Crop and Vegetable Physiology under Environmental Stresses

Water availability is a limiting factor for plant production, especially in Brazilian semi-arid regions. The main aim of the study was to investigate the physiological effects of drought during the fruiting stage of watermelon cultivation. A completely randomized block design with four replications and six treatments varied by the number of lateral drip tapes (1 or 2) and the duration of drought stress (0, 4, and 8 days) was used. The following parameters were evaluated: relative chlorophyll content, relative leaf water content, electrolyte leakage, CO₂ assimilation (A), stomatal conductance (g_s), internal CO₂ concentration, leaf temperature, transpiration (E), water use efficiency (WUE), carboxylation efficiency (CE), yield, thickness, diameter, length, and fruit °brix, at 4 and 8 days of drought. Drought negatively affected photosynthesis, particularly in treatments with a single dripper and 4 days of drought, resulting in reductions of up to 60% in A, 68% in g_s, 44% in E, 58% in WUE, and 59% in CE, but did not have a significant effect on watermelon yield after 4 or 8 days of irrigation. It was concluded that drought influences the physiological responses of watermelon plants, mainly in reducing photosynthesis, but does not drastically affect fruit productivity in short periods of stress. Full article

Plant plasma membrane H⁺-ATPase is a transport protein that is generally located on the plasma membrane and generates energy by hydrolyzing adenosine triphosphate (ATP) to pump hydrogen ions (H⁺) in the cytoplasm out of the cell against a concentration gradient. The plasma membrane H⁺-ATPases in plants are encoded by a multigene family and potentially play a fundamental role in regulating plant responses to various abiotic stresses, thus contributing to plant adaptation under adverse conditions. To understand the characteristics of the plasma membrane H⁺-ATPase family in peach (Prunus persica), this study analyzed the plasma membrane H⁺-ATPase family genes in peach. The results showed that there were 27 members of the plasma membrane H⁺-ATPase family in peach with amino acid sequences ranging from 943 to 1327. Subcellular localization showed that 23 of the 27 members were located on the cell membrane, and the phylogenetic tree analysis indicated that peach plasma membrane H⁺-ATPase members were divided into five groups. There were four genes with tandem repeat relationships, and six plasma membrane H⁺-ATPase genes were differentially expressed after 5 days of flooding and under non-flooding conditions based on the RNA-seq and RT-qPCR analyses. This study also investigated the characteristics and possible functions of the plasma membrane H⁺-ATPase family members in peach. The results provide theoretical support for further studies on their biological functions in peach. Full article

SOSs are key genes in the SOS (salt overly sensitive) signaling pathway, which plays an important role in maintaining ion homeostasis in plants under salt stress. Our aim was to clarify the biological function of the SOS gene family in tomato plants. We identified 14 SpeSOS genes, 10 SpiSOS genes, 11 SpmSOS genes, 9 SlmSOS genes, and 11 SlySOS genes from the genomes of “LA0716” (Spe), “LA2093” (Spi), “LA1589” (Spm), “M82” (Slm), and “Heinz 1706” (Sly) separately. The SOS protein family in tomatoes was divided into five subgroups (SOS1, SOS2, SOS3, SOS4, and SOS5) through phylogenetic analysis. The SOS proteins of the same subgroup in tomatoes contained similar conserved domains and motif structures. A subcellular localization prediction showed that the SOS1, SOS3, and SOS5 proteins in tomatoes were located on the cell membrane, while the SOS2 and SOS4 proteins in tomatoes were located on the cytoplasm and chloroplast, respectively. SlSOS1 contained the most exons and introns (23 and 22, respectively), while SlSOS5 contained only one exon. Via the analysis of the cis-elements in the promoters of those SOS genes in tomatoes, several hormone-, light-, and abiotic stress-related cis-elements were found. In addition, qRT-PCR revealed that the SpeSOS, SpiSOS, and SlySOS genes were induced by salt stress with similar expression patterns. Additionally, the expressions of SOS1-1, SOS1-2, SOS2-2, SOS3-3, SOS4-1, and SOS5-2 were higher in salt-tolerant tomatoes compared with salt-sensitive tomatoes under salt stress. In the salt-sensitive “LA1698” tomato and salt-tolerant “LA0516” tomato, most SOS genes had the highest expression in the roots. The expressions of SOS1-1, SOS1-2, SOS2-1, SOS2-2, SOS3-2, SOS3-3, and SOS5-1 in the leaves of salt-tolerant tomatoes were significantly higher than those in salt-sensitive tomatoes. Thereby, the SOS genes in tomatoes were induced by salt stress, indicating that they participated in the regulation mechanism of tomato salt tolerance. This study laid the foundation for further study on the function of the SOS gene family and revealed the molecular mechanism of tomato salt resistance. Full article

Basil (Ocimum basilicum L.) contains abundant nutrients and is considered an economically important edible vegetable. The optimal nutrient levels will increase the productivity and basil quality. However, prominent research on basil regarding the diagnostic nutrient deficiency standard and the corresponding nutrient uptake is still scarce. To this end, the basil plants were hydroponically cultured and subjected to one of 14 nutrient solution treatments, corresponding to the omission of a single nutrient element (designated as -N, -P, -K, -Ca, -Mg, -NH₄⁺, -NO₃⁻, -S, -Fe, -Mn, -B, -Zn, -Mo, and -Cu) and a complete nutrient solution (CS) as the control. The most common nutrient deficiency symptoms were chlorosis, stunted roots and growth, and even leaf necrosis and abscission, in particular of -N, -P, -NO₃⁻, and -Fe. We also found that basil is a NH₄⁺-sensitive species. The photosynthetic capacity (photosynthesis pigments, Fv/Fm ratio, and greenness index) was disturbed to varying degrees when a single nutrient was omitted from the nutrient solution. Additionally, the omission of a specific single nutrient confers significant differences in the tissue nutrients, regardless of the macronutrients and micronutrients considered. Concomitantly, multivariate analysis suggested the correlations among certain important nutrients were distinctly different under different treatments (correlation analysis); the influences of different nutrient deficiencies on the tissue nutrient concentrations showed similarity (principal component analysis). Collectively, the growth, physiological, and biochemical changes studied in this trial not only improved our knowledge for diagnosing nutrient deficiency symptoms for practical cultivation but also provided a comprehensive understanding of the internal nutrient associations in basil. Full article

Sweet cherry producers must deal with different climactic challenges annually, specifically the impact of spring frost and the inherent risk of fruit cracking. This susceptibility arises from the simultaneous occurrence of spring frost during the bloom stage or the sweet cherry cracking at vulnerable maturity stages in sweet cherry trees during persistent rainfall. Given the change in climatic patterns, the implementation of new strategies and innovative approaches becomes imperative to alleviate potential damage from these climatic adversities. This study aims to explore—for the first time—the effectiveness of preharvest putrescine applications during the flowering stage and ripening on-tree to increase tolerance in sweet cherry against adverse climatic events throughout its on-tree development and at the time of harvest. In this context, foliar applications of putrescine at concentrations of 1 and 10 mM were administered to distinct sweet cherry cultivars, namely, ‘Prime Giant’ and ‘Sweetheart’. Over the course of four growing seasons, our investigation focused on evaluating the influence of this natural elicitor on the frost resilience of flower buds during the preharvest period and its impact on reducing fruit cracking in these selected cultivars. In this sense, the overall malondialdehyde content exhibited a reduction in flower buds treated with putrescine, and the fruit set experienced an increase across the majority of evaluated growing seasons. On the other hand, the incidence of sweet cherry cracking in putrescine-treated sweet cherries showed a consistent reduction in all the studied growing seasons. Our results indicate that preharvest treatments with putrescine effectively alleviate the susceptibility of flower buds to spring frost and significantly diminish fruit cracking, thereby enhancing the overall tolerance to abiotic stress. Furthermore, we evaluated different quality parameters at the time of harvest, including fruit firmness, external color, total soluble solids, and total acidity. Generally, the observed changes in these parameters were delayed in putrescine-treated fruit as compared to the control batch or remained unaffected. For this reason, the implementation of preharvest treatments based on putrescine emerges as a valuable strategy for adapting to climate change and mitigating the impact of abiotic stress, potentially increasing sweet cherry production. Full article

To study the impact of nitrogen application on the photosynthetic structure and photosystem activity of tomato (Lycopersicon esculentum Mill.) leaves during the recovery stage after heat stress, the OJIP curve and JIP parameters were determined through a control experiment in an artificial climate chamber. The tomato variety was “Jinfen No. 1”. Four day/night temperature levels (25 °C/15 °C as control CKT; 30 °C/20 °C, lightly high-temperature LHT; 35 °C/25 °C, moderate high-temperature MHT; 40 °C/30 °C, severe high-temperature SHT) were set for a duration of 7 days. Five nitrogen supply levels (N1–N5: 0, 1.3, 1.95, 2.6 and 3.75 g/plant, respectively; 2.6 g/plant is the recommended nitrogen application rate, CKTN4) were applied. The results showed that the O, K, J, I and P phases on the chlorophyll a fluorescence curve were significantly affected by different nitrogen treatments in heat stress recovery. Compared with CKT, with the increase in nitrogen supply, the fluorescence intensity of SHTN2-SHTN5 treatment increased significantly at P, I and J phases, while that of MHTN1-MHTN4 treatment decreased. The fluorescence intensity of SHTN5 and SHTN3 increased by 13.27% and 10.10% in the P phase, 13.52% and 12.1% in the I phase and 20.16% and 26.18% in the J phase, respectively. There were highly significant differences (p < 0.01) in the impact of high temperatures and nitrogen levels on the fluorescence parameters. On the 1st day after short-term heat stress, N had no significant effect on ${\mathrm{F}}_{\mathrm{v}}/{\mathrm{F}}_{\mathrm{M}}$, ${\mathrm{F}}_{\mathrm{v}}$, ${\mathrm{F}}_{\mathrm{o}}$ and ${\mathrm{F}}_{\mathrm{M}}$; however, their interaction was significant (p < 0.05). On the 8th day, there were no significant interaction effects between HT and N for ${\mathrm{F}}_{\mathrm{v}}/{\mathrm{F}}_{\mathrm{o}}$, ABS/RC and ${\mathrm{D}\mathrm{I}}_{\mathrm{o}}/\mathrm{R}\mathrm{C}$. ${\mathrm{F}}_{\mathrm{v}}/{\mathrm{F}}_{\mathrm{o}}$ proved to be sensitive to the application of both high temperatures and nitrogen. Under all five nitrogen applications, temperature played a significant role in increasing ${\mathrm{D}\mathrm{I}}_{\mathrm{o}}/\mathrm{R}\mathrm{C}$, especially for N2 and N3. The results indicated that decreasing the nitrogen application under SHT resulted in a higher number of active $\mathrm{R}\mathrm{C}\mathrm{s}$ and an increased value of specific energy flux ($\mathrm{A}\mathrm{B}\mathrm{S}/\mathrm{R}\mathrm{C}$, ${\mathrm{T}\mathrm{R}}_{\mathrm{o}}/\mathrm{R}\mathrm{C}$ and ${\mathrm{D}\mathrm{I}}_{\mathrm{o}}/\mathrm{R}\mathrm{C}$), indicating the enhanced ability of $\mathrm{R}\mathrm{C}$ to reduce plastoquinone. The study provides a reference for the diagnosis of nitrogen nutrition under high-temperature stress using chlorophyll fluorescence methods. Full article

Fenugreek (Trigonella foenum-graecum) is an annual plant belonging to the family Fabaceae and has fodder, medicinal and spice uses, and is also used as an organic fertilizer. A total of 18 treatments including the combination of two light environments (with and without supplementary blue light), three concentrations of potassium iodate (0, 2 and 4 mg L⁻¹) and four concentrations of sodium selenate (0, 2 and 4 mg L⁻¹) were organized in a three-way factorial experiment to evaluate the growth characteristics, pigments, trigonelline and seed yield of fenugreek in a greenhouse. The application of 4 mg L⁻¹ of Se resulted in the highest carotenoid, anthocyanin, plant length, fresh weight, chlorophyll and relative water content. The fresh and dry weight of the shoot and the anthocyanin increased with the 2 h supplementation of sunlight with a blue spectrum; however, the fresh root decreased. The interaction of blue light with 0 mg L⁻¹ of Se significantly reduced the plant length. The content of trigonelline was significantly improved with the application of blue light supplementation without negatively affecting the seed yield. In general, 2 h supplementing of sunlight with blue light and feeding with 4 mg L⁻¹ of selenium and iodine are recommended to improve various traits, including trigonelline content. Full article

High temperatures have become a severe factor limiting growth and yield for tomatoes (Lycopersicon esculentum Mill.) due to unfavorable, above-optimum temperatures. Temperature and nitrogen application were the main regulatory factors in tomato plant cultivation. This research was undertaken to evaluate the effects of nitrogen application and high temperature on tomato morphology, dry matter accumulation and distribution, root vitality and nitrogen content of the above ground. Tomato variety “Jinfen No. 1” was planted and exposed to 4 day/night temperature levels (25 °C/15 °C as control CKT; 30 °C/20 °C, lightly high-temperature LHT; 35 °C/25 °C, moderate high-temperature MHT; 40 °C/30 °C, severe high temperature SHT) for 7 days after five nitrogen supply levels (N1–N5: 0, 1.3, 1.95, 2.6 and 3.75 g/plant, respectively; 2.6 g/plant is the recommended nitrogen-application rate, as control CKTN4). Within conditions, there was an extremely significant difference (p < 0.01) in all tomato plant parameters and an extremely significant interaction (p < 0.01) between high temperatures and nitrogen supply levels, except for plant height sampling on the 1st day in the recovery period. Dry matter accumulation decreased, and the accumulation rate slowed down. Dry matter accumulation under low nitrogen treatment was higher than in high nitrogen treatment. The proportion of dry matter in leaves decreased, the proportion of dry matter in stems increased and the difference in dry matter accumulation and proportion of dry matter between different nitrogen treatments decreased. Under LHT, the root activity of the tomato was increased under all nitrogen levels, while under MHT and SHT, high nitrogen and low nitrogen supply significantly inhibited root activity. Lightly high-temperature stress can increase root activity, and LHTN4 can increase by 5.15% compared with CKTN4. Appropriate nitrogen application can alleviate the damage caused by high-temperature stress on tomato plants and enhance the resistance of tomato plants, while excessive nitrogen application will aggravate the damage degree of tomato plants. In this study, the optimal nitrogen application rates under CKT-SHT treatment were 2.6, 2.6, 1.95 and 1.3 g/plant, respectively. Full article

Water salinity is a critical cause of the decrease in quality of fodder plants. The use of saline water as an alternative to fresh water requires the production of elite plant varieties that can tolerate excess amounts of sodium chloride. In this study, we evaluated six genotypes of barley (Hordeum vulgare L.) used as sprout fodder for their tolerance to saline water conditions. The six genotypes were tested for their germination vigor, α-amylase activity, root system architecture (RSA) phenotyping, relative water content (RWC), chlorophyll content (ChC), reactive oxygen species accumulation (ROS), and total antioxidant capacity. Increasing the salt concentration caused a significant decrease in the germination time, α-amylase activity, germination percentage, ChC, and RWC of all the genotypes, but significant differences in the RSA and ChC were detected. In addition, the plasticity of these characteristics at the seedling stage increased their potential to select varieties that could produce high amounts of green fodder when fresh water alternatives are used. Strong and positive correlations were detected between the green carpet formed under the salt treatment and ChC at the seedling stage for a local genotype and G134. Full article

The present study aimed to discover the effects of exogenously foliar-applied salicylic acid (SA) in concentrations of 0, 1 and 15 mM (applied 7 and 21 days after heading) on oxidative stress. The effects were monitored through the concentrations of phytoprostanes (PhytoPs) and phytofurans (PhytoFs) in immature and mature grains of three genotypes of rice (‘R52’, ‘R45’ and ‘Yerua’), and their influence on grains per panicle and chalkiness. Chromatographic separation of PhytoPs and PhytoFs was performed using a UHPLC coupled to triple quadrupole-MS/MS (Agilent Technologies, Germany). The concentrations of oxylipins showed differences in both harvest times (immature and mature) for each genotype. The advanced lines, ‘R52’ and ‘R45’, showed concentrations that were 24.0 and 79.0% lower than those of the immature grains, respectively. The PhytoFs concentration in “R45” was 46.0% lower in the mature grains. In unripe grains, SA reduced a single oxylipin of all those analyzed, while in mature grains, a significant decrease in six of the ten monitored biomarkers was observed. The SA produced an increase in grains per panicle, and a decrease in chalkiness. Therefore, salicylic acid-mediated antioxidant regulatory capacities due to oxylipin down-regulation could favor grain filling and, hence, rice production. Full article

Aluminum (Al) toxicity is the primary factor limiting agricultural productivity in acid soils. The cell wall is mainly composed of saccharides and the first barrier for aluminum (Al) to enter plant root cells, but it is unknown whether and how root saccharide components are involved in regulating the Al tolerance of Lespedeza that is well adapted to acid soils. Here, we used Al-tolerant Lespedeza bicolor and Al-sensitive Lespedeza cuneata to examine the association of root saccharide components with Lespedeza Al tolerance through analyzing the saccharide changes of roots exposed to Al toxicity. Al-sensitive Lespedeza accumulated more Al and pectin but less hemicellulose in the root cell walls than Al-tolerant Lespedeza. Al treatment decreased the amounts of total sugar secreted from and within the roots of only Al-tolerant Lespedeza. Al treatment decreased the content of root monosaccharides including glucose and mannose in both Lespedeza species, but increased the xylose contents in only Al-sensitive Lespedeza. Taken together, less cell wall pectin rather than hemicellulose is responsible for less root Al accumulation, and Al-decreased root saccharide contents may enhance root organic-acid secretion to chelate toxic Al, both of which contribute to Lespedeza Al tolerance. Full article

Changes in plant metabolism due to water deficit combined with other stresses, such as high irradiance and high temperatures, cause damage to the physiology and development of crops, which can lead to significant yield losses. The aim of this study was to determine the potential of potassium phosphite (PP) to induce tolerance to water deficit combined with high irradiance in soybean plants. The experiment was carried out in an acclimatized growth chamber. Soybean plants, upon reaching the R1 developmental stage, received the following treatments: PP application (0 L ha⁻¹–control; 0.6 L ha⁻¹ PP; and 1.2 L ha⁻¹ PP), two levels of PAR irradiance (650 µmol m⁻² s⁻¹–control; and 1500 µmol m⁻² s⁻¹–high irradiance (HI)), and three water availability levels (90% of field capacity (FC), and water deficit at 40% FC and 50% FC). The treatments were maintained for 12 days. The PP increased the photosynthetic rate of plants submitted to a dosage of 1.2 L ha⁻¹ and stresses of 50% FC + HI. PP also decreased the intensity of lipid peroxidation, and rate of electrolyte leakage, which suggests stability of cell membranes. These responses may have occurred due to the activation of the antioxidant enzymes superoxide dismutase and peroxidase. Furthermore, the application of PP increased the proline concentrations, suggesting osmotic adjustment in response to stress. These results provide the first record of PP-induced tolerance in plants under combined water and HI stresses. PP proves to be a potential alternative method to reduce the harmful effects caused by the combined stresses of water deficit and high irradiance in soybean. Full article