Global warming may cause overwintering plants to lose tolerance to low temperatures owing to de-acclimation caused by winter temperature fluctuations. The effect of elevated temperatures is regulated by the endogenous levels of phytohormones, including brassinosteroids, which allow the maintenance of high productivity under stressful conditions This study examined barley (Hordeum vulgare) de-acclimation tolerance using two mutant lines: BW084, harbouring a mutation in the HvCPD gene, and BW312, harbouring a mutation in the HvBRI1 gene. Both mutants were more tolerant to de-acclimation than the reference cultivar and displayed downregulation of chloroplast genes expression in response to de-acclimation, but differed in physiological traits related to photosynthesis and soluble carbohydrates metabolism. After 1 day of de-acclimation, biosynthesis mutant BW084 was characterized by a greater increase in the net photosynthesis rate than signalling mutant BW312. In turn after 10 days of de-acclimation, signalling mutant BW312 was characterized by the largest decrease in the fructan pool and degree of polymerization in leaves and crowns while biosynthesis mutant BW084 showed a significantly smaller decrease. In both mutants, de-acclimation tolerance was associated with maintenance of optimal tissue hydration, as evidenced by lower osmotic potential and higher cell hydration compared to the reference cultivar.

Ranges of portable systems to measure leaf gas-exchange parameters are available. They allow real-time measurements of the photosynthesis rate (A), transpiration rate (E), stomatal conductance (gs), and intercellular CO2 concentration (Ci). Photosynthetic CO2 uptake is one of the most frequently studied plant physiological processes. The measurement is precise, simple, and noninvasive to perform in vivo. We describe the use of this method in environmental-controlled plant production systems at different temperatures on the growth and development of common buckwheat.

Changes in precipitation and snow melt during warmer winters can increase low-temperature waterlogging. Such conditions may bring about different effects when compared with a single stress trigger, such as low-temperature or water excess. The effects of waterlogging are clearly related to water temperature, and the consequences of water excess might be less severe, as more oxygen is dissolved in colder water. The effect of waterlogging during cold acclimation (CA) is poorly understood; most experiments concerning water excess are performed at relatively high-temperatures. In this study, we examined the effect of 3 weeks of waterlogging (approx. 2 cm above the soil level) on CA in Festuca pratensis Huds. (Fp), a cool-season grass. Measurements were taken before CA (after prehardening, before flooding) and after 3 weeks of CA in waterlogged (treated) and non-waterlogged (control) plants. The work included: (i) freezing tolerance test (regrowth after freezing), (ii) analysis of abscisic acid (ABA) content in the leaf, (iii) leaf stomatal conductance, (iv) leaf water content, (v) carbohydrates analysis, including fructans, and (vi) transcript levels of selected genes involved in freezing tolerance, ABA signalling and fructan biosynthesis. The aim of the study was to test a hypothesis that low-temperature waterlogging in Fp enhances freezing tolerance (plant regrowth after freezing) related to increased ABA accumulation, increased C-repeat-binding transcription factor expression and/or increased carbohydrate accumulation, including fructans. Two out of four genotypes exhibited enhanced regrowth following freezing due to waterlogging relative to control. Principal component analysis (PCA) revealed a positive correlation between ABA levels and freezing tolerance in both treatments, with a more pronounced effect observed in the waterlogged plants. However, the phytohormone played different roles in these two treatments. In the context of low-temperature waterlogging, ABA may be involved in the dehydration tolerance response in genotypes suffering from physiological drought, as well as the induction of C-repeat-binding transcription factors (CBFs) and sucrose, which may improve freezing tolerance. The increased fructan amount and polymerisation degree due to waterlogging may provide a carbohydrate sink to maintain a high photosynthetic efficiency, but are not directly responsible for freezing tolerance changes. The study indicates that tolerance mechanisms of Fp exposed to low-temperature waterlogging involve maintaining a high photosynthetic rate, as well as oxidative and dehydration stress tolerance.

Water stress in agricultural systems may occur slowly or abruptly. Plant reactions to stress differ with regard to its level and duration. The level of plant susceptibility to water deprivation primarily depends on the management of the water content and metabolism adjustments. The aim of this study was to determine the correlation between water-based plant parameters and the yield components of 90 genotypes of winter wheat (Triticum aestivum L.). Since the loss of water is frequently used as a selection criterion to assess drought tolerance, the relationships between the yield and leaf water content, osmotic potential, and gas exchange characteristics were examined. Genotypes 1, 25, 34, 36, 42, 43, 46, 57, 66, 73, and 90 showed 33–45% larger numbers of grains/plant, 19–25% higher weights of grains/plant, and 4% higher thousand grain weights compared to other genotypes. The higher values of the yield components were accompanied by 20–30% lower leaf water content, 39–52% lower osmotic potential, and 4–39% lower water use efficiency. The principal component analysis revealed that the wheat genotypes had noticeable differences in a few physiological parameters that depended on the sowing date. Electrolyte leakage showed a substantial correlation with the sowing date, suggesting that it may not be a suitable factor for the prediction of drought tolerance. The factors that distinguished the examined genotypes the most were the leaf water content, osmotic potential, and water use efficiency. In addition, a significant correlation was observed between the mentioned parameters and yield components. As a result, these parameters may be helpful in genotype characterization in relation to water stress susceptibility, offering a trustworthy plant selection test.

Water deficit affects the growth as well as physiological and biochemical processes in plants. The aim of this study was to determine differences in physiological and biochemical responses to drought stress in two wheat cultivars—Chinese Spring (CS) and SQ1 (which are parents of a mapping population of doubled haploid lines)—and to relate these responses to final yield and agronomic traits. Drought stress was induced by withholding water for 14 days, after which plants were re-watered and maintained until harvest. Instantaneous gas exchange parameters were evaluated on the 3rd, 5th, 10th, and 14th days of seedling growth under drought. After 14 days, water content and levels of chlorophyll a+b, carotenoids, malondialdehyde, soluble carbohydrates, phenolics, salicylic acid, abscisic acid (ABA), and polyamines were measured. At final maturity, yield components (grain number and weight), biomass, straw weight, and harvest index were evaluated. Physiological and biochemical parameters of CS responded more than those of SQ1 to the 14-day drought, reflected in a greater reduction in final biomass and yield in CS. Marked biochemical differences between responses of CS and SQ1 to the drought were found for soluble carbohydrates and polyamines. These would be good candidates for testing in the mapping population for the coincidence of the genetic control of these traits and final biomass and yield.

In this study, we examined responses of maize hybrids differing in susceptibility to soil compaction and drought in the case of their separate or combined action. We ran field and greenhouse experiments and determined effects on grain yield, biomass, weight of 1000 grains, shoot and roots dry matter (DM), shoot-to-roots ratio, harvest index, plant height, emergence index, leaf area and greening and root number and length. Individual and combined effects of both stresses were observed in the field and greenhouse. Compared with plants growing in loose soil and optimal irrigation (LI), the resistant hybrids in treatments HI, LD and HD showed a smaller reduction in GY, BY, S, R, R-N and R-L than the sensitive. In both groups, stress influence on HA, W-1000, LA and SPAD was smaller and the differences were insignificant. Compared with LI treatment, the roots of LD, HI and HD increased their DM, number and length in the upper level of the soil profile and the number of roots developed at 0-30 degrees and 30-60 degrees in relation to the root main axis. Analysis of those traits in the hybrids resistant and sensitive to both stress factors enabled to explain a defence response. Our study demonstrated that soil compaction and soil drought, which usually occurs simultaneously, caused significant changes in components of plant yield and showed plant plasticity in response to environmental factors under natural conditions.

In the natural environment, plants are subjected to simultaneous or sequential presence of various abiotic and/or biotic stresses, including soil compaction and soil drought. The effects of these stresses tested separately are relatively well understood, but still little is known about their simultaneous effects on plants. Our research involved four single hybrids of maize differing in their degree of susceptibility to soil compaction and drought. We investigated the effects of low and high soil compaction under optimal irrigation (LI, HI) and under three-week long soil drought (LD, HD), on the gas exchange (Pn, E, g(S), Ci) and chlorophyll fluorescence parameters (F-0, F-m, F-v, F-v/F-m), total leaf area (LA), leaf greening (SPAD), leaf water deficit (WD), leaf water potential (psi) and membrane injury (MI). The plants experiencing high soil compaction (HI) showed a decrease in all parameters of gas exchange (Pn, E, g(S), Ci), leaf area (LA), leaf greening (SPAD) and the maximal quantum efficiency of PSII (F-v/F-m) in comparison with plants growing in non-compacted soil (LI). An increase was observed in the other fluorescence parameters, i.e., F-0, F-m and F-v and leaf WD, psi and MI in HI vs. LI variants. In the plants exposed to drought (LD, HD), the changes in the measured traits were greater, especially for the sensitive hybrids P-8400 and NS-3023, than for the plants from LI treatment. A significant interaction between the degree of stress susceptibility and relative trait change was observed for practically all of the measured features. Moreover, in the short recovery period after the end of drought, the measured traits in LD and HD plants did not fully return to the control level, especially in the case of the sensitive hybrids (P-8400 NS-3023). The physiological reaction of maize hybrids to soil compaction and/or soil drought indicated the genetically determined variability of tolerance to those stresses. Significant correlation between RTC and stress susceptibility indexes (S-SI) provided suitable criteria for the hybrid selection. Also, our results showed the plasticity and capability of maize hybrids to respond to environmental conditions.

Effects of soil compaction stress were investigated in maize hybrids subjected to low (L-1.10), medium (M-1.30) and high (H-1.60 g/cm(3)) soil compaction. The hybrids selected for the study differed in their susceptibility to growth under soil compaction stress conditions. We used appropriate methods of non-destructive cleaning and analysis of all intact compartments of the root system. Petrolatum-wax test, proved as an effective screening technique for selecting resistant and sensitive maize hybrids, was also employed. The seedlings were grown in custom-made 'root-box' and 'root-basket' containers. The penetration resistance (PR) strength of 0.52 and 1.07 MPa was satisfactory for estimating root penetration index (RPA) among maize hybrids. The soil compaction stress affected root system structure (RSS) in maize hybrids. The resistant hybrids showed a lower decrease in root dry matter (DM) in M and H treatments at 0.0-15 cm soil depth, and an increase in the number of roots growing at an angle of 0 degrees-30 degrees in relation to the main growth axis, comparing to sensitive hybrids. The soil compaction stress lowered root number (R-N) and length (R-L), shoot and root DM, and increased shoot to root ratio (S/R). The changes were greater in sensitive than in resistant hybrids. In addition, a regression coefficient (R-2) between stress susceptibility index (SSI) and relative trace change (RTC) marked for changes in dry matter of shoot (S), roots (R), shoot to root (S/R) ratio and root length (R-L) and number R-N was statistically significant. Seedlings of maize single-cross hybrids demonstrated differences in their responses to soil compaction stress, which caused changes in shoot and root dry matter and the distribution of roots in the soil profile.

Soil drought is a major problem in plant cultivation. This is particularly true for thermophilic plants, such as maize, which grow in areas often affected by precipitation shortage. The problem may be alleviated using plant growth and development stimulators. Therefore, the aim of the study was to analyze the effects of 5-aminolevulinic acid (5-ALA), zearalenone (ZEN), triacontanol (TRIA) and silicon (Si) on water management and photosynthetic activity of maize under soil drought. The experiments covered three developmental stages: three leaves, stem elongation and heading. The impact of these substances applied during drought stress depended on the plant development stage. 5-ALA affected chlorophyll levels, gas exchange and photochemical activity of PSII. Similar effects were observed for ZEN, which additionally induced stem elongation and limited dehydration. Beneficial effects of TRIA were visible at the stage of three leaves and involved leaf hydration and plant growth. A silicon preparation applied at the same developmental stage triggered similar effects and additionally induced changes in chlorophyll levels. All the stimulators significantly affected transpiration intensity at the heading stage.

Soil compaction stress can strongly affect plant growth, development and productivity. Effects of different levels of soil compaction were investigated in 18 maize hybrids during field and greenhouse experiments. Maize hybrids in the field experiments were subjected to low (L) or high (H) and in the greenhouse experiments to low (L: 1.10) and high (C: 1.60 g cm(-3) soil) soil compaction level. Differences between maize hybrids grown under non-stress and stress conditions were found in a decrease in grain yield (GY), grain number (GN), weight of 1,000 grain (W-1000), seedling dry matter (DM), emergence (EM), plant height (H), leaf area (LA) and leaf greening (SPAD). Stress susceptibility index (SSI), geometric mean productivity index (GMP) and tolerance index (TI) were evaluated by determining the effects of low (L) or high (H) soil compaction levels on grain yield (GY) or dry matter of the above-ground part (DM). The values of SSI, GMP and TI enabled us to rank the tested hybrids with respect to their susceptibility to soil compaction stress. SSI and TI made it possible to identify maize hybrids resistant and sensitive to soil compaction stress. Changes in growth traits were greater in the hybrids with high SSI and TI. Correlation coefficient (r) between stress susceptibility index (SSI) of maize hybrids in the field and greenhouse experiment was high and statistically significant. This observation may indicate that genetically determined susceptibility to soil compaction stress in maize hybrids was similar throughout ontogenesis.

W upowszechnianiu wiedzy o biologii stresu u roślin ważną rolę odgrywają konferencje i sympozja naukowe mające na celu przedstawienie aktualnego stanu wiedzy, wymianę opinii i podejmowanie wspólnych, często międzynarodowych projektów badawczych. Na świecie, każdego roku odbywa się bardzo wiele tego typu wydarzeń i są one organizowane przez różne ośrodki badawcze. Tematyka dotyczy zarówno specyficznej problematyki, jak i bardziej ogólnych rozważań będących syntezą dotychczas uzyskanych wyników. Urodzony w Polsce, amerykański profesor Jacob O. Levitt podczas wykładu plenarnego na konferencji w East Lansing (1988) pt. „Stress interaction – back to the future” postulował, że dla osiągnięcia postępu w biologii stresu, konieczne jest przeanalizowanie starszych, często zapomnianych badań i podjęcie próby syntetycznego ich opracowania. Problemy związane ze stresem zgodnie z terminologią Hansa Selye’a (twórcy pojęcia stresu) dotyczące działania ABA, uszkodzenia błon komórkowych, reakcji z tlenem mogą być uznane za Ogólny Zespół Adaptacji (GAS), a istnienie wspólnych odpowiedzi fizjologicznych odgrywa rolę w poprawie tolerancji stresu u roślin za pomocą metod biotechnologicznych.

(1) Background: The study analyzed wheat morphological traits to assess the role of roots structure in the tolerance of drought and to recognize the mechanisms of root structure adjustment to dry soil environment. (2) Methods: Root-box and root-basket methods were applied to maintain an intact root system for analysis. (3) Results: Phenotypic differences among six genotypes with variable drought susceptibility index were found. Under drought, the resistant genotypes lowered their shoot-to-root ratio. Dry matter, number, length, and diameter of nodal and lateral roots were higher in drought-tolerant genotypes than in sensitive ones. The differences in the surface area of the roots were greater in the upper parts of the root system (in the soil layer between 0 and 15 cm) and resulted from the growth of roots of the tolerant plant at an angle of 0-30° and 30-60°. (4) Conclusions: Regulation of root bending in a more downward direction can be important but is not a priority in avoiding drought effects by tolerant plants. If this trait is reduced and accompanied by restricted root development in the upper part of the soil, it becomes a critical factor promoting plant sensitivity to water-limiting conditions.

5-Aminolevulinic acid relieves the effects of environmental stresses in plants. Therefore, the aim of our study was to evaluate the effects of 5-aminolevulinic acid (5-ALA) on the activity of the photosynthetic apparatus in spring wheat. Other analyzed parameters involved plant height, relative turgidity, membrane status, and chlorophyll level. The plant material consisted of three genotypes of spring wheat (J × Z, R × K, K × M), subjected to mild and severe drought in the early phase of vegetative development. 5-ALA showed a positive effect on the activity of the photosynthetic apparatus under water stress. The relieving action of 5-ALA on PSII was the most evident in J × Z genotype during severe soil drought. 5-ALA positively influenced the maximum photochemical efficiency of PSII (Fv/Fm), the overall performance index of PSII photochemistry (PI) and the effective quantum field of PSII (φEo). In the same genotype, the investigated acid stimulated light energy absorption (ABS/CSm), and enhanced the amount of excitation energy trapped in PSII reaction centers (TRo/CSm) and the amount of energy used for electron transport (ETo/CSm). Moreover, 5-aminolevulinic acid showed its potential to overcome the adverse effects of water deficit on Triticum aestivum L. by increasing plant growth, relative turgidity, and chlorophyll content and reducing the degree of damage to cell membranes at the early phase of vegetative development.

Lettuce (Lactuca sativa L.) is an important dietary component and its biofortification in selenium (Se) may have health-promoting effects for humans. Selenium fertilization may change plant resistance to abiotic and biotic stresses. The aim of this study was to determine the effects of Se (IV) has on lettuce resistance to biotic stress induced by Botrytis cinerea (gray mold). The results have been discussed in relation to: (1) the potential use of Se for supplementation of crops to counteract Se deficiency in diet and (2) to the effect of Se-enrichment on the susceptibility of plants to pathogens.

Photosynthetic acclimation to cold conditions is an important factor influencing freezing tolerance of plants. Photosynthetic enzyme activities increase as part of a photochemical mechanism underlying photosynthetic acclimation to low temperatures. Additionally, a non-photochemical mechanism may be activated to minimize photooxidative damage. The aim of this study was to test the hypothesis that differences in stomatal conductance in Hordeum vulgare plants with contrasting freezing tolerances induce various strategies for photosynthetic acclimation to cold stress. Different stomatal behaviors during the prehardening step resulted in diverse plant reactions to low-temperature stress. Plants with a relatively low freezing tolerance exhibited decreased stomatal conductance, resulting in decreased photochemical activity, faster induction of the non-photochemical mechanism, and downregulated expression of two Rubisco activase (RcaA) splicing variants. In contrast, plants with a relatively high freezing tolerance that underwent a prehardening step maintained the stomatal conductance at control level and exhibited delayed photochemical activity and RcaA expression decrease, and increased Rubisco activity, which increased net photosynthetic rate. Thus, in barley, the induction of photoinhibition avoidance (i.e., non-photochemical photoacclimation mechanism) is insufficient for an effective cold acclimation. An increase in cold-induced net photosynthetic rate due to open stomata is also necessary.

The agronomic and physiological traits, drought tolerance indexes, principal component analysis and Ward`s method were applied to assess the differences among 20 wheat genotypes in response to drought. Statistically significant correlation was observed for measured traits. Drought susceptibility index (DSI), stress tolerance index (STI) and stress index (SI) were most useful to identify genotypes differing in their response to drought. Utility of the indexes was confirmed by physiological markers of drought tolerance i.e. membrane injury and leaf water status. Variation of the genotypes in biomass and grain yield during drought stress was also verified by clustering methods. Finally, integration of physiological and statistical methods presented in this work, allows to both, indicate that tolerance to drought in wheat has a common genetic background, and select the most diverse genotypes. Based on the results, we recommend a tool for breeders, useful to select the genotypes resistant and sensitive to drought.

The tibial tubercle-trochlear groove distance (TT-TG) is an established measurement to assist diagnosis and treatment of patellofemoral instability. However, little is known about the distribution of TT-TG in osteoarthritic knees. The purpose of the current study is to investigate the TT-TG in a large cohort of osteoarthritic knees and to analyse in particular the association of knee alignment and TT-TG. Data from 962 consecutive patients [455 male, 507 female; mean age ± SD 70.8 ± 9.3 (37–96)] who had undergone 3D-CT and preoperative knee planning with validated commercial 3D planning software before total knee arthroplasty (TKA) were collected prospectively. The TT-TG, coronal hip knee ankle angle (HKA), femoral anteversion (AVF), external tibial torsion (ETT) and femorotibial rotation (Rot FT) were analysed. Pearson correlations were performed to assess for correlations between TT-TG, mechanical axis and rotational parameters (p < 0.05). HKA showed a strong correlation with TT-TG (r = 0.488; p < 0.001) with 98 (67.1%) and 45 (30.8%) of valgus knees having respective abnormal and pathological TT-TG values. There were no significant correlations between parameters of rotational alignment (AVF, ETT, Rot FT) and TT-TG. Mean TT-TG was 12.9 ± 5.6 mm, ranging from 0.0 to 33.7 mm. 325 (33.8%) of all patients had abnormal (> 15 mm) and 101 (10.5%) had pathological (> 20 mm) values. A varus alignment was present in 716 (74.4%) of the cases (HKA < − 1.5°), a neutral alignment in 100 (10.4%) and a valgus alignment in 146 (15.2%) (HKA > 1.5°). Our results show a wide variation of TT-TG values in osteoarthritic knees. There was a relevant influence of coronal limb alignment on the TT-TG—the more valgus the higher and more pathological the TT-TG. With the aim of having a more personalized TKA, the individual TT-TG should be taken into account to improve the outcome. III. Retrospective cohort study.

The aim of the study was to determine molecular basis of plant photosynthetic activity during soil drought and under rapid (unfavorable) and gradual (favorable) rehydration. We analyzed the content of proteins associated with the photosynthetic apparatus and photosynthetic fixation of CO2. The experiment involved two genotypes of triticale showing complete and incomplete recovery from drought stress. The reason for irreversible changes in the activity of the photosynthetic apparatus was stress-induced decrease in the content of Rieske protein (PetC) of cytochrome complex b(6)f. Intensification of metabolic processes during rehydration and following overload the electron transport chain led to electron transfer from primary acceptors Q(A)/Q(B) in PSII and ferredoxin in PSI to oxygen. The resulting reactive oxygen species oxidized proteins and inhibited synthesis of those controlling the photosynthetic apparatus and carbon fixation. The consequence was a reduction of quantum yield of electron transport to their final acceptors in PSI and lowering of plant photosynthetic activity and biomass. Simultaneous utilization of H2O2 during saturation of cell wall with phenolic compounds ensured restoration of desired level of proteins controlling the photosynthetic apparatus and photosynthetic carbon fixation, as well as high photosynthetic activity.