Decrease In Water Potential Research Articles

Effects of Drought and Flooding on Growth and Physiology of Cinnamomum camphora Seedlings

In the context of climate change, future patterns of precipitation are expected to increase the intensity and frequency of drought and flooding stress. This is also likely to result in more frequent flooding–drought alternation events. Drought and flooding stress can have negative effects on tree morphology, physiology, and biochemistry, which can potentially pose long-term threats to tree survival and further disrupt the stability of forest ecosystems. However, it remains unclear how trees would cope with these stressors and their alternations through growth and physiology responses. Potted seedlings of C. camphora were grown under a rainout shelter in the field with four water treatments for 40 days: well-watered (WW), drought stress (DS), flooding stress (FS) and flooding–drought alternation (FDF). Growth, leaf gas exchange, water potential, and biochemical traits were measured. Results show different seedling growth patterns under drought and flooding stress. Drought increased the root-to-shoot ratio (+25%) but flooding favored leaf growth (+33%). Decreases in photosynthesis under drought and flooding were mainly related to stomatal limitations, accompanied by abscisic acid accumulation under drought but not under flooding. Drought reduced water potential, and flooding–drought alternation only decreased water potential in its drought phase. Flooding treatment had no effect on water potential. Drought treatment increased the proline concentrations (+74%) and carbon isotopic composition (+3.7%), but all treatments had no effect on the concentrations of elements in leaves. Drought stress led to carbon depletion in both stem and root, whereas flooding stress primarily induced carbon depletion in the root. Flooding–drought alternation was accompanied by complex physiological responses, including physiological recovery when the stress (flood, drought) was relieved. Our results have shown the different effects of drought and flooding on the growth and physiology of C. camphora seedlings, emphasizing the need to consider specific water stress conditions in future studies and providing a theoretical basis for better management of this tree species in urban areas under variable rainfall patterns.

Creatıng Antalya Drought Maps and Assocıatıng It Wıth Agrıcultural Lands

Aims: Drought is described as an insidious disaster that threatens a significant part of the world, including our country, in recent years. This study was carried out in order to examine the drought in depth and to associate it with Antalya agriculture.
 Study Design: Drought is one of the most dangerous natural disasters in terms of both the damage it will cause and the lack of awareness on this issue. Decreased water potential as a result of climate change due to global warming necessitates effective use of water resources. With this study, the drought situation in agricultural lands, which is one of the most important livelihoods of Antalya, was studied.
 Place and Duration of Study: The study area covers the province of Antalya and its districts. The project was completed between 2021 and 2022.
 Methodology: With this study, the drought situation of Antalya province was determined and mapped on the basis of districts with the Standard Precipitation Index (SPI), De Martonne Drought Index, Percent of Normal Index (PNI), Erinç Method, Aydeniz Method and NDVI methods.
 Results: Upon calculating each drought method in the area, some differences were observed. This study aimed to address this issue by conducting separate analyses for each district of Antalya province using internationally recognized meteorological and agricultural drought methods based on meteorological data. The results of each analysis were evaluated separately to provide a comprehensive understanding of the drought situation in the region.
 Conclusion: (Wild irrigation) Drip irrigation methods should be preferred instead of wild irrigation. In regions where the risk of drought is high or likely to occur in the near future, it is important to select drought-resistant plant patterns and gradually replace varieties and species that consume excessive amounts of water with drought-resistant ones.

New findings on the effects of different factors involved in fig limb dieback caused by Neoscytalidium dimidiatum in California

The San Joaquin Valley (California, USA) represents an important fig (Ficus carica) production area in the United States. Fig limb dieback represents a serious and emerging disease of fig caused by Neoscytalidium dimidiatum. In the present study we evaluated the effect of tissue age on canker development, the recovery of the fungus from fruit mummies collected in the field, the ability of N. dimidiatum to colonize, under laboratory condition, fig fruits, and the in vitro effects of different water potentials (Ψs) on mycelial growth rate.Results of our study showed that the older branches (> 3-year-old) resulted in longer canker compared to the younger ages. N. dimidiatum was not recovered from the mummies, instead they were colonized by many other fungal saprophytes. Laboratory experiments showed the ability of this species to colonize dried fig fruits from 20 °C to 35 °C. In vitro water potentials experiment showed that the mycelial growth was reduced with the decrease of water potential (from 1–3 -MPa), depending on salt type.

Onion (Allium cepa L.) seed germination affected by temperature and water potential: Hydrothermal time model

A useful implement for seed ecological studies is quantifying the germination behavior against variable environmental conditions. The influences of temperature and water potential on the germination response of onion seeds can be described by using the thermal time (TT), hydrotime (HT), and hydrothermal time (HTT) models. The germination behaviour of onion seeds (Allium cepa L.) was studied over a range of constant temperatures and water availability. The efficiency of hydrothermal time models was evaluated by the germination parameters for two onion cultivars (‘Sepidan’ and ‘Zargan’). The onion seeds were germinated in the laboratory over a water potential range from 0 to − 1 MPa at 5, 10, 15, 20, 25, 30, 35, and 40 °C. Final germination dropped with decreasing water potential, particularly at water potential less than − 0.2 MPa. The model analysis indicated that the dynamics of seed germination was generally well described by the TT model within water potential less than − 1 MPa (R2 = 0.69–0.97), HT (R2 = 0.94–0.99), and HTT models (R2 = 0.95–0.96). The Dent-like was found to be the best model to predict germination rate (RMSE = 0.00006, and 0.000133, R2 = 0.98, and 0.97 for ‘Sepidan’ and ‘Zargan’, respectively). The base, sub-optimum, supra-optimum and the ceiling temperatures for onion seed germination were estimated − 2.5, 19.3, 29.8, and 39.3 °C for ‘Sepidan’ and 0, 25.19, 27.37, and 42.39 °C for ‘Zargan’ at 0 MPa. Thermal time constants were 2650 and 3329.67 °C.h at − 0.8 MPa and 1602.83 and 1521.44 °C.h for ‘Sepidan’ and ‘Zargan’ seeds at 0 MPa. Hydrotime constants for ‘Sepidan’ and ‘Zargan’ seeds were 115.54 and 128.037 MPa.h at 5 °C and 20.8 and 26.93 MPa.h at 30 °C. Hydrothermal time constants for ‘Sepidan’ and ‘Zargan’ seeds were 1249.792 and 1122.78 MPa.°C.h.

Sensitivity of seed germination to water stress in high-altitude populations of a threatened palm species.

Divergence in seed germination patterns among populations of the same species is important for understanding plant responses to environmental gradients and potential plant sensitivity to climate change. In order to test the responses to flooding and decreasing water potentials we germinated and grew seeds of three habitats of Euterpe edulis Mart. occurring along an altitudinal gradient, over a period of three years. Seed germination and root growth were evaluated under different water availability treatments: control, flood, -0.4MPa, -0.8MPa, for 2012, 2013 and 2014 years, and in the last year of the experiment (2014), -1.0MPa and -1.5MPa. Seeds of the montane habitat did not germinate in the flood treatment. Seed germination of all three habitats decreased in the -1.5MPa treatment. Montane habitat had the lowest seed germination at -1.5MPa. Time required for half of the seeds to germinate increased up to -0.8MPa. Seeds of montane habitats germinated slower in all the treatments. The only difference observed in seed germination synchrony was an increase in submontane population in flooding treatment. However, synchrony decreased at the lowest water potential treatments. Roots of montane population were more vigorous in most treatments, except in -0.8 MPa. The unusual ability of seeds to germinate at low water potentials might be related to early seed germination at the onset of the rainy season, potentially decreasing seed predation pressure. Seeds of the montane population were more sensitive to both types of water stress. A predicted increase in the frequency and intensity of extreme high rainfall or drought events may predispose early stages of this population to adverse factors, which might negatively affect population viability along elevational in future climate change scenarios.

Biochemical and physiological changes in Zea mays L. after exposure to the environmental pharmaceutical pollutant carbamazepine

The presence of pharmaceuticals in the environment is a matter of great concern. They are consistently found in the environment, raising concerns regarding human exposure through dietary intake. In this study, we observed the effect of the application of carbamazepine at 0.1, 1, 10, and 1000 μg per kg of soil contamination levels to assess stress metabolism in Zea mays L. cv. Ronaldinio at the 4th leaf, tasselling, and dent phenological stages. The transfer of carbamazepine to the aboveground and root biomass was assessed, and uptake increased dose-dependently. No direct effect on biomass production was observed, but multiple physiological and chemical changes were observed. Major effects were consistently observed at the 4th leaf phenological stage for all contamination levels, including reduced photosynthetic rate, reduced maximal and potential activity of photosystem II, decreased water potential, decreased carbohydrates (glucose and fructose) and γ-aminobutyric acid in roots, and increased maleic acid and phenylpropanoids (chlorogenic acid and its isomer, 5-O-caffeoylquinic acid) in aboveground biomass. A reduction in net photosynthesis was observed for the older phenological stages, whereas no other relevant and consistent physiological and metabolic changes related to contamination exposure were detected. Our results indicate that Z. mays can overcome the environmental stress caused by the accumulation of carbamazepine with notable metabolic changes at the early phenological stage; however, older plants adapted and only exhibited minor effects in the presence of the contaminant. The potential implications for agricultural practice could be associated with the plant's response to simultaneous stresses due to metabolite changes associated with oxidative stress.

Different effects of gellan gum and agar on change in root elongation in Arabidopsis thaliana by polyploidization: the key role of aluminum.

Agar and gellan gum have been considered to have different effects on polyploidy-dependent growth in plants. We aim to demonstrate that agar and gellan gum differently affect the change in root elongation in Arabidopsis thaliana by polyploidization and examined the physico-chemical parameters in each gelling agent to elucidate key factors that caused the differences. Each polyploid strain was cultured vertically on agar and gellan gum solidified medium under fixed conditions. Root elongation rate was measured during 4-10 days after sowing. As a result, agar promoted root elongation of polyploids more than the gellan gum. Then water potential, gel hardness, and trace elements of each medium were quantified in each medium. Water potential and gel hardness of agar medium were significantly higher than those of gellan gum medium. The decrease in water potential and gel hardness in agar medium, however, did not affect the change in polyploidy-dependent growth. Elemental analysis showed that gellan gum contained more aluminum than agar. Subsequently, the polyploids were grown on agar media with additional aluminum, on which the root elongation in tetraploids and octoploids was significantly suppressed. These results revealed that agar and gellan gum affect the change in growth of root elongation in A. thaliana by polyploidization in different ways and the different effects on change in polyploidy-dependent growth is partially caused by aluminum in the gellan gum, which may be due to cell wall composition of polyploids.

Soil-plant hydraulics explain stomatal efficiency-safety tradeoff.

The efficiency-safety tradeoff has been thoroughly investigated in plants, especially concerning their capacity to transport water and avoid embolism. Stomatal regulation is a vital plant behaviour to respond to soil and atmospheric water limitation. Recently, a stomatal efficiency-safety tradeoff was reported where plants with higher maximum stomatal conductance (gmax ) exhibited greater sensitivity to stomatal closure during soil drying, that is, less negative leaf water potential at 50% gmax (ψgs50 ). However, the underlying mechanism of this gmax -ψgs50 tradeoff remains unknown. Here, we utilized a soil-plant hydraulic model, in which stomatal closure is triggered by nonlinearity in soil-plant hydraulics, to investigate such tradeoff. Our simulations show that increasing gmax is aligned with less negative ψgs50 . Plants with higher gmax (also higher transpiration) require larger quantities of water to be moved across the rhizosphere, which results in a precipitous decrease in water potential at the soil-root interface, and therefore in the leaves. We demonstrated that the gmax -ψgs50 tradeoff can be predicted based on soil-plant hydraulics, and is impacted by plant hydraulic properties, such as plant hydraulic conductance, active root lengthand embolism resistance. We conclude that plants may therefore adjust their growth and/or their hydraulic properties to adapt to contrasting habitats and climate conditions.

Spatio-Temporal Analysis on Groundwater - Case Study for Thiruvallur District

Thiruvallur District in Tamil Nadu is one such district, with groundwater levels reaching depths of 50m to 60m below the surface. Growing populations, variations in land use patterns, reduction in rainfall depth, and other factors all contributed to an increase in water demand and a decrease in water potential. This affects the quality of groundwater as well. In this study, the variation of both Groundwater potential and Groundwater Quality is analyzed. The collected data has undergone thorough processing to ensure its accuracy and relevance for the area to be studied. (Thiruvallur District). The base map for the place to be analyzed and the well-map are created in the QGIS software with the data. The processed data is imported into the QGIS to create a database. With the database, the spatial variation between the stations is mapped. The temporal variation of the stations is carried out. The spatial map is done for the groundwater level and Groundwater quality parameters like pH, TDS, Cl, etc. The temporal variation is shown in the graph for the GW level and GW quality parameters with respect to the well-points.

ACC deaminase-producing endophytic fungal consortia promotes drought stress tolerance in M.oleifera by mitigating ethylene and H2O2.

Drought has become more prevalent due to dramatic climate change worldwide. Consequently, the most compatible fungal communities collaborate to boost plant development and ecophysiological responses under environmental constraints. However, little is known about the specific interactions between non-host plants and endophytic fungal symbionts that produce growth-promoting and stress-alleviating hormones during water deficits. The current research was rationalized and aimed at exploring the influence of the newly isolated, drought-resistant, ACC deaminase enzyme-producing endophytic fungi Trichoderma gamsii (TP), Fusarium proliferatum (TR), and its consortium (TP+TR) from a xerophytic plant Carthamus oxycantha L. on Moringa oleifera L. grown under water deficit induced by PEG-8000 (8% osmoticum solution). The current findings revealed that the co-inoculation promoted a significant enhancement in growth traits such as dry weight (217%), fresh weight (123%), root length (65%), shoot length (53%), carotenoids (87%), and chlorophyll content (76%) in comparison to control plants under water deficit. Total soluble sugars (0.56%), proteins (132%), lipids (43%), flavonoids (52%), phenols (34%), proline (55%), GA3 (86%), IAA (35%), AsA (170%), SA (87%), were also induced, while H2O2 (-45%), ABA (-60%) and ACC level (-77%) was decreased by co-inoculation of TP and TR in M. oleifera plants, compared with the non-inoculated plants under water deficit. The co-inoculum (TP+TR) also induced the antioxidant potential and enzyme activities POX (325%), CAT activity (166%), and AsA (21%), along with a lesser decrease (-2%) in water potential in M. oleifera plants with co-inoculation under water deficit compared with non-inoculated control. The molecular analysis for gene expression unraveled the reduced expression of ethylene biosynthesis and signaling-related genes up to an optimal level, with an induction of antioxidant enzymatic genes by endophytic co-inoculation in M. oleifera plants under water deficit, suggesting their role in drought stress tolerance as an essential regulatory function. The finding may alert scientists to consider the impacts of optimal reduction of ethylene and induction of antioxidant potential on drought stress tolerance in M. oleifera. Hence, the present study supports the use of compatible endophytic fungi to build a bipartite mutualistic symbiosis in M. oleifera non-host plants to mitigate the negative impacts of water scarcity in arid regions throughout the world.

Transcriptomic Analysis of Distal Parts of Roots Reveals Potentially Important Mechanisms Contributing to Limited Flooding Tolerance of Canola (Brassica napus) Plants.

Since most of the root metabolic activities as well as root elongation and the uptake of water and mineral nutrients take place in the distal parts of roots, we aimed to gain insight into the physiological and transcriptional changes induced by root hypoxia in the distal parts of roots in canola (Brassica napus) plants, which are relatively sensitive to flooding conditions. Plants were subject to three days of root hypoxia via lowering oxygen content in hydroponic medium, and various physiological and anatomical features were examined to characterize plant responses. Untargeted transcriptomic profiling approaches were also applied to investigate changes in gene expression that took place in the distal root tissues in response to hypoxia. Plants responded to three days of root hypoxia by reducing growth and gas exchange rates. These changes were accompanied by decreases in leaf water potential (Ψleaf) and root hydraulic conductivity (Lpr). Increased deposition of lignin and suberin was also observed in the root tissues of hypoxic plants. The transcriptomic data demonstrated that the effect of hypoxia on plant water relations involved downregulation of most BnPIPs in the root tissues with the exception of BnPIP1;3 and BnPIP2;7, which were upregulated. Since some members of the PIP1 subfamily of aquaporins are known to transport oxygen, the increase in BnPIP1;3 may represent an important hypoxia tolerance strategy in plants. The results also demonstrated substantial rearrangements of different signaling pathways and transcription factors (TFs), which resulted in alterations of genes involved in the regulation of Lpr, TCA (tricarboxylic acid) cycle-related enzymes, antioxidant enzymes, and cell wall modifications. An integration of these data enabled us to draft a comprehensive model of the molecular pathways involved in the responses of distal parts of roots in B. napus. The model highlights systematic transcriptomic reprogramming aimed at explaining the relative sensitivity of Brassica napus to root hypoxia.

Continuous and Real-Time Measurement of Plant Water Potential Using an AAO-Based Capacitive Humidity Sensor for Irrigation Control

Water potential measurement is an essential factor in determining water consumption management and recycling in the agricultural field. We report the development of a continuous water potential measurement system using sensors for water stress analysis in tomato plants with better irrigation plan feedback. The water potential sensor uses the capacitive sensing principle which measures humidity inside an anodic aluminum oxide (AAO) layer. An analog to digital converter with a wireless communication module system records the capacitance data of the sensing system. Calibration data of sensors derived from superabsorbent polymer (SP) and deionized water (DIW) mixtures can represent their water potential value. The method showed good matching of capacitance and water potential values above −7 MPa, matching the result obtained in tomato stem. The measurements were conducted for a few days with the sap flow and water potential sensors connected in series on a tomato stem. When sunlight is sufficient, sap flow increases; meanwhile, water potential decreases. The opposite phenomenon could be observed during the nighttime. With irrigation restricting conditions, both sap flow and water potential signal decrease, triggering the emergency watering signals. This continuous water potential sensing system can quantitatively monitor the plant stem’s water stress and set irrigation schedules to achieve high-quality products in the agricultural field.

Dimethylthiourea Alleviates Drought Stress by Suppressing Hydrogen Peroxide-Dependent Abscisic Acid-Mediated Oxidative Responses in an Antagonistic Interaction with Salicylic Acid in Brassica napus Leaves.

In plants, prolonged drought induces oxidative stress, leading to a loss of reducing potential in redox components. Abscisic acid (ABA) is a representative hormonal signal regulating stress responses. This study aimed to investigate the physiological significance of dimethylthiourea (DMTU, an H2O2 scavenger) in the hormonal regulation of the antioxidant system and redox control in rapeseed (Brassica napus L.) leaves under drought stress. Drought treatment for 10 days provoked oxidative stress, as evidenced by the increase in O2•- and H2O2 concentrations, and lipid peroxidation levels, and a decrease in leaf water potential. Drought-induced oxidative responses were significantly alleviated by DMTU treatment. The accumulation of O2•- and H2O2 in drought-treated plants coincided with the enhanced expression of the NADPH oxidase and Cu/Zn-SOD genes, leading to an up-regulation in oxidative signal-inducible 1 (OXI1) and mitogen-activated protein kinase 6 (MAPK6), with a concomitant increase in ABA levels and the up-regulation of ABA-related genes. DMTU treatment under drought largely suppressed the drought-responsive up-regulation of these genes by depressing ABA responses through an antagonistic interaction with salicylic acid (SA). DMTU treatment also alleviated the drought-induced loss of reducing potential in GSH- and NADPH-based redox by the enhanced expression of glutathione reductase 1 (GR1) and up-regulation of oxidoreductase genes (TRXh5 and GRXC9). These results indicate that DMTU effectively alleviates drought-induced oxidative responses by suppressing ABA-mediated oxidative burst signaling in an antagonistic regulation of SA.

Influence of drought stress and N addition on the gas exchange, biochemical and growth traits in Quercus ithaburensis

Forest tree species are likely to be affected by drought due to global climate change. Drought and nitrogen (N) affect plant growth. Therefore, we should understand the mechanisms underlying the N availability and species response to drought for plant development. This paper had two objectives. First, it determined the effects of N addition on water potential, gas exchange parameters, soluble sugar and photosynthetic pigment content, leaf N concentration, and growth parameters under drought stress and well-watered conditions. Second, it searched the drought response of Quercus ithaburensis Decne. subsp. macrolepis (Kotschy) Hedge&Yaltırık seedlings under N conditions with drought stress. In a greenhouse, one-year-old seedlings were exposed to two drought stress and nitrogen addition and three drought cycles. Drought stress significantly reduced stem water potential, relative water content, net photosynthetic rate, stomatal conductance, transpiration rate, leaf area, root collar diameter, seedling height, shoot and root dry weight. On the other hand, it increased water use efficiency and soluble sugar content. N addition is effective on soluble sugar content and photosynthetic pigment content, and promoted leaf N concentra­tions. Nitrogen addition under well-watered conditions stimulated the growth of Q. ithaburensis seedlings. Drought stress changed the physiological response of Q. ithaburensis seedlings (decreased water potential, net photosynthetic rate, stomatal conductance, and transpiration rate) in the short term, although nitrogen addition under drought stress has not changed the decreasing trend overall.

High relative humidity improves leaf burn resistance in flowering Chinese cabbage seedlings cultured in a closed plant factory.

Plant factories that ensure the annual production of vegetable crops have sparked much attention. In the present study, thirty types of common vegetable crops from 25 species and eight families, were grown in a multi-layer hydroponic system in a closed-type plant factory to evaluate the adaptive performance. A total of 20 vegetable crops, belonging to 14 species and 4 families, unexpectedly exhibited different degrees of leaf margin necrosis in lower leaves firstly, then the upper leaves gradually. We defined this new physiological disorder as "leaf burn". It occurred more commonly and severely in cruciferous leafy vegetables. Two different light intensities (150 and 105 µmolm-2s-1 photosynthetic photon flux density (PPFD)), three photoperiod conditions (12, 10 and 8 hd-1) and two canopy relative air humidity (RH) (70% and 90% RH) were set to evaluate the suppression effects on leaf burn occurrence in two commercial flowering Chinese cabbage cultivars ('Sijiu' and 'Chixin'), the special cruciferous vegetable in South China. We discovered that changing light conditions did not fully suppress leaf burn occurrence in the cultivar 'Sijiu', though lower light intensity and shorter photoperiod partly did. Interestingly, the occurrence of leaf burn was completely restrained by an increased canopy RH from 70% to 90%. Specifically, the low RH-treated seedlings occurred varying degree of leaf burn symptoms, along with rapidly decreased water potential in leaves, while the high RH treatment significantly lessened the drop in leaf water potential, together with increased photosynthetic pigment contents, net photosynthetic rate, stomatal conductance and transpiration rate, decreased leaf stomatal aperture and density, and thus reduced the incidence of leaf burn in 'Sijiu' and 'Chixin', from 28.89% and 18.52% to zero, respectively. Taken together, high canopy RH may favor maintaining leaf water potential and improving photosynthesis performance, jointly regulating leaf burn incidence and plant growth.

DROUGHT EFFECTS ON PHYSIOLOGICAL PARAMETERS OF DURUM AND BREAD WHEAT

The present research discusses the dynamics of changes in the surface of assimilation organs of different durum and bread wheat genotypes differing in the maturation period due to drought conditions. Under drought conditions, the soil water potential decreases, and in the later stages of the plants, the turgor pressure decreases, the stomata close, and a sharp decrease in photosynthetic activities. The situation creates stress in the crop plant, and various biochemical, physiological, and molecular reactions arise to overcome and protect itself from stress, allowing the plant to develop resistant mechanisms to adapt to the external environment. The existent research aimed to determine drought effects on assimilating surface areas and productivity traits of durum and bread wheat genotypes differing in their maturation periods grown under various climatic and soil conditions, with the comparison of the physiological indices. The experiments proceeded on wheat genotypes with contrasting maturation periods (early, medium, and late) during 2021–2022 at the Research Institute of Crop Husbandry, Absheron, Azerbaijan. The assimilating surface area of various organs underwent comparative studies in two durum (Garagylchyg-2 and Alinja-84) and two bread wheat (Nurlu-99 and Gobustan) cultivars under normal water supply and drought conditions. Post anthesis water stress caused a 34% and 27% reduction in grain yield and 1000-grain weight, respectively, while no significant effect on the grains per spike and spikes per m2. The averages of grain yield and 1000-grain weight of different wheat cultivars in the controlled condition showed 696±36 g/m2 and 43.1±0.8 g/m2, respectively, while under water-stress conditions, these values significantly decreased to 452±57 g/m2 and 31.6±1.4 g. The significant reduction in grain yield due to post-anthesis water stress might be due to a reduction in photo-assimilates production.

Physiological effects of salt stress on plant growth

Salinity affects plant growth by causing physiological and morphological changes, which reduces its vegetative system. This appears through decreases in stem length, number of leaves, as well as lateral branches and diameter of plant organs.There are two types of salinity: soil salinity and water salinity. Soil salinity means soil characterized by a high percentage of dissolved salts, mostly of which are chlorides, sulfates and carbonates, to a degree harmful to plant growth. If the soil contains dissolved salts in high quantities, water potential can be reduced to negative level. A distinction between salt stress and ionic stress must be noticed. The first term is used when salt concentration is so high that water potential of growing substrate drops to a significant level (05.0 - 1.0 MPa). If the decrease in water potential was slight and undetectable, the effect here is in the form of ionic stress. A simplified definition of salt stress can be given as an increase in the concentration of salt in plant cells to the degree that affects the physiological properties. This is due to a decrease in the water potential of growing substrate which negatively affects the morphological characteristics of plant. Water potential determines the water movement from the soil to the root or from one cell to another.

Endophytic Fungal Consortia Enhance Basal Drought-Tolerance in Moringa oleifera by Upregulating the Antioxidant Enzyme (APX) through Heat Shock Factors.

Global climate change has imposed harsh environmental conditions such as drought. Naturally, the most compatible fungal consortia operate synergistically to enhance plant growth and ecophysiological responses against abiotic strains. Yet, little is known about the interactions between phytohormone-producing endophytic fungal symbionts and plant growth under drought stress. The existing research was rationalized to recognize the role of newly isolated drought-resistant, antioxidant-rich endophytic fungal consortia hosting a xerophytic plant, Carthamus oxycantha L., inoculated to Moringa oleifera L. grown under drought stress of 8% PEG (polyethylene glycol-8000). Under drought stress, the combined inoculation of endophytic strain Microdochium majus (WA), Meyerozyma guilliermondi (TG), and Aspergillus aculeatus (TL3) exhibited a significant improvement in growth attributes such as shoot fresh weight (1.71-fold), shoot length (0.86-fold), root length (0.65-fold), dry weight (2.18-fold), total chlorophyll (0.46-fold), and carotenoids (0.87-fold) in comparison to control (8% PEG). Primary and secondary metabolites were also increased in M. oleifera inoculated with endophytic consortia, under drought stress, such as proteins (1.3-fold), sugars (0.58-fold), lipids (0.41-fold), phenols (0.36-fold), flavonoids (0.52-fold), proline (0.6-fold), indole acetic acid (IAA) (4.5-fold), gibberellic acid (GA) (0.7-fold), salicylic acid (SA) (0.8-fold), ascorbic acid (ASA) (1.85-fold), while abscisic acid (ABA) level was decreased (−0.61-fold) in comparison to the control (8% PEG). Under drought stress, combined inoculation (WA, TG, TL3) also promoted the antioxidant activities of enzymes such as ascorbate peroxidase (APX) (3.5-fold), catalase (CAT) activity (1.7-fold), and increased the total antioxidant capacity (TAC) (0.78-fold) with reduced reactive oxygen species (ROS) such as H2O2 production (−0.4-fold), compared to control (8% PEG), and stomatal aperture was larger (3.5-fold) with a lesser decrease (−0.02-fold) in water potential. Moreover, combined inoculation (WA, TG, TL3) up regulated the expression of MolHSF3, MolHSF19, and MolAPX genes in M. oleifera under drought stress, compared to the control (8% PEG), is suggestive of an important regulatory role for drought stress tolerance governed by fungal endophytes. The current research supports the exploitation of the compatible endophytic fungi for establishing the tripartite mutualistic symbiosis in M. oleifera to alleviate the adverse effects of drought stress through strong antioxidant activities.

ECO-PHYSIOLOGICAL BEHAVIOR OF TAMARIND (TAMARINDUS INDICA L.) IN DRY ENVIRONMENT OF WEST AFRICA (CASE STUDY OF SENEGAL).

Water deficit is considered by several authors to be the most limiting factor for agricultural production in the subtropics (Kizito et al., 2006; Porcel and Ruiz-Lozano, 2004; Bader et al., 2006; Logan et al., 2010; Rodriguez-Gamir et al., 2011; Conedera et al., 2011). On woody plants, only a few isolated studies (on Acacia, and combretaceae) exist in the tropical zone south of the Sahara. Noteworthy are the works done on Sahelian forest species, Acacia tortilis (Diouf, 1996), Combretum glutinosum, Guiera senegalensis; Piliostigma reticulatum; Balanites aegyptica, Boscia senegalensis, A. senegal and Ziziphus mauritiana (Fournier, 1995; Kizito et al., 2006; Lufafa et al., 2008). Characterization of plant water functioning is a tool for selecting plants and/or varieties for their tolerance to water deficit (Lufafa et al., 2008; Zhu Qiuan et al., 2011; Logan et al., 2010). It is most often done at young age for ease of use (nursery and early field establishment of seedlings). However, even as adults, woody plants remain dependent on climatic factors such as rainfall (Kisito et al., 2007; Lufafa et al., 2008). It is therefore important to understand the in situ water functioning of adult plants to better explain the depressive effects of such complex water stress at a young age. However, the behavior of plants in situ is influenced by the climatic conditions and the uniformity (age) of the subjects (tamarind plants) to be followed. The present work was carried out on adult T. indica plants in situ in Senegal (Niokhoul in the Sahelian zone and Mbassis in the Sudano-Sahelian zone) and aimed mainly to: (1) understand and describe the physiological water management strategies of tamarind under arid conditions; and (2) understand the impact of this water management strategy on phenology and productivity. The study was conducted in Senegal, characterized by a dry and arid climate. It adopted a field approach (Seghieri, 2010; Conedera et al., 2010) based on adult stands and climatic data collected at the study sites. Ultimately, the adaptation mechanism of tamarind to water deficit would be that of avoidance, described by various authors (Khalfaoui, 1985; Lacape, 1996; Nwalozie and Annerose, 1996; Rouhi et al., 2007; Roussel, 2008; Maes et al., 2009). Indeed, the plant first proceeds to a decrease in water potential (case of the Mbassis stand) and in case of continuous water deficit, it integrates the reduction of the leaf surface by the progressive fall of the leaves and flowers which can go up to the total defoliation (case of the stand of the Sahelian zone in Niokhoul).

Age-specific and species-specific tree response to seasonal drought in tropical dry forests

Millions of people depend on ecosystem services provided by Tropical Dry Forests (TDFs), yet their proximity to population centers, seasonally dry climate, and the ease at which they are converted to agriculture has left only 10 % of their original extent globally. As more TDFs become protected, basic information relating TDF age to subsurface water resources will help guide forest recovery. Severe deforestation and recent reforestation around Bahía de Caráquez, Ecuador produced a mosaic of different successional stages ideal for exploring relationships between TDF age, subsurface water availability and species-specific responses to seasonal drought. Over one year, we measured gravimetric water content, predawn and midday leaf water potential, and the stable isotope composition of xylem and source waters in two regenerating and one primary forest. Over the transition from wet to dry season, we discovered a sharper decrease in predawn water potential in younger successional forests than in the primary forest. Growing in degraded subsurface environments under increased competition, successional forest trees accessed deeper sources of moisture from unsaturated weathered bedrock and groundwater through the dry season; however, different species employed distinct water use strategies. Ceiba trichistandra maintained midday water potentials above −1.27 MPa through a drought avoidance strategy dependent on groundwater. Sideroxylon celastrinum tolerated drought by lowering predawn and midday water potential through the early dry season but took up greater proportions of saprolite moisture and groundwater as the dry season progressed. Contrastingly, Handroanthus chrysanthus maintained access to shallow soil and saprolite moisture by dropping midday water potential to −4.30 MPa, reflecting drought tolerance. Our results show that limited subsurface water resources in regenerating TDF's lead to species-specific adaptations reliant on deeper sources of moisture. The recovery of soil and saprolite hydrologic properties following disturbances is likely to exceed 100 years, highlighting the importance of forest conservation.