Abstract
Soybean (Glicyne max (L.) Merrill) is one of the most important food legumes because of its high protein (about 40%) and oil (about 20%) concentrations, in addition to carbohydrates and minerals. Soybean has the highest average harvested area among all legumes, and it has the highest harvested area of all oilseed crops as well. The current global climatic changes have put this crop under certain periods of drought stress during different stages of its vegetative growth, and soybean is reported to be sensitive to several abiotic stresses as compared to other legumes and crops. Moreover, soybean is currently sown as a rainfed crop in many regions, that’s why drought is continuously affecting soybean production and quality, especially with the fact that drought intensively increased over the past decades, altering precipitation amounts and distribution, and is predicted to further increase in frequencies and intensities, putting the production of soybean, and other sensitive crops, under serious challenges and raising the concern about the world’s food security, especially with the fact that global population is continuously increasing. Understanding the influence of drought stress on crops becomes vital, as such understanding can be exploited in irrigation-scheduling practices which, in part, reduces drought-related fluctuations in food production. However, the response to drought stress is a very complex process that involves multiple mechanisms on different morphological, physiological and metabolic levels. Under drought conditions, reactive oxygen species (ROS) are produced in higher concentrations, resulting in cellular damage and, eventually, cell death. However, despite the fact that high concentrations of ROS cause damages to the cells, yet low concentrations play the role of signaling molecules that can ease several processes like germination and growth. For example, ROS play noticeable role in regulating stomatal closure in order to optimize water use efficiency. Hydrogen peroxide (H2O2) is a compound that belongs to non-radical ROS; it regulates many physiological mechanisms such as growth and development under both normal and stressed conditions, playing a major role in activating various signal molecules in plants leading to inducing different mechanisms of tolerance. Nitrogen (N) is one of the most important macronutrients for plant vegetative growth and development, affecting several functions and components such as enzymes, proteins and cell walls. In addition, N represents a major component of the chlorophyll; as such, it affects chlorophyll formation and, consequently, photosynthesis. Moreover, N is essentially needed for soybean in order to produce optimum biomass. Because of its high protein concentration in the seeds, soybean plants have high N requirements. The two main sources of nitrogen for soybean plants are biologically-fixed N2 and mineral N fertilizer. N is particularly important under drought stress conditions for improving shoot nitrogen and shoot biomass accumulation. Accordingly, N fertilization might be introduced as an efficient application to partially overcome the negative effects expected from drought periods. Phosphorus (P), after nitrogen, is also one of the most important mineral nutrients for plant development and energy conservation and transfer. In addition, P has a vital role in photosynthesis and chloroplast composition. Considerable amounts of P, in the form of ATP, are needed for biological N2-fixation process by the nodules in legume plants. Although soil might have high concentrations of P, yet most of it can be unavailable for plants due to its poor solubility and fixation. As a result, N2-fixation rate in legumes and, consequently, the advantage of this ecologically friendly process can be decreased. P deficiency can also decrease seedling vigor and root development. Like N, soybean has high requirements of available P (10-15 mg kg-1 soil), and low soil-P availability limits soybean yields. However, excessive amounts of P resulted in growth inhibition in soybean, in addition to the fact that only 10%–45% of P- fertilizer added to the soil is readily usable, so it’s of high importance to determine the best P-rate application that can be optimally used by plants. P application was reported to enhance drought stress tolerance. The current and the predicted climatic changes are and will certainly affect the yields of plants, which means putting food production for the growing world population under serious challenges, especially those species which can not properly tolerate abiotic stresses. Moreover, using the chemical fertilizers to re-enrich soils with nutrients is not without consequences on the environment, in addition to the higher costs of the production process. Hence, understanding the mechanisms that susceptible crops utilize to cope with changing climate can provide a more-clear idea on on-field applications that can lead to the optimum production. Thus, this study aimed at revealing the sole effect of on-field drought stress on 7 soybean genotypes, with evaluating the sole and combined influence of drought stress and nitrogen fertilizer application on 2 soybean genotypes; ‘Pannonia Kincse’ and ‘Boglár’. This study also monitored the sole and combined effects of P fertilization and drought stress on the 2 soybean genotypes, in addition to revealing the probable positive effects of exogenously spraying H2O2 at early bloom (R1) stage on the physiology and the seed yield of the 2 soybean genotypes. Besides the on-field experiments, this study illustrated the influence of PEG-induced drought stress on the germination parameters and the physiology of 2 soybean genotypes; ‘ES Mentor’ and ‘Pedro’ under controlled environment (climate chamber) conditions. The results of the field experiments showed that under both drought stress and irrigated regimes, the seed yield of Ananda, ES Pallador and Pannonia Kincse genotypes was significantly higher than the other genotypes, suggesting that these genotypes might be more suitable for cultivation in the study area, especially under drought conditions. Moreover, the 100-seed weight of Ananda did not differ under drought stress conditions, and that of ES Mentor was even higher, suggesting that these two genotypes could be adopted under drought stress conditions in the study area in case the seed size is a matter of concern. In ‘Pannonia Kincse’ genotype, N fertilization significantly affected plant height, flower and pod number per plant, 100-seed weight, and protein and oil concentrations and yield as well. Irrigation, on the other hand, had significant effects on plant height, flower and pod number per plant and protein and oil concentrations; however, no significant effect was recorded on 100-seed weight or yield. Fertilization increased the yield under all irrigation regimes except when high rate was applied with the absence of drought, so a conclusion that low-rate fertilization is recommended under all irrigation regimes, whereas high rates of N are only recommended under relative drought conditions could be introduced. In ‘Boglár’ genotype, on the other hand, both drought stress and mineral N-deficiency decreased flower and pod number per plant, 100-seed weight, seed yield and seed protein concentration; however, they increased oil concentration in the seeds. Inoculation, on the other hand, enhanced flower number per plant, seed yield and seed oil concentration, but reduced pod number per plant, 100-seed weight and, interestingly, seed protein concentration. Regardless of inoculation, high mineral N application under drought stress conditions resulted in better yield, emphasizing the importance of relatively-high mineral N rates under drought stress conditions whether the seeds were pre-inoculated or not. The morpho-physiology of both ‘Pannonia Kincse’ and ‘Boglár’ genotypes was measurably affected by P fertilization, with more significant effects on stomatal conductance and plant height traits. In addition, pod number per plant and, consequently, the final seed yield were noticeably affected by the application of P fertilizer, however, the high rate (90P) did not significantly increase these traits compared to the lower rate (45P). P application significantly increased the oil concentration in the produced seeds, with more significant effect under drought stress conditions, whereas it did not affect the protein concentration trait. Treating drought-stressed soybean plants with 1 mM of H2O2 could alleviate the negative influence of drought and enhance both the morpho-physiology and the yield of both ‘Pannonia Kincse’ and ‘Boglár’ genotypes; its effect was more noticeable on the leaf area index (LAI) as H2O2-sprayed plants had higher (LAI) values than both drought-stressed and fully-irrigated counterparts. The effect size was also noticeable on the relative water content (RWC) of both genotypes. It can be reported that SPAD is not recommended as a reliable trait when evaluating the effect of drought stress on soybean, at least on the studied genotypes, in the study area, as it showed different trends through stages of different genotypes. On the contrary, LAI trait presented a steady trend through stages and genotypes under both drought stress and irrigated conditions, which might suggest this trait to be the most reliable physiological trait to count on in evaluating soybean’s performance in the study area. In the chamber room experiments, the results showed that significant differences among PEG concentrations, between genotypes and their interaction were recorded. For both “ES Mentor” and “Pedro” genotypes, germination ratio (GR) and root elongation (RE) decreased as the PEG concentration increased. Both germination energy (GE) and ultimate germination (UG) decreased, whereas mean period of ultimate germination (MPUG) and percenta
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Claims 20
Claim · model-written summary
Ananda, ES Pallador and Pannonia Kincse had significantly higher seed yield than other genotypes under drought and irrigation.
Verbatim
e0“under both drought stress and irrigated regimes, the seed yield of Ananda, ES Pallador and Pannonia Kincse genotypes was significantly higher than the other genotypes”
Claim · model-written summary
Ananda 100-seed weight did not differ under drought.
- Material
- Anandae0
- Treatment
- drought stress conditionse0
- Outcome
- 100-seed weighte0
- Direction
- did not differe0
Not reportedTaxonComparator
Verbatim
e0“the 100-seed weight of Ananda did not differ under drought stress conditions”
Claim · model-written summary
ES Mentor 100-seed weight was higher under drought.
Not reportedTaxonComparator
Verbatim
e0“that of ES Mentor was even higher, suggesting that these two genotypes could be adopted under drought stress conditions”
Claim · model-written summary
Nitrogen fertilization significantly affected height, flower and pod number, 100-seed weight, and seed protein and oil concentrations and yield in Pannonia Kincse.
- Material
- Pannonia Kincsee0
- Treatment
- N fertilizatione0
- Outcome
- plant height, flower and pod number per plante0
Not reportedTaxonComparatorDirection
Verbatim
e0“In ‘Pannonia Kincse’ genotype, N fertilization significantly affected plant height, flower and pod number per plant, 100-seed weight, and protein and oil concentrations and yield as well.”
Claim · model-written summary
Irrigation significantly affected height, flower and pod number, and protein and oil concentrations in Pannonia Kincse.
Not reportedTaxonComparatorDirection
Verbatim
e0“Irrigation, on the other hand, had significant effects on plant height, flower and pod number per plant and protein and oil concentrations”
Claim · model-written summary
Irrigation had no significant effect on 100-seed weight or yield in Pannonia Kincse.
- Outcome
- 100-seed weight or yielde0
Not reportedTaxonTreatmentComparatorDirection
Verbatim
e0“no significant effect was recorded on 100-seed weight or yield”
Claim · model-written summary
Fertilization increased yield under all irrigation regimes except high rate without drought.
- Treatment
- Fertilizatione0
- Outcome
- yielde0
- Direction
- increasede0
- Qualifier
- except when high rate was applied with the absence of droughte0
Not reportedTaxonComparator
Verbatim
e0“Fertilization increased the yield under all irrigation regimes except when high rate was applied with the absence of drought”
Claim · model-written summary
Low-rate fertilization was recommended under all irrigation regimes.
Not reportedTaxon
Verbatim
e0“low-rate fertilization is recommended under all irrigation regimes”
Claim · model-written summary
High nitrogen rates were recommended only under relative drought.
Not reportedTaxon
Verbatim
e0“high rates of N are only recommended under relative drought conditions”
Claim · model-written summary
Drought and mineral nitrogen deficiency reduced flower and pod number, seed weight, yield and protein in Boglár.
- Treatment
- drought stress and mineral N-deficiencye0
- Outcome
- flower and pod number per plante0
- Direction
- decreasede0
Not reportedTaxonMaterialComparator
Verbatim
e0“both drought stress and mineral N-deficiency decreased flower and pod number per plant, 100-seed weight, seed yield and seed protein concentration”
Claim · model-written summary
Drought and mineral nitrogen deficiency increased seed oil concentration in Boglár.
Not reportedTaxonTreatmentComparator
Verbatim
e0“they increased oil concentration in the seeds”
Claim · model-written summary
Inoculation enhanced flower number, seed yield and oil concentration in Boglár.
- Treatment
- Inoculatione0
- Outcome
- flower number per plant, seed yield and seed oil concentratione0
- Direction
- enhancede0
Not reportedTaxonComparator
Verbatim
e0“Inoculation, on the other hand, enhanced flower number per plant, seed yield and seed oil concentration”
Claim · model-written summary
Inoculation reduced pod number, seed weight and protein concentration in Boglár.
- Outcome
- pod number per plant, 100-seed weight and, interestingly, seed protein concentratione0
- Direction
- reducede0
Not reportedTaxonTreatmentComparator
Verbatim
e0“but reduced pod number per plant, 100-seed weight and, interestingly, seed protein concentration”
Claim · model-written summary
High mineral nitrogen under drought produced better yield regardless of inoculation.
- Treatment
- high mineral N application under drought stress conditionse0
- Outcome
- yielde0
- Direction
- bettere0
Not reportedTaxonComparator
Verbatim
e0“Regardless of inoculation, high mineral N application under drought stress conditions resulted in better yield”
Claim · model-written summary
Phosphorus fertilization affected stomatal conductance and plant height.
Not reportedTaxonComparatorDirection
Verbatim
e0“The morpho-physiology of both ‘Pannonia Kincse’ and ‘Boglár’ genotypes was measurably affected by P fertilization, with more significant effects on stomatal conductance and plant height traits.”
Claim · model-written summary
The high phosphorus rate did not significantly increase pod number or final seed yield over the lower rate.
- Treatment
- high rate (90P)e0
- Outcome
- pod number per plant and, consequently, the final seed yielde0
- Direction
- did not significantly increasee0
- Comparator
- lower rate (45P)e0
Not reportedTaxon
Verbatim
e0“pod number per plant and, consequently, the final seed yield were noticeably affected by the application of P fertilizer, however, the high rate (90P) did not significantly increase these traits compared to the lower rate (45P)”
Claim · model-written summary
Phosphorus increased seed oil concentration, particularly under drought, but did not affect protein concentration.
- Treatment
- P applicatione0
- Outcome
- oil concentration in the produced seedse0
- Direction
- increasede0
- Qualifier
- under drought stress conditionse0
Not reportedTaxonComparator
Verbatim
e0“P application significantly increased the oil concentration in the produced seeds, with more significant effect under drought stress conditions, whereas it did not affect the protein concentration trait.”
Claim · model-written summary
Hydrogen peroxide treatment improved soybean physiology and yield under drought.
- Taxon
- soybean
Glycine maxe0 - Treatment
- 1 mM of H2O2e0
- Outcome
- morpho-physiology and the yielde0
- Direction
- enhancee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Treating drought-stressed soybean plants with 1 mM of H2O2 could alleviate the negative influence of drought and enhance both the morpho-physiology and the yield of both ‘Pannonia Kincse’ and ‘Boglár’ genotypes”
Claim · model-written summary
Hydrogen peroxide sprayed plants had higher leaf area index than drought stressed and irrigated counterparts.
- Treatment
- H2O2-sprayede0
- Outcome
- (LAI) valuese0
- Direction
- highere0
- Comparator
- drought-stressed and fully-irrigated counterpartse0
Not reportedTaxon
Verbatim
e0“H2O2-sprayed plants had higher (LAI) values than both drought-stressed and fully-irrigated counterparts”
Claim · model-written summary
Germination ratio and root elongation declined as PEG concentration rose in ES Mentor and Pedro.
- Material
- ES Mentore0
- Treatment
- PEG concentratione0
- Outcome
- germination ratio (GR) and root elongation (RE)e0
- Direction
- decreasede0
Not reportedTaxon
Verbatim
e0“For both “ES Mentor” and “Pedro” genotypes, germination ratio (GR) and root elongation (RE) decreased as the PEG concentration increased.”
The same questions in other papers
hydrogen peroxide · yield · Glycine max (soybean)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- no effect
- positive
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.