Special Issue "Plant Responses to Biotic and Abiotic Stresses: Crosstalk between Biochemistry and Ecophysiology"

A special issue of Plants (ISSN 2223-7747). This special issue belongs to the section "Plant Response to Abiotic Stress and Climate Change".

Deadline for manuscript submissions: closed (31 May 2022) | Viewed by 24112

Special Issue Editors

Dr. M. Iftikhar Hussain
E-Mail Website
Guest Editor
Department of Plant Biology & Soil Science, Universidad de Vigo, 36310 Vigo (Pontevedra), Spain
Interests: plant abiotic stress (allelochemicals, salinity, heavy metals) study; plant ecophysiology—photosynthesis (photosystem II photochemistry, stomatal conductance, water use efficiency, carbon isotope discrimination) and leaf water relations; screening, selection, and genotypic evaluation in the plant–soil–environment nexus through agronomic tools and physiological perspective; study of mode of action of plant natural compounds with strong bio-herbicide potential
Prof. Dr. Adele Muscolo
E-Mail Website
Guest Editor
Department of Agriculture, Mediterranea University, Feo di Vito, 89122 Reggio Calabria, Italy
Interests: salinity, drought, and heat impact on seed germination, seedling growth and metabolism; forest soil management; adaptive response of plants to different environmental constraints; halophytes for the restoration and rehabilitation of salinized or contaminated soils
Special Issues, Collections and Topics in MDPI journals
Dr. Mukhtar Ahmed
E-Mail Website1 Website2
Guest Editor
1. Swedish University of Agricultural Sciences, Uppsala, Sweden
2. PMAS Arid Agriculture University, Rawalpindi, Punjab , Pakistan
Interests: agronomy; agroecosystems modeling; cropping systems; farm modeling; crop physiology; nutrients cycling; climate change; impact assessments; adaptation and mitigation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Biotic and abiotic stress adversely affect crops’, fruit trees’, legumes’, and halophytes’ growth, development, and productivity. Biotic stress in plants is caused by living organisms that directly deprive their host of its nutrients, leading to reduced plant vigor and in many cases to the death of the host plant. In agriculture, biotic stress is a major cause of pre- and postharvest losses. In contrast, abiotic stress (drought, salinity, cold, heat, and heavy metals) is the principal cause of crop yield loss worldwide, reducing normal yields of the major food, oil-seed, and cash crops by more than 50 percent. In general, biotic and abiotic stresses often cause a series of morphological, physiological, biochemical, and molecular changes that unfavorably affect plant growth and productivity and cause interference in stress tolerance and adaptation. Biotic and abiotic stresses such as drought, salinity, extreme temperatures (cold and heat), and oxidative stress are often interrelated; these conditions, singularly or in combination, induce cellular damage. These stress stimuli are complex in nature and may induce responses that are equally, if not more, complex in nature. For example, severe stresses during critical growth phases may directly result in mechanical damage and changes in the synthesis of macromolecules in cellular settings. In addition, all of these stresses lead to oxidative damage and involve the formation of reactive oxygen species (ROS) in plant cells. Usually, plants have mechanisms to reduce their oxidative damage by the activation of antioxidant enzymes and the accumulation of compatible solutes that effectively scavenge ROS. However, if the production of activated oxygen exceeds the plant’s capacity to detoxify it, deleterious degenerative reactions do occur, typical symptoms being loss of osmotic responsiveness, wilting, and necrosis. Facing stressful conditions, imposed by the changing environmental conditions that affect their growth and development during their whole life cycle, plants have to be able to perceive, process, and translate different stimuli into adaptive responses.

Plant responses to different stresses are highly complex and involve changes at the physiological, biochemical, transcriptome, and cellular levels. Understanding the organism-coordinated responses involves a fine description of the mechanisms occurring at the cellular and molecular level. The current Special Issue of Plants aims to analyze, from a multi-perspective approach (ranging from gas exchange, metabolomics, proteomics, isotopic and genomics, etc.), drivers (e.g., trait selection, phenotypic plasticity) and specific strategies used by the plants at physiological and molecular levels for their better adaptations to stressful growth conditions.

Dr. M. Iftikhar Hussain
Prof. Dr. Adele Muscolo
Dr. Mukhtar Ahmed
Guest Editors

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Keywords

  • Abiotic stress
  • Photosynthesis
  • Plant development
  • Plant growth
  • Plant metabolism
  • Signal transduction
  • Stress combinations
  • Agricultural sustainable development
  • Physiological mechanisms
  • Adaptations

Published Papers (20 papers)

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Article
Biomass Production and Predicted Ethanol Yield Are Linked with Optimum Photosynthesis in Phragmites karka under Salinity and Drought Conditions
Plants 2022, 11(13), 1657; https://doi.org/10.3390/plants11131657 - 23 Jun 2022
Viewed by 278
Abstract
Plant photosynthesis and biomass production are closely associated traits but critical to unfavorable environmental constraints such as salinity and drought. The relationships among stress tolerance, photosynthetic mechanisms, biomass and ethanol yield were assessed in Phragmites karka. The growth parameters, leaf gas exchange [...] Read more.
Plant photosynthesis and biomass production are closely associated traits but critical to unfavorable environmental constraints such as salinity and drought. The relationships among stress tolerance, photosynthetic mechanisms, biomass and ethanol yield were assessed in Phragmites karka. The growth parameters, leaf gas exchange and chlorophyll fluorescence of P. karka were studied when irrigated with the control and 100 and 300 mM NaCl in a nutrient solution and water deficit conditions (drought, at 50% water holding capacity). The plant shoot fresh biomass was increased in the low NaCl concentration; however, it significantly declined in high salinity and drought. Interestingly the addition of low salinity increased the shoot biomass and ethanol yield. The number of tillers was increased at 100 mM NaCl in comparison to the control treatment. High salinity increased the photosynthetic performance, but there were no significant changes in drought-treated plants. The saturated irradiance (Is) for photosynthesis increased significantly in low salinity, but it declined (about 50%) in high salt-stressed and (about 20%) in drought-treated plants compared to the control. The rates of dark respiration (Rd) and compensation irradiance (Ic) were decreased significantly under all treatments of salinity and drought, with the exception of unchanged Rd values in the control and drought treatments. A-Ci curve analyses revealed a significant improvement in the Jmax, Vc, max, and triose-phosphate utilization (TPU) at lower salinity levels but decreased at 300 mM NaCl and drought treatments compared to the control. In the chlorophyll fluorescence parameters (Fv/Fm, maximum photochemical quantum yield of PSII, and Y(NO)), the non-photochemical yields were not affected under the salt and drought treatments, although an effective photochemical quantum yield (YII) and electron transport rate (ETR) were significantly enhanced in water deficit compared to control plants. P. karka regulates an efficient photosynthesis mechanism to grow in saline and arid areas and can therefore be used as a sustainable biofuel crop. Full article
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Article
Assessment of Uptake, Accumulation and Degradation of Paracetamol in Spinach (Spinacia oleracea L.) under Controlled Laboratory Conditions
Plants 2022, 11(13), 1626; https://doi.org/10.3390/plants11131626 - 21 Jun 2022
Viewed by 211
Abstract
The occurrence and persistence of pharmaceuticals in the food chain, particularly edible crops, can adversely affect human and environmental health. In this study, the impacts of the absorption, translocation, accumulation, and degradation of paracetamol in different organs of the leafy vegetable crop spinach [...] Read more.
The occurrence and persistence of pharmaceuticals in the food chain, particularly edible crops, can adversely affect human and environmental health. In this study, the impacts of the absorption, translocation, accumulation, and degradation of paracetamol in different organs of the leafy vegetable crop spinach (Spinacia oleracea) were assessed under controlled laboratory conditions. Spinach plants were exposed to 50 mg/L, 100 mg/L, and 200 mg/L paracetamol in 20% Hoagland solution at the vegetative phase in a hydroponic system. Exposed plants exhibited pronounced phytotoxic effects during the eight days trial period, with highly significant reductions seen in the plants’ morphological parameters. The increasing paracetamol stress levels adversely affected the plants’ photosynthetic machinery, altering the chlorophyll fluorescence parameters (Fv/Fm and PSII), photosynthetic pigments (Chl a, Chl b and carotenoid contents), and composition of essential nutrients and elements. The LC-MS results indicated that the spinach organs receiving various paracetamol levels on day four exhibited significant uptake and translocation of the drug from roots to aerial parts, while degradation of the drug was observed after eight days. The VITEK® 2 system identified several bacterial strains (e.g., members of Burkhulderia, Sphingomonas, Pseudomonas, Staphylococcus, Stenotrophomonas and Kocuria) isolated from spinach shoots and roots. These microbes have the potential to biodegrade paracetamol and other organic micro-pollutants. Our findings provide novel insights to mitigate the risks associated with pharmaceutical pollution in the environment and explore the bioremediation potential of edible crops and their associated microbial consortium to remove these pollutants effectively. Full article
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Article
Comparative Plasticity Responses of Stable Isotopes of Carbon (δ13C) and Nitrogen (δ15N), Ion Homeostasis and Yield Attributes in Barley Exposed to Saline Environment
Plants 2022, 11(11), 1516; https://doi.org/10.3390/plants11111516 - 05 Jun 2022
Viewed by 411
Abstract
Salinity is a major threat to agricultural productivity worldwide. The selection and evaluation of crop varieties that can tolerate salt stress are the main components for the rehabilitation of salt-degraded marginal soils. A field experiment was conducted to evaluate salinity tolerance potential, growth [...] Read more.
Salinity is a major threat to agricultural productivity worldwide. The selection and evaluation of crop varieties that can tolerate salt stress are the main components for the rehabilitation of salt-degraded marginal soils. A field experiment was conducted to evaluate salinity tolerance potential, growth performance, carbon (δ13C) and nitrogen isotope composition (δ15N), intrinsic water use efficiency (iWUE), harvest index, and yield stability attributes in six barley genotypes (113/1B, 59/3A, N1-10, N1-29, Barjouj, Alanda01) at three salinity levels (0, 7, and 14 dS m−1). The number of spikes m−2 was highest in Alanda01 (620.8) while the lowest (556.2) was exhibited by Barjouj. Alanda01 produced the highest grain yield (3.96 t ha−1), while the lowest yield was obtained in 59/3A (2.31 t ha−1). Genotypes 113/1B, Barjouj, and Alanda01 demonstrate the highest negative δ13C values (−27.10‰, −26.49‰, −26.45‰), while the lowest values were obtained in N1-29 (−21.63‰) under salt stress. The δ15N was increased (4.93‰ and 4.59‰) after 7 and 14 dS m−1 as compared to control (3.12‰). The iWUE was higher in N1-29 (144.5) and N1-10 (131.8), while lowest in Barjouj (81.4). Grain protein contents were higher in 113/1B and Barjouj than other genotypes. We concluded that salt tolerant barley genotypes can be cultivated in saline marginal soils for food and nutrition security and can help in the rehabilitation of marginal lands. Full article
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Article
Variations in Morphological Characters and Antioxidant Potential of Different Plant Parts of Four Ziziphus Mill. Species from the Cholistan
Plants 2021, 10(12), 2734; https://doi.org/10.3390/plants10122734 - 12 Dec 2021
Cited by 1 | Viewed by 957
Abstract
Genus Ziziphus (Z.) contains various important species in tropical and subtropical regions that are globally famous for their food and medicinal uses. However, no comprehensive study was available on the morphology and phytochemistry of Ziziphus species, mainly under different growth conditions, [...] Read more.
Genus Ziziphus (Z.) contains various important species in tropical and subtropical regions that are globally famous for their food and medicinal uses. However, no comprehensive study was available on the morphology and phytochemistry of Ziziphus species, mainly under different growth conditions, i.e., irrigated and desert (Cholistan). Therefore, this study was carried out to evaluate the morphological and phytochemical characteristics of Ziziphus species, i.e., Z. jujuba, Z. mauritiana, Z. spina-christi, and Z. nummularia, found in the irrigated and desert conditions. Our results revealed significant variations for most of the measured parameters, showing a large-scale diversity among Ziziphus species under irrigated and desert conditions. Specifically, Ziziphus species showed better morphology of all measured parameters of leaves and fruits under irrigated conditions compared to desert conditions, indicating that the optimum water availability in irrigated conditions improved the morphological parameters of Z. species. Meanwhile, among all Ziziphus species, the maximum leaf length (7.4 cm), leaf width (4.1 cm), leaf area (30.6 cm2), and leaf petiole length (1.3 cm) were observed for Z. jujuba, and the highest leaf dry weight (55.4%) was recorded for Z. mauritiana. Similarly, the highest fruit length (3.9 cm), fruit stalk length (1.5 cm), fruit diameter (3.6 cm), fruit width (3.8 cm), fruit area (66.1 cm2), seed length (2 cm), and seed diameter (1.1 cm) were measured for species Z. jujuba, while the maximum fruit dry weight (49.9%) and seed width (1.4 cm) were recorded for species Z. nummularia. Interestingly, compared to irrigated conditions, higher values of bioactive contents, i.e., phenol, flavonoid, and antioxidant activity, in fruits and leaves of Ziziphus species under desert conditions indicated the positive impact of desert climate on the phytochemistry of the Z. plants. Among Ziziphus species, Z. nummularia accumulated the maximum fruit phenols (304.4 mg GAE/100 g), leaf phenols (314.2 mg GAE/100 g), fruit flavonoids (123.7 mg QE/100 g), and leaf flavonoids (113.4 mg QE/100 g). Overall, this study demonstrated the significant morphological and phytochemical variations of the Ziziphus species under irrigated and desert conditions, which could be utilized for future studies to improve the production and medicinal potential of the Ziziphus, especially in desert areas. Full article
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Article
Responses of Lowland Rice Genotypes under Terminal Water Stress and Identification of Drought Tolerance to Stabilize Rice Productivity in Southern Thailand
Plants 2021, 10(12), 2565; https://doi.org/10.3390/plants10122565 - 24 Nov 2021
Cited by 4 | Viewed by 780
Abstract
Lowland rice is an important cereal crop that plays a key role in the food security and the economy of Thailand. Terminal water stress (TWS) in rainfed lowland areas poses threats to rice productivity due to stress occurrence at terminal crop stages and [...] Read more.
Lowland rice is an important cereal crop that plays a key role in the food security and the economy of Thailand. Terminal water stress (TWS) in rainfed lowland areas poses threats to rice productivity due to stress occurrence at terminal crop stages and extreme sensitivity of rice to TWS. A two-year study was conducted to characterize the performance of yield and yield attributes of twelve Thai lowland rice genotypes under TWS, to identify stress-tolerant genotypes using stress response indices and to identify promising stress indices which are correlated with grain yield (GY) under well-watered (WW) and TWS conditions for their use as rapid identifiers in a rice crop breeding program for enhancing drought stress tolerance. Measurements were recorded under WW and TWS conditions. Highly significant variations were observed amongst assessed genotypes for their yield productivity responses. According to stress response indices, genotypes were categorized into stress-tolerant and stress susceptible genotypes. Genotypes Hom Pathum, Sang Yod, Dum Ja and Pathum Thani-1 were found highly stress tolerant and relatively high yielding; genotypes Look Pla and Lep Nok were stress tolerant, whereas genotypes Chor Lung, Hom Nang Kaew and Hom Chan were moderately tolerant genotypes. Hence, stress-tolerant genotypes could be potentially used for cultivation under rainfed and water-limited conditions, where TWS is predicted particularly in southern Thailand to stabilize rice productivity. Stress tolerance indices, including stress tolerance index (STI), geometric mean productivity (GMP), mean productivity index (MPRO) and harmonic mean index (MHAR), indicated strong and positive associations with GY under WW and TWS; thus, these indices could be used to indicate stress tolerance in rice crop breeding program aimed at a rapid screening of lowland rice genotypes for stress tolerance. Full article
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Article
Co-Application of Biochar and Arbuscular mycorrhizal Fungi Improves Salinity Tolerance, Growth and Lipid Metabolism of Maize (Zea mays L.) in an Alkaline Soil
Plants 2021, 10(11), 2490; https://doi.org/10.3390/plants10112490 - 17 Nov 2021
Cited by 1 | Viewed by 752
Abstract
This study reports the mitigating strategy against salinity by exploring the potential effects of biochar (5%), Arbuscular mycorrhizal fungi (20 g/pot, AMF), and biochar + AMF on maize (Zea mays L.) plants grown under saline stress in a greenhouse. The maize was [...] Read more.
This study reports the mitigating strategy against salinity by exploring the potential effects of biochar (5%), Arbuscular mycorrhizal fungi (20 g/pot, AMF), and biochar + AMF on maize (Zea mays L.) plants grown under saline stress in a greenhouse. The maize was grown on alkaline soil and subjected to four different saline levels; 0, 50, 100, and 150 mM NaCl. After 90 d for 100 mM NaCl treatment, the plant’s height and fresh weight were reduced by 17.84% and 39.28%, respectively, compared to the control. When the saline-treated soil (100 mM NaCl) was amended with AMF, biochar, and biochar + AMF, the growth parameters were increased by 22.04%, 26.97%, 30.92% (height) and 24.79%, 62.36%, and 107.7% (fresh weight), respectively. Compared to the control and single AMF/biochar treatments, the combined application of biochar and AMF showed the most significant effect in improving maize growth under saline stress. The superior mitigating effect of biochar + AMF was attributed to its effective ability in (i) improving soil nutrient content, (ii) enhancing plant nutrient uptake, (iii) increasing the activities of antioxidant enzymes, and (iv improving the contents of palmitoleic acid (C16:1), oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:3). Thus, our study shows that amending alkaline and saline soils with a combination of biochar-AMF can effectively mitigate abiotic stress and improve plant growth. Therefore, it can serve as a reference for managing salinity stress in agricultural soils. Full article
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Article
Roles of Exogenous α-Lipoic Acid and Cysteine in Mitigation of Drought Stress and Restoration of Grain Quality in Wheat
Plants 2021, 10(11), 2318; https://doi.org/10.3390/plants10112318 - 28 Oct 2021
Cited by 7 | Viewed by 1510
Abstract
Cysteine (Cys) and α-lipoic acid (ALA) are naturally occurring antioxidants (sulfur-containing compounds) that can protect plants against a wide spectrum of environmental stresses. However, up to now, there are no conclusive data on their integrative roles in mitigation of drought stress in wheat [...] Read more.
Cysteine (Cys) and α-lipoic acid (ALA) are naturally occurring antioxidants (sulfur-containing compounds) that can protect plants against a wide spectrum of environmental stresses. However, up to now, there are no conclusive data on their integrative roles in mitigation of drought stress in wheat plants. Here, we studied the influence of ALA at 0.02 mM (grain dipping pre-cultivation treatment) and Cys (25 and 50 ppm as a foliar application) under well watered and deficit irrigation (100% and 70% of recommended dose). The results showed that deficit irrigation markedly caused obvious cellular oxidative damage as indicated by elevating the malondialdehyde (MDA) and hydrogen peroxide content (H2O2). Moreover, water stressed plants exhibited multiple changes in physiological metabolism, which affected the quantitative and qualitative variables of grain yield. The enzymatic antioxidants, including superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POX) were improved by Cys application. SOD and APX had the same response when treated with ALA, but CAT and POX did not. Moreover, both studied molecules stimulated chlorophyll (Chl) and osmolytes’ biosynthesis. In contrast, the Chl a/b ratio was decreased, while flavonoids were not affected by either of the examined molecules. Interestingly, all above-mentioned changes were associated with an improvement in the scavenging capacity of reactive oxygen species (ROS), leaf relative water content (RWC), grain number, total grain yield, weight of 1000 kernels, gluten index, falling number, and alveographic parameters (P, W, and P/L values). Furthermore, heatmap plot analysis revealed several significant correlations between different studied parameters, which may explore the importance of applied Cys and ALA as effective compounds in wheat cultivation under water deficit conditions. Full article
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Article
Seed Priming with Silicon as a Potential to Increase Salt Stress Tolerance in Lathyrus odoratus
Plants 2021, 10(10), 2140; https://doi.org/10.3390/plants10102140 - 09 Oct 2021
Cited by 10 | Viewed by 862
Abstract
Water shortage is a major problem limiting the expansion of green areas and landscapes. Using seawater as an alternative source of potable water is not a novel idea, but the issue of salt stress needs to be resolved. Salinity has a negative impact [...] Read more.
Water shortage is a major problem limiting the expansion of green areas and landscapes. Using seawater as an alternative source of potable water is not a novel idea, but the issue of salt stress needs to be resolved. Salinity has a negative impact on growth and the aesthetic value of ornamental plants. In order to overcome these challenges, Lathyrus odoratus seeds were hydro-primed and halo-primed with silicon (Si) and silicon nanoparticles (SiNPs), and exposed to seawater levels. Seawater markedly reduced seed germination and growth of Lathyrus seedlings, but halo-priming was shown to significantly alleviate its negative effects. Broadly, SiNPs increased the germination percentage, reduced photosynthetic pigments and carbohydrates decrease, and enhanced water relations, despite having a negative effect on germination speed. Halo-priming significantly increased the proline content and the activities of certain enzymatic (SOD, APX and CAT) and nonenzymatic (phenolic and flavonoids) compounds, that positively influenced oxidative stress (lower MDA and H2O2 accumulation), resulting in seedlings with more salt stress tolerance. Halo-priming with Si or SiNPs enhanced the Si and K+ contents, and K+/Na+ ratio, associated with a reduction in Na+ accumulation. Generally, halo-priming with Si or SiNPs increased Lathyrus seedlings salt stress tolerance, which was confirmed using seawater treatments via improving germination percentage, seedlings growth and activation of the antioxidant machinery, which detoxifies reactive oxygen species (ROS). Full article
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Article
Exogenous Nitric Oxide Reinforces Photosynthetic Efficiency, Osmolyte, Mineral Uptake, Antioxidant, Expression of Stress-Responsive Genes and Ameliorates the Effects of Salinity Stress in Wheat
Plants 2021, 10(8), 1693; https://doi.org/10.3390/plants10081693 - 18 Aug 2021
Cited by 18 | Viewed by 1288 | Correction
Abstract
Salinity stress is one of the major environmental constraints responsible for a reduction in agricultural productivity. This study investigated the effect of exogenously applied nitric oxide (NO) (50 μM and 100 μM) in protecting wheat plants from NaCl-induced oxidative damage by modulating protective [...] Read more.
Salinity stress is one of the major environmental constraints responsible for a reduction in agricultural productivity. This study investigated the effect of exogenously applied nitric oxide (NO) (50 μM and 100 μM) in protecting wheat plants from NaCl-induced oxidative damage by modulating protective mechanisms, including osmolyte accumulation and the antioxidant system. Exogenously sourced NO proved effective in ameliorating the deleterious effects of salinity on the growth parameters studied. NO was beneficial in improving the photosynthetic efficiency, stomatal conductance, and chlorophyll content in normal and NaCl-treated wheat plants. Moreover, NO-treated plants maintained a greater accumulation of proline and soluble sugars, leading to higher relative water content maintenance. Exogenous-sourced NO at both concentrations up-regulated the antioxidant system for averting the NaCl-mediated oxidative damage on membranes. The activity of antioxidant enzymes increased the protection of membrane structural and functional integrity and photosynthetic efficiency. NO application imparted a marked effect on uptake of key mineral elements such as nitrogen (N), potassium (K), and calcium (Ca) with a concomitant reduction in the deleterious ions such as Na+. Greater K and reduced Na uptake in NO-treated plants lead to a considerable decline in the Na/K ratio. Enhancing of salt tolerance by NO was concomitant with an obvious down-regulation in the relative expression of SOS1, NHX1, AQP, and OSM-34, while D2-protein was up-regulated. Full article
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Article
Unraveling the Influence of Land-Use Change on δ13C, δ15N, and Soil Nutritional Status in Coniferous, Broadleaved, and Mixed Forests in Southern China: A Field Investigation
Plants 2021, 10(8), 1499; https://doi.org/10.3390/plants10081499 - 21 Jul 2021
Cited by 5 | Viewed by 905
Abstract
Natural isotopic abundance in soil and foliar can provide integrated information related to the long-term alterations of carbon (C) and nitrogen (N) cycles in forest ecosystems. We evaluated total carbon (TC), total nitrogen (TN), and isotopic natural abundance of C (δ13C) [...] Read more.
Natural isotopic abundance in soil and foliar can provide integrated information related to the long-term alterations of carbon (C) and nitrogen (N) cycles in forest ecosystems. We evaluated total carbon (TC), total nitrogen (TN), and isotopic natural abundance of C (δ13C) and N (δ15N) in soil and foliar of coniferous plantation (CPF), natural broadleaved forest (NBF), and mixed forest stands at three different soil depths (i.e., 0–10, 10–20, and 20–40 cm). This study also explored how soil available nutrients are affected by different forest types. Lutou forest research station, located in Hunan Province, central China, was used as the study area. Results demonstrated that the topsoil layer had higher TC and TN content in the mixed forest stand, resulting in a better quality of organic materials in the topsoil layer in the mixed forest than NBF and CPF. In general, soil TC, TN, and δ15N varied significantly in different soil depths and forest types. However, the forest type did not exhibit any significant effect on δ13C. Overall, soil δ13C was significantly enriched in CPF, and δ15N values were enriched in mixed forest. Foliar C content varied significantly among forest types, whereas foliar N content was not significantly different. No big differences were observed for foliar δ15N and δ13C across forest types. However, foliar δ13C and δ15N were positively related to soil δ13C and δ15N, respectively. Foliar N, soil and foliar C:N ratio, soil moisture content (SMC), and forest type were observed as the major influential factors affecting isotopic natural abundance, whereas soil pH was not significantly correlated. In addition, forest type change and soil depth increment had a significant effect on soil nutrient availability. In general, soil nutrient availability was higher in mixed forest. Our findings implied that forest type and soil depth alter TC, TN, and soil δ15N, whereas δ13C was only driven by soil depth. Moreover, plantations led to a decline in soil available nutrient content compared with NBF and mixed forest stands. Full article
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Article
Intercropping of Peanut–Tea Enhances Soil Enzymatic Activity and Soil Nutrient Status at Different Soil Profiles in Subtropical Southern China
Plants 2021, 10(5), 881; https://doi.org/10.3390/plants10050881 - 27 Apr 2021
Cited by 7 | Viewed by 1526
Abstract
Intercropping is one of the most widely used agroforestry techniques, reducing the harmful impacts of external inputs such as fertilizers. It also controls soil erosion, increases soil nutrients availability, and reduces weed growth. In this study, the intercropping of peanut (Arachishypogaea L.) [...] Read more.
Intercropping is one of the most widely used agroforestry techniques, reducing the harmful impacts of external inputs such as fertilizers. It also controls soil erosion, increases soil nutrients availability, and reduces weed growth. In this study, the intercropping of peanut (Arachishypogaea L.) was done with tea plants (Camellia oleifera), and it was compared with the mono-cropping of tea and peanut. Soil health and fertility were examined by analyzing the variability in soil enzymatic activity and soil nutrients availability at different soil depths (0–10 cm, 10–20 cm, 20–30 cm, and 30–40 cm). Results showed that the peanut–tea intercropping considerably impacted the soil organic carbon (SOC), soil nutrient availability, and soil enzymatic responses at different soil depths. The activity of protease, sucrase, and acid phosphatase was higher in intercropping, while the activity of urease and catalase was higher in peanut monoculture. In intercropping, total phosphorus (TP) was 14.2%, 34.2%, 77.7%, 61.9%; total potassium (TK) was 13.4%, 20%, 27.4%, 20%; available phosphorus (AP) was 52.9%, 26.56%, 61.1%; 146.15% and available potassium (AK) was 11.1%, 43.06%, 46.79% higher than the mono-cropping of tea in respective soil layers. Additionally, available nitrogen (AN) was 51.78%, 5.92%, and 15.32% lower in the 10–20 cm, 20–30 cm, and 30–40 cm layers of the intercropping system than in the mono-cropping system of peanut. Moreover, the soil enzymatic activity was significantly correlated with SOC and total nitrogen (TN) content across all soil depths and cropping systems. The depth and path analysis effect revealed that SOC directly affected sucrase, protease, urease, and catalase enzymes in an intercropping system. It was concluded that an increase in the soil enzymatic activity in the intercropping pattern improved the reaction rate at which organic matter decomposed and released nutrients into the soil environment. Enzyme activity in the decomposition process plays a vital role in forest soil morphology and function. For efficient land use in the cropping system, it is necessary to develop coherent agroforestry practices. The results in this study revealed that intercropping certainly enhance soil nutrients status and positively impacts soil conservation. Full article
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Article
Evaluation of Physiological and Morphological Traits for Improving Spring Wheat Adaptation to Terminal Heat Stress
Plants 2021, 10(3), 455; https://doi.org/10.3390/plants10030455 - 28 Feb 2021
Cited by 9 | Viewed by 1556
Abstract
Wheat crop experiences high temperature stress during flowering and grain-filling stages, which is termed as “terminal heat stress”. Characterizing genotypes for adaptive traits could increase their selection for better performance under terminal heat stress. The present study evaluated the morpho-physiological traits of two [...] Read more.
Wheat crop experiences high temperature stress during flowering and grain-filling stages, which is termed as “terminal heat stress”. Characterizing genotypes for adaptive traits could increase their selection for better performance under terminal heat stress. The present study evaluated the morpho-physiological traits of two spring wheat cultivars (Millet-11, Punjab-11) and two advanced lines (V-07096, V-10110) exposed to terminal heat stress under late sowing. Early maturing Millet-11 was used as heat-tolerant control. Late sowing reduced spike length (13%), number of grains per spike (10%), 1000-grain weight (13%) and biological yield (15–20%) compared to timely sowing. Nonetheless, higher number of productive tillers per plant (19–20%) and grain yield (9%) were recorded under late sowing. Advanced lines and genotype Punjab-11 had delayed maturity and better agronomic performance than early maturing heat-tolerant Millet-11. Advanced lines expressed reduced canopy temperature during grain filling and high leaf chlorophyll a (20%) and b (71–125%) contents during anthesis under late sowing. All wheat genotypes expressed improved stem water-soluble carbohydrates under terminal heat stress that were highest for heat-tolerant Millet-11 genotype during anthesis. Improved grain yield was associated with the highest chlorophyll contents showing stay green characteristics with maintenance of high photosynthetic rates and cooler canopies under late sowing. The results revealed that advanced lines and Punjab-11 with heat adaptive traits could be promising source for further use in the selection of heat-tolerant wheat genotypes. Full article
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Article
Elevated Nitrogen Priming Induced Oxinitro-Responses and Water Deficit Tolerance in Rice
Plants 2021, 10(2), 381; https://doi.org/10.3390/plants10020381 - 17 Feb 2021
Cited by 3 | Viewed by 1178
Abstract
Under water deficit conditions, the essential macronutrient nitrogen becomes limited as a result of reduced dissolved nitrogen and root nitrogen uptake. An elevated nitrogen level might be able to mitigate these effects, integrated with the idea of using nitric oxide as abiotic stress [...] Read more.
Under water deficit conditions, the essential macronutrient nitrogen becomes limited as a result of reduced dissolved nitrogen and root nitrogen uptake. An elevated nitrogen level might be able to mitigate these effects, integrated with the idea of using nitric oxide as abiotic stress tolerant inducers. In this study, we evaluated the potential of using elevated nitrogen priming prior to water shortage to mitigate plant stress through nitric oxide accumulation. We grew rice plants in 300 mg L−1 nitrogen for 10 weeks, then we primed plants with four different nitrogen concentrations: 100, 300 (control), 500 and 1000 mg L−1 nitrogen prior to inducing water deficit conditions. Plants primed with 500 mg L−1 nitrogen possessed a higher photosynthetic rate, relative water content, electrolyte leakage and lipid peroxidation under water deficit conditions, compared to control plants. The induction of water deficit tolerance was supported with the activation of antioxidant defense system, induced by the accumulation of nitric oxide in leaves and roots of rice plants. We originally demonstrated the accumulation of nitric oxide in leaves of rice plants. The elevated nitrogen priming can be used to enhance water deficit tolerance in irrigated paddy fields, instead of nitric oxide donors. Full article
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Article
Agro-Morphological, Yield and Quality Traits and Interrelationship with Yield Stability in Quinoa (Chenopodium quinoa Willd.) Genotypes under Saline Marginal Environment
Plants 2020, 9(12), 1763; https://doi.org/10.3390/plants9121763 - 13 Dec 2020
Cited by 10 | Viewed by 1188
Abstract
Quinoa (Chenopodium quinoa Willd.) is a halophytic crop that shows resistance to multiple abiotic stresses, including salinity. In this study we investigated the salinity tolerance mechanisms of six contrasting quinoa cultivars belonging to the coastal region of Chile using agro-physiological parameters (plant [...] Read more.
Quinoa (Chenopodium quinoa Willd.) is a halophytic crop that shows resistance to multiple abiotic stresses, including salinity. In this study we investigated the salinity tolerance mechanisms of six contrasting quinoa cultivars belonging to the coastal region of Chile using agro-physiological parameters (plant height (PH), number of branches/plant (BN), number of panicles/plant (PN), panicle length (PL), biochemical traits (leaf C%, leaf N%, grain protein contents); harvest index and yield (seed yield and plant dry biomass (PDM) under three salinity levels (0, 10, and 20 d Sm−1 NaCl). The yield stability was evaluated through comparision of seed yield characteristics [(static environmental variance (S2) and dynamic Wricke’s ecovalence (W2)]. Results showed that significant variations existed in agro-morphological and yield attributes. With increasing salinity levels, yield contributing parameters (number of panicles and panicle length) decreased. Salt stress reduced the leaf carbon and nitrogen contents. Genotypes Q21, and AMES13761 showed higher seed yield (2.30 t ha−1), more productivity and stability at various salinities as compared to the other genotypes. Salinity reduced seed yield to 44.48% and 60% at lower (10 dS m−1) and higher salinity (20 dS m−1), respectively. Grain protein content was highest in NSL106398 and lowest in Q29 when treated with saline water. Seed yield was positively correlated with PH, TB, HI, and C%. Significant and negative correlations were observed between N%, protein contents and seed yield. PH showed significant positive correlation with APL, HI, C% and C:N ratio. HI displayed positive correlations with C%, N% and protein content., All measured plant traits, except for C:N ratio, responded to salt in a genotype-specific way. Our results indicate that the genotypes (Q21 and AMES13761) proved their suitability under sandy desert soils of Dubai, UAE as they exhibited higher seed yield while NSL106398 showed an higher seed protein content. The present research highlights the need to preserve quinoa biodiversity for a better seedling establishment, survival and stable yield in the sandy desertic UAE environment. Full article
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Article
Effect of Cadmium Toxicity on Growth, Oxidative Damage, Antioxidant Defense System and Cadmium Accumulation in Two Sorghum Cultivars
Plants 2020, 9(11), 1575; https://doi.org/10.3390/plants9111575 - 13 Nov 2020
Cited by 17 | Viewed by 1463
Abstract
Heavy metal stress is a leading environmental issue reducing crop growth and productivity, particularly in arid and semi-arid agro-ecological zones. Cadmium (Cd), a non-redox heavy metal, can indirectly increase the production of reactive oxygen species (ROS), inducing cell death. A pot experiment was [...] Read more.
Heavy metal stress is a leading environmental issue reducing crop growth and productivity, particularly in arid and semi-arid agro-ecological zones. Cadmium (Cd), a non-redox heavy metal, can indirectly increase the production of reactive oxygen species (ROS), inducing cell death. A pot experiment was conducted to investigate the effects of different concentrations of Cd (0, 5, 25, 50, 100 µM) on physiological and biochemical parameters in two sorghum (Sorghum bicolor L.) cultivars: JS-2002 and Chakwal Sorghum. The results showed that various concentrations of Cd significantly increased the Cd uptake in both cultivars; however, the uptake was higher in JS-2002 compared to Chakwal Sorghum in leaf, stem and root. Regardless of the cultivars, there was a higher accumulation of the Cd in roots than in shoots. The Cd stress significantly reduced the growth and increased the electrolyte leakage (EL), hydrogen peroxide (H2O2) concentration and malondialdehyde (MDA) content in both cultivars, but the Chakwal Sorghum showed more pronounced oxidative damage than the JS-2002, as reflected by higher H2O2, MDA and EL. Moreover, Cd stress, particularly 50 µM and 100 µM, decreased the activity of different antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). However, the JS-2002 exhibited higher SOD, POD and CAT activities than the Chakwal Sorghum under different Cd-levels. These findings revealed that JS-2002 had a stronger Cd enrichment capacity and also exhibited a better tolerance to Cd stress due to its efficient antioxidant defense system than Chakwal Sorghum. The present study provides the available information about Cd enrichment and tolerance in S. bicolor, which is used as an important agricultural crop for livestock feed in arid and semi-arid regions. Full article
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Article
Allelopathic Potential of Aqueous Extract from Acacia melanoxylon R. Br. on Lactuca sativa
Plants 2020, 9(9), 1228; https://doi.org/10.3390/plants9091228 - 18 Sep 2020
Cited by 15 | Viewed by 1410
Abstract
We studied the polyphenol (phenolic compounds and flavonoids) composition and allelopathic effects of Acacia melanoxylon R. Br. aerial foliage aqueous extract (0%, 25%, 50%, 75% and 100%) on the seedling growth and plant biomass of the general biotest species, lettuce (Lactuca sativa). [...] Read more.
We studied the polyphenol (phenolic compounds and flavonoids) composition and allelopathic effects of Acacia melanoxylon R. Br. aerial foliage aqueous extract (0%, 25%, 50%, 75% and 100%) on the seedling growth and plant biomass of the general biotest species, lettuce (Lactuca sativa). Mean leaf fresh weight, leaf dry weight, root fresh weight and root dry weight were decreased following exposure to Acacia aerial foliage, flowers aqueous extract (AFE) and phyllodes aqueous extract (APE) after 6 days. The reduction in plant dry biomass was more than 50% following treatment with AFE. The decrease in mean root length was approximately 37.7% and 29.20% following treatment with Acacia flowers extract (AFE) at 75% and 100% concentration, respectively. Root dry weight of L. sativa was reduced by both flowers and phyllodes extract. The reduction of protein contents in lettuce leaves following Acacia foliage extract proved that both AFE and APE exhibit polyphenols that causes the toxicity which led to decrease in leaf protein contents. High-Performance Liquid Chromatography (HPLC) was employed to analyze the A. melanoxylon flowers and phyllodes. A total of 13 compounds (accounting for most abundant compounds in flowers and phyllodes) include different flavonoids and phenolic compounds. The phytochemical compounds detected were: Gallic acid, protocatechuic acid, p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillic acid, syringic acid, p-coumaric acid, and ferulic acid. The major flavonoid compounds identified include rutin, luteolin, apigenin, and catechin. Allelopathic effects of flower and phyllodes extracts from A. melanoxylon may be due to the presence of above compounds identified by HPLC analysis. Full article
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Review

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Review
Unraveling Sorghum Allelopathy in Agriculture: Concepts and Implications
Plants 2021, 10(9), 1795; https://doi.org/10.3390/plants10091795 - 28 Aug 2021
Cited by 5 | Viewed by 1721
Abstract
Allelopathy is an ecological phenomenon that involves the production and release of biomolecules from different crops, cultivated plants, and bacteria or fungi into the soil rhizosphere and impacts other organisms in the vicinity. Sorghum possesses vital allelopathic characteristics due to which it produces [...] Read more.
Allelopathy is an ecological phenomenon that involves the production and release of biomolecules from different crops, cultivated plants, and bacteria or fungi into the soil rhizosphere and impacts other organisms in the vicinity. Sorghum possesses vital allelopathic characteristics due to which it produces and releases different biomolecules from its root hairs, stems, and grains. Several studies have reported that sorghum acts as an allelopathic crop, decreasing the growth and eco-physiological attributes of surrounding plants and weeds growing simultaneously or subsequently in the field. Sorghum allelopathy has been exploited in the context of green manure, crop rotations, cover crops, and intercropping or mulching, whereas plant aqueous extracts or powder might be an alternate method of weed control. A diverse group of allelochemicals, including benzoic acid, p-hydroxybenzoic acid, vanillic acid, ferulic acid, chlorogenic acid, m-coumaric acid, p-coumaric acid, gallic acid, caffeic acid, p-hydroxibenzaldehyde, dhurrin, sorgoleone, m-hydroxybenzoic acid and protocatechuic acid, have been isolated and identified from different plant tissues of sorghum and root exudates. These allelochemicals, especially sorgoleone, have been investigated in terms of their mode(s) of action, specific activity and selectivity, release in the rhizosphere and uptake and translocation in sensitive species. The present review describes the importance of sorghum allelopathy as an ecological tool in managing weeds, highlighting the most recent advances in the allelochemicals present in sorghum, their modes of action, and their fate in the ecosystem. Further research should focus on the evaluation and selection of sorghum cultivars with high allelopathic potential, so that sorghum allelopathy can be better utilized for weed control and yield enhancement. Full article
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Review
Rising Atmospheric Temperature Impact on Wheat and Thermotolerance Strategies
Plants 2021, 10(1), 43; https://doi.org/10.3390/plants10010043 - 27 Dec 2020
Cited by 15 | Viewed by 1871
Abstract
Temperature across the globe is increasing continuously at the rate of 0.15–0.17 °C per decade since the industrial revolution. It is influencing agricultural crop productivity. Therefore, thermotolerance strategies are needed to have sustainability in crop yield under higher temperature. However, improving thermotolerance in [...] Read more.
Temperature across the globe is increasing continuously at the rate of 0.15–0.17 °C per decade since the industrial revolution. It is influencing agricultural crop productivity. Therefore, thermotolerance strategies are needed to have sustainability in crop yield under higher temperature. However, improving thermotolerance in the crop is a challenging task for crop scientists. Therefore, this review work was conducted with the aim of providing information on the wheat response in three research areas, i.e., physiology, breeding, and advances in genetics, which could assist the researchers in improving thermotolerance. The optimum temperature for wheat growth at the heading, anthesis, and grain filling duration is 16 ± 2.3 °C, 23 ± 1.75 °C, and 26 ± 1.53 °C, respectively. The high temperature adversely influences the crop phenology, growth, and development. The pre-anthesis high temperature retards the pollen viability, seed formation, and embryo development. The post-anthesis high temperature declines the starch granules accumulation, stem reserve carbohydrates, and translocation of photosynthates into grains. A high temperature above 40 °C inhibits the photosynthesis by damaging the photosystem-II, electron transport chain, and photosystem-I. Our review work highlighted that genotypes which can maintain a higher accumulation of proline, glycine betaine, expression of heat shock proteins, stay green and antioxidant enzymes activity viz., catalase, peroxidase, super oxide dismutase, and glutathione reductase can tolerate high temperature efficiently through sustaining cellular physiology. Similarly, the pre-anthesis acclimation with heat treatment, inorganic fertilizer such as nitrogen, potassium nitrate and potassium chloride, mulches with rice husk, early sowing, presoaking of a 6.6 mM solution of thiourea, foliar application of 50 ppm dithiothreitol, 10 mg per kg of silicon at heading and zinc ameliorate the crop against the high temperature. Finally, it has been suggested that modern genomics and omics techniques should be used to develop thermotolerance in wheat. Full article
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Review
Agro-Techniques for Lodging Stress Management in Maize-Soybean Intercropping System—A Review
Plants 2020, 9(11), 1592; https://doi.org/10.3390/plants9111592 - 17 Nov 2020
Cited by 4 | Viewed by 1512
Abstract
Lodging is one of the most chronic restraints of the maize-soybean intercropping system, which causes a serious threat to agriculture development and sustainability. In the maize-soybean intercropping system, shade is a major causative agent that is triggered by the higher stem length of [...] Read more.
Lodging is one of the most chronic restraints of the maize-soybean intercropping system, which causes a serious threat to agriculture development and sustainability. In the maize-soybean intercropping system, shade is a major causative agent that is triggered by the higher stem length of a maize plant. Many morphological and anatomical characteristics are involved in the lodging phenomenon, along with the chemical configuration of the stem. Due to maize shading, soybean stem evolves the shade avoidance response and resulting in the stem elongation that leads to severe lodging stress. However, the major agro-techniques that are required to explore the lodging stress in the maize-soybean intercropping system for sustainable agriculture have not been precisely elucidated yet. Therefore, the present review is tempted to compare the conceptual insights with preceding published researches and proposed the important techniques which could be applied to overcome the devastating effects of lodging. We further explored that, lodging stress management is dependent on multiple approaches such as agronomical, chemical and genetics which could be helpful to reduce the lodging threats in the maize-soybean intercropping system. Nonetheless, many queries needed to explicate the complex phenomenon of lodging. Henceforth, the agronomists, physiologists, molecular actors and breeders require further exploration to fix this challenging problem. Full article
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Correction
Correction: Alnusairi et al. Exogenous Nitric Oxide Reinforces Photosynthetic Efficiency, Osmolyte, Mineral Uptake, Antioxidant, Expression of Stress-Responsive Genes and Ameliorates the Effects of Salinity Stress in Wheat. Plants 2021, 10, 1693
Plants 2022, 11(5), 576; https://doi.org/10.3390/plants11050576 - 22 Feb 2022
Viewed by 319
Abstract
In the original publication [...] Full article
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