes and number of organs” are not very informative of   measures done.

Variables measured were included in the   abstract.

Introduction

L65: When flowering, plants enter the   reproductive phase, why to name this phase “generative”? I recommend change   “generative” for “reproductive” throughout the manuscript.

We agree, and the term “generative” was   changed for the term “reproductive” 8 times throughout the text.

L73: Correct the sentence by “at 50%   podding stage”

Sentence was corrected as suggested.

Material and methods

L102-106: Bean plants were subjected to two   watering treatments depending on the development stage, some at the onset of   the flowering and others at the onset of pod formation. But, likely,   flowering and podding were not synchronized for all plants. Explain which   criteria was used to start with the watering treatments.

Plants were subjected to the same   conditions of air temperature, photoperiod and irrigation until the beginning   of the flowering and the pod formation stages, when the treatments started.   The criteria to stablish the beginning of the two stages as inserted in the   text as follows: “The onset of the flowering and pod formation stages was   considered when 50% of the plants presented one open flower and one pod at   maximum length, respectively.”.

L116: Leave a space “biomass(stem”

Space was inserted between ”biomass”  and “(“.

L159: Was the internode diameter measured   at the base, middle or the top? Please, specify.

Diameter was measured in the middle of the   internodes to ensure a representative mean value of them, as in common bean   plants, internodes are slightly wider in the base and top and narrower in the   middle. A better description was included in the text.

L192-202: Specify the variables and factors   used in the ANOVA analyses? Any variable was transformed?

A normality test by Shapiro-Wilk’s test was   conducted to the variables evapotranspiration, grain yield, shoot biomass,   harvest index, number of pods per plant, length of pods, phyllochron, final   number of phytomers and leaflet blades, and the angle between the petiolules   and top leaflet blades. The factor used was the irrigation treatments. All of   them followed a normal distribution. It was not necessary to transform any of   these variables. This information was not available in the original manuscript   but is now included in the revised version.

Results

L208: Why is “depth water” used instead of   “water” alone? Better delete depth to avoid confusion.

The word depth was deleted in the text to   avoid confusion as suggested by the reviewer.

L208-209: Two watering treatments (30% Low   and 50% High reduction) were applied. Hence, it would be better to provide   the irrigation deficit treatment separately for each watering condition.

The sentence was rewritten as follows: “(-30%-Low   deficit (L) and -50%-High deficit (H))”.

Figure 2: CPN 1 and CPN2 have not been   taken into account?

CPN 1 was not taken into account in the   fitting processes because the counting of CPNs for branches starts on CPN 2   and the fitting was done with data of main stems and branches together.   Indeed, Figure 1 still is not completely correct because CPN2 should be   included. In the revised manuscript, Figure 2 was changed.

Table 2: At first glance, it’s nearly   impossible to visualize which coefficient data fit with each variable. Adding   horizontal lines would help to separate information for the distinct variables.

Thin black lines were inserted horizontally   in Table 2 to separate values of each variable.

L281-282: In which figure this information   is available?

In L281-282, the following sentence is   presented: “Applying dummy variables, smaller AIC values were obtained when   equation 3 fitting coefficient a was determined for each irrigation treatment   (Figure 4; Table 2).”. Information is available in Figure 4 and Table 2, as   indicated in the end of the sentence.

Discussion

L352: The different parameters studied are   mainly discussed separately even though they are close related. In this   sense, I miss any discussion on the relationship between shoot biomass   reduction due to water shortage and those parameters describing plant   architecture. For instances, which structural parameters contribute more to   shoot biomass reduction?

The relation and the discussion suggested   by the reviewer were not widely done in our original manuscript. We fully   agree but including this would add too much information to be handled in one paper.   We are working on another article that will extensively determine the shoot   biomass sinks-sources between organs of bean plants under water stress   throughout and in the end of the cycle, since we have data of biomass   distribution in 3 moments along the cycle, in addition to data of   architecture variables that were measured weekly throughout the cycle. In   general, preliminarily, leaflet blades represent 12.6%, petioles + petiolules   4.1%, internodes 13.5% and pods 69.8% of the final shoot biomass of the   plants. This distribution changes among treatments. Regarding the control   treatment, plants of the treatments started in the beginning of the flowering   stage increased the proportion of leaflet blades, petioles, petiolules and   internodes, and decreased the proportion of pods. Plants of the treatments   initiated at the pod filling stag, decreased the proportion of leaflet blades   and pods, but increased the petioles, petiolules and internodes relative to   the control treatment. These are preliminary results that still need to be   analyzed in detail and will be published in due time.

L395-397: Different response of petioles   and petioulules to water shortage in comparison to leaf size could suggest   that there is not an allometric relationship between them? Any comment about this subject would be   interesting.

The effect of the irrigation treatments was   clear in petioles, petiolules and leaf size, but the irrigation shortage   clearly affected more the petioles and petiolules than the stage of its   occurrence. Leaf size was reduced on irrigation treatments, but a clear   conclusion on the effect of the timing of water shortage occurrence and the   irrigation intensity could not be addressed. As well indicated by the   reviewer, it could be a loss of the allometric relationship between these   organs in water shortage conditions. A complementary observation was included   in the Discussion section as follows:

“The effect of the irrigation treatments   was clear in petioles, petiolules and leaf size, but the irrigation deficit   clearly affected more the petioles and petiolules than the stage of its   occurrence, and a clear tendency for leaf size could not be found. This   result could indicate a loss of the allometric relationship between petioles,   petiolules and leaves in water deficit conditions.”.

L437: “Those” to what refers.

The sentence was rewritten as follows:   “Those effects were mainly observed in the plants in treatment FH.”.

L454: “field” instead of “filed”

The word “filed” was changed by “field”.

- why did you chose that specific cultivar?   Is that cultivar drought tolerant? You may want to add some information in   the introduction.

The aim of this study was to apply the   methodology of characterization of the shoot architecture in a crop that had   not yet been studied in this way and exposed to water shortage. In general,   common bean cultivars are sensitive to water deficit, as already reported in   the literature and also shown in our results. Besides, the shoot architecture   of bean plants has many lateral branches and high leaf area, which   significantly modifies the canopy microclimate, and can be even more altered   in adverse conditions, such as when water deficit occurs, when compared to   ideal conditions of water availability. The study was carried out in The   Netherlands, where seeds of the common bean cultivar Berna were available.   Plants of this cultivar are well representative of the common bean cultivars   and present mean architectural features as intermediary height, prominent   lateral branch system and high leaf area. However, specific studies on the   tolerance of this cultivar to water deficit were not found in the literature.   Our results, in addition to the proposed characterization, show that Berna   cultivar is relatively sensitive to water deficit and that its yield is   reduced under water shortage.

- are the drought levels imposed common in   your region?

Common bean production regions are located   mainly in developing tropical and subtropical areas. The drought levels can   vary enormously in the field. In Brazil, production regions present a   climatic rainy season with dry winter (Cwa – Köppen   classification) or a climatic rainy year (Cfa-Cfb - Köppen   classification). In Cf conditions, common bean can usually be   grown without severe water shortage, although in abnormal climatic years   plants can be subjected to more than a month of drought. In the Cw climate,   common bean is frequently grown in the (dry) winter season, under partial   irrigation, involving crop water stress. So, the imposed irrigation levels of   our study are relevant to field conditions.

- it will be nice, for future studies, to   compare different bean varieties and see differences based on the drought   tolerance or sensitivity.

We agree with the reviewer and an   observation was included in the Outlook section as follow, combined with an   observation of the Reviewer 1:

“Two limitations of our study can be   addressed and better explored in a future work. First, only one growing   season was analyzed (2015). Data is not enough or representative to establish   a strong conclusion to support findings of the effects of water shortage on common   bean yield through modifications of plant shoot architecture. Moreover, only one   cultivar was used (cv. Berna). A comparison between different common bean   cultivars taking into account their water shortage tolerance or sensitivity   conducted in broader environmental conditions expressed in different growing   seasons can support and clarify the results of our study.”

- The english is good but please double   check the all manuscript and make sure there are no grammar errors.

As indicated by the reviewer, some grammar   errors were found in the original manuscript. The text was double checked and   errors were corrected.