Effects of Exogenous Melatonin on Chrysanthemum Physiological Characteristics and Photosynthesis under Drought Stress
Round 1
Reviewer 1 Report
The submitted manuscript deals with the use of the anti-stress substance melatonin in ornamental horticulture. This is a current issue and an interesting one. A water deficit was chosen as a stressor, but it was adjusted using PEG. Terminologically, however, this is not a water deficit, but an osmotic stress. The abstract affects the main results of the work, but it would be appropriate to supplement it with, for example, numerical values. The methodological part needs to be supplemented and modified. It is not entirely clear from the text what the application dose of melatonin was to the plants. What was the source of the plants? What were the plants spiced with? Was it hydroponics? Were the plants fertilized? As part of measuring the rate of gas exchange, I recommend completing the device settings (lighting, air movement, pressure, etc.). The results are focused on the description of individual parameters, but their interrelatedness is missing, for example by means of correlation relations. The graphical representation of the results is fine. The discussion is therefore also rather descriptive. References must be unified, as journal names are written in either capital or small letters. Further, some of them are briefly presented.
Author Response
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Reviewer 2 Report
The MS 'Effects of exogenous melatonin on chrysanthemum physiological characteristics and photosynthesis under drought stress' confirmed that already known and reported effects of exogenous melatonin on enhancment of drought tolerance in plants also can be reported for one more species. Therefore the novelty of the research is very doubtful. The species is very important indeed. But it is not clear under what circumstaces chrysanthemum being economically important may suffer from long drought stress. Cut flowers and pot plants are usually grown with strict watering regime. Please, explaine in the introduction the aim to treat these plants in order to enhance drought tolerance.
Why authors suggested that the mechanism of enhancing stress resistance in chrtsanthemum should differ from other plants and need to be elucidated (line 9)?
Line 100: Parameters described do not correspond those in the results (fig. 6) in discussion. Please, provide a reference to calculations. In the discussion explane what was the reason to measure these parameters. Fluorescence parameters are not recommended to use when water relatuions are studied.
In many cases, the obtained results are wrongly interpreted. Some are lisred in minor concerrns.
Minor concerns.
Line 12 - indexes, but on line 13 - index. What is physiological index?
Lines 13-16: How photosynthetic activity reduces MDA accumulation?
Line 19: How photosynthesis is promoted by increased transpiration rate and decreased intercellular CO2 concentration?
Line 30, 55, 56, 58, 67 and throughout the text: latin namres should be italicazed.
Line 84: Whether all those methods are Gao's or they just decribed in the paper by Gao?
Line 86-87: Did you measure the activities or concentrations of H2O2 and proline? I think content.
Line 90: Provide a reference, please.
Line 101: what fluorimeter model was used?
Lines 116, 119. Why the values are identical? 26,94. For the SPAD it is wrong.
Lines 116, 119, 136, 140 and throughout the text: round the values, for instance 27% instead of 26,94%. Hundrend do not have biological value in this case.
SPAD values can not be compared in % as it is a measure of relative chl content.
Are there any suggestion why MT treatment decreased chl content? Usually, the effect is opposite.
Line 123, 126 and fig. 2, 153: CONTENT of photosynthetic pigments, ROS CONTENT, the ACTIVITY of antioxidant enzymes, the ACTIVITY of SOD, POD, CAT.
Line 157: the levels can not be inhobited, can be decreased. Moreover, they were higher in fact unfer PEG treatment.
Lines 166-168: not nessesaryly all changes in the content of substances measured enhance drought tolerance, they may change indepenently.
Line 185: inhibitory effect - not correct
Line 214: Pn (not Tn), net (not tet)
Lines 231-232: there is no stress process described on the figure. What this paramerer means? Is it important to discuss not obvious trend if there is no significant difference.
Is there any suggestion why qP is decreased significantly by MT treatment compared to CK, while Pn ibcreased? It needs explanation, otherwise measuremenr errors are suspected.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors submitted a revised version of their manuscript. The submitted manuscript was modified based on comments and comments of opponents. In the text, these changes have been color-coded from the original text. Changes to the text and responses to opponents' comments have been explained. Currently, the text is edited and meets the standards of a scientific article. The methodology was supplemented and the use of PEG was explained. The discussion is already appropriate
Author Response
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Reviewer 2 Report
The MS has been improved, but still some comments were left without abswers.
Comment 1 is left without an answer: The MS 'Effects of exogenous melatonin on chrysanthemum physiological characteristics and photosynthesis under drought stress' confirmed already known and reported effects of exogenous melatonin on enhancement of drought tolerance in plants. The MS reports the same effects on one more species. Therefore the novelty of the research is very doubtful.
Comment 2 is also left without an answer: Why authors suggested that the mechanism of enhancing stress resistance in chrysanthemum should differ from other plants and need to be elucidated? I mean that mechanisms are already known and the MS did not reveal any new specific for chrysanthemum. In the introduction provide information (from numerous reviews) what is known regarding mechanisms of Mel effects on drought tolerance in plants.
To comment 3: Parameters described still do not correspond to those in the results (fig. 6). In the Methods you introduced 3 parameters (qP, NPQ and Fv/Fm), then provided formula for 4 parameters (+ETR without full name) and in fig. 6 you used 6 parameters. Describe the method properly – provide a reference for calculations and indicate a producer of Micro-Pam.
As for the drought stress, please, take into account the following: Certain stress conditions such as drought might not only inactivate PSII reaction centres and reduce Fv/Fm through a rise in Fo, but they might also change the optical properties of the leaf, in which case the individual observed values of Fm and Fo may be a result of changes in leaf absorptance (Murchie & Lawson, 2013). This will affect the estimation of NPQ but has, a priori, no effect on Fv/Fm since the reduction in F due to absorption cancels out in the ratio. Additionally, a decline in Fv/Fm does not necessarily imply that the photosynthetic performance of the plant is compromised (Demmig‐Adams & Adams, 2006; Murchie & Niyogi, 2011; Murchie & Lawson, 2013).
To comment 17: The content also can not be inhibited. It can be decreased. Only processes can be inhibited, for instance, accumulation of proline can be inhibited.
Lines 21-22: “photosynthetic” written 2 times.
Line 113 – dark adaptation (not domestication)
Line 256: ‘photochemical chemical’
Author Response
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Round 3
Reviewer 2 Report
The MS has been sufficiently improved.
