Decrease In Relative Water Content Research Articles

Effects of Cd Stress on Morphological and Physiological Characteristics of Maize Seedlings

Heavy metal (HM) contamination poses a serious threat to safe crop production and human health, and different maize inbred lines respond differently to cadmium (Cd) stress. However, the morphological and physiological characteristics of maize inbred lines seedlings are not clear under Cd stress. In this study, we analyzed the agronomic traits and physiological and biochemical indices of inbred maize seedlings under Cd stress in the seedling stage using the inbred lines Kui3, CML118, Mo17, B73, and B77 as the materials. These five inbred maizes were treated with five different concentrations of Cd (0, 1, 3, 5, and 7 mg L−1, respectively) were applied and the indices of the maize seedlings determined on day 15. The aboveground and belowground biomass of five maize inbred lines seedlings showed a decreasing trend under Cd stress. Leaf relative water content and SPAD values also decreased, but the overall decrease in relative water content was small, and the differences were not significant. Surprisingly, Cd stress affected the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), leading to enhanced mem-brane lipid peroxidation. The cadmium content varied greatly between varieties under Cd stress, but all of them had lower Cd content above ground than below ground, and the varieties with the highest and lowest transfer coefficients were Mo17 (0.33–0.83) and B73 (0.06–0.44), respectively. Kui3 had the greatest difference in soluble protein content under Cd stress, which showed a de-creasing trend, and the soluble sugar content was significantly decreased in general compared to that of CK. The soluble sugar content was higher than CK under Cd treatment, and the proline content of the maize seedlings of all of the inbred lines showed an increasing trend compared to CK. Overall, there were significant genotypic differences in the Cd stress response to Cd toxicity in the maize inbred lines seedlings, and, in general, this study helps us to understand the mechanism of maize inbred lines seedlings response to Cd stress. It provides a theoretical basis for the se-lection and breeding of varieties, and food safety.

Differential physiological and production responses of C3 and C4 crops to climate factor interactions.

This study examined the effect of the interactions of key factors associated with predicted climate change (increased temperature, and drought) and elevated CO2 concentration on C3 and C4 crop representatives, barley and sorghum. The effect of two levels of atmospheric CO2 concentration (400 and 800 ppm), three levels of temperature regime (21/7, 26/12 and 33/19°C) and two regimes of water availability (simulation of drought by gradual reduction of irrigation and well-watered control) in all combinations was investigated in a pot experiment within growth chambers for barley variety Bojos and sorghum variety Ruby. Due to differences in photosynthetic metabolism in C3 barley and C4 sorghum, leading to different responses to elevated CO2 concentration, we hypothesized mitigation of the negative drought impact in barley under elevated CO2 concentration and, conversely, improved performance of sorghum at high temperatures. The results demonstrate the decoupling of photosynthetic CO2 assimilation and production parameters in sorghum. High temperatures and elevated CO2 concentration resulted in a significant increase in sorghum above- and below-ground biomass under sufficient water availability despite the enhanced sensitivity of photosynthesis to high temperatures. However, the negative effect of drought is amplified by the effect of high temperature, similarly for biomass and photosynthetic rates. Sorghum also showed a mitigating effect of elevated CO2 concentration on the negative drought impact, particularly in reducing the decrease of relative water content in leaves. In barley, no significant factor interactions were observed, indicating the absence of mitigating the negative drought effects by elevated CO2 concentration. These complex interactions imply that, unlike barley, sorghum can be predicted to have a much higher variability in response to climate change. However, under conditions combining elevated CO2 concentration, high temperature, and sufficient water availability, the outperforming of C4 crops can be expected. On the contrary, the C3 crops can be expected to perform even better under drought conditions when accompanied by lower temperatures.

Potassium humate and cobalt enhance peanut tolerance to water stress through regulation of proline, antioxidants, and maintenance of nutrient homeostasis

Water stress is an important factor that substantially impacts crop production. As a result, there is a need for various strategies that can mitigate these negative effects. One such strategy is the application of potassium humate (Kh) and cobalt (Co), which have been reported to enhance the resistance of crop plants. Therefore, the present experiment was designed to investigate whether the application of Kh and Co could positively affect proline, chlorophyll and mineral elements contents, and antioxidant defense systems which in turn will mitigate the negative impact of water stress under different irrigation strategies. In 2021 and 2022, an open-field experiments were conducted by using a split-plot design. The main plots were divided to represent different irrigation strategies (ST), with additional control of full irrigation requirements (ST1). Four STs were implemented, with ST1, followed by the application of 75%, 50%, and 25% irrigation strategies in ST2, ST3, and ST4 respectively, in the next irrigation, followed by the full requirements, and so on. In the subplots, peanut plants were treated with tap water (Control), Kh at 2 g l−1 and 3 g l−1, Co, Co + Kh 2 g l−1 and Co + Kh 3 g l−1. The yield was negatively affected by the implementation of ST4, despite the increase in proline contents. Furthermore, there was a decrease in relative water content, chlorophyll content, antioxidant enzymes, protein, and mineral nutrient elements. However, the application of Kh or Co showed better improvements in most of the studied parameters. It is worth noting that there was an antagonistic relationship between Co and iron/manganese, and the intensity of this relationship was found to depend on the STs implemented. The highest mineral nutrient accumulation, chlorophyll content, relative water content, protein content, oil content, seed yield, and water productivity were observed when peanut plants were treated with Kh 3 g l−1 + Co under the ST2 water strategy.

IMPACT OF POLYETHYLENE GLYCOL-INDUCED OSMOTIC STRESS ON MAIZE GERMINATION, GROWTH, AND PHYSIOLOGICAL RESPONSE

Drought stress is a significant environmental concern affecting crop growth, development, and yield. A laboratory experiment was conducted to examine the germination characteristics of four maize genotypes under varying levels of osmotic stress (0%, 2.5%, 5%, 7.5%, 10%) using polyethylene glycol (PEG) 6000 as an osmoticum. The experiment followed a factorial design within a Completely Randomized Design (CRD) framework with three replications. Varying concentrations of PEG influenced the germination and early growth of plants. An interesting finding was that as the concentration of PEG increased, there was a noticeable decrease in plant growth, indicating a negative correlation between the two. The findings indicated that subjecting maize plants to water stress treatments significantly affected various growth parameters (with a statistical significance level of P<0.05). Furthermore, with the increase in PEG concentration, there was a gradual decline in both respiration and transpiration rates, resulting in a decrease in protein concentration. There is a significant decrease in relative water content (RWC) in both shoot and root by 28.65% and 11.13%, respectively, compared with the control. When maize seedlings were subjected to water deficit by treating them with 2.5 to 10% PEG, there was a significant decrease (by 60.05%) in the level of chlorophyll 'b' while the decrease (by 33.25%) in chlorophyll 'a' content was comparatively less pronounced.

Enhancing Chickpea (Cicer arietinum L.) Tolerance to Salinity through Plant Growth Regulators

During the period of 2020-21, a research study was carried out at the Plant Protective Culture Unit within the semi-controlled environmental settings of the Bangladesh Agricultural Research Institute. The aim of the study was to mitigate the negative impacts of salinity stress on chickpea by applying various concentrations of salicylic acid (SA) and gibberellic acid (GA3). Plants were subjected to four different levels of salinity stress, including a control group, mild stress, moderate stress, and severe stress. This was achieved by irrigating them with four varying concentrations of saline water (5, 7.5, 10 and 12.5 dSm-1) starting from the 14th day after sowing (DAS) and continuing until maturity at 100 DAS. On the other hand, the control plants received regular irrigation with tap water. Two concentrations of salicylic acid (SA) specifically 200 ppm and 400 ppm, along with gibberellic acid (GA3) at 10 ppm and 20 ppm, were administered as a foliar spray once a week, commencing at 20 days after sowing (DAS) and continuing until the flowering stage. Data related to chlorophyll levels in the leaves and water-related traits, including relative water content (RWC) and water retention capacity (WRC) were collected seven days after the foliar spray of these plant growth regulators at the flowering stage. Additionally, measurements of total dry weight, yield, and various yield-contributing factors were taken at the point of maturity. The results indicated that chickpea suffered adverse consequences due to salinity stress which included a reduction in chlorophyll content, a decrease in relative water content, a decline in water retention capacity, a decrease in total dry weight and a lower overall yield. However, the foliar application of different doses of salicylic acid (SA) and gibberellic acid (GA3) under varying levels of salinity stress had beneficial effects in alleviating the impact of salinity stress. Interestingly, it was observed that lower concentrations of SA at 200 ppm and GA3 at 10 ppm were more effective in mitigating the adverse effects of salinity stress and improving salinity tolerance in chickpea, especially under mild salinity stress conditions (5 dSm-1) as evidenced by the positive influence on the parameters mentioned above.

Chemical composition and herbicidal potential of essential oil of Eucalyptus maculata Hook

In continuation of the search of eco-friendly and safe alternatives for chemical pesticide for weeds management, essential oils (EOs) of forestry tree may be a good candidate. Here, the EOs of Eucalyptus maculata were extracted by hydrodistillation and the study of their chemical composition was carried out by GC and GC/MS analysis. The allelopathic effects of E. maculata EOs was tested against two common weeds in Tunisia: Sinapis arvensis (dicot) and Phalaris canariensis (monocot) and Triticum durum as cereal monocot cultivated crop. The application of EOs has been carried out in two stages of growth: pre-emergence and post emergence. Analysis of the EOs resulted in the identification of 46 components representing 97.7% of the total oil. 1.8-Cineole was detected as the principal compound accounted for 42% of the oil totality and oxygenated monoterpenes (61.5%) was the major subclass that characterize E. maculata growing in Tunisia. On pre-emergence stage, Eucalyptus EOs significantly reduced germination and seedling growth of all tested species in a dose dependent manner and the phytotoxic effect of the EOs was differently effective depending on doses and tested species. On post-emergence stage, volatile oil induces a phytotoxic effect against all tested plants, a decrease in relative water content, an increase of relative electrolyte leakage percentage and levels of proline and malondialdehyde contents which explain their significant phytotoxic potential. Thus, E. maculata EOs inhibits germination and seedling growth of tested herbs in pre-emergence stage and post emergence stage, therefore E. maculata EOs shows potential towards weed management.

Response of banana (Musa spp.) to drought stress based on phenotypic and physiological traits

ABSTRACT Banana (Musa spp.), an important staple food in the tropical and subtropical regions, is highly susceptible to drought. Developing drought-tolerant bananas using available germplasm offers a long-term solution to mitigate drought effects. The East and Central Africa Banana Germplasm Collection in Uganda contains genetically diverse genotypes whose potential for drought tolerance breeding is yet to be established. This study aimed to determine the response of 14 Musa spp. genotypes to drought stress using phenotypic and physiological traits in order to select promising genotypes for use in breeding. Two genotypes with a known reaction to water deficit conditions were included as local checks. Three-month-old tissue culture-derived plantlets were completely deprived of water for four weeks while control plants were regularly irrigated back to field capacity, and both sets maintained under screen-house conditions. Drought stress resulted in significant reductions in plant height, total leaf area, number of leaf cigars and functional leaves, total dry matter, chlorophyll and relative water content. Water use efficiency (WUE) of 12 genotypes increased under stress conditions. Stomatal conductance was affected by the genotype-porometer reading time interaction. Genotype “ITC.0987” was the most tolerant, considering that moisture stress had the least effect on its above-ground growth. Among the improved diploids, “TMB2x9722-1” had the least total dry matter reduction and highest WUE, while “TMB2x9172” showed the least decrease in relative water content and highest root-shoot ratio increase under stress. Thus, “ITC.0987”, “TMB2x9722-1” and “TMB2x9172” are essential drought-tolerant candidates that may be utilized in breeding.

Tonoplast Sucrose Trafficking Modulates Starch Utilization and Water Deficit Behavior in Poplar Leaves.

Leaf osmotic adjustment by the active accrual of compatible organic solutes (e.g. sucrose) contributes to drought tolerance throughout the plant kingdom. In Populus tremula x alba, PtaSUT4 encodes a tonoplast sucrose–proton symporter, whose downregulation by chronic mild drought or transgenic manipulation is known to increase leaf sucrose and turgor. While this may constitute a single drought tolerance mechanism, we now report that other adjustments which can occur during a worsening water deficit are damped when PtaSUT4 is constitutively downregulated. Specifically, we report that starch use and leaf relative water content (RWC) dynamics were compromised when plants with constitutively downregulated PtaSUT4 were subjected to a water deficit. Leaf RWC decreased more in wild-type and vector control lines than in transgenic PtaSUT4-RNAi (RNA-interference) or CRISPR (clustered regularly interspersed short palindromic repeats) knockout (KO) lines. The control line RWC decrease was accompanied by increased PtaSUT4 transcript levels and a mobilization of sucrose from the mesophyll-enriched leaf lamina into the midvein. The findings suggest that changes in SUT4 expression can increase turgor or decrease RWC as different tolerance mechanisms to reduced water availability. Evidence is presented that PtaSUT4-mediated sucrose partitioning between the vacuole and the cytosol is important not only for overall sucrose abundance and turgor, but also for reactive oxygen species (ROS) and antioxidant dynamics. Interestingly, the reduced capacity for accelerated starch breakdown under worsening water-deficit conditions was correlated with reduced ROS in the RNAi and KO lines. A role for PtaSUT4 in the orchestration of ROS, antioxidant, starch utilization and RWC dynamics during water stress and its importance in trees especially, with their high hydraulic resistances, is considered.

Physiological insights on soybean response to drought

As most of the soybean in Europe is grown in rainfed conditions, climate aberrations are causing significant crop yield variability. To stabilise the yield and shift the sources of supply to European-grown soybean, stable and adaptable cultivars must be created by breeding. To better understand the mechanism of drought tolerance in specific germplasm, more knowledge needs to be acquired by research. Therefore, this research aimed to examine the physiological insights on soybean response to drought exposed plants (50% available water holding capacity) by monitoring the relative water content (RWC), lipid peroxidation (TBARS), pigments (Chl a and b), proteins and photosynthetic efficiency during five days in the pod stage. The decrease of RWC in both tested genotypes due to the drought effect, coupled with TBARS increase, indicates lipid peroxidation, which resulted in photosynthetic pigment and protein changes. Most of the chlorophyll a fluorescence parameters suggested plants initiated a defence mechanism to water deficiency, i.e. there was an initial adjustment on the first and second day of drought exposed plants, followed by drastic changes in electron flow in photosystem II (PSII). According to the correlation analysis, the effect of drought was prevalent for Chl b, Chl a/b, relative variable fluorescence at 30 ms (VI), the density of reaction centres (RC/CS0), absorption, trapping, electron transport and dissipation flux per reaction centre (ABS/RC, TR0/RC, ET0/RC and DI0/RC), plastoquinone at quinone A binding niche reducing RCs per PSII antenna chlorophylls (RC/ABS) and performance index (PIABS), meaning these parameters are good indicators of drought stress, that can facilitate the selection of genotypes and increase the efficiency of breeding programmes. Among tested materials, Korana had lower sensitivity to drought and smaller reduction of yield components than OS-211, indicating a better response of its defence mechanism to oxidative stress caused by lack of water. The methods tested and confirmed in this research could be used for screening large numbers of genotypes to determine in the soybean breeding programs aiming to select superior genotypes adaptable to weather changes.

METABOLIC CHANGES IN WOMEN AND MEN WITH TYPE 2 DM ON ISLGT-2 TREATMEN

The use of morpho-metabolic approaches has a great practical importance in evaluation of the effectiveness of antihyperglycemic therapy in clinical trials, in particular those related to new classes of inhibitors of sodiumdependent glucose-2 cotransporter inhibitors that have the ability to counteract many diabetic complications and cardiovascular disease. The aim of the study was to study the effect of treatment with SLGT2 inhibitors on morphological and metabolic parameters in men and women with type 2 diabetes. Materials and methods. During the study, 205 patients with type 2 diabetes, aged 30 to 81, with a disease duration of 1 to 20 years were examined. Patients underwent a clinical examination in the Department of Age Endocrinology and Clinical Pharmacology of the Institute of Endocrinology and Metabolism. V.P. Komissarenko of the National Academy of Medical Sciences of Ukraine. Patients received antihyperglycemic, antihypertensive and dyslipidemic therapy. Results.The study of anthropometric, morphological and biochemical parameters in groups of men and women with type 2 diabetes in the dynamics of longterm (12 month) use of iSLGT2- dapagliflozin allowed to identify certain sexual characteristics of the effects of this drug. In men group have been seen a gradual decrease in visceral fat levels during therapy. A decrease in BMI, BP, body weight and uricemia in men is most likely associated with a decrease in abdominal obesity and decreased insulin secretion. In women group use of dapagliflozin showed a significant decrease in total and visceral fat, accompanied by a decrease in relative water content, muscle and bone mass. Conclusions. Treatment of patients with type 2 diabetes with drugs of the group iSLGT2 for 12 months has reduced the degree of obesity and improved some indicators of body composition, uric acid.

Functional Identification of ICE Transcription Factors in Rubber Tree

ICE (inducer of CBF expression) is a positive regulator of cold signaling pathway in plants. Identification of ICE transcription factors is important for the sustainable development of the natural rubber planting industry in nontraditional regions where sudden cold waves often occur. In this study, five ICE genes were isolated from genome of rubber tree (Hevea brasiliensis Muell. Arg.) for analysing tolerance to cold stress. They shared an ICE-specific region in the highly conserved bHLH-ZIP domain and were localized in the nucleus. The HbICEs were different in transcript abundance and expression patterns in response to cold and drought stresses and among different rubber tree clones. Generally, the expression level of HbICEs was significantly higher in the cold-tolerant rubber tree clones than that in the cold-sensitive rubber tree clones. Overexpression of HbICE1, HbICE2, and HbICE4 significantly enhanced the cold tolerance of transgenic Arabidopsis and tobacco, which showed a significant increase in chlorophyll content and decrease in relative water content and conductivity at the early stage of cold stress in comparison with wild-type plants. Furthermore, overexpression of HbICE2 and HbICE4, but also HbICE1 enhanced drought tolerance in transgenic Arabidopsis. The cold tolerance of rubber tree clones is positively controlled by the expression level of HbICE1, HbICE2, and HbICE4.

Salt Stress Affects Plastid Ultrastructure and Photosynthetic Activity but Not the Essential Oil Composition in Spearmint (Mentha spicata L. var. crispa "Moroccan").

High levels of soil salinity affect plant growth, reproduction, water and ion uptake, and plant metabolism in a complex manner. In this work, the effect of salt stress on vegetative growth, photosynthetic activity, and chloroplast ultrastructure of spearmint (Mentha spicata L. var. crispa “Moroccan”) was investigated. After 2 weeks of low concentration treatments (5, 25, and 50 mM NaCl) of freshly cut shoots, we observed that the stem-derived adventitious root formation, which is a major mean for vegetative reproduction among mints, was completely inhibited at 50 mM NaCl concentration. One-week-long, high concentration (150 mM NaCl) salt stress, and isosmotic polyethylene glycol (PEG) 6000 treatments were compared in intact (rooted) plants and freshly cut, i.e., rootless shoots. Our data showed that roots have an important role in mitigating the deleterious effects of both the osmotic (PEG treatment) and specific ionic components of high salinity stress. At 50 mM NaCl or above, the ionic component of salt stress caused strong and irreversible physiological alterations. The effects include a decrease in relative water content, the maximal and actual quantum efficiency of photosystem II, relative chlorophyll content, as well as disorganization of the native chlorophyll-protein complexes as revealed by 77 K fluorescence spectroscopy. In addition, important ultrastructural damage was observed by transmission electron microscopy such as the swelling of the thylakoid lumen at 50 mM NaCl treatment. Interestingly, in almost fully dry leaf regions and leaves, granum structure was relatively well retained, however, their disorganization occurred in leaf chloroplasts of rooted spearmint treated with 150 mM NaCl. This loss of granum regularity was also confirmed in the leaves of these plants using small-angle neutron scattering measurements of intact leaves of 150 mM NaCl-stressed rooted plants. At the same time, solid-phase microextraction of spearmint leaves followed by gas chromatography and mass spectrometry (GC/MS) analyses revealed that the essential oil composition of spearmint was unaffected by the treatments applied in this work. Taken together, the used spearmint cultivar tolerates low salinity levels. However, at 50 mM NaCl concentration and above, the ionic components of the stress strongly inhibit adventitious root formation and thus their clonal propagation, and severely damage the photosynthetic apparatus.

Rachis browning and water loss description during postharvest storage of ‘Krissy’ and ‘Thompson Seedless’ table grapes

Rachis browning is a serious symptom of water loss affecting the quality of table grapes (Vitis vinifera L.) during storage. It has been evaluated subjectively based on a color scale or by image analysis, while water loss, which is considered as the main factor behind this problem, is mostly measured on basis of whole-cluster weight loss, with only few studies focusing on the rachis exclusively. Our main objective was to compare the sensitivity to water loss and rachis browning of ‘Krissy’ and ‘Thompson Seedless’ cultivars under different storage conditions and using different methods of evaluation (NIR spectrometry, image analysis, colorimeter, weight loss from initial weight and relative water content). The rachises were evaluated during 3 d subjected to a combination of temperatures (0 °C or 20 °C), relative humidity (Saturated or reduced RH), and previous storage at 0 °C for 0 (HT, Harvest Time) and 30 days (ST, Storage Time). NIR spectra (896−2500 nm) were collected, and Partial Least Squares regression (PLS) models were calculated to test the correlation between the spectra and the measurements from other evaluation techniques. Results showed that ‘Krissy’ is more sensitive to dehydration symptoms than ‘Thompson Seedless’. Saturated RH combined with low temperature (0 °C) are the most suitable to reduce rachis browning and water loss during the 3 d of storage at both HT and ST. The decrease in RWC (Relative Water Content) coincided with an increase in rachis browning throughout storage. Additionally, results provided six NIRS-based prediction models for browning severity (R2 = 0.82 and 0.84), hue color (R2 = 0.68 and 0.72) and water loss (R2 = 0.63 and 0.90) in rachises of ‘Krissy’ and ‘Thompson Seedless’, respectively. These results demonstrate that the NIRS can be a suitable non-destructive method to quantify a range of rachis browning severity produced under different storage conditions.

Limoniastrum guyonianum behavior under seasonal conditions fluctuations of Sabkha Aïn Maïder (Tunisia)

In Sabkha biotope, several environmental factors (i.e., salinity, drought, temperature, etc.) especially during dry season affect halophytes developments. To cope with these harmful conditions, halophytes use multiple mechanisms of adaptations. In this study, we focused on the effect of environmental condition changes over a year in the Sabkha of Aïn Maïder (Medenine - Tunisia) on the physiological and biochemical behavior of Limoniastrum guyonianum using a modeling approach. Our study showed that the model depicted well (R2 > 0.75) the monthly fluctuations of the studied parameters in this habitat. During the dry period (June to September), the salinity of the soil increased remarkably (high level of EC and Na+ content), resulting in high Na+ content in the aerial parts followed by a nutrient deficiency in K+, Ca2+, and Mg2+. As a result of this disruption, L. guyonianum decreased its water potential to more negative values to maintain osmotic potential using inorganic osmolytes (i.e., Na+) and organic osmolytes (i.e., sugars: sucrose, fructose, glucose, and xylitol, and organic acids: citric and malic acids). In addition, CO2 assimilation rate, stomatal conductance, transpiration rate, and photosynthetic pigments decreased significantly with increasing salinity. The phenolic compounds contents and the antioxidant activity increased significantly in the dry period as a result of increased levels of H2O2 and lipid peroxidation. This increase was highly correlated with soil salinity and air temperature. The maintenance of tissue hydration (i.e., moderate decrease of relative water content), the accumulation of sugars and organic acids, the enhancement of phenolic compounds amounts, and the increase of antioxidant activity during the dry period suggest that L. guyonianum possesses an efficient tolerance mechanism that allows the plant to withstand the seasonal fluctuations of climatic conditions in its natural biotope.

Physiological Variations in Cucurbita moschata Duch. Ex. Poir Due to a Nigerian Strain of Moroccan Watermelon Virus: Lagenaria breviflora Isolate

Aim: Physiological variations in Cucurbita moschata due to infection with a Nigerian strain of Moroccan watermelon virus (MWMV): Lagenaria breviflora isolate was studied.
 Study Design: Randomized block design was used.
 Place and Duration of Study: Botany Department, University of Calabar, Calabar, Nigeria between March and May, 2015.
 Methodology: Seeds of C. moschata were sown, on germination inoculated with the virus and analyzed for possible variations between healthy and inoculated plants.
 Results: Results analysis revealed increase in all amino acids investigated. Highest significant (P=0.05) percentage variation in amino acids of inoculated and healthy were -40.0% for aspartic acid, -36.1% (histidine), -29.7% (proline), -28.8% (lysine), -23.3% (glysine), -16.6% (phenylalanine) and -12.6% (glutamic acid). Infection of C. moschata with a Nigerian Strain of MWMV: Lagenaria breviflora isolate caused significant decrease in leaf nitrogen and relative water content of inoculated plants compared to the healthy. Highest percentage decrease in leaf nitrogen was 40.7% at 2 weeks after inoculation (WAI) and lowest of 25.0% at 10 WAI. The virus caused decrease in relative water content of 29.6% at 6 WAI. Activity of oxidative stress enzymes: peroxidase (POD) and polyphenol oxidase (PPO) and enzymes of the oxidative pentose phosphate pathway: glucose-6-phosphate dehydrogenase (6PGdH) and 6-phosphogluconic acid dehydrogenase (G6PdH) were significantly (P=0.05) increased in infected C. moschata- MWMV plant. Enzymes activity was significantly higher in inoculated than in healthy plants at all stages of growth with decrease at later periods for both inoculated and healthy plants. Percentage increase in POD, PPO, G6PdH and 6PGdH activity due to infection at 8 WAI had values of -40.5%, -46.7%, -98.9% and -89.1% respectively.
 Conclusion: The Nigerian strain of MWMV: Lagenaria breviflora isolate caused significant variations with increase and decrease in biochemical and physiological components of C. moschata affecting its growth and yield.

Root damages induced by extended phytotoxic effects of cadmium pre-exposure against subsequent lindane uptake in rice seedlings

The heavy metal accumulation in plants via uptake generally poses some phytotoxic effects on plant roots, which may in turn impact the plant uptake process. The present study was conducted to evaluate the phytotoxic effects of cadmium (Cd) pre-exposure (2 and 40 mg L−1) on rice (Oryza sativa) root at organ, tissue and cellular levels, and to investigate the subsequent uptake performance of the affected rice seedlings by re-exposing to lindane (4 mg L−1). Biomass, relative water content (RWC), fatty acid (FA) profiles were quantified as the indicators for phytotoxicity. Following the Cd pretreatment, varying degrees of water deficit and lipid peroxidation of rice seedlings were found compared to the control, as evidenced by the decrease in RWC and the increase in FA saturation degree, with no significant effect on root biomass. Meanwhile, damages to root tissue structure were confirmed microscopically. All these symptoms did not show any signs of recovery after the Cd stress was removed, but even deteriorated especially in the high-level Cd pretreatment. The root function of uptake, which was interrelated to the above indicators, was consequently impaired, verified by the decrease in active root uptake area (ARUA). In addition, pre-exposure to much higher levels of Cd brought about lower lindane uptake in roots and lower lindane root-to-shoot translocation. After 5-d lindane exposure, lindane concentrations decreased by 15.8 ± 0.5 % and 30.3 ± 0.4 % respectively compared to the control in seedling roots of two Cd pretreatments, and 34.1 ± 0.6 % and 59.2 ± 1.2 % respectively in shoots. The lindane proportions in shoots of Cd pretreatment were approximately 20 % and 40 % while that from the control exceeded 45 %. These results demonstrated the “uptake-phytotoxicity” cycle, and indicated that the hampered uptake and translocation progresses in plant appeared to depend on the severity of root damages, which was induced by the extended phytotoxic effects.

Physiological and anatomical responses to drought stress differ between two larch species and their hybrid

Key MessageHybrid saplings were more reactive to soil water deficit than Japanese and European larch. European larch had hydraulically safer wood and anisohydric behavior, Japanese and hybrid larch showed isohydric strategy.Deciduous larch species could be an alternative to evergreen conifers in reforestation, but little is known about drought sensitivity of their saplings. The effect of an experimental drought on hydraulics and quantitative wood anatomy was tested on saplings of European larch (EL, Larix decidua), Japanese larch (JL, Larix kaempferi) and their hybrid (HL). Across species, biomass, transpiration rate and relative water content were higher in controls than in drought stressed trees, but transpiration efficiency was lower. JL had the highest transpiration efficiency under drought, and EL the lowest, coinciding with slower growth of EL. Wood of EL formed before drought was hydraulically safer as shown by higher wall/lumen ratio and lower pit cavity area. EL neither had a significant increase in transpiration efficiency nor a reduction in transpiration rate under drought, suggesting that the stomata remained open under soil water deficit. HL saplings were the most reactive to water shortage, indicated by intra-annual density fluctuations and a decrease in relative water content of the sapwood. Significant reduction in transpiration by HL suggested a higher stomatal sensitivity, while the same leaf surface area was maintained and radial growth was still similar to its best parent, the JL. The latter showed a significantly lower leaf surface area under drought than controls. EL, with its hydraulically safer wood, followed an anisohydric behavior, while JL and HL revealed an isohydric strategy. Altogether, our results suggest species dependent acclimations to drought stress, whereby HL followed the strategy of JL rather than that of EL.

Effects of salt stress on physiological and biochemical responses of three maize genotypes at the early seedling stage

Salt stress is one of the major global problems for crop productivity in the arid and semi-arid regions of the world. In this study, variations in some physiological parameters, water relations, and antioxidant systems under salinity (300 mM NaCl) among three maize (Zea mays L.) genotypes (‘P3167’, ‘32K61’, and ‘Bora’) were investigated. Our result indicated that shoot growth is more sensitive to salinity as compared to root growth. Salt stress led to physiological drought in all maize genotypes as indicated by the significant decrease in relative water content and increase in water deficit index. Salt stress increased SOD activity in all genotypes showing an efficient formation and detoxification of superoxide radical. The constant level of oxidative markers (MDA and H2O2) and the increased level of the reduced ascorbate and phenolic may indicate that non-enzymatic antioxidants are responsible for the elimination of oxidative stress. Changes in ascorbate peroxidase and glutathione reductase activities under salinity demonstrated a functional failure in the ascorbate-glutathione cycle, especially in ‘P3167’ and ‘32K61’. Based on the presented results we may conclude that the genotype ‘Bora’ is tolerant to salinity while ‘P3167’ and ‘32K61’ are sensitive.

海岸抗风植物黑松对净风和风沙流的生理响应

PDF HTML阅读 XML下载 导出引用 引用提醒 海岸抗风植物黑松对净风和风沙流的生理响应 DOI: 10.5846/stxb201912202754 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31770762） Physiologial response of Pinus thunbergii Parl in wind resistant to coastal wind blowing and win-drift blowing Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用野外便携式风洞仪对盆栽黑松（Pinus thunbergii Parl）幼株在不同风速（6、9、12、15、18 m/s）、不同风沙流强度（0、1.00、28.30、63.28、111.82、172.93 g cm-1 min-1）、不同时间（10、20、30、40、50 min）进行了净风和风沙流吹袭，通过测定其叶片相对含水量（Relative water content，RWC）、丙二醛（Malondialdehyde，MDA）、可溶性糖、脯氨酸含量，及超氧化物歧化酶（superoxide dismutase，SOD）、过氧化氢酶（Catalase，CAT）、过氧化物酶（Peroxidase，POD）活力等变化规律以揭示黑松抗风沙流生长的生理适应机制。结果表明，在净风吹袭下，随着风速提高至15 m/s，黑松叶片RWC相对稳定，MDA含量和细胞膜透性小幅增加且较低，而脯氨酸含量下降17.5%。同时叶片SOD、CAT、POD活力也小幅增加。在风沙流吹袭下，随着风沙流风速提高至15 m/s，黑松在短时低风速吹袭时叶片RWC就开始下降（4.4%），叶片平均MDA含量、细胞膜透性分别较对照增加61.3%、25.6%，脯氨酸含量增加8.9%，叶片SOD、CAT、POD活力分别较对照增加21.5%、30.4%、13.9%。同风速吹袭下，风沙流处理组叶片抗逆生理指标均高于净风处理。如15 m/s风速下，风沙流处理组叶片平均MDA、脯氨酸、可溶性糖含量分别较净风处理组高4.7%、36.6%、22.1%，SOD和CAT活力较净风处理组高21.5%、36.5%。在高风速（18 m/s）净风和风沙流吹袭中，随着风吹时间延长（50 min），叶片MDA、脯氨酸、可溶性糖含量和SOD、CAT、POD活力均下降。研究表明，风吹袭中黑松叶片较高抗脱水力与其抗风性相关。风沙流引发的叶片失水可能是黑松抗逆生理变化的诱因。风吹袭下叶片失水能快速促使脯氨酸的积累和维持可溶性糖含量，以维护细胞中水分平衡。同时，叶片失水又快速激活抗氧化保护酶系统来防御和清除氧自由基、抑制膜脂过氧化维护细胞膜的完整性使黑松在风沙流吹袭中生存。黑松较强的渗透调节能力和抗氧化防御系统在其适应风沙流吹袭中起重要的生理调控作用。 Abstract:The experiment was designed that there were different wind speed (6, 9, 12, 15 and 18m/s), different wind-drift blowing (0.00, 1.00, 28.30, 63.28, 111.82 and 172.93 g cm-1 min-1), and five wind blowing times (10, 20, 30, 40 and 50 min) in spring, 2018 in Yantai, Shandong Province by using outdoor portable wind tunnel to understand the how physiological responses of Pinus thunbergii Parl seedlings to wind blowing and wind-drift blowing. The relative water content (RWC), malondialdehyde (MDA) contents, membrane permeability, osmotic regulators (soluble sugar, proline), and antioxidant enzyme activities (superoxide dismutase (SOD), catalase(CAT), peroxidase(POD)) were tested in the leaves of seedlings of Pinus thunbergii Parl under the previous treatments. The results showed that under treatment of wind blowing, with increasing of wind speed to 15m/s, the RWC was not changed, MDA content and membrane permeability increased slightly, while the proline content decreased, and the activities of SOD, CAT, and POD were slightly enhanced in the leaves of Pinus thunbergii Parl.. Under treatment of wind-drift blowing, with increasing of wind speed to 15 m/s, the RWC decrease, the membrane permeability and the contents of MDA and proline increased, and the activities of SOD, CAT, POD enhanced. At same wind speed, the value of each resistant physiological index under treatment of wind-drift blowing was higher than those under treatment of wind blowing in the leaves of Pinus thunbergii Parl. However, under wind blowing and wind-drift blowing at 18 m/s, the contents of MDA, proline, soluble sugar, and the activities of SOD, CAT, POD decreased with time extension to 50 min in the leaves of Pinus thunbergii Parl. It indicated that leaves of Pinus thunbergii Parl had stronger capacity of resistant dehydration, which was correlated with its ability of resistance to wind blowing. But cell dehydration induced by wind-drift blowing would be a main factor, which could not only promote the accumulation of proline and keeping on soluble sugar content to maintain water balance, but also activate antioxidant defense system to scavenge oxygen free radicals, and inhibit membrane lipid peroxidation to preserve the integrity of cell membranes. It suggested that Pinus thunbwould beergii had stronger capacity of osmotic adjustment and antioxidant defense system could be an important physiological adaptation mechanism for it to resistance to wind-drift blowing. 参考文献 相似文献 引证文献

Short-term drought triggers defence mechanisms faster than ABA accumulation in the epiphytic bromeliad Acanthostachys strobilacea

Epiphytic bromeliads might experience drought after a few hours without water, which is especially critical during early life stages. Consequently, juvenile epiphytic bromeliads probably rely on short-term activation of drought tolerance strategies, although the biochemical processes involved are still poorly understood. In this study, we aimed to evaluate the short-term drought response of juvenile plants of the epiphytic bromeliad Acanthostachys strobilacea (Schult. & Schult. f.) Klotzsch. We hypothesized that short-term drought would induce the accumulation of abscisic acid (ABA) and secondary messengers such as reactive oxygen and nitrogen species (ROS and RNS, respectively) before the activation of defence mechanisms. Three-month-old plants were transferred from well-watered to dry substrates and stress markers were assessed at 0, 2, 5, 10, 24, 48, and 72 h. Drought caused a 27.3% decrease in relative water content compared to the well-watered control at 72 h. A nearly 5-fold increment in the ABA content occurred at 72 h of stress, which was about two days after the first detection of peaks in RNS levels and defence mechanisms activation. Indeed, ascorbate peroxidase (EC 1.11.1.11) activities and proline content increased after 10 h, whereas after 24 h a higher catalase (EC 1.11.1.6) activity and osmotic adjustment occurred. Oxidative stress markers and photochemical efficiency of photosystem II indicated no significant damage induced by drought. We concluded that defence mechanisms activation during early drought in juvenile A. strobilacea might be regulated initially by ABA-independent pathways and RNS, while ABA-induced responses are triggered at subsequent stages of stress.