Water Stress Tolerance Research Articles

Perspectiva paleobotánica y geológica de la biodiversidad en México

El origen de la vegetación actual de México y su diversidad tiene larga historia. Posiblemente es la extensión de esta historia el punto en que discrepan las propuestas, una planteando que inicia en el Cretácico (ca. 132 ma) y otras haciendo énfasis en procesos restringidos al Plio-Pleistoceno (5.3 ma), sobre todo si se refieren al origen de la vegetación actual. El aumento del conocimiento sobre la evolución geológica de México, y del constante cambio en su fisiografía, así como del estudio de las angiospermas fósiles de la región, genera un concepto más claro de cómo y cuándo las formas de vida fueron llegando y asociándose. Se presenta una hipótesis en la que se combinan procesos geológicos y cambios fisiográficos, con la presencia de plantas y vegetación en las partes emergidas que se van desarrollando. Se propone que la biodiversidad actual efectivamente inicia hace ca. 132 millones de años, aunque linajes que hoy viven en México se pueden reconocer desde este tiempo, es complicado ubicarlos en familias, pues posiblemente representen miembros del grupo troncal. En el Paleógeno (65-32 ma) las familias, y aun géneros, que continúan viviendo en el país son más fácilmente reconocidos, pero grupos extintos o que hoy crecen en otras regiones siguen siendo comunes. Es en el Neógeno (32-1.8 ma) que desde un punto de vista de la morfológico/anatómico las plantas fósiles se parecen más a las que viven de forma natural actualmente en el país, pero muestran diferencias que en general permiten proponer nuevas especies. Si las plantas fósiles y actuales de México se relacionan morfo/anatómicamente más solo en tiempos relativamente recientes, es de esperar que con los tipos de vegetación suceda algo similar. El registro fósil sugiere que a partir de comunidades que se desarrollaron bajo condiciones cálido-húmedas en el Cretácico, divergieron tipos de vegetación con capacidades diferentes ante el estrés hídrico, y comunidades que se favorecieron de condiciones templadas a frías. Esto sucede aparentemente en dos momentos distintos en dos regiones diferentes; durante el Paleógeno se afecta al norte y en al Neógeno al centro y sur del país. Trabajo geológico y paleobotánico conjunto y comparativo permitirá refinar esta propuesta que sugiere que los cambios que activan o restringen respuestas biológicas forman parte de otros componentes del Sistema Tierra.

Enzymatic and non-enzymatic response of grafted and ungrafted young European pear (Pyrus communis L.) trees to drought stress

The optimization and selection of the scion-rootstock combination are commonly based on its physiological and biochemical alterations capacity, especially in the rootstock, which is significant to elucidate the mechanisms associated with water stress tolerance. To verify the antioxidant defense systems under drought stress, two ungrafted rootstocks, `Dargazi᾿ seedling (D) and `Pyrodwarf᾿ clonal (P), and two pear scion cultivars including `Dargazi᾿ (D) and `Louise Bonne᾿ (L), that were grafted on the studied rootstocks were examined. We considered growth and chlorophyll fluorescence traits, some oxidative stress markers, and non-enzymatic and enzymatic antioxidant parameters in plants subjected to different soil water regimes. Treatments were, well-watered as control (100% FC), moderate (60% FC), and severe drought (30% FC) under greenhouse conditions. Drought stress influenced chlorophyll fluorescence contents and limited the quantum yield of PSII (Fv/Fm), mainly in P rootstock. In contrast, the highest specific leaf area (SLA), and lowest leaf mass area (LMA) was observed in the P rootstock, which indicated that the P rootstock was more sensitive to drought stress. Physiological and biochemical alterations and the main components of multivariate analysis showed that hydrogen peroxide (H2O2) and malondialdehyde (MDA) were accumulated under water deficit conditions, and P and D rootstocks showed a higher level of H2O2. We found a reduction in chlorophyll pigments, carotenoid (CAR), and ascorbic acid (AA), by drought stress, which had the highest amount in P and D rootstocks. Water stress directly influenced anthocyanin (ANT), total phenolic content (TPC), total flavonoid content (TFC), catalase (CAT), guaiacol peroxidase (GPOX), and ascorbate peroxidase (APOX) activity, especially under severe stress levels, and there was a high activity of GPOX in grafted combinations. In general, rootstocks showed more oxidative stress than grafted combinations because of the high increase in H2O2 and MDA, and response to stress by the accumulation of some enzymatic and non-enzymatic factors. However, grafted combinations mostly showed better tolerance with the enzymatic antioxidant defense system, which can be the result of resistance induced by rootstocks and the cultivar's capacity to minimize the negative effects of drought stress.

Genome-Wide Analysis of AP2/ERF Gene Superfamily in Ramie (Boehmeria nivea L.) Revealed Their Synergistic Roles in Regulating Abiotic Stress Resistance and Ramet Development

AP2/ERF transcription factors (TFs) are one of the largest superfamilies in plants, and play vital roles in growth and response to biotic/abiotic stresses. Although the AP2/ERF family has been extensively characterized in many species, very little is known about this family in ramie (Boehmeria nivea L.). In this study, 138 AP2/ERF TFs were identified from the ramie genome and were grouped into five subfamilies, including the AP2 (19), RAV (5), Soloist (1), ERF (77), and DREB (36). Unique motifs were found in the DREB/ERF subfamily members, implying significance to the AP2/ERF TF functions in these evolutionary branches. Segmental duplication events were found to play predominant roles in the BnAP2/ERF TF family expansion. Light-, stress-, and phytohormone-responsive elements were identified in the promoter region of BnAP2/ERF genes, with abscisic acid response elements (ABRE), methyl jasmonate response elements, and the dehydration response element (DRE) being dominant. The integrated transcriptome and quantitative real-time PCR (qPCR) revealed 12 key BnAP2/ERF genes positively responding to waterlogging. Five of the genes are also involved in ramet development, with two (BnERF-30 and BnERF-32) further showing multifunctional roles. The protein interaction prediction analysis further verified their crosstalk mechanism in coordinating waterlogging resistance and ramet development. Our study provides new insights into the presence of AP2/ERF TFs in ramie, and provides candidate AP2/ERF TFs for further studies on breeding varieties with coupling between water stress tolerance and high yield.

Foliar spray of silica improved water stress tolerance in rice (Oryza sativa L.) cultivars.

Rice (Oryza sativa L.) is a major cereal crop and a staple food across the world, mainly in developing countries. Drought is one of the most important limiting factors for rice production, which negatively affects food security worldwide. Silica enhances antioxidant activity and reduces oxidative damage in plants. The current study evaluated the efficiency of foliar spray of silica in alleviating water stress of three rice cultivars (Giza178, Sakha102, and Sakha107). The seedlings of the three cultivars were foliar sprayed with 200 or 400 mg l-1 silica under well-watered [80% water holding capacity (WHC)] and drought-stressed (40% WHC)] conditions for two summer seasons of 2019 and 2020. The obtained results demonstrated that drought stress caused significant decreases in growth, yield, and physiological parameters but increases in biochemical parameters (except proline) of leaves in all rice cultivars compared to well-irrigated plants (control). The roots of drought-stressed seedlings exhibited smaller diameters, fewer numbers, and narrower areas of xylem vessels compared to those well-watered. Regardless of its concentration, the application of silica was found to increase the contents of photosynthetic pigments and proline. Water relation also increased in seedlings of the three tested rice cultivars that were treated with silica in comparison to their corresponding control cultivars when no silica was sprayed. Foliar application of 400mg l-1 silica improved the physiological and biochemical parameters and plant growth. Overall, foliar application of silica proved to be beneficial for mitigating drought stress in the tested rice cultivars, among which Giza178 was the most drought-tolerant cultivar. The integration of silica in breeding programs is recommended to improve the quality of yield and to provide drought-tolerant rice cultivars under drought-stress conditions.

Effect of different waterlogging periods on biochemistry, growth, and chlorophyll a fluorescence of Arachis hypogaea L.

Peanut is among the main oil crops in India with huge economic importance. The unpredictable rainy season during the growing time of peanuts causes waterlogging in peanut fields. Waterlogging triggers major environmental limitations that negatively affect the growth, physiology, and development of peanuts. Thus, the export and production of peanuts are severely affected by waterlogging. Therefore, the understanding of metabolic mechanisms under waterlogging is important to future water-stress tolerance breeding in peanuts. This study aimed to evaluate how peanuts responded to various waterlogging conditions in terms of their development, metabolic processes, and chlorophyll fluorescence characteristics. The evaluations were carried out at different stages of peanut variety DH-86 treated with waterlogging. The peanut plants were subjected to different waterlogging periods of 20, 40, 60, 80, and 100 days. The growth parameters including total dry mass, total leaf area, and total leaves number were calculated in all treatments. The phenomenological and specific energy fluxes and maximum photosystem II efficiency (FV/Fm) were also determined. The measurements were done statistically using PCA, G-Means clustering, and correlation analysis to explore the interaction between different physiological parameters. The waterlogging for 100 days caused a significant reduction in the total number of leaves, dry mass, and total leaf area. The most sensitive parameters are specific and phenomenological energy fluxes and Fv/Fm, which notably decreased as waterlogging duration increased. The results indicated the growth and physiological performance of the peanut cv. DH-86 was affected significantly due to waterlogging and the interaction between all these parameters in waterlogging. This research focused on how peanuts respond to waterlogging stress and provides the basis for future plant breeding efforts to improve peanut waterlogging tolerance, especially in rainy regions. This will improve the sustainability of the entire peanut industry.

Impact of substrate depth and irrigation regime on growth, flowering and physiological indices of Greek sage (Salvia fruticosa Mill.) grown on urban extensive green roof systems

The broad application of extensive green roofs in the Mediterranean region is hindered by the stressful climatic conditions of the summer period, which is characterized by drought and heat extremes that challenge plant survival and growth. The use of native plants can provide a sustainable solution in overcoming these challenges. The aim of the present study was twofold: Firstly, to investigate the growth and flowering of the native Greek sage (Salvia fruticosa Mill.) when grown as part of an extensive green roof phytocommunity under two different substrate depths (either 8 cm or 15 cm) and two levels of irrigation (either high or low). Secondly, to determine several physiological indices in order to quantify the water stress tolerance response of Greek sage when grown under the above-mentioned green roof conditions with the imposition of three drought periods (20–25 July, 22–31 August, 23 September–10 October 2014). The deeper substrate (15 cm) promoted growth regardless of the level of irrigation and the number of flowers was favored by the deeper substrate with the higher water regime treatment. Although the shallow substrate depth and the low irrigation regime reduced growth and flowering, all plants survived. The imposition of drought stress periods resulted in a gradual decrease of total soluble sugars, proline and electrolyte leakage. Chlorophyll fluorescence (Fv/Fm) fluctuated between the three drought periods and SPAD increased in the drought period that was imposed during fall. During the first drought period, plants subjected to the shallow depth (8 cm) and irrigated with the low water regime, accumulated more sugars and had a higher chlorophyll fluorescence. By contrast, plants growing in the deeper substrate depth of 15 cm provided moderate sugars, but the lowest chlorophyll fluorescence. In the second drought period, the only index that varied between treatments was proline, which was increased for the plants growing in the shallow substrate depth and irrigated with the high-water regime. The lowest proline concentration occurred in plants growing in the deeper substrate depth receiving low irrigation. SPAD increased on the third drought period for plants growing in the deeper substrate. It was concluded that Greek sage can be successfully grown in extensive green roof systems with minimal inputs of water resources even at substrate depths of 8 cm. Out of the tested physiological indices, none could be employed as a standalone indicator of the Greek sage water stress magnitude.

Tomato deploys defence and growth simultaneously to resist bacterial wilt disease.

Plant disease limits crop production, and host genetic resistance is a major means of control. Plant pathogenic Ralstonia causes bacterial wilt disease and is best controlled with resistant varieties. Tomato wilt resistance is multigenic, yet the mechanisms of resistance remain largely unknown. We combined metaRNAseq analysis and functional experiments to identify core Ralstonia-responsive genes and the corresponding biological mechanisms in wilt-resistant and wilt-susceptible tomatoes. While trade-offs between growth and defence are common in plants, wilt-resistant plants activated both defence responses and growth processes. Measurements of innate immunity and growth, including reactive oxygen species production and root system growth, respectively, validated that resistant plants executed defence-related processes at the same time they increased root growth. In contrast, in wilt-susceptible plants roots senesced and root surface area declined following Ralstonia inoculation. Wilt-resistant plants repressed genes predicted to negatively regulate water stress tolerance, while susceptible plants repressed genes predicted to promote water stress tolerance. Our results suggest that wilt-resistant plants can simultaneously promote growth and defence by investing in resources that act in both processes. Infected susceptible plants activate defences, but fail to grow and so succumb to Ralstonia, likely because they cannot tolerate the water stress induced by vascular wilt.

Enhancement of the Expression of ZmBZR1 and ZmBES1 Regulatory Genes and Antioxidant Defense Genes Triggers Water Stress Mitigation in Maize (Zea mays L.) Plants Treated with 24-Epibrassinolide in Combination with Spermine

Water shortages greatly threaten global food security and limit crop production. Hence, increasing crop water stress tolerance is a critical way to secure agricultural production. 24-Epibrassinolide (EBL) and spermine (Spm) are closely involved in plant growth and development, as well as stress tolerance. In this study, the potential role of 0.1 mg L−1 EBL and/or 25 mg L−1 Spm foliage applications in improving the tolerance of maize to water-deficit conditions (50% and 75% field capacity) was investigated. We found that EBL, either alone or in combination with Spm, plays a major role in maize drought tolerance through upregulating the expression of both regulatory genes (ZmBZR1 and ZmBES1) of the brassinosteroid signal transduction pathway and gene-encoding antioxidant defense enzymes ZmSOD, ZmCAT, ZmAPX, ZmMDHAR, ZmDHAR, and ZmGR. Moreover, exogenous treatments alleviated the inhibition of maize plant growth and productivity and mitigated drought-induced oxidative stress by improving antioxidant enzyme (superoxide dismutase, catalase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase) activity, enhancing antioxidant molecule (ascorbate, glutathione) content, preventing reactive oxygen species accumulation, and maintaining cell membrane integrity. These findings reveal that the application of EBL, either individually or in combination with Spm, can be a good strategy for ameliorating water stress in sustainable agricultural systems.

Lack of Tradeoff between Leaf Hydraulic Efficiency and Safety across Six Contrasting Water-Stress Tolerant Fruit Tree Species

Water deficits affect the capacity of leaves to transport water, a process that is related to the obstruction of air in the xylem (embolism). The tolerance to this process has been negatively associated with water-transport efficiency at the xylem level across species, suggesting a tradeoff between hydraulic efficiency and safety. But there is a lack of observation at higher integration levels, i.e., organs. This study aimed to evaluate this tradeoff across six fruit tree species with a wide range of water-stress tolerance: pomegranate, olive, fig tree, mandarin, avocado, and vine. Efficiency was represented by the maximum foliar hydraulic conductance (Kmax) and stomatal conductance, whereas hydraulic security by water potential in which the leaf loses 50% of its water-transport capacity (P50), and at the point of loss of leaf turgor (Ψtlp). Results suggest that the compensation is weak or null at the foliar level. We observed that species with higher hydraulic efficiency tend to be more tolerant to leaf dehydration (higher hydraulic safety), except mandarin, which had lower Kmax and relatively higher P50. Morphological traits associated with carbon investment dynamic (leaf mass per area and petiole density) were highly correlated to water-stress tolerance across fruit tree species.

Metabolomic analyses reveal potential mechanisms induced by melatonin application for tolerance of water deficit in loquat (Eriobotrya japonica Lindl.)

Melatonin participates in the response to abiotic stressors in plants and enhances tolerance to water stress tolerance in loquat seedlings; however, the underlying mechanism remains unknown. In this study, we conducted physiological and metabolomic analyses to identify the metabolic processes associated with enhanced tolerance of melatonin-treated loquat seedlings under conditions of water deficit. Loquat seedlings were pre-irrigated with either 150 μM of melatonin or water and dehydrated for the next 13 days. Our results showed that water deficit reduced the relative water content and increased the relative electrolyte leakage in the leaves. Compared with untreated plants, melatonin-treated loquat leaves exhibited lower relative conductance and higher relative water content and antioxidant enzyme activity under water deficit conditions. Additionally, after melatonin application, the total phenolic and flavonoid content in the leaves had increased on day 7 but had decreased on day 13. Metabolomic analysis on days 1 and 13 revealed 108 and 196 metabolites, respectively, that were regulated by melatonin in loquat leaves. Importantly, melatonin application enhanced phenylpropanoid biosynthesis and the tricarboxylic acid (TCA) cycle and altered flavone and flavonol biosynthesis and galactose metabolism. Melatonin-treated plants exhibited higher levels of amino acids (threonine, asparagine, glutamate, and valine) and hydroxycinnamic acid derivatives (m-coumaric acid, shikimic acid, ferulic acid, coumaroylquinic acid, and 2-hydroxycinnamic acid). Thus, this study deepens our understanding of melatonin-mediated reprograming of metabolites in loquat to cope with water deficits.

Beneficial effects of antitranspirants on water stress tolerance in maize under different plant densities in newly reclaimed land

BackgroundThe global freshwater shortage is an important issue threatening the sustainable development of agriculture and food security. A field study was conducted in two seasons, i.e., 2019 and 2020, in the newly reclaimed land at Village 8, El-Minia Governorate, Egypt, to evaluate maize crop response to three irrigation levels (IL1 = 80, IL2 = 70, and IL3 = 60% of the crop evapotranspiration “ETc”), three plant densities (PD1 = 17.500, PD2 = 23.333, and PD3 = 35.000 plants fed−1), and three antitranspirants treatments (An1 = control, An2 = kaolin at 6%, and An3 = chitosan at 150 L fed−1). The experiment was designed as a randomized complete block design (RCBD) using a split plot in strips.ResultsResults revealed that the irrigated maize plants with IL1 (80% of ETc) recorded the maximum values for all traits such as vegetative growth, phenology, and yield and its attributes in both seasons. The heaviest value of grain yield (3.15 and 3.10 tonnes fed−1, where 1 feddan = 0.42 hectare) was realized from IL1 treatment in the 1st and 2nd seasons, respectively. Plant density of 35.000 plants fed−1 (PD3) produced the greatest values of leaf area index (6.70 and 6.85), more days to 50% for each of tasseling (62.16 and 61.99 days), and silking (63.63 and 63.73 days), heaviest grain yield (3.11 and 3.16 ton fed−1) and greater water use efficiency WUE (1.46 and 1.48 kg m−3) in both seasons, respectively.ConclusionsFoliar spraying with antitranspirants, i.e., kaolin at 6%, led to a tremendous impact on all studied traits by alleviating the water stress and reducing the rate of transpiration. The effect of second-order interaction among IL1 × PD3 × An3 indicated a significant increase in grain yield by 69.91% as compared with the interaction of IL3 × PD1 × An1 in the 2020 season only. CS 10 single-cross maize realized the highest productivity and most efficient use of available resources via using a sowing density of 35.000 plant fed−1, foliar spraying with kaolin at 6%, and irrigation level (80% of ETc) under El-Minia conditions.

Selected Indices to Identify Water-Stress-Tolerant Tropical Forage Grasses.

Periods of soil water stress have been recurrent in the Cerrado region and have become a growing concern for Brazilian tropical pasture areas. Thus, the search for forage grasses more tolerant to water stress has intensified recently in order to promote more sustainable livestock. In a greenhouse experiment, the degree of water stress tolerance of nine tropical forage grass cultivars was studied under different soil water regimes. The investigation followed a 9 × 3 factorial design in four randomized blocks. Nine cultivars from five species of perennial forage grasses were tested: Urochloa brizantha (‘BRS Piatã’, ‘Marandu’, and ‘Xaraés’), Panicum maximum (‘Aruana’, ‘Mombaça’, and ‘Tanzânia’), Pennisetum glaucum (‘ADR 300’), Urochloa ruziziensis (‘Comum’), and Paspalum atratum (‘Pojuca’). These cultivars were grown in pots under three soil water regimes (high soil water regime—HSW (non-stressful condition), middle soil water regime—MSW (moderate water stress), and low soil water regime—LSW (severe water stress)). Plants were exposed to soil water stress for 25 days during the tillering and stalk elongation phases. Twelve tolerance indices, including tolerance index (TOL), mean production (MP), yield stability index (YSI), drought resistance index (DI), stress tolerance index (STI), geometric mean production (GMP), yield index (YI), modified stress tolerance (k1STI and k2STI), stress susceptibility percentage index (SSPI), abiotic tolerance index (ATI), and harmonic mean (HM), were calculated based on shoot biomass production under non-stressful (YP) and stressful (YS) conditions. Soil water stress decreased leaf area, plant height, tillering capacity, root volume, and shoot and root dry matter production in most cultivars, with varying degrees of reduction among tropical forage grasses. Based on shoot biomass production under controlled greenhouse conditions, the most water-stress-tolerant cultivars were P. maximum cv. Mombaça and cv. Tanzânia under the MSW regime and P. maximum cv. Aruana and cv. Mombaça under the LSW regime. P. maximum cv. Mombaça has greater adaptability and stability of shoot biomass production when grown under greenhouse conditions and subjected to soil water stress. Therefore, this forage grass should be tested under field conditions to confirm its forage production potential for cultivation in tropical regions with the occurrence of water stress. The MP, DI, STI, GMP, YI, k2STI, and HM tolerance indices were the most suitable for identifying forage grass cultivars with greater water stress tolerance and a high potential for shoot biomass production under LSW regime.

Effect of Glycine Betaine and Chitosan on Water Stress Tolerance of Summer Squash Plants.

Effect of Glycine Betaine and Chitosan on Water Stress Tolerance of Summer Squash Plants.

How can redox systems explain water stress tolerance in the grain legume Lathyrus sativus – preliminary results

How can redox systems explain water stress tolerance in the grain legume Lathyrus sativus – preliminary results

Co-inoculation of biochar and arbuscular mycorrhizae for growth promotion and nutrient fortification in soybean under drought conditions

Drought is significant abiotic stress that affects the development and yield of many crops. The present study is to investigate the effect of arbuscular mycorrhizal fungi (AMF) and biochar on root morphological traits, growth, and physiological traits in soybean under water stress. Impact of AMF and biochar on development and root morphological traits in soybean and AMF spores number and the soil enzymes’ activities were studied under drought conditions. After 40 days, plant growth parameters were measured. Drought stress negatively affected soybean growth, root parameters, physiological traits, microbial biomass, and soil enzyme activities. Biochar and AMF individually increase significantly plant growth (plant height, root dry weight, and nodule number), root parameters such as root diameter, root surface area, total root length, root volume, and projected area, total chlorophyll content, and nitrogen content in soybean over to control in water stress. In drought conditions, dual applications of AMF and biochar significantly enhanced shoot and root growth parameters, total chlorophyll, and nitrogen contents in soybean than control. Combined with biochar and AMF positively affects AMF spores number, microbial biomass, and soil enzyme activities in water stress conditions. In drought stress, dual applications of biochar and AMF increase microbial biomass by 28.3%, AMF spores number by 52.0%, alkaline phosphomonoesterase by 45.9%, dehydrogenase by 46.5%, and fluorescein diacetate by 52.2%, activities. The combined application of biochar and AMF enhance growth, root parameters in soybean and soil enzyme activities, and water stress tolerance. Dual applications with biochar and AMF benefit soybean cultivation under water stress conditions.

The effect of deficit irrigation and fertilizer on quantitative and qualitative yield of quinoa (Chenopodium quinoa)

In order to investigate the effect of deficit irrigation and chemical fertilizers on yield and some physiological traits of quinoa an experiment was conducted in 2019 as split plot based on a randomized complete block design in two locations (Mashhad and Neishabour). Irrigation included, I0: full irrigation, I1: no irrigation at emergence stage, I2: no irrigation at stem elongation stage, I3: no irrigation at flowering stage, I4: no irrigation at seed setting stage. Fertilizer treatments included control (no fertilizer application); chemical fertilizer application according to local practices; manure application of 10 tons; and manure application of 20 tons per hectare. In general, seed yield, percentage of protein and seed oil in Mashhad was higher than in Neishabour. I2 treatment had the least negative effect on relative leaf water content. Application of chemical fertilizers, 10 tons and 20 tons of animal manure increased the percent of seed protein by 1.43, 1.66 and 2.37 compared to the control, respectively. The highest percentage of seed oil (5.91%) was obtained for treatment I2 in Mashhad and the lowest percentage of seed oil (4.18%) was obtained for treatment I4 in Neishabour. The lowest seed yield due to I1 treatment was observed in Neishabour and the highest seed yield was related to I0 treatment with 20 tons of manure and was observed in Mashhad. The results showed that the yield and water stress tolerance potential of quinoa can be modified by irrigation, fertilizer source and location.

Biochar as a soil amendment in the tree establishment phase: What are the consequences for tree physiology, soil quality and carbon sequestration?

Trees play a pivotal role in the urban environment alleviating the negative impacts of urbanization, and for this reason, local governments have promoted strongly tree planting policies. However, poor soil quality and neglect tree maintenance (e.g., irrigation and fertilization) can seriously mine the plant health status during the tree establishment phase. The use of biochar to provide long-lasting C to the soil and, at the same time, improving soil properties (e.g., improved water holding capacity), soil enzymes activities and NPK concentrations, is a promising research field. Therefore, with a two-step experiment, the study aimed to assay the physiological responses of a commonly used urban tree species (Tilia × europaea L.) to 1.5 % (w/w) biochar amendment (B), and secondly, to assess the ability of trees, grown in biochar amended soil, to tolerate a period of drought. Biochar amendment increased P and K availability in the soil, resulting in higher P and K concentrations in B than control leaves, according to the leaf stage. This induced B trees, higher values in both total biomass than controls (+22 %) in well-watered plants. Moreover, the higher water availability in soil amended with biochar helped B trees to tolerate water stress, with better leaf photosynthetic performances and a faster recovery than stressed controls after the re-watering. This study highlights the dual function of the biochar, improving CO2 sequestration and soil properties, and at the same time, enhancing plant physiological responses to environmental constraints. The use of biochar at the tree planting, especially in an urban environment, is a feasible and environmentally sustainable strategy to improve the success during the tree establishment phase.

Assessment of some sesame mutants under normal and water-stress conditions

ABSTRACT Sesame (Sesamum indicum L.) is a tropical oilseed crop that is also cultivated in arid and semi-arid environments, where drought occurs frequently. The objective of this study was to assess the performance of some sesame mutants, developed by our team through EMS-mutagenesis in 2020, under well-watered conditions and restricted irrigation by analyzing certain morphological, physiological, and agronomic attributes. The experiment was conducted in pots under field conditions according to a completely randomized design with three replications. The stress was simulated by suspending and reducing irrigation to 50% of the control, from the beginning of flowering until the appearance of the first capsule. The results showed variation attributable to genotypes, water regimes and their interaction was significant for all parameters studied, except the number of seeds per capsule. The mutants “ML2-5”, “ML2-72” and “ML2-37” were found to be the most tolerant to drought, exhibiting lowest stress sensitivity index and highest seed yield were associated with higher proline content in the leaves, more developed root system, higher chlorophyll content, and higher stomatal conductance than the rest of the mutants studied. This is the first report of sesame mutant lines with such high tolerance to drought during flowering. They could be used for developing high-performing cultivars with tolerance to drought during the flowering stage. The number of capsules per plant and stomatal conductance can be considered selection criteria to improve water-stress tolerance in sesame.

Assessment of different salt concentrations on the growth and phytochemical change of the ice plants

The ice plant (Mesembryanthemum crystallinum L.) has become a halophyte model to study the plant photosynthetic responses C3 photosynthesis to crassulacean acid metabolism (CAM), which is accelerated by salt stress. However, this adaptive mechanism improves water use efficiency, and water stress tolerance is still poorly known. This study examined the effect of individual and mixture of NaCl and CaCl2 concentrations on morphological parameters and bioactive component contents of ice plants in a plant factory system. Eight salt treatments individually and a combination of sodium chloride (NaCl) and calcium chloride (CaCl2), and Hoagland solutions were applied after the transplanting of ice plants. Morphological parameters like the number of leaves and lateral stems, leaf chlorophyll content (SPAD value), fresh weight, and dry weight of shoots and roots were measured at the adult stage. Concurrently, in the juvenile phase, the area of a canopy was evaluated using an image processing technique in HSV (hue, saturation, value) colour space. Correspondingly, ice plant secondary metabolites such as cations, anions, and radical scavenging activity were assayed in the adult phase correlated to the salt stress. The effects of salt stress on the growth of ice plants and secondary metabolite production were analysed using completely randomized block designs through the variance by one-way ANOVA with a significance level of p < 0.05. This study demonstrated that 400 mM CaCl2 (T4) enhanced the biomass and high sodium (Na+) and calcium (Ca2+) accumulations, and 200 mM CaCl2 (T3) accelerated the potassium (K+), magnesium (Mg2+), phosphate (PO43−), and sulfate (SO42−) accumulations. Moreover, NaCl 400 mM (T1) and combination of 100 mM NaCl and 300 mM CaCl2 (T5) positively influenced the chloride (Cl−) deposition and combination of 200 mM NaCl and 200 mM CaCl2 (T6) improved nitrate (NO3–) accretion. Furthermore, 100 mM CaCl2 (T2) exhibited the highest antioxidant activity in ice plants grown under the plant factory system.

Genetic Analysis of Water Stress Tolerance Attributes in F1 Maize Diallel Crosses

A half diallel set of crosses involving 10 inbred lines of maize along with commercial hybrid ARCGH 128 were evaluated at two different irrigation treatment during two season 2019 and 2020 using RCBD design with three replications at two locations (Minia and Assuit governorates), to determine combining ability and gene action for grain yield and its components. the most superior crosses for the economic traits were detected in L1 X L2 for leaf proline content, ear weight and number of rows/ear, L1 X L8 for number of ear /plot and number of rows/ear, L4 X L9 for Days to tasseling and Days to silking, L3 X L8 for Leaf angle, leaf rolling, number of kernels/ear, number of rows/ear and number of kernels/row and L3 X L10 for days to tasseling, days to silking,leaf rolling, relative water content (RWC %), kernel fresh weight, number of rows/ear and yield. Highly significant and larger in magnitude values of dominance (H1 and H2) components were found to be at the significant level at (5%) for all studied characters which confirmed their importance in the expression of these characters. However (D) dominance component was reached to the significant level only for the normal irrigation treatment for the leaf angel at both locations, all irrigation treatment for leaf proline content at both locations, normal irrigation treatment for number of kernel/row at Assuit location and all irrigation treatment for 100 kernel weight and number of ear/plot at both locations. The (F) component was significant and positive for all irrigation treatment for leaf proline content at both location, normal irrigation treatment for number of kernel/row at Assuit location, all irrigation treatments for 100 kernel weight at both location, stress irrigation treatment for number of ear/plot at Minia location. Significant differences of environmental variance (E) components were recorded for all irrigation treatment for leaf rolling at Assuit location, all irrigation treatment for ear weight at Minia location and all irrigation treatment for number of rows/ear and number of ear/plot at both locations. Dominance component of variance (H1 and H2) were significant and/or highly significant for all studied traits and (H1) was greater than (H2) in F1 indicating that positive and negative alleles at loci of these trait were not in proportional equal for parents. The estimator (h2) were refers to the dominance effect overall heterozygous loci was significant for all studied traits except days to tasseling for normal irrigation treatment at both locations, stress irrigation treatment for leaf angel at Minia location, all irrigation treatment for leaf rolling at both locations, normal irrigation treatment for ear weight/kg/plot at both locations and for stress irrigation treatment for number of rows/ear at Minia location. Average degree of dominance (H1/D) 0.5 was more than unity for all traits, these finding indicated the involved of an over dominance expression for all characters. However the over dominance observed in such character may not be an index of true over dominance could be based due to linkage epistasis or both together. Since the ratio of dominance (KD) recessive (KR) alleles was more than one for all the studied characters, these indicates a preponderance of dominant gene in the parents for the characters. The value of K (h2/H2, which stands for the number of groups of genes that exhibit dominance for each character) was <1 for all the studied characters for normal irrigation treatment at Assuit location and all irrigation treatment at Minia location and all irrigation treatment at Minia location for number of rows/ear and 100 kernel weight/gm. This suggested that just one group of genes showed dominance governed all of them while this parameter could be underestimated, when the dominance effects of all genes was not concerned with equivalent, size and distribution, where the distribution of genes was correlated, or complementary gene interactions occur. Heritability values in bored sense (h2b) were relatively low for all characters. However, heritability in narrow sense (h2n) was high scored values more 50% except leaf rolling for stress irrigation treatment at Minia location (0.48%) these results confirmed that the environmental effects constitute a major portion of the total phenotypic variation in these characters.