Search Results (91)

Calcium (Ca²⁺) is a macronutrient essential for the growth, development, yield, and quality of vegetables and fruits. It performs structural, enzymatic, and signaling functions in plants. This review examines Ca²⁺ translocation from soil to the fruit via the plant xylem network, emphasizing the importance of Ca²⁺ compartmentalization within fruit cell organelles in the development of calcium deficiency disorders such as blossom-end rot (BER). The underlying causes of BER and potential control measures are also discussed. Soil-available Ca²⁺, transported by water flow, enters the root apoplast through membrane channels and moves toward the xylem via apoplastic or symplastic routes. The transpiration force and the growth of organs determine the movement of Ca²⁺-containing xylem sap to aerial plant parts, including fruits. At the fruit level, the final step of Ca²⁺ regulation is intracellular partitioning among organelles and cellular compartments. This distribution ultimately determines the fruit’s susceptibility to Ca²⁺-deficiency disorders such as BER. Excessive sequestration of Ca²⁺ into organelles such as vacuoles may deplete cytosolic and apoplastic Ca²⁺ pools, compromising membrane integrity and leading to BER, even when overall Ca²⁺ levels are adequate at the blossom end. Effective BER management requires cultural and physiological practices that promote Ca²⁺ uptake, translocation to the fruit, and appropriate intracellular distribution. Additionally, the use of BER-resistant and Ca²⁺-efficient cultivars can help mitigate this disorder. Therefore, a comprehensive understanding of Ca²⁺ dynamics in plants is critical for managing BER, minimizing production loss and environmental impacts, and maximizing overall crop productivity. Full article

To understand the mechanisms underlying species assemblage along salt gradients in intertidal zones, we measured the xylem hydraulic vulnerability curves (HVCs), leaf water potential (ψ), stomatal conductance (g_s), specific leaf area (SLA), and wood density (WD) for six mangrove species of Avicennia marina, Bruguiera gymnorrhiza, Aegiceras corniculatum, Kandelia obovata, Sonneratia apetala, and Sonneratia caseolaris. We found the following: (1) A. marina and B. gymnorhiza had the most negative P₅₀ (water potential at which 50% of hydraulic conductivity was lost), while S. caseolaris and S. apetala had the least negative P₅₀, indicating different resistance to embolism in xylem; (2) P₅₀ and P₈₈ (water potential at which 88% of hydraulic conductivity was lost) declined with increasing salinity from the onshore to offshore species, as their water regulation strategy meanwhile transitioned from isohydry to anisohydry; (3) B. gymnorhiza had smaller SLA but larger hydraulic safety margin (HSM), implying potentially higher capacity of water retention in leaves and lower risk of hydraulic failure in xylem. These results suggest that hydraulic traits play an important role in shaping the salt-driven niche segregation of mangroves along intertidal zones. Our research contributes to a more comprehensive understanding of the hydraulic physiology of mangroves in salt adaption and may facilitate a general modeling framework for examining and predicting mangrove resilience to a changing climate. Full article

The use of chemical stimulants in resin tapping is essential for prolonging the resin flow and enhancing production. Traditional stimulants, primarily composed of sulfuric acid, pose concerns related to workplace safety, environmental impact, and tree health. In this study, we compared alternative stimulant pastes containing ethrel, salicylic acid, and citric acid with the traditional Spanish and Brazilian stimulant pastes with higher contents of sulfuric acid. We tapped Pinus pinaster seedlings with five different stimulants, using untreated and mechanically wounded plants as controls. The resin yield, tree growth, and physiological parameters were compared. The pines stimulated with citric acid released ca. 50% more resin, while ethrel and salicylic acid yielded similar amounts to the traditional paste, suggesting their potential as viable alternatives. Although all stimulants reduced the seedling growth, no significant differences were observed in the midday water potential or stomatal conductance. The internal resin accumulation and resin canal density were strongly correlated with the total resin production, and more-acidic pastes tended to cause xylem damage and resin retention. Our findings suggest that moderate acidity is sufficient to trigger resin biosynthesis and release, and that safer, less corrosive formulations, like citric acid, may provide viable, safer, and more sustainable alternatives to conventional stimulants. While the results from the seedlings provide a rapid and cost-effective screening tool, anatomical and physiological differences from mature trees should be considered when extrapolating findings to operational settings. Full article

European mistletoe is a hemi-parasitic plant increasingly infesting forests in Central Europe, causing premature tree death, and is anticipated to expand its range due to global warming. This study aimed to describe the unique anatomical features of mistletoe and examine the morpho-anatomical response of pine trees to infestation. Anatomical analyses were conducted on mistletoe internodes and the branch wood of affected pines. The findings revealed that mistletoe infestation triggers callose deposition in the cell walls of pine tracheids, a defense mechanism that restricts water flow to the mistletoe. Unique structural features of mistletoe were also identified, including structural dimorphism with the inner system forming only vessels and parenchyma cells, in contrast to the outer system, composed of protective, ground, and conductive tissues, and which displays an uneven distribution of chlorophyll and starch grains along the plant axis. Additionally, starch and chlorophyll were present in the parenchyma cells of the haustorium. Starch presence there may potentially enable internal photosynthesis, and the compounds formed after starch hydrolysis may facilitate water uptake from the host’s xylem sap. These results provide new insights into the anatomical adaptations of mistletoe and the defensive responses of pine trees, contributing to a deeper understanding of host–parasite interactions in forest ecosystems. Full article

Hyperhydricity is a significant challenge in the tissue culture of blueberry plantlets, affecting their propagation, survival and quality, which results in economic losses for industrial blueberry micropropagation. The in vitro liquid propagation of two half-highbush blueberry hybrids, HB₁ and HB₂, showed that a Growtek stationary bioreactor culture system containing a liquid medium exhibited a higher hyperhydricity percentage than a Sigma glass culture system with a semi-solid medium. The percentage of hyperhydricity (75.21 ± 1.89%) and water content (72%) of HB₂ was more than that of HB₁. A scanning electron microscopy study revealed that hyperhydric plantlets from both genotypes developed slowly, had closed stomata, and displayed enlarged intercellular spaces between the palisade and spongy parenchyma layers. Disrupted vascular bundles, underdeveloped sieve elements and a weak connection between phloem and xylem tissue were also observed in hyperhydric plantlets. An analysis of mesophyll and stem tissues highlighted a compressed adaxial epidermis, which led to compact palisade parenchyma, with irregularly shaped mesophyll cells. Hyperhydric plants showed strong nuclear magnetic resonance (NMR) signals in the aliphatic, aromatic, and sugar regions, specifically at peaks of 2.0, 2.5, 4.0, 4.5, 6.0, and 6.7 ppm. These signals were attributed to the presence of catechin (C₁₅H₁₄O₆), a flavonoid compound, suggesting its significant role or accumulation in these plants under hyperhydric conditions. Despite the negative effects of hyperhydricity on commercial propagation, hyperhydric plants were found to contain higher levels of valuable untargeted metabolites, such as β-P-arbutin, chlorogenic acid, quercetin-3-O-glucoside, epicatechin, 2-O-caffeoyl arbutin, various fatty acids, β-glucose, linolenic acid, and acetyl than both in vitro and ex vitro conditions. The enrichment of bioactive compounds in blueberry enhances its antioxidant properties, nutritional profile, and potential health benefits, making them significant for plant defense mechanisms and stress adaptation. Full article

A syndrome called “Kiwifruit Decline Syndrome” (KiDS) affects kiwifruit in several Mediterranean areas, causing growth arrest and wilt that rapidly progress to desiccation, scarce root growth, absence of fibrous roots, brown soft-rotting areas, and cortical detachment from the central cylinder. The origin is considered multifactorial, and a correlation with hydraulic conductance impairment caused by a high vapor pressure deficit (VPD) and temperature was detected. In this work, over-tree micro-sprinkler irrigation and shading nets were tested to protect leaves from overheating and locally decrease VPD. Leaf gas exchanges, leaf temperature, stem water potential, stem growth, root starch content, root xylem vessel diameter, density, and vulnerability to cavitation were assessed. A positive effect of over-tree irrigation associated with shading was observed: lower leaf temperature, higher stem water potential, stomatal conductance, and photosynthesis were detected; moreover, root starch content was higher in the summer. Narrow xylem vessel diameters were observed, indicating a long-term adaptation to rising VPD for lower vulnerability to cavitation, in all plants, but higher diameter, lower density, and higher vulnerability index indicated lower plant water stress under over-tree irrigation associated with shading. These results indicate that microclimate control by proper agronomic management can protect kiwifruit from climate stress, decreasing the risk of KiDS onset. Full article

Drought is a problematic abiotic stress affecting citrus crops in the Mediterranean basin and the rootstock plays a fundamental role in adopting adaptive mechanisms in response to water deficit. The aim of this study is to evaluate the response of eight rootstocks under three treatments imposed: control (100% of reference evapotranspiration, Et₀), 66% Et₀ and 50% Et₀. The rootstock genotypes studied were C35 citrange, Bitters, Carpenter and Furr which have been recently spread and so far, little investigated, while others have been widely used especially in the Mediterranean citrus industry, i.e., Citrus macrophylla, C. volkameriana, Swingle citrumelo and Carrizo citrange. Morphological analyses, leaf chlorophyll content determination, physiological measurement, proline accumulation, malondialdehyde determination and antioxidant enzyme activities were measured. The results exhibited that Bitters and Furr showed an increment in leaf area to reduce the effects of drought conditions. A decrement in gas exchanges and xylem water potential was noticed in Carrizo and C35 citrange at both water shortage treatments. Carrizo exhibited a significant increase in malondialdehyde at both stresses (90.3 and 103.3%, for 66 and 50% Et₀). Bitters and Furr performed better than the other rootstocks with regard to enzymatic and hormonal assays. Specifically, Bitters showed a significant reduction in CAT (−68.6%), SOD (−82.5%) and APX (−36.7%). Furthermore, Bitters and Furr were closely related to morphological parameters, e.g., leaf area and root length, and physiological measurements. C. volkameriana showed a decrease in xylem water potential, while overall Carrizo and C35 citranges showed a susceptible response to water stress reducing morphological and physiological measurements. Full article

Recent changes in rainfall patterns driven by climate change, including localized heavy rainfall, droughts, and prolonged rainy seasons, have significantly impacted grapevine growth and quality. An analysis of rainfall patterns in South Korea from 1995 to 2024 revealed that 54.5–58.0% of the annual average precipitation of 1357 mm occurs during the fruit enlargement period from June to August, at an average of seven consecutive days of rainfall, indicating a heightened potential for exposure to increased soil moisture stress for seven days annually. This study evaluated the physiological responses of grapevine cultivars ‘Campbell Early’ and ‘Jinok’ under flooding and excessive soil moisture conditions over a seven-day period. Both cultivars exhibited reductions in leaf (LWP) and stem (SWP) water potential, cumulative sap flow in the xylem (CSF), and photosynthetic rate (Pr) under flooding or excessive soil moisture conditions. At the same time, an increase was observed in the crop water stress index (CWSI) and relative leaf electrolyte leakage (REL). Several investigated parameters indicated impaired water uptake and transport under soil moisture stress conditions. Correlation analysis revealed that soil moisture was negatively correlated with the Pr and CSF, while it was positively correlated with LWP, SWP, REL, and CWSI. Our findings provide critical insights into the physiological responses of grapevines to rainfall variability and offer valuable guidance for future research in this field. Full article

Climate change has reshaped global weather patterns and intensified extreme events, with drought and soil salinity negatively impacting the yield and quality of crop production. To mitigate the detrimental effects of drought stress, the introduction of beneficial plant growth-promoting rhizobacteria (PGPR) has proven to be a promising approach. In this study, we evaluated a synthetic microbial community (SynCom) comprising bacterial strains belonging to the species Bacillus velezensis, Pseudomonas simiae, P. salmasensis, Glutamicibacter halophytocola, and Leclercia sp., which have been demonstrated to promote tomato growth both individually and collectively. The SynCom and most of its individual bacterial strains were shown to mitigate the detrimental effects of polyethylene glycol (PEG)-induced drought stress in vitro in Arabidopsis thaliana seedlings, either by reducing alterations in xylem elements or promoting the formation of new xylem strands. In a greenhouse trial, soil drenching with the SynCom and two individual strains, B. velezensis PSE31B and P. salmasensis POE54, improved the water stress response in soilless-grown tomato plants under a 40% reduced irrigation regime. Additionally, bacterial treatments positively influenced the diversity of rhizosphere bacterial communities, with distinct changes in bacterial composition, which suggest a treatment-specific interplay between the introduced strains and the native microbiome. These findings highlight the potential of microbial consortia and individual PGPR strains as sustainable tools to improve plant resilience to abiotic stresses. Full article

Tree growth potential is crucial for maintaining forest health and sustainable development. Traditional expert-based assessments of growth potential are inherently subjective. To address this subjectivity and improve accuracy, this study proposed a method of using Backpropagation Neural network (BPNN) to classify tree growth potential. 60 Pinus tabulaeformis (Carr.) and 60 Platycladus orientalis (Linn.) were selected as experimental trees in the Miyun Reservoir Water Conservation Forest Demonstration Zone in Beijing, and 95 Pinus massoniana (Lamb.) and 60 Cunninghamia lanceolate (Linn.) were selected as experimental trees in the Jigongshan Nature Reserve. The average annual ring width of the outermost 2 cm xylem of the experimental trees were measured by discs or increment cores, and the wood volume increment of each experimental trees in recent years were calculated. According to wood volume increment, the growth potential of experimental trees was divided into three levels: strong, medium, and weak. Using tree height, breast height diameter, average crown width as input variables, using growth potential level as output variables, four sub models for each tree species were established; Using tree species, tree height, breast height diameter, average crown width as input variables, using growth potential level as output variables, a generalized model was established for these four tree species. The test results showed that the accuracy of the sub models for Pinus tabulaeformis, Platycladus orientalis, Pinus massoniana, and Cunninghamia lanceolate were 68.42%, 77.78%, 86.21%, and 78.95%, respectively, and the accuracy of the generalized model was 71.19%. These findings suggested that employing BPNN is a viable approach for accurately estimating tree growth potential. Full article

Water scarcity leads to significant ecological challenges for global farming production. Sustainable agriculture depends on developing strategies to overcome the impacts of drought on important crops, including soybean. In this present study, seven promising soybean genotypes were evaluated for their drought tolerance potential by exposing them to water deficit conditions. The control group was maintained at 100% field capacity (FC), while the drought-treated group was maintained at 50% FC on a volume/weight basis. This treatment was applied at the second trifoliate leaf stage and continued until maturity. Our results demonstrated that water shortage exerted negative impacts on soybean phenotypic traits, physiological and biochemical mechanisms, and yield output in comparison with normal conditions. Our results showed that genotype G00001 exhibited the highest leaf area plant⁻¹ (483.70 cm²), photosynthetic attributes like stomatal conductance (gs) (0.15 mol H₂O m⁻² s⁻¹) and photosynthetic rate (Pn) (13.73 μmol CO₂ m⁻² s⁻¹), and xylem exudation rate (0.25 g h⁻¹) under drought conditions. The G00001 genotype showed greater leaf greenness by preserving photosynthetic pigments (total chlorophylls (Chls) and carotenoids; 4.23 and 7.34 mg g⁻¹ FW, respectively) in response to drought conditions. Soybean plants accumulated high levels of stress indicators like proline and malondialdehyde when subjected to drought stress. However, genotype G00001 displayed lower levels of proline (4.49 μg g⁻¹ FW) and malondialdehyde (3.70 μmol g⁻¹ FW), indicating that this genotype suffered from less oxidative stress induced by drought stress compared to the other investigated soybean genotypes. Eventually, the G00001 genotype had a greater yield in terms of seeds pod⁻¹ (SP) (1.90) and 100-seed weight (HSW) (14.60 g) under drought conditions. On the other hand, BD2333 exhibited the largest decrease in plant height (37.10%), pod number plant⁻¹ (85.90%), SP (56.20%), HSW (54.20%), gs (90.50%), Pn (71.00%), transpiration rate (59.40%), relative water content (34.40%), Chl a (79.50%), total Chls (72.70%), and carotenoids (56.70%), along with the maximum increase in water saturation deficit (290.40%) and malondialdehyde content (280.30%) under drought compared to control conditions, indicating its higher sensitivity to drought stress. Our findings suggest that G00001 is a promising candidate to consider for field trials and further evaluation of its molecular signature may help breeding other elite cultivars to develop drought-tolerant, high-yielding soybean varieties. Full article

Plywood is lightweight, strong, and durable, making it a widely used material in building decoration and furniture areas. In this study, formaldehyde-free, high-strength plywood was prepared through the incorporation of carbon fiber fabrics (CFFs) as reinforcement layers and their bonding with maleic anhydride polyethylene (MAPE) films. Various tests were performed to assess the impact of the carbon fiber fabric positioning on the physical and mechanical properties of plywood, including tensile shear strength, flexural strength, water absorption, thickness swelling, and electro-thermal properties. The results revealed that the plywood with CFFs exhibited significantly higher mechanical properties than plywood without CFFs. Particularly, the addition of CFFs increased the tensile strength of the plywood by nearly 54.43%, regardless of the CFFs’ position. The symmetric placement of CFFs near the bottom and upper layers of the plywood resulted in a maximum modulus of rupture of 85.6 MPa. These findings were validated by numerical simulations. Scanning electron microscopy analysis of the plywood microstructures revealed that MAPE penetrated both the vessels and xylem of the wood veneers and the pores of the CFFs, thereby improving the mechanical properties of the plywood. Plywood reinforced with CFFs exhibited increased water absorption and thickness swelling after immersion. Additionally, the placement of CFFs influenced the electro-thermal properties of the plywood. Plywood with CFFs positioned near the bottom and upper surfaces exhibited superior thermal conductivity. Overall, this study presents a feasible method for developing high-performance, formaldehyde-free plywood and sustainable wood-based structural materials with potential applications in geothermal flooring. Full article

Understanding the dynamics of physiological changes involved in the acclimation responses of plants after their exposure to repeated cycles of water stress is crucial to selecting resilient genotypes for regions with recurrent drought episodes. Under such background, we tried to respond to questions as: (1) Are there differences in the stomatal-related and non-stomatal responses during water stress cycles in different clones of Coffea canephora Pierre ex A. Froehner? (2) Do these C. canephora clones show a different response in each of the two sequential water stress events? (3) Is one previous drought stress event sufficient to induce a kind of “memory” in C. canephora? Seven-month-old plants of two clones (’3V’ and ‘A1’, previously characterized as deeper and lesser deep root growth, respectively) were maintained well-watered (WW) or fully withholding the irrigation, inducing soil water stress (WS) until the soil matric water potential (Ψ_msoil) reached ≅ −0.5 MPa (−500 kPa) at a soil depth of 500 mm. Two sequential drought events (drought-1 and drought-2) attained this Ψ_msoil after 19 days and were followed by soil rewatering until a complete recovery of leaf net CO₂ assimilation rate (A_net) during the recovery-1 and recovery-2 events. The leaf gas exchange, chlorophyll a fluorescence, and leaf reflectance parameters were measured in six-day frequency, while the leaf anatomy was examined only at the end of the second drought cycle. In both drought events, the WS plants showed reduction in stomatal conductance and leaf transpiration. The reduction in internal CO₂ diffusion was observed in the second drought cycle, expressed by increased thickness of spongy parenchyma in both clones. Those stomatal and anatomical traits impacted decreasing the A_net in both drought events. The ‘3V’ was less influenced by water stress than the ‘A1’ genotype in A_net, effective quantum yield in PSII photochemistry, photochemical quenching, linear electron transport rate, and photochemical reflectance index during the drought-1, but during the drought-2 event such an advantage disappeared. Such physiological genotype differences were supported by the medium xylem vessel area diminished only in ‘3V’ under WS. In both drought cycles, the recovery of all observed stomatal and non-stomatal responses was usually complete after 12 days of rewatering. The absence of photochemical impacts, namely in the maximum quantum yield of primary photochemical reactions, photosynthetic performance index, and density of reaction centers capable of Q_A reduction during the drought-2 event, might result from an acclimation response of the clones to WS. In the second drought cycle, the plants showed some improved responses to stress, suggesting “memory” effects as drought acclimation at a recurrent drought. Full article

The success of using active restoration in Mediterranean-type climate zones mostly depends on an appropriate matching of plant species and specific management prescriptions upon establishment. In this study, we assessed the early growth and short-term physiological acclimation of seven common species found in the sclerophyllous forests in central Chile to water restriction and shading. We established a nursery experiment that included three treatments (T0: sun-exposed and water-restricted, T1: sun-exposed and fully irrigated, and T2: shaded and fully irrigated) and seven tree species differing in their shade and drought tolerance (Quillaja saponaria Molina, Aristotelia chilensis (Mol.) Stuntz, Peumus boldus Molina, Lithraea caustica (Mol.) Hook. and Arn, Luma apiculata (DC.) Burret, Colliguaja odorifera Molina, and Escallonia pulverulenta (Ruiz and Prav.) Pers). We measured the increment in seedling height and different leaf morpho-physiological traits during two months in the dry season. Based on the measured traits, none of the species took advantage of the higher water availability in T1 relative to T0, but most of the species responded to the shade in T2, regardless of their shade or drought tolerance. Height increments due to shade varied from 0% in P. boldus to 203% in L. apiculata. Overall, all the species responded similarly to the treatments in specific leaf area, chlorophyll content index, photosynthetic rate, stomatal conductance, and intrinsic water use efficiency. This suggests that the species exhibited similar acclimation patterns of these parameters to shade and drought, even regarding the variation in midday xylem water potential found in the water-restricted treatment T0 (from −1.5 MPa in P. boldus to −3.1 MPa in E. pulverulenta). In this study, shading had a higher positive effect on the seedling performance of sclerophyllous species than watering, which at operational level highlights the need for investing in tree shelters when using these species in restoration programs. Full article

Pinus thunbergii and Euonymus japonicus are two species commonly found in arid and semi-arid areas; however, their responses in terms of physiological traits and soil properties under drought and cadmium (Cd) stress are not clear. In this study, we carried out single and combined stress treatments consisting of drought and Cd on saplings of P. thunbergii and E. japonicus and investigated the responses in terms of the physiological traits and soil properties of both species. For both species, under single Cd stress, Cd was observed in both the xylem and phloem, while the root Cd²⁺ flow rate fluctuated at different levels of Cd stress. Under both single and combined stress, as the stress level increased, the abscisic acid (ABA) content of the leaves and roots increased significantly, while the indole-3-acetic acid (IAA) content of the leaves and roots decreased significantly. Moreover, the non-structural carbohydrate (NSC) content of the leaves, stems, and roots, as well as the leaf chlorophyll content, decreased significantly. Under drought stress, the xylem water potential and hydraulic conductivity significantly decreased, which was exacerbated by Cd stress; this led to a more significant decrease in water potential and hydraulic conductivity under the combined stresses. Meanwhile, no significant changes in the conduit lumen diameter and double-wall thickness were observed, except for the double cell wall thickness of the P. thunbergii tracheid, which increased. In addition, both the single stresses and the combined stress of drought and Cd induced significant changes in the soil properties of the two species, i.e., the ammonium nitrogen, nitrate nitrogen, and effective phosphorus of the soil increased significantly, and the increase in content was more significant under combined stress. The diversity of the soil microbial community of P. thunbergii saplings significantly increased, while no change was found in its microbial community abundance under the single stresses and combined stress; however, the diversity and abundance of the soil microbial community in E. japonicus saplings showed the opposite pattern, which indicates that the effect of Cd on soil microorganisms is more significant than the effect of drought. The activity of sucrase and catalase in P. thunbergii soil fluctuated under the single stress and combined stress when compared, and the activity of sucrase in the soil of the E. japonicus species decreased. However, its catalase activity increased significantly under the single drought and Cd stress and combined stress when compared. We found that the combined stresses exacerbated the effects of the single stress in both species. Our study provides more detailed information on the responses in terms of the physiological traits and soil properties of the two species under single and combined stress consisting of drought and Cd. Full article