Decrease In Water Potential Research Articles

Potassium deficiency limits water deficit tolerance of rice by reducing leaf water potential and stomatal area

A pot experiment with two potassium (K) levels 0.15 (+K) and 0 (−K) g K2O kg−1 soil and two irrigation regimes well-watered (Ww) and water-deficit (Wd) imposed on two rice genotypes drought-sensitive (CR) and drought-resistant (WDR) was conducted to explore the effects of K deficiency on water use efficiency, leaf water status, osmotic adjustment, gas exchange traits and stomatal characteristics of rice under water deficit. The results showed that K deficiency broke water balance of plants under deficit irrigation by reducing relative water content and water potential of leaf, thereby limited water deficit tolerance of both rice genotypes. In addition, K deficiency resulted in a reduction in stomatal area and conductance, which aggravated the negative impact of water deficit on leaf gas exchange, thereby reduced grain yield and water use efficiency of rice. It should be noted that sufficient K is an important prerequisite for WDR to show water deficit tolerance. The decrease of leaf water potential and stomatal area was the main reason for the limited water deficit tolerance of WDR caused by K deficiency. Our results indicated that K plays an important role in maintaining water deficit tolerance of rice, which provides scientific basis for the breeding of drought-resistant genotypes and management of water and K in paddy fields.

Adaçayının PEG ile İndüklenen Kuraklık Stresine Antioksidatif Yanıtları

The current study was conducted to find out the effect of two polyethylene glycol (PEG) induced drought treatments (-0.4 and -0.8 MPa) on sage (Salvia officinalis L.). Twenty five-day old cuttings were exposed to drought treatments for seven days. Membrane damage and water loss were gradually increased with the severity of drought. While reductions in membrane integrity and water content showed that sage was affected by drought, even increased flavonoid and antioxidant enzyme activities could not alleviate this effect. H2O2 content of leaves increased with decreasing water potential conditions, indication an oxidative stress caused by drought. Elevated levels of SOD and POD activities indicated that the enzymes were involved in scavenging of H2O2. Sage was successfully increased the tolerance to withstand to drought.

Aqueous smoke and karrikin influence seed germination of Amaranthus dubius in varying light, temperature and osmotic stress conditions

Amaranthus dubius is a green leafy vegetable that contributes significantly to food and nutrition security in sub-Saharan Africa. We explored the influence of plant-derived aqueous smoke and karrikin on Amaranthus dubius seed germination under varying environmental conditions. Final germination percentage, germination index, mean germination time, coefficient of velocity of germination and germination rate index were measured in a completely randomized design consisting of smoke-water and karrikin treatments with four replications. Light conditions significantly influenced germination of Amaranthus dubius seeds, with constant dark and constant light conditions stimulating the greatest and least response, respectively. High temperatures favored the best seed germination response, irrespective of smoke-water or karrikin treatments. The optimum temperature for seed germination of 35 °C suggests high tolerance to heat stress conditions. Decrease in water potential significantly reduced germination irrespective of seed treatments with aqueous smoke and karrikin solutions. However, aqueous smoke seemed to have mitigated drought stress under moderate water potential (-0.15 MPa). The capacity of Amaranthus dubius seeds to germinate under high temperatures and seed treatment with aqueous smoke could extend its cultivation in heat-prone and moderately dry environments, thus broadening the food base in such environments.

Soil dwelling springtails are resilient to extreme drought in soil, but their reproduction is highly sensitive to small decreases in soil water potential

Understanding the physiology and ecology of springtails and their responses to environmental conditions in the soil is important for many aspects of soil ecology. Many springtails spend most of their lives in the soil where humidity is high, and several euedaphic species are considered semi-aquatic animals. Climate models predict that summer soil moisture in many regions will decrease in the future, and our aim with this laboratory study was to investigate the importance of soil water potentials in the range between field capacity to the wilting point on the survival, growth and reproduction of the euedaphic springtail, Folsomia candida Willem. Our results show that reproduction was, by far, the most sensitive life-history trait. Reproduction stopped already at very modest soil water potentials (-15 kPa), which did not influence body water content or growth. These results suggest that recruitment in populations of F. candida is restricted to periods where soil moisture is high. Body growth and activities of juveniles and adults, however, may continue in moderately dry soil until the soil water potential reaches ca. −100 kPa. Should severe drought occur, normal body functions are paused, but surviving adults and juvenile individuals would contribute to the resilience of this species at low soil moisture. We discuss the implications of drought for the ecological functions of springtails.

Avaliação das Mudanças Climáticas Usando o índice de Humidade da Classificação Climática Thornthwaite no Bioma Pantanal

Abstract Thornthwaite climate classification indices are essential to interpret climate types in the state of the pantanal biome (Mato Grosso do Sul), simplifying calculation process and interpretation of climatological water balance by farmers. However, there are few studies found in the literature that characterize the climate of pantanel biome in different climatic scenarios. We seek to assess climate change using humidity index of Thornthwaite climate classification in pantanal biome. We used historical series of climate data from all 79 municipalities of Mato Grosso do Sul between 1987 and 2017, which were divided into microregions. Air temperature and precipitation were collected on a daily scale. Precipitation and potential evapotranspiration data allowed calculating water balance by the Thornthwaite and Mather method. We characterized all locations as wet and dry using aridity indices proposed by Thornthwaite. The global climate model used was BCC-CSM 1.1 developed at the Beijing Climate Center (BCC) with a resolution of 125 x 125 km. We used the scenarios RCP-2.6, RCP-4, RCP-6 and RCP-8.5 for analyzing 21st century projections (2041-2060 and 2061-2080 periods). Maps were generated from climate indices of Mato Grosso do Sul using kriging interpolation method with spherical model, one neighbor, and 0.25° resolution. The microregions showed different patterns regarding water balance components and humidity index. Humidity index had a mean of 15.94. The prevailing climate in the state of Mato Grosso do Sul is C2 (moist subhumid). The state of Mato Grosso do Sul has two well-defined periods during the year: a dry and a rainy period. Three climate types predominate in Mato Grosso do Sul and, according to the Thornthwaite classification, are B1 (humid), C2 (moist subhumid), and C1 (dry subhumid). Water characterization in Mato Grosso do Sul showed 234.78 mm year−1 of water surplus, 80.8 mm year−1 of water deficit, and 1,114.8 mm year−1 of potential evapotranspiration. Water deficit and potential evapotranspiration decrease as latitude increases. The climatic projections show, in all scenarios, reduce the area classified as umida in the state (B1, B2 and B3), besides adding the dry subhumid class (C1). The Scenario RCP 8.5 in 2061 - 2080 is the most worrisome situation of all, because the state can undergo major changes, especially in the pantanal biome region.

Tolerance and Recovery Capacity to Reclaimed Wastewater Irrigation of Salvia officinalis and Asteriscus maritimus Plants Inoculated with Arbuscular Mycorrhizae

This work attempts to identify which of two species with different levels of salinity tolerance, Salvia officinalis L. or Asteriscus maritimus L., is more suitable for irrigation with reclaimed wastewater, as well as the effect of the arbuscular mycorrhiza Glomus iranicum on the plant. The experiment was carried out in a growth chamber with a first phase, where both species were irrigated with good quality water, a second phase in which the plants were irrigated with reclaimed wastewater, and a third phase in which the plants were irrigated with good quality water again (recovery). Salinity caused a reduction in leaf water potential, stomatal conductance and net photosynthesis in both species. The percentage of mycorrhization was higher in Asteriscus than in Salvia, mitigating the decrease in leaf water potential. There was osmotic adjustment in Salvia, although the proline content increased in both species. The damages produced were clearer in Salvia, in which lipid peroxidation values were higher. Likewise, the visual appearance of the leaves showed symptoms of toxicity in this species, although the mycorrhizae diminished these effects. Irrigation with good quality water induced the recovery of lipid peroxidation in both species, as well as the appearance of new leaves in Salvia.

Contrasted effects of climate change on low-altitude relict Pinus uncinata stands in the Northern French Alps

This paper reports on climate-induced growth changes in relict, low-altitude mountain pines (Pinus uncinata Mill. ex. Mirb.) from two refugia with cold microclimates located in the Northern French Alps. The P. uncinata stands analyzed grow at the lower bound of their ecological limit and are thus thought to be sensitive indicators of ongoing climate change. Using dendroecological approaches, we compare tree-ring growth at two closely spaced low-altitude stands in the Chartreuse massif (French Alps): La Plagne and Cirque de Bresson. La Plagne is a N-NW-exposed, ventilated slope with cold air circulating in the scree during summer, and the presence of sporadic permafrost as well as ground overcooling, whereas Cirque de Bresson is located on a small, S-exposed fan with sporadic avalanche activity. At both sites, growth responses of P. uncinata to changes in twentieth and twenty-first centuries temperature and precipitation conditions were investigated by means of moving correlation analyses. At Cirque de Bresson, a significant and rapid decline in tree-ring widths has been observed since the early 1990s. We attribute this decline to (i) increasing air temperatures at the beginning of the growing season (May–June) as well as to (ii) a decrease in soil water potential. At La Plagne, we do not detect any significant trend between the higher summer temperatures and tree growth, presumably as a result of the circulation of cold air in the scree slope, which is thought to maintain fresh and humid soil conditions and therefore favor tree growth. These forest stands provide prime examples on how dendroecology can contribute to the study of the dynamics and local variability of tree growth and climate change in relict forest populations with high ecological and conservation values.

Selenium nanoparticles reduced cadmium uptake, regulated nutritional homeostasis and antioxidative system in Coriandrum sativum grown in cadmium toxic conditions

Nanotechnology has become a valuable novel approach to manage several environmental challenges through providing innovative and effective solutions. Heavy metal stress is an important abiotic limiting factor. Seed priming with selenium (Se) alleviates various kinds of environmental stresses; yet, the potential of seed priming with selenium nanoparticles (SeNPs) under cadmium (Cd) stress for coriander crop has never been evaluated. This research work was designed to explore the effects of seed priming with three levels (0, 5, 10 and 15 mg L−1) of SeNPs solution on the physio-biochemical characteristics, nutrition, antioxidative defense system and growth of coriander under Cd stress. Cadmium toxicity reduced chlorophyll content, photosynthetic activity and growth of treated plants. Moreover, Cd stressed plants exhibited modulations in proline level, together with decreased water potential, and leaf osmotic potential. However, SeNPs increased growth attributes, chlorophyll content, total soluble sugars, leaf relative water content, and gas exchange parameters in treated plants which were conversely decreased by Cd toxicity. The seeds priming with SeNPs promoted antioxidant response by increasing catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POX) activity and safeguarding cellular structures through scavenging free radicals and reactive oxygen species. Furthermore, Cd stressed plants displayed an upper level of MDA (1.91 fold) while SeNPs improved membranous integrity through detoxification of hydrogen peroxide. Additionally, SeNPs enhanced nutrients contents (P, K, Ca, Mg, Zn), metal tolerance index and diminished Cd content in plants resulting in the improved growth and development of Cd affected coriander plants.

A new protein hydrolysate-based biostimulant applied by fertigation promotes relief from drought stress in Capsicum annuum L.

Recently, biostimulants have been used in sustainable agriculture as priming agents able to increase crop tolerance to abiotic stressors. Here, a soil application of GHI_16_VHL, a plant protein hydrolysate-based biostimulant, was tested for its capability to mitigate severe water stress effects on Capsicum annuum at flowering time. The biostimulant influence on plant physiological status was monitored upon stress and its relief, by measuring chlorophyll levels, stomatal density, stem water potential, leaf gas exchanges and plant growth. Moreover, leaf osmoregulation and oxidative stress levels were also evaluated by quantifying free proline, total non-structural carbohydrates (NSC), ROS-scavenging activity and H2O2 level.Although biostimulant-primed plants showed a quicker decrease of stem water potential with respect to untreated plants upon drought imposition, they recovered faster probably due to the higher leaf osmolyte accumulation, namely NSC during drought. Moreover, leaf gas exchange recovery was prompted in biostimulant-treated plants, which showed an incremented stomatal density and the same chlorophyll level of well-watered plants at the end of the recovery phase. Hydrogen peroxide level was significantly lower during stress and early recovery in biostimulant primed plants, probably due to the higher catalase activity in treated plants before drought or to the higher level of non-enzymatic antioxidant scavengers in primed stressed plants. Finally, the biostimulant priming increased aboveground relative growth rate and final fruit yield of stressed plants. Taken together, our data suggest that the biostimulant priming treatment promotes a faster and more efficient plant recovery after drought.

Impact of Slight Change in Water Potential of Culture Media on In vitro Shoot Multiplication and Esterase and Protein Patterns of Simmondsia chinensis L.

Amplification of DNA on ten jojoba shrubs using 7 RAPD primers indicated that seed propagation of jojoba results in high genetic variation. To produce true to type clones, micropropagation technique was applied. Medium (MS) containing relatively low concentrations of BAP (1 or 2 mg/l) did not stimulate shoot formation on nodal explants of jojoba. The best shoot cloning on nodal explant was established on MS medium containing 3 mg/l BAP and 0.1 mg/l NAA. Shoot formation was more sensitive than growth of the formed shoots to change in water potential of culture medium. Decrease in water potential (Ψ) of medium by the addition of 0.5 mg/l of mannitol slightly increased the number of formed shoots, further decrease in the medium Ψ by increase the concentration of NaCl or mannitol resulted in retardation of shoot formation. Data indicated that shoot formation was more sensitive than shoot growth to change the Ψ of the medium. Callus weight was decreased by decrease of medium Ψ less than – 435.014 MPa using 1 g/l of NaCl, while application of mannitol to decrease Ψ of the medium up to 435.054 MPa (4 g/l) significantly increased callus fresh weights. Jojoba calli clearly expressed the effect of decrease in Ψ of MS medium on esterase and protein pattens.

Evaluation of the physiological significance of leaf wetting by dew as a supplemental water resource in semi-arid crop production

Dew is a frequently observed meteorological phenomenon and its importance to the water balance in arid and semi-arid regions has been recognized. The focus of our study was to evaluate the potential significance of leaf wetting by dew on semi-arid crop production in terms of its effects on plant physiological functions. We conducted a field experiment in a maizefield in northwest China. Leaf wetting by dew occurred on 45% of days during cultivation periods, and leaf water potential was higher for leaves wetted by dew than for those not wetted during the morning. In addition, we conducted a potted maize control experiment consisting of four treatments (two different soil water treatments: water-stressed and well-watered, and two different leaf wetting treatments: with and without leaf wetting). The water-stressed treatment strongly inhibited plant physiological functions (decrease in leaf water potential, stomatal closure, decrease in photosynthetic rate); therefore, growth rate decreased. However, in the water-stressed with leaf wetting plot, the maize leaves absorbed water from their surfaces during nighttime, which significantly increased pre-dawn leaf water potential. Consequently, this plot showed a higher photosynthetic rate than did the water-stressed without leaf wetting plot during daytime. The positive effects of leaf wetting on plant physiological functions were not explicit in the well-watered plots. We assumed that the positive effects of leaf wetting were mainly manifest as effects on plant–water relations; such effects may be limited when plants have sufficient water. As a result, water-stressed plants with leaf wetting showed greater water use efficiency. Our results indicate the importance of leaf wetting by dew as a water resource in semi-arid crop production owing its effects on plant physiological functions.

More sensitive to drought of young tissues with weak water potential adjustment capacity in two desert shrubs

Water is the main limiting factor for survival and growth for desert plants, and plants can alleviate water deficits under drought by adjusting water potential (Ψ). However, the water potential adjustment capacity and water-sensitivity at the tissue level among shrub species remains unclear. The objective of this study was to evaluate water potential adjustment capacity and water-sensitivity of different tissues in Artemisia ordosica and Caragana korshinskii through calculating the water relation parameters from pressure-volume (P-V) curves. The present study found that the sensitivity coefficients, −1/β and −1/b, were gradually decreased with increasing degree of lignification in A. ordosica and C. korshinskii, suggesting that younger tissues with low lignification are more sensitive to water deficit. Additionally, the younger tissues with more negative osmotic potential at full turgor (Ψπ, sat), water potential at turgor loss point (Ψtlp), and lower the bulk modulus of elasticity (ε), the relative water deficit at turgor loss point (RWDtlp), apoplastic water fraction (AWF) and total hydraulic capacitance (Ctotal), which indicated that younger tissues have stronger turgor adjustment capacity compared to osmotic adjustment capacity and them were more easily lose water during times of decreased water potential because of higher cell wall elasticity and weaker water storage capacity. Collectively, the present study highlighted that younger tissues are more sensitive to drought due to their weaker water potential adjustment capacity and provided critical insight into water physiological mechanism or sensitivity of species to drought.

Combined effect of temperature and water stress on seed germination of four Leptocereus spp. (Cactaceae) from Cuban dry forests

AbstractCactus seeds have developed adaptations to survive with high temperatures and low soil moisture in their habitats. We studied the effect of the combination of four water potentials (0, −0.2, −0.4 and −0.6 MPa) and two temperatures (25°C and 35°C) on germination and seedling mass of four endemic Leptocereus species from Cuba. There were two semi‐arid coast species (L. arboreus and L. santamarinae) and two species inhabiting dry inland karstic hills (L. ekmanii and L. scopulophilus). We hypothesized that: (a) a decrease in water potential and an increase in temperature would result in low and slow germination, as well as in low seedling mass, and (b) ungerminated cactus seeds after exposure to combined water and temperature stress would have a high recovery capacity. The minimum time required for the seeds to start germination (Tmin), mean germination time (MGT) and germinability were evaluated. In addition, seed mass, the recovery after treatments of non‐germinated seeds, and the seedling fresh mass obtained under different treatments were compared between species. In general, germination was only obtained at 25°C and germinability and seedling mass were drastically affected by the reduction from 0 MPa to −0.2 MPa. Seeds showed thermoinhibition at 35°C at all water potentials. There was a tendency to increase the MGT with decreasing water potential in three species. Low seed recovery occurred at all combined treatments for three species. If the predictions of increased temperature and decreased rainfall for the Caribbean region occur, a reduction in the germination of the Leptocereus species studied is expected.

Effect of Pisolithus tinctorious on Physiological and Hormonal Traits in Cistus Plants to Water Deficit: Relationships among Water Status, Photosynthetic Activity and Plant Quality.

Cistus species can form ectomycorrhizae and arbuscular mycorrhizal fungus that can bring benefits when plants are under water stress conditions. However, the application of some ectomycorrhizae on the water uptake under drought through physiological traits and hormonal regulation is less known. The experiment was performed during three months in a growth chamber with Cistus albidus plants in which the combined effect of the ectomycorrhiza Pisolithus tinctorious inoculation and two irrigation treatments (control and water-stressed plants) were applied. Irrigation absence caused significant decrease in aerial growth and tended to decrease soil water potential at the root surface, leading to a decrease in leaf water potential. Under these conditions, the abscisic acid and salicylic acid content increased while the precursor of ethylene decreased. Although the mycorrhization percentages were not high, the inoculation of P. tinctorious improved the water status and slightly cushioned the rise in leaf temperature of water-stressed plants. The ectomycorrhiza decreased the scopoletin values in leaves of plants subjected to deficit irrigation, indicating that inoculated plants had been able to synthesize defense mechanisms. Therefore, Pisolithus tinctorious alleviated some of the harmful effects of water scarcity in Cistus plants, being its use a sustainable option in gardening or restoration projects.

Salinity Stress Affects Photosynthesis, Malondialdehyde Formation, and Proline Content in Portulaca oleracea L.

In this investigation, the effect of salt stress on Portulaca oleracea L. was monitored at salinity levels of 100 and 300 mM NaCl. At a concentration of 100 mM NaCl there was a decrease in stomatal conductance (gs) simultaneously with an increase in CO2 assimilation (A) at the beginning of salt exposure (day 3). However, the leaf water potential (ψw), the substomatal concentration of CO2 (Ci), the maximum quantum yield of photosystem II (Fv/Fm), and the proline and malondialdehyde (MDA) content remained unchanged. Exposure to 300 mM NaCl caused a decrease in gs from day 3 and a decrease in water potential, CO2 assimilation, and Fv/Fm from day 9. There was a large increase in proline content and a significantly higher MDA concentration on days 6 and 9 of salt stress compared to the control group. After 22 days of exposure to 300 mM NaCl, there was a transition from the C4 cycle to crassulacean acid metabolism (CAM), manifested by a rapid increase in substomatal CO2 concentration and negative CO2 assimilation values. These results document the tolerance of P. oleracea to a lower level of salt stress and the possibility of its use in saline localities.

Evaluation of morphological, physiological, and biochemical traits for assessing drought resistance in eleven tree species.

The frequency and severity of drought are expected to increase due to climate change; therefore, selection of tree species for afforestation should consider drought resistance of the species for maximum survival and conservation of natural habitats. In this study, three soil moisture regimes: control (100% precipitation), mild drought (40% reduction in precipitation), and severe drought (80% reduction in precipitation) were applied to six gymnosperm and five angiosperm species for two consecutive years. We quantified the drought resistance index based on the root collar diameter and assessed the correlation between species drought resistance and other morphological, physiological, and biochemical traits by regression analysis. The prolonged drought stress altered the morphological, physiological, and biochemical traits, but the responses were species-specific. The species with high drought resistance had high leaf mass per area (LMA), photosynthetic rate (Pn), and midday leaf water potential (ΨMD), and low carbon isotopic discrimination (δ13C), flavonoid and polyphenol content, superoxide dismutase and DPPH radical scavenging activity. The highly drought-resistant species had a relatively less decrease in leaf size, Pn, and predawn leaf water potential (ΨPD), and less increase in δ13C, abscisic acid and sucrose content, and LMA compared to the control. The interannual variation in drought resistance (∆Rd) was positively correlated with the species hydroscopic slope (isohydric and anisohydric). Korean pine was highly resistant, sawtooth oak, hinoki cypress, East Asian white birch, East Asian ash, and mono maple were highly susceptible, and Korean red pine, Japanese larch, Sargent cherry, needle fir, and black pine were moderate in drought resistance under long-term drought. These findings will help species selection for afforestation programs and establishment of sustainable forests, especially of drought-tolerant species, under increased frequency and intensity of spring and summer droughts.

Dew absorption by leaf trichomes in Caragana korshinskii: An alternative water acquisition strategy for withstanding drought in arid environments.

Investigating plant morphological traits can provide insights into plant drought tolerance. To date, many papers have focused on plant hydraulic responses to drought during dehydration, but atmospheric water absorption by trichomes to mitigate drought stress by influencing leaf hydraulics in plant species that inhabit arid environments has been largely ignored. The experiment in this study was designed to assess how dew absorbed by leaf trichomes helps Caragana korshinskii withstand drought. The results showed that under a drought stress and dew (DS & D) treatment, C. korshinskii displayed a strong capacity to absorb dew with trichomes; exhibited slow decreases in leaf water potential (Ψleaf ), leaf hydraulic conductivity (Kleaf ), and gas exchange; experienced 50% Kleaf and gas exchange losses at lower relative soil water content levels than plants treated with drought stress and no dew (DS & ND); and experienced 50% Kleaf loss (Kleaf P50 ) at similar Ψleaf levels as DS & ND plants. Its congener C. sinica, which does not have leaf trichomes, displayed little ability to absorb dew under drought stress and did not show any remarkable improvement in the above parameters under the DS & D treatment. Our results indicated that leaf trichomes are important epidermal dew-uptake structures that assist in partially sustaining the leaf hydraulic assimilation system, mitigate the adverse effects of drought stress and contribute to the distribution of C. korshinskii in arid environments.

НАКОПЛЕНИЕ, РАСПРЕДЕЛЕНИЕ И ФУНКЦИОНАЛЬНАЯ РОЛЬ АБК ПРИ КРАТКОВРЕМЕННОМ ДЕЙСТВИИ ЗАСОЛЕНИЯ НА РАСТЕНИЯ ПШЕНИЦЫ

Local effects on plant roots or shoots are accompanied by a change of plant hormones concentration providing signal transduction in plants and their adaptation to changing environmental conditions. It is known that plants respond to drought stress by increasing the concentration of abscisic acid (ABA) in xylem sap which leads to decrease in stomatal conductance to prevent plant water loss from transpirational pathways. Earlier, we found a rapid leaf ABA accumulation in barley and wheat plants under influence of the shortterm salinity. However, the mechanism of the salt stress induced rapid accumulation of abscisic acid in plant leaves remained unclear. The aim of this study was to investigate whether the salt-induced rapid accumulation of abscisic acid in the leaves was the result of its inflow from the roots (as a root signal). In our experiments the short-term salinity did not increase but decreased the concentration of abscisic acid in xylem sap of wheat plants. Thus, detected accumulation of ABA in the leaves did not result from an increase in its inflow from the roots. Apparently leaf ABA accumulation already detected in 15 min after the onset of salinity stress could be a local reaction due to its metabolism in the shoot itself. The decrease in the leaf water potential could induce the change of abscisic acid metabolism pathways in the shoot that led to the accumulation of this hormone. A small short-term accumulation of ABA in the roots did not lead to an increase in their hydraulic conductivity.

Genotype-dependent architectural and physiological responses regulate the strategies of two oregano cultivars to water excess and deficiency regimes

Plants can exhibit alternative strategies to cope with water stress regimes by reconfiguring different morphophysiological processes. Nonetheless, the physiological bases that define the response of oregano genotypes to water stress are still poorly understood. A pot experiment in a greenhouse was conducted to evaluate the changes in the configuration of plant architecture and physiological traits and the strategies displayed by two novel oregano cultivars (Origanum vulgare ssp. hirtum ‘Alpa Sumaj FCA-INTA’ and Origanum x majoricum Cambess. ‘Aguanda FCA-INTA’) in response to two water stress regimes (water excess and deficit) in vegetative phenological stages. To do this, water relations and morphological, developmental, and physiological traits were measured. The architectural and physiological responses were dependent upon stressful water regimes and oregano cultivars. Two strategies were found to face water excess regime: Alpa Sumaj remained quiescent whereas Aguanda followed an escape strategy. Biomass production of Alpa Sumaj was halved since physiological and architectural traits were mostly reduced, especially the leaf area. In contrast, Aguanda was more tolerant because of its altered biomass allocation pattern, leading to taller plants with mild reductions of the leaf area and transpiration rate. Therefore, relative water content and biomass yield were preserved. Contrastingly, the strategy to face water deficit regime in both cultivars was dehydration avoidance. All traits were reduced in a similar way, but interesting genotypic differences in water relation traits were observed. Thereby, leaf water potential decrease was highlighted in Alpa Sumaj cultivar, whereas the lessening in transpiration rate as the leaf area is reduced represented the outstanding physiological trait of Aguanda.

EFFECTS OF DIFFERENT SOURCES OF IRRIGATION WATER ON THE GROWTH OF ZINNIA ELEGANS L. UNDER DROUGHT STRESS

The application of deficit irrigation water strategies to floriculture may make a significant contribution to irrigation water conservation. The purpose of this research was to evaluate the effects of different irrigation regimes for Zinnia ‘Solmar Yellow’ plants grown in an open field using different sources of irrigation water. Zinnia plants were grown in a field under three irrigation regimes, corresponding to 100% (control) of field capacity, 75%, and 50% of the irrigation needs. The water used for irrigation was derived from three sources: groundwater, distilled water, and blended water (50% ground-water + 50% distilled-water). In this investigation the vegetative growth, flower yield, pigment characteristics, ion content, leaf water potential, and leaf osmotic potential of plants exposed to these treatments were determined. Under the imposed drought conditions, the irrigation regimes with high or moderate quality water had the following effects: (i) a negative effect on the vegetative growth and flower yield, but a later flowering date; (ii) higher levels of leaf pigments in both distilled water and blended water irrigations at the 100% level; (iii) a decrease in leaf water potential and leaf osmotic potential; and (iv) a decrease in calcium, magnesium, and potassium ion contents but an increase in chloride and sodium ions under distilled water irrigation. In conclusion, irrigation with blended water (50% + 50%) at the 100% and/or 75% levels can be recommended for open field-grown Zinnia ‘Solmar Yellow’ production to enhance host plant tolerance to saline water and decrease the high cost burden of water desalinization.