Water Status Research Articles

Infection prevention and control and water, sanitation, and hygiene status of healthcare facilities in the Greater Kampala Metropolitan region during the COVID-19 pandemic in Uganda

Infection Prevention and Control (IPC) and Water Sanitation and Hygiene (WASH) are critical in preventing the spread of healthcare Associated Infections, including COVID-19. However, there was limited evidence on the status of IPC/WASH in healthcare facilities (HCFs) in Uganda amidst the COVID-19 pandemic which complicated IPC/WASH planning for the COVID-19 response. This study assessed IPC/WASH status for HCFs in the Greater Kampala Metropolitan Area (GKMA), during the COVID-19 pandemic, so as to inform programming and policy. A mixed methods cross-sectional study was conducted in 75 HCFs following the first wave of COVID-19 in Uganda. The mWater tool was used to collect quantitative data which were then analyzed into STATA version 16. A key informants’ guide was used to collect qualitative data, which was analyzed thematically and themes and quotes used to support the quantitative findings. Overall, 86.7% (65/75) of HCFs had an IPC committee and 72.3% (47/65) of these were functional. Besides, 90.7% (68/75) of the HCFs had an IPC focal person, and 49.3% (37/75) had a clear annual IPC activity plan. Unfortunately, only 32.3% (21/65) of the functional IPC committees received budgetary support for their activities. In terms of WASH infrastructure, 96.0% (72/75), 10.7% (8/75), 60.0% (45/75), and 22.7% (17/75) had access to a basic water service, a basic sanitation service, a basic hand hygiene service and a basic environmental cleaning respectively. Our study reveals that while most HCFs have IPC committees and focal persons, functional support remains limited, with half having a clear annual plan and less than a third receiving budgetary support. Nearly all HCFs have basic water services, but there are significant gaps in sanitation and environmental cleanliness domains. These findings highlight the urgent need for improved support and investment in IPC/WASH supplies and infrastructure to enhance infection control and public health outcomes in Uganda.

Mind the Data Gap: Using a Multi-Measurement Synthesis for Identifying the Challenges and Opportunities in Studying Plant Drought Response and Recovery.

Understanding and predicting plant water dynamics during and after water stress is increasingly important but challenging because the high-dimensional nature of the soil-plant-atmosphere system makes it difficult to identify mechanisms and constrain behaviour. Datasets that capture hydrological, physiological and meteorological variation during changing water availability are relatively rare but offer a potentially valuable resource to constrain plant water dynamics. This study reports on a drydown and re-wetting experiment of potted Populus trichocarpa, which intensively characterised plant water fluxes, water status and water sources. We synthesised the data qualitatively to assess the ability to better identify possible mechanisms and quantitatively, using information theory metrics, to measure the value of different measurements in constraining plant water fluxes and water status. Transpiration rates declined during the drydown and then showed a delayed and partial recovery following rewatering. After rewatering, plant water potentials also became decoupled from transpiration rates and the canopies experienced significant yellowing and leaf loss. Hormonal mechanisms were identified as a likely driver, demonstrating a mechanism with sustained impacts on plant water fluxes in the absence of xylem hydraulic damage. Quantitatively, the constraints offered by different measurements varied with the dynamic of interest, and temporally, with behaviour during recovery more difficult to constrain than during water stress. The study provides a uniquely diverse dataset offering insight into mechanisms of plant water stress response and approaches for studying these responses.

Response mechanism of water status and photosynthetic characteristics of Cotoneaster multiflorus under drought stress and rehydrated conditions

IntroductionPlant physiology response and adaptation to drought stress has become a hotspot in plant ecology and evolution. Cotoneaster multiflorus possesses high ecological, ornamental and economic benefits. It has large root system and tolerance to cold, drought and poor soil. Therefore, C. multiflorus is considered as one of the most important tree species for ecological restoration in arid and semi-arid areas. However, little is known about the physiological mechanisms, molecular mechanisms and drought strategies of how C. multiflorus responds to drought stress. Therefore, exploring the physiological response mechanisms, molecular mechanisms and adaptive strategies of C. multiflorus in response to drought is important for its growth in arid and semi-arid regions.MethodsWe investigated the response and coupling mechanisms of water status, photosynthetic properties and chloroplast fluorescence parameters in C. multiflorus in response to drought and rehydrated after drought, especially the importance of nocturnal sap flow and nocturnal water refilling to maintain its own water balance in response to drought stress. In addition, we studied the stress response of C. multiflorus transcriptome factors, and we also discussed drought adaptation strategies of C. multiflorus.ResultsC. multiflorus adapted to drought stress by a series of structural and physiological mechanisms, such as promoting closing stomata, increasing nocturnal sap flow. When rehydrated after undergoing severe drought stress, its physiological activities such as photosynthesis, water status, chlorophyll fluorescence parameters and other physiological activities have rapidly resumed. This showed C. multiflorus had strong tolerance to drought. In addition, water status, photosynthetic characteristics, and chloroplast fluorescence parameters of C. multiflorus were highly coupled. Nocturnal sap flow and nocturnal water refilling were very important for C. multiflorus to maintain its own water balance in response to drought stress. Finally, C. multiflorus will strengthen the drought defense mechanism by gene regulation of various metabolisms, such as promoting stomatal closure, reducing transpiration water loss, and vigorously regulating water balance. C. multiflorus responded to drought stress by avoiding or reducing water deficit in plant organs and tissues. Therefore, the shrub C. multiflorus is a drought-tolerant plant.DiscussionWe explored the response mechanisms of water status, photosynthetic characteristics, and chloroplast fluorescence parameters of C. multiflorus in drought and rehydrated after drought stress, especially the response mechanisms of nocturnal sap flow and nocturnal water refilling in response to drought stress, and identified the physiological coupling mechanisms, molecular mechanisms and drought types of C. multiflorus in response to drought.

Hydraulic Properties of a Rock-Soil-Root System: Insights From Fraxinus ornus L. Saplings Growing on Different Carbonate Rocks.

Drought impacts trees in varied temporal and spatial patterns, suggesting that heterogeneity of below-ground water stores influences the fate of trees under water stress. Karst ecosystems rely on shallow soil overlying bedrock that can store available water in primary pores. A contribution of rock moisture to tree water status has been previously demonstrated, but actual mechanisms and rates of rock-to-root water delivery remain unknown. We report accurate measurements of hydraulic properties of two rock types (Breccia and Dolostone), of typical Karst red soil, and of roots of a common Karst tree species grown under different rock-soil combinations. Experimental data were used to build a water exchange model that supported the hypothesis that roots can extract water from porous and highly conductive rocks (Breccia), but not from more compact ones (Dolostone), especially when plants grow in rocky substrate or experience water stress, and thus have low root hydraulic conductivity and low rates of water extraction from rocks. Our data support the hypothesis that rocks represent important water stores for plants growing in rock-dominated habitats. Heterogeneous rock properties translate into different rates of water delivery to root systems, underlying complex patterns of tree mortality under severe drought stress.

Increasing photosynthetic benefit with decreasing irrigation frequency in an Australian temperate pasture exposed to elevated carbon dioxide.

Elevated atmospheric CO2 (e[CO2]) often enhances plant photosynthesis and improves water status. However, the effects of e[CO2] vary significantly and are believed to be influenced by water availability. With the future warmer climate expected to increase the frequency and severity of extreme rainfall, the response of plants to e[CO2] under changing precipitation patterns remains uncertain. We examined the effects of e[CO2] and different irrigation regimes on perennial ryegrass in a Free-Air CO2 Enrichment (FACE) experiment. Immediately after irrigation, the mean net photosynthetic rate was 21.2% higher under e[CO2] compared to ambient conditions. This benefit increased over time, reaching 31.3% higher as days since watering increased, indicating a substantial increase in photosynthetic benefit with longer intervals between watering. Mean stomatal conductance was 21% lower in ryegrass under e[CO2] immediately after irrigation compared to ambient plots. However, the reduction in stomatal conductance under e[CO2] decreased as the interval between irrigation events increased, showing no difference 7-10 days after an irrigation event. These results imply that plants benefit most from carbon fertilisation, assimilating relatively more carbon and losing less water, during periods with less frequent rainfall. These findings have significant implications for understanding leaf-level responses to climate change.

Potential of a Remotely Piloted Aircraft System with Multispectral and Thermal Sensors to Monitor Vineyard Characteristics for Precision Viticulture.

Grapevines are subjected to many physiological and environmental stresses that influence their vegetative and reproductive growth. Water stress, cold damage, and pathogen attacks are highly relevant stresses in many grape-growing regions. Precision viticulture can be used to determine and manage the spatial variation in grapevine health within a single vineyard block. Newer technologies such as remotely piloted aircraft systems (RPASs) with remote sensing capabilities can enhance the application of precision viticulture. The use of remote sensing for vineyard variation detection has been extensively investigated; however, there is still a dearth of literature regarding its potential for detecting key stresses such as winter hardiness, water status, and virus infection. The main objective of this research is to examine the performance of modern remote sensing technologies to determine if their application can enhance vineyard management by providing evidence-based stress detection. To accomplish the objective, remotely sensed data such as the normalized difference vegetation index (NDVI) and thermal imaging from RPAS flights were measured from six commercial vineyards in Niagara, ON, along with the manual measurement of key viticultural data including vine water stress, cold stress, vine size, and virus titre. This study verified that the NDVI could be a useful metric to detect variation across vineyards for agriculturally important variables including vine size and soil moisture. The red-edge and near-infrared regions of the electromagnetic reflectance spectra could also have a potential application in detecting virus infection in vineyards.

Chrysanthemum morifolium Ramat. as a traditional tea material: Unraveling the influence of kill-green process on drying characteristics, phytochemical compounds, and volatile profile

The dried capitulum of chrysanthemums is a traditional material in scented tea, and the kill-green process is a critical step in determining their quality. However, the changes in the physicochemical properties during kill-green and the mechanisms by which these changes affect drying characteristics, metabolic components, and aroma profiles remain unclear. Therefore, this study investigated the changes in water status, polyphenol oxidase and peroxidase activities, and microstructure during high-humidity air impingement kill-green (HHAIK) and steam kill-green (SK), and their effects on drying behavior, color, phytochemicals, and volatile profile of dried chrysanthemums. Results showed that the kill-green process increased the freedom degree of immobile water, reduced the relative content of free water, and induced microstructure alterations, thus enhancing the water diffusion and shortening the subsequent drying time by up to 46.15 %. Compared to SK, HHAIK more rapidly inactivated PPO and POD, causing an improved color profile of dried samples. Dried samples treated with HHAIK for 60 s exhibited higher retention of 9 individual phenolics, total sugar, amino acids, and volatile compounds, thus resulting in higher sensorial acceptance than those treated with SK for 60 s. This study offers theoretical insights and technical support for the future development of high-quality chrysanthemum products.

Potential of clay‐rich waste and industrial by‐products as effective inorganic soil amendments to enhance soil physical properties

AbstractClay minerals play a crucial role in regulating the structure and functions of soils because of their chemical nature and their interactions with other soil constituents. In this context, a key objective of the research described in this article was to assess the extent to which the addition of various types of recycled clay‐rich materials to soils prone to crusting and erosion increase their clay content and improve their physical properties. Excavated soil (ExS), considered waste under European Union law, and quarry sludge (QS), an industrial by‐product of the washing process in mining operations, were used as soil amendments. ExS is dominated by swelling clay mineralogy such as interstratified illite‐smectite, whereas QS contains high level of non‐swelling clay minerals such as kaolinite and illite, and a low level of interstratified illite‐smectite. Lysimeters were filled with topsoil (0–30 cm) from an agricultural field. Treatments where the soil was amended with these materials were compared with a control without amendment. Lettuce was cultivated for three growing seasons. After 250‐days, the aggregate stability and water retention of the topsoil were measured. The equivalent pore‐size distribution (PSD), derived from the soil water retention curve, was analysed to predict soil water and aeration status. The application of QS to the topsoil enhanced soil structure without compromising lettuce productivity compared with the control and other treatments. However, amending topsoil with ExS decreased the stability because of the abundance of swelling clay minerals. Soil water retention at saturation increased from 27% in the control to 42% and 36% with ExS and QS amendments, respectively. At a pressure head >15,000 cm (residual pores <0.2 μm), water retention rose from 6% in the control to 19% with ExS and 14% with QS. The application of the clay‐rich material increased small pores compared with larger ones. This led to a minor increase in porosity responsible for water movement, aeration and root growth. This observation highlights the limitations of clay application benefits, which depend on the quantity and mineralogy of the clay and the presence of other binding agents. Further research is needed to investigate the combined effects of organic matter and clay‐rich materials on improving the soil structure and optimizing the pore size distribution for multiple functions.

Effects of organic mulching and regulated deficit irrigation on crop water status, soil and yield features in an orange orchard under Mediterranean climate

The adoption of soil and water conservation measures (SWCM) is essential for improving the use of natural resources and making the agro-systems more resilient to climate change. In this context, a three-years trial was carried-out in an orange orchard characterized by different soil management (SM, i.e., bare and organic mulched soils) and water regimes (WR, i.e., full irrigation, FI, and regulated deficit irrigation, RDI). In response to the applied SWCM, crop water status (CWS), soil and yield main features were explored using multiple soil-plant-atmosphere continuum (SPAC) monitoring approaches.Overall average water saving of 24 % was achieved under RDI in comparison to FI. The stem water potential revealed a year-dependent behaviour in accordance to the patterns of the main ancillary physiological indicators. The adoption of additional plant-based measurements provided continuous information on the CWS, both in terms of trunk water potential (TWP) and sap flow fluxes, resulting in higher absolute values of TWP (−0.93 ± 0.01 MPa versus −0.83 ± 0.00 MPa) and lower transpiration rates (0.64 ± 0.00 mm d−1 versus 0.88 ± 0.01 mm d−1) in mulched compared to bare soils. The soil water content showed higher rates under mulched soils than in bare soil condition, both in FI (up to 15 %) and RDI (up to 27 %) at 0.75 m from the tree trunk to the inter-row. Soil temperature was lower in mulched soils under RDI. However, a great time-variability was observed for most of the soil physical-chemical variables under study. Nevertheless, the application of SWCM improved the yield over the years, resulting in higher fruit weights under mulched FI conditions.Finally, the study suggests that the adoption of SWCM can serve as an efficient strategy to enhance soil and yield features, highlighting the critical role of using SPAC methodological tools for monitoring the CWS at the field level.

Prevalence of plant parasitic nematodes in irrigation water and soil in clove and tomato greenhouses in Isparta Province of Türkiye

The study was carried out to determine the contamination status of irrigation water with plant parasitic nematodes and the effect of their spread in the greenhouse soil. For this purpose, soil samples and water samples from the irrigation source of the greenhouse were taken from the same greenhouses in May and October in Isparta Province of Türkiye. A total of 20 samplings were collected from 13 tomato and 7 clove greenhouses. The irrigation sources of these greenhouses were notedas 8 wells and 12 open pools. Nematode densities in 100 g of soil and 1 l of water were determined. In the study, 8 economically important plant parasitic nematode genera (Meloidogyne spp., Criconemoides spp., Helicotylenchus spp., Ditylenchus spp., Pratylenchus spp., Paratylenchus spp., Xiphinema spp. and Tylenchus spp.) were detected in irrigation water and soil samples. The percentages of presence of Criconemoides spp., Helicotylenchus spp., Ditylenchus spp., Pratylenchus spp., Paratylenchus spp., Xiphinema spp. and Tylenchus spp. in soil were found to be 15%, 35%, 25%, 45%, 25%, 25% and 45%, respectively. The percentages of their presence in water samples were determined as 25%, 35%, 35%, 25%, 25%, 30% and 30%, respectively. In seven soil samples (S1, S6, S7, S13, S17, S20) Meloidogyne spp. has been found. Five of these samples (S6, S7, S12, S17, S20) belong to tomato greenhouses irrigated with pool water. While the S13 sample belongs to the clove greenhouse soil irrigated with pool water, the S1 sample was taken from the tomato greenhouse irrigated with well water. Meloidogyne spp. were in both soil and water samples of S1, S6, S7, S12, S13, S17 and S20. While S9 and S18 were only found in water samples. It appears that the likelihood of root knot nematodes being present is higher in greenhouses irrigated from open pools. In general, nematode densities were found to be higher in soil and water samples in October. While Meloidogyne spp. densities varied between 100-900 individuals/100 g of soil, they varied between 200-1400 individuals/1 L of water samples. In the study, significant evidence was obtained regarding the transmission of plant parasitic nematodes to greenhouse soil through irrigation water.

Potential of the Advanced Precision Irrigation Techniques for Enhanced Protected Cultivation Systems in the Developing Nations

Precision irrigation techniques have revolutionized protected cultivation systems worldwide by optimizing water use efficiency, reducing resource consumption, and enhancing crop yield and quality. Key technologies covered include drip irrigation, micro-sprinklers, subsurface irrigation, sensors for monitoring soil moisture and crop water status, automated irrigation scheduling software, and the integration of these tools with fertigation systems. Case studies from leading horticultural regions illustrate best practices and the benefits of precision irrigation, such as water savings of 40-70%, fertilizer reductions of 30-50%, and yield improvements of 20-40% compared to conventional irrigation. However, challenges remain in terms of high initial costs, maintenance requirements, and the need for grower training and technical support. In Asia and India, government initiatives and public-private partnerships are driving the expansion of protected cultivation with precision irrigation to boost productivity, conserve resources, ensure food security, and increase smallholder incomes. Future directions emphasize sensor-based automation, data-driven decision support systems, crop-specific precision irrigation strategies, and the integration of precision irrigation with other technologies like hydroponics, vertical farming, and renewable energy to further enhance the sustainability and profitability of protected cultivation.

IoT technology as a support tool for the calculation of Crop Water Stress Index in a Vitis vinifera L. cv. Chardonnay vineyard in Northern Italy

Nowadays agriculture is one of the main sectors affected by climate change. The continuous increase of temperature and drought periods are posing serious problems in terms of shift of plants’ phenological phases and a reduction of crop yield quantity and quality. Among the indexes used to assess plant water status, the Crop Water Stress Index (CWSI) is one of the most studied due to its ease of calculation. We performed a study in a vineyard in Trentino (San Michele all’Adige, Northern Italy) where we took advantage of IoT Technology to build a device to measure leaf temperature and automatically calculate the CWSI. Parameters necessary to determine the CWSI were the temperature of a non-transpiring leaf, (artificial 3D printed black leaf), and the temperature of a fully-transpiring leaf (wet bulb temperature of the air). We compared various types of thermometers to measure temperatures of the real leaves, and with repeated measuring campaigns performed during the summer of 2022 we could obtain spatial maps of CWSI that could highlight the stress levels of the vineyard and therefore address the irrigation management in a context of precision agriculture.

Mitigating Drought by Exogenous Potassium-mediated Improvements in Water Relation, Antioxidant Defense, Morpho-physiological and Biochemical Attributes of Black Gram [Vigna mungo (L.) Hepper

Background: Globally, drought stress (DS) incidence in early development and grain-filling stages of crops like black gram has posed a serious constraint to the growth and yield of legume crops. To ensure the food and nutritional security of the rising human population, requisites developing eco-friendly, pro-farmers and cost-effective DS mitigation strategies for imparting yield sustainability to black gram. Methods: In this trial, treatments included control group entailing control (normal watering), water spray (WA, positive control), control+50 mg L-1 K2SO4, control +100 mg L-1 K2SO4, control +150 mg L-1 K2SO4, while drought treatment included drought stress (plant exposed to 15-20% by suspending water supply), water spray (WA, positive control), drought +50 mg L-1 K2SO4, drought +100 mg L-1 K2SO4 and drought +150 mg L-1 K2SO4. Result: The results exhibited that the DS seriously declined plant growth, relative water content and water potential by 24.2% and 39.3%, respectively, inducing higher levels of malondialdehyde (MDA) content and hydrogen peroxide (H2O2) concentration that reduced cell membrane stability, stomatal conductance and photosynthetic rate, than the control. However, the foliar applied K significantly improved plant growth, plant water status, gas exchange and photosynthetic performance, chlorophyll content and antioxidant enzyme activity. Exogenous application of K further reduced lipid peroxidation, cell membrane injury and hydrogen peroxide by 12.7, 17.6 and 8.70%, respectively.

Multifaceted Responses to Heat Stress in Plants: A Review of the Morpho-physiological, Biochemical and Anatomical Changes

Heat stress, a significant abiotic factor, adversely affects plant growth and productivity by disrupting various physiological and biochemical processes. Plants, being immobile, respond to environmental changes through alterations in gene expression, metabolism, and growth dynamics. Elevated temperatures, exceeding the threshold for heat tolerance, negatively influence critical functions such as photosynthesis, respiration, water balance, and membrane stability. Root development is particularly sensitive to heat stress, resulting in reduced root mass and impaired water and nutrient uptake. Photosynthetic capacity diminishes due to decreased chlorophyll content and impaired photochemical reactions, leading to reduced biomass and yield. Heat stress impacts plant water status by disturbing hydraulic conductivity and increasing membrane permeability, leading to dehydration and a decline in water potential. This stress reduces membrane stability, resulting in electrolyte leakage and cellular damage. It also induces the production of reactive oxygen species (ROS), which requires the activation of antioxidant enzymes to minimize oxidative stress. Also, to maintain osmotic balance and enhance stress tolerance, plants accumulate osmolytes such as proline. Additionally, anatomical adaptations in leaves, stems, and roots, such as changes in stomatal density, xylem vessel size, and gas exchange patterns, highlight the plant's strategies to cope with heat stress. Understanding these varied responses is crucial for developing strategies to enhance crop resilience in the face of increasing global temperatures and climate change.

Disguised Blessings: A Mechanistic Understanding of the Beneficial Outcomes Triggered by Partial K Replacement With Na in Two Eucalyptus Species Under Drought Stress.

While not essential for most plants, sodium (Na+) can partially substitute for potassium (K+) in some metabolic functions. Thus, understanding the mechanisms underlying K+ and Na+ uptake, transport, utilization, and ion replacement is crucial to sustain forest production. A pot experiment was designed with 6 K/Na ratios (100/0, 85/15, 70/30, 55/45, 40/60, and 0/0%) and two water conditions (well-watered, W+; and water-stressed, W-) on two Eucalyptus species with contrasting drought tolerance. In a multi-level analysis, we measured morphological, nutritional, physiological, biochemical, molecular, and anatomical traits. Low to moderate K replacement with Na (85/15%-55/45%) provided partial and faster stomatal closure (lower δ13C), thereby enhancing plants' water status (WUE, RLWC, ΨPD, ΨMD), photosynthetic capacity (gs, E, A, Ci/Ca), photoprotection (NPQ, qP, ETR, Fv/FM, ΦPSII), and growth (height, collar diameter, LA, TDM) relative to exclusive K supply. The 70/30% K/Na replacement was defined as the ideal ratio, upregulating K+ and water uptake (overexpression of AKT1, PIP2;5, PIP2;7 and TIP1;3), maximizing enzymatic antioxidant performance and biomass production, and reducing oxidative stress. High K replacement with Na (40/60%) and K deficiency (0/0%) led to incomplete stomatal closure reduced water status, photosynthetic capacity, photoprotection, and growth, especially in the species with low drought tolerance.

Contrasting the soil-plant hydraulics of beech and spruce by linking root water uptake to transpiration dynamics.

Tree water status is mainly determined by the amount of water taken up from roots and lost through leaves by transpiration. Variations in transpiration and stomatal conductance, are often related to atmospheric conditions and leaf water potential. Yet, few experimental datasets exist, that enable relating leaf water potential and transpiration dynamics to temporal variation of root water uptake from different depths during soil drying. Here we explored the soil-plant hydraulic system using field measurements of water potentials and fluxes in soils, roots, stems, and leaves of beech and spruce trees. Spruce maintained less negative water potentials than beech during soil drying, reflecting a more stringent stomatal control. While root water uptake depths were similar between species, water potentials in plant tissues of spruce were rather constant and less correlated across roots and the stem, possibly because of large water storage and hydraulic capacitance in these tissues. Root water uptake from deep soil layers increased during dry periods, particularly for beech. Our data suggest that species-specific root hydraulic conductance, capacitance and water uptake strategy are linked and affect transpiration dynamics. Thus, it is important to include such species-specific hydraulics when predicting transpiration rates based on plant water status.

A Comparative Study on Rapeseed Sprayed with Film Antitranspirant Under Two Contrasting Rates of Soil Water Depletion

Rapeseed (Brassica napus L.), as one of the most important oil crops around the world, has been affected by drought considerably, particularly at flowering when crops are most sensitive to water stress. It has been shown that film antitranspirant (AT) can effectively reduce the yield loss of droughted crops if applied at the critical stage. However, the mechanism remains unclear by which AT mitigates drought damage to plants under different rates of water depletion. Two experiments in randomised complete block designs were conducted on spring rapeseed with two levels of irrigation, well-watered (WW) and water-stressed (WS), where slow and fast soil water depletion were imposed during the flowering stage in mesocosms (Expt 1_SD) and pots (Expt 2_FD), respectively, and different concentrations of AT, 0, 0.25%, 0.5%, and 1% and 0, 0.5%, and 1%, were applied. Leaf physiological traits, seed yield, and yield components were determined. The results showed that compared to WW, water stress reduced leaf relative water content (RWC) by 2% and 6% in Expt 1_SD and Expt 2_FD, respectively, and had detrimental effects on stomatal conductance, CO2 assimilation rate, and intrinsic water use efficiency. Following AT application, a positive linear relationship was observed in leaf RWC against AT concentrations, albeit with large variations. In Expt 1_SD, seed dry weight and aboveground biomass increased significantly with increasing AT concentrations, while no yield responses were observed in Expt 2_FD, indicating that soil water status may play an important role in rapeseed responses to AT application regardless of concentrations. Therefore, the timing of AT application needs to consider soil water conditions in addition to the growth development of rapeseed plants.

Combined Effects of Deficit Irrigation and Biostimulation on Water Productivity in Table Grapes.

Biostimulation and precision irrigation are strategies that increase the sustainability of agriculture, and both have been widely studied in table grapes, but their interaction is a new approach for viticulture. The objective of this field trial was to assess the physiological effects of water deficit on table grapes pretreated for two consecutive years with five different biostimulation programs. Therefore, during the first year, vines were preconditioned with biostimulants composed of microorganisms, seaweed, and plant extracts and compared to an untreated control. During the second year, the same biostimulation treatments were evaluated under two different irrigation schedules: (i) farmer irrigation (FI), according to a farmer's criteria; and (ii) a deficit irrigation program, precision irrigation (PI), in which irrigation water was reduced from the post-veraison period to harvest, setting a threshold for allowable soil water depletion of 10% with respect to field capacity in order to minimize water leaching. The water inputs in the treatments under PI were reduced by 30% with respect to the FI treatment. While the deficit irrigation treatment clearly affected the plant water status indicators, biostimulation enhanced the root colonization by mycorrhizae and showed a trend of increased new root density. The combined effect of biostimulation and PI was shown to be an efficient strategy for optimizing the available resources, promoting the yield precocity.

Evidence For Decoupled Water Potential Between Myco- And Photobionts During Desiccation In The Tripartite Lichen Peltigera britannica.

In lichens, accurate description of thallus water status is required to understand growth and photosynthesis dynamics. A recent model suggested that myco- and photobiont layers could have a different water energy status (i.e., a different water potential, Ψ) during thallus desiccation, but data supporting this hypothesis were presented only for one chlorolichen. We compared water relations and maximum photosystem II (PSII) efficiency during desiccation in the tripartite lichen Peltigera britannica and its axenically cultured photobionts, the green alga Coccomyxa sp. and the cyanobacterium Nostoc sp. To assess whether myco- and photobiont layers had different Ψ during desiccation, we expected that: i) water relation parameters differ between cultured photobionts and entire thalli; ii) Ψ values inducing a significant drop of PSII efficiency are lower for entire thalli than for cultured photobionts. We found that photobionts had very different water relations parameters than entire thalli, i.e., lower water potential at turgor loss point and higher cell wall elasticity, irrespective of photobiont type, potentially underlying a different drought tolerance. PSII efficiency in entire thalli and cultured photobionts started to decrease below Ψ values inducing turgor loss. Importantly, PSII efficiency in entire thalli decreased at Ψ values significantly more negative than those inducing turgor loss in cultured photobionts. These data support the hypothesis of decoupled Ψ between myco- and photobionts in lichens during desiccation. A higher Ψ ensured to the photobiont layer might represent a key adaptation to prolong photosynthesis during desiccation.

Arbuscular Mycorrhiza Fungi's Effects on Gt 1 Hevea brasiliensis Seedlings' Growth and Physiological Performance in a Drought-Stressed Environment

Drought significantly affects rubber (Hevea brasiliensis Muell. Arg.) cultivation, especially in marginal regions with limited rainfall. This study investigates the potential benefits of arbuscular mycorrhizal fungi (AMF) inoculation on GT 1 rubber seedlings' growth and physiology under drought stress. Topsoil samples were collected and either sterilised or left non-sterilised. AMF inocula were prepared, and GT 1 rubber seedlings were transplanted into bags with different soil types and subjected to watering or drought. Growth parameters and water deficit were measured and analysed. Growth parameters revealed complex interactions between soil type, AMF inoculation, and watering regimes. Well-watered seedlings generally outperformed drought-stressed ones, but certain AMF treatments showed higher stem height. Percentage growth in girth size and height varied among treatments, emphasising the influence of AMF and drought. Leaf area measurements indicated the positive effect of AMF on physiological performance. Results showed the highest girth size at 30 WAT with NS/C/W (0.61 cm). Significant differences in seedling height were observed, with AMF-OP9 in the watered regimen having the highest stem height (62.25 cm at 30 WAT). The highest percentage increase in girth size at 30 WAT was noted in the S/GD/D treatment combination (64.29%). The highest percentage increase in height was in the NS/N4/D treatment combination (20.90 cm at 30 WAT). AMF inoculation enhanced seedling growth, but the response depended on specific conditions. Drought stress negatively impacted growth and water status, with AMF-OP9 demonstrating potential drought tolerance. Water potential and relative water content varied with AMF treatments, soil types, and watering regimes. AMF-OP9 showed promise in improving drought tolerance and water retention. This study highlights AMF's potential to enhance GT 1 rubber seedling growth and physiology in drought-prone regions. Understanding the context-dependent effects of AMF is crucial for optimizing rubber tree cultivation. Further research is needed to elucidate AMF-mediated drought tolerance mechanisms.