Modulating seed reserve mobilization and antioxidant systems contributes to resilience to water stress in Mauritia flexuosa (Arecaceae) seedlings

Water stress is one of the main factors affecting the development of agricultural crops. An innovative alternative to improve tolerance to water stress is the application of biostimulants. In the present study, the efficacy and physiological and biochemical responses of different biostimulants were evaluated in beans under moderate and severe stress. The treatments consisted of three types of irrigation: FC100, without water stress; FC75, irrigation reduced by 25% (moderate water stress); and FC50, irrigation reduced by 50% (severe water stress). In the treatments with water deficits, foliar biostimulants were applied: zinc oxide nanoparticles plus chitosan, Codasil®, Osmoplant®, Stimplex® and salicylic acid. Foliar application of ZnO + chitosan nanoparticles benefited biomass accumulation and yield under moderate water stress (FC75) and Codasil® and Osmoplant® under severe water stress (FC50). Proline, free sugars and gas exchange were higher with the application of ZnO + chitosan nanoparticles under moderate water stress and with Codasil® and Osmoplant® under severe water stress. Depending on the severity of water stress, ZnO + chitosan nanoparticles, Codasil® and Osmoplant® are viable products to increase tolerance in green bean cv. Strike plants.

We compared effects of different growing water potential conditions on physiological and morphological water–use properties of Sabina vulgaris Ant., which is an evergreen shrub that is widely distributed in arid and semi-arid environments of the Mu Us Sandy Land, China. Measurements were taken of cuttings grown for eight years under -0.02 MPa (control), -0.10 MPa (moderate water stress), and -0.34 MPa (severe water stress) water potential conditions. The transpiration rate (Tr) under moderate stress was significantly lower than that under severe stress and control water conditions (49% and 45% lower, respectively, than severe stress and the control on average). The leaf-specific hydraulic conductivity (LSC) in shrubs growing under moderate water stress was also significantly lower than for those under the severe water potential condition. In contrast, S. vulgaris growing under severe water stress had less leaf biomass than under moderate stress or control conditions. These results suggest that S. vulgaris growing under moderate water stress tends to show a reduced transpiration rate derived from its low LSC; therefore it avoids water loss in response to chronic water stress, while plants growing under severe water stress tends to reduce water loss through decreased leaf biomass. These results suggest that S. vulgaris has a high capacity for acclimation to different water potential conditions through physiological and morphological flexibility.

This study aimed to examine the influence of long-lasting moderate (45% field water capacity—FWC) and severe (30% FWC) water stress and application of sulphur (elemental sulphur or sulphate) on the growth, yield and mineral composition of wheat and maize. Concentrations of macro- and micronutrients were determined in the aboveground parts of the plants. Drought stress caused a marked decrease in the growth parameters of both plants. Under both optimal water conditions (60% FWC) and moderate water stress (45% FWC), grain yields of wheat grown without sulphur application were not significantly different. Applying elemental sulphur caused an increase in grain yield under moderate stress, whereas sulphate was more effective in wheat grown under adequate water supply. Severe water stress significantly lowered wheat yield, regardless of sulphur fertilisation. Increasing water stress resulted in a greater reduction in maize growth, with an average 50% decrease in dry mass under severe water stress. Both crops maintained relatively high levels of macro- (N, P, K, Mg, Ca, S) and microelements (Mn, Fe, Cu, Zn) and did not suffer noticeably from deficiencies in such. Sulphur application did not modify these relationships. In conclusion, sulphur fertilisation may be recommended in wheat cultivation when plants are exposed to moderate water stress.

Drought is an abiotic stress that affects the growth of cowpea genotypes in Sub-saharan Africa One of the first physiological responses to water stress in crops is the functioning of the leaf. The aim of the present study is to determine leaf physiological responses of cowpea to water stress. The study was conducted at International Institute of Agriculture (IITA) Kano state, Nigeria during the period of 17th November to 23rd December 2009. Seven cowpea genotypes differing in drought resistance were evaluated. The experiment was laid out in randomized complete design with three treatment regime, which include unstressed (control), moderate and severe water stress condition. The criteria measured include, Chlorophyll fluorescence parameters, chlorophyll content (SPAD), Water Use Efficiency (WUE) specific leaf area (SLA), shoot and root biomass. The results showed that water stress significantly reduced chlorophyll content (SPAD). 100% reduction was recorded in moderate and severe water stress. The results of photochemical yield (Fv/Fm) indicated that 71% of the genotypes at severe stress had reduction in Fv/Fm, while 42% was recorded in moderate stress. Genotype IT98K-555-1 recorded the highest reduction in Fv/Fm. The result showed a positive correlation between photochemical yield and chlorophyll content (SPAD) at unstressed (r= 0.921), moderate (r=0.903) and severe (r= 0.861) at 5%. Water stress significantly reduced above ground biomass. Lower biomass was recorded more under severe water stress. Reductions in shoot biomass were more significant in IT0K-835-45 and IT98K-555-1. At severe water stress, most of the genotypes recorded lower water use efficiency, except in genotype IT00K-901-5. The results showed a general increase in root biomass in moderate and severe water stress condition, except in IT00K-835-45 and IT96D-610. Increases in the root biomass were recorded more under moderate stress. Keywords: Water stress, Water Use Efficiency, Leaf physiology, Drought Resistance, Cowpea ( Vigna unguiculata (L.) walp)

The influence of soil water stress on plant height, fresh and dry weight and essential oil content of Iranian Satureja hortensis L. was investigated. The volatile constituents of the aerial parts of cultivated S. hortensis were isolated by steam distillation and analysed by GC–MS. The results showed that greater soil water stress decreased plant height and total fresh and dry weight. The accumulation of oil increased significantly under severe water stress at the flowering stage, when the mean leaf water potential decreased from −0.5 to −1.6 MPa. This treatment affected the quantity of the essential oils more than moderate water stress during the vegetative and flowering stages. The main oil constituents are carvacrol and γ‐terpinene. The amount of carvacrol increased under moderate stress, while γ‐terpinene content decreased under moderate and severe water stress treatments. Copyright © 2002 John Wiley & Sons, Ltd.

Water stress is one of the critical abiotic stresses and limiting factors in the productivity of plants, especially in arid and semi-arid regions. In recent years, the application of bio-fertilizer and stress-modulating nanoparticles (NPs) is known as one of the eco-friendly strategies for improving plants quantity and quality under stressful conditions. In order to achieve the desirable essential oil (EO) quality and quantity of thyme in water deficit conditions, a 2-year field experiment was carried out as a split plot based on the randomized complete block design (RCBD), with 12 treatments and three replications. The treatments included different irrigation levels, containing irrigation at 80% field capacity (FC80) as no stress, 60% FC as moderate water stress (FC60) and 40% FC as severe water stress (FC40), as well as four different fertilizer sources, including non-application of fertilizer (control), application of arbuscular mycorrhizal fungi (AMF), chitosan NPs (CHT) and co-application of AMF+CHT NPs. The results demonstrated that the dry yield of thyme decreased by 13% and 40.3% under FC60 and FC40 water stress conditions. However, co-application of AMF+CHT NPs enhanced the dry yield of thyme by 21.7% in comparison to the control (non-application of fertilizer). The maximum EO content (2.03%) and EO yield (10.04 g 7 g m−2) of thyme were obtained under moderate water stress (FC60) fertilized with AMF+CHT NPs. Co-application of AMF+CHT NPs enhanced the EO content and EO yield of thyme by 17.1% and 42.7%, respectively. Based on the GC-MS and GC-FID analysis, 38 constituents were identified in the thyme EO, with the major constituents being thymol (35.64–41.31%), p-cymene (16.35–19.38%), γ-terpinene (12.61–13.98%) and carvacrol (2.78–3.93%) respectively. The highest content of thymol and γ-terpinene was obtained under moderate water stress (FC60) fertilized with AMF+CHT NPs. In addition, the highest content of p-cymene and carvacrol was observed in the severe water stress (FC40) fertilized with AMF+CHT NPs. The present research suggests that the co-application of AMF+CHT NPs represents a sustainable and eco-friendly strategy for improving the EO quantity and quality of thyme under water stress conditions.

Water stress is the most critical aspect restricting the development of agriculture in regions with scarce water resources, which requires enhancing irrigation water-saving strategies. The current work discusses the potential application of the plant-strengthening root endophyte Piriformospora indica against moderate (25% less irrigation water) and severe (50% less irrigation water) water stress in comparison to the optimum irrigation conditions of greenhouse cucumbers. P. indica improved growth, nutrient content, and photosynthesis apparatus under normal or water-stress conditions. On the other hand, moderate and severe water stress reduced yield up to 47% and 83%, respectively, in non-colonized cucumber plants, while up to 28 and 78%, respectively, in P. indica-colonized plants. In terms of water-use efficiency (WUE), P. indica improved the WUE of colonized cucumber plants grown under moderate (26 L/kg) or severe stress (73 L/kg) by supporting colonized plants in producing higher yield per unit volume of water consumed by the crop in comparison to non-colonized plants under the same level of moderate (43 L/kg) or severe (81 L/kg) water stress. Furthermore, P. indica increased the indole-3-acetic acid (IAA) content, activity levels of catalase (CAT) and peroxidase (POD) with an apparent clear reduction in the abscisic acid (ABA), ethylene, malondialdehyde (MDA), proline contents and stomatal closure compared to non-stressed plants under both water-stress levels. In addition, chlorophyll a, b, a + b contents were increased in the leaves of the colonized plants under water-stress conditions. This improvement in chlorophyll content could be correlated with a significant increment in the transcripts of chlorophyll biosynthesis genes (protochlorophyllide oxidoreductase [POR], chlorophyll a oxygenase [CAO]) and a reduction in the chlorophyll degradation genes (PPH, pheophorbide a oxygenase [PAO], and red chlorophyll catabolite reductase [RCCR]). In conclusion, P. indica has the potential to enhance the cucumber yield grown under moderate water stress rather than severe water stress by improving WUE and altering the activity levels of antioxidant enzymes and chlorophyll metabolism-related genes.

In crops like wheat, terminal drought is one of the principal stress factors limiting productivity in rain-fed systems. However, little is known about root development after heading, when water uptake can be critical to wheat crops. The impact of water-stress on root growth was investigated in two wheat cultivars, Scout and Mace, under well-watered and post-anthesis water stress in three experiments. Plants were grown outside in 1.5-m long pots at a density similar to local recommended farming practice. Differences in root development were observed between genotypes, especially for water stress conditions under which Scout developed and maintained a larger root system than Mace. While under well-watered conditions both genotypes had shallow roots that appeared to senesce after heading, a moderate water stress stimulated shallow-root growth in Scout but accelerated senescence in Mace. For deep roots, post-heading biomass growth was observed for both genotypes in well-watered conditions, while under moderate water stress, only Scout maintained net growth as Mace deep roots senesced. Water stress of severe intensity affected both genotypes similarly, with root senescence at all depths. Senescence was also observed above ground. Under well-watered conditions, Scout retained leaf greenness (i.e. stay-green phenotype) for slightly longer than Mace. The difference between genotypes accentuated under moderate water stress, with rapid post-anthesis leaf senescence in Mace while Scout leaf greenness was affected little if at all by the stress. As an overall result, grain biomass per plant ('yield') was similar in the two genotypes under well-watered conditions, but more affected by a moderate stress in Mace than Scout. The findings from this study will assist improvement in modelling root systems of crop models, development of relevant phenotyping methods and selection of cultivars with better adaptation to drought.

The online version contains supplementary material available at 10.1007/s12298-021-01084-1.

To investigate the effect of water stress on carbon metabolism in growing potato tubers (Solanum tuberosum L.), freshly cut and washed discs were incubated in a range of mannitol concentrations corresponding to external water potential between 0 and −1.2 MPa. (i) Incorporation of [14C]glucose into starch was inhibited in water-stressed discs, and labeling of sucrose was increased. High glucose overrode the changes at low water stress (up to −0.5 MPa) but not at high water stress. (ii) Although [14C]sucrose uptake increased in water-stressed discs, less of the absorbed [14C]sucrose was metabolised. (iii) Analysis of the sucrose content of the discs confirmed that increasing water deficit leads to a switch, from net sucrose degradation to net sucrose synthesis. (iv) In parallel incubations containing identical concentrations of sugars but differing in which sugar was labeled, degradation of [14C]sucrose and labeling of sucrose from [14C]glucose and fructose was found at each mannitol concentration. This shows that there is a cycle of sucrose degradation and resynthesis in these tuber discs. Increasing the extent of water stress changed the relation between sucrose breakdown and sucrose synthesis, in favour of synthesis. (v) Analysis of metabolites showed a biphasic response to increasing water deficit. Moderate water stress (0–200 mM mannitol) led to a decrease of the phosphorylated intermediates, especially 3-phosphoglycerate (3PGA). The decrease of metabolites at moderate water stress was not seen when high concentrations of glucose were supplied to the discs. More extreme water stress (300–500 mM mannitol) was accompanied by an accumulation of metabolites at low and high glucose. (vi) Moderate water stress led to an activation of sucrose phosphate synthase (SPS) in discs, and in intact tubers. The stimulation involved a change in the kinetic properties of SPS, and was blocked␣by protein phosphatase inhibitors. (vii) The amount of ADP-glucose (ADPGlc) decreased when discs were incubated on 100 or 200 mM mannitol. There was a strong correlation between the in vivo levels of ADPGlc and 3PGA when discs were subjected to moderate water stress, and when the sugar supply was varied. (viii) The level of ADPGlc increased and starch synthesis was further inhibited when discs were incubated in 300–500 mM mannitol. (ix) It is proposed that moderate water stress leads to an activation of SPS and stimulates sucrose synthesis. The resulting decline of 3PGA leads to a partial inhibition of ADP-glucose pyrophosphorylase and starch synthesis. More-extreme water stress leads to a further alteration of partitioning, because it inhibits the activities of one or more of the enzymes involved in the terminal reactions of starch synthesis.

Exogenous spermidine enhanced the water deficit tolerance of Anoectochilus roxburghii by modulating plant antioxidant enzymes and polyamine metabolism

The separate and combined effects of water and Al stress on concentrations of P, K, Ca, Mg, Fe, Mn, Zn, Cu, B, Al, Sr, and Ba were determined in tops of ‘Dayton’ (Al‐tolerant) and ‘Kearney’ (Al‐sensitive) barley (Hordeum vulgäre L.) grown in an acid, Al‐toxic, Tatum subsoil (clayey, mixed, thermic, Typic Hapludult). Plants were grown 4 weeks in a plant growth chamber at high (pH 4.7) or low (pH 6.6) Al stress. During the last 2 weeks they were also subjected to low (‐20 to ‐40 kPa), moderate (‐40 to ‐60 kPa), or high (‐60 to ‐80 kPa) water stress. In general, Al stress had a greater overall effect on mineral element concentration of tops than water stress. Aluminum stress significantly decreased concentrations of P, Ca, and Mg and increased concentrations of Zn, Sr, and Ba, irrespective of the cultivar or water stress treatment. Cultivar differences in Mn concentration were observed with Al stress under all water stress conditions. In each case, Mn concentration was lower in ‘Kearney’ than in ‘Dayton’. Potassium, Ca, and Mg were lower in ‘Kearney’ than in ‘Dayton’ only at low and moderate water stress, under low Al stress, ‘Kearney’ had significantly higher concentrations of K and Ca than did ‘Dayton’ under all water stress conditions. The effects of water stress on mineral element concentration varied greatly with cultivar, Al stress treatment, and severity of water stress. Under high Al stress, increasing drought conditions from low water stress (‐20 to ‐40 kPa) to high water stress (‐60 to ‐80 kPa) significantly increased the concentrations of Ca, K, Zn, Sr, and Ba in Al‐sensitive ‘Kearney’ and reduced the concentrations of Zn, Sr, and Ba in Al‐tolerant ‘Dayton'; P and Mg concentration were unaffected by water stress. In contrast, under low Al stress, a corresponding increase in water stress significantly increased the concentrations of Ca and reduced that of P in ‘Kearney’ and increased Ca and B concentration in ‘Dayton'; Mg concentrations were unaffected in either cultivar. Thus, it appears that Al stress and water stress had opposite effects on Ca accumulation in barley tissue.

The management of cultivation technology and fertilizer application may adjust adverse effects of abiotic stresses such as water deficit on agricultural products. Therefore, a field experiment was carried out on growth, yield, nutrient uptake and anatomical properties of maize under three water regimes (well-watered, moderate stress and severe stress as 25%, 50% and 75% soil moisture depletion), two cultivations methods (direct seeding and transplanting), and two Arbuscular Mycorrhizal Fungi (AMF) levels (inoculated with Glomus mosae and uninoculated). The results showed that in plants under moderate water stress, the AMF inoculation percent was significantly higher than those under well-watered and sever stress condition. Inoculation percent in direct seeding was lower than transplanting. Transplanting plants had higher biological and kernel yield compared to direct seeding plants. Water stress reduced the total chlorophyll (Chl) content. Transplanting had greater Chl content in comparison with direct seeding. In all irrigation regimes, transplanting significantly increased N content. In direct seeding, the highest P content was observed in moderate stress and uninoculated plants. Stomatal density increased under water stress, but stomatal size decreased. Plants under severe water stress showed increased stomatal density compared with well waterbed conditions. In addition, severe water stress enhanced the UCT compared to well-watered condition. This study suggests the use of transplanting with AMF application to cope with the adverse effects of severe water stress on maize.

Roles of abscisic acid (ABA) in water stress-induced oxidative stress were investigated in leaves of maize ( Zea mays L.) seedlings exposed to water stress induced by polyethylene glycol (PEG 6000). Treatment with PEG at m 0.7 MPa for 12 and 24 h led to a reduction in leaf relative water content (RWC) by 7.8 and 14.1%, respectively. Duration of the osmotic treatments is considered as mild and moderate water stress. The mild water stress caused significant increases in the generation of superoxide radical ( O 2 m ) and hydrogen peroxide (H 2 O 2 ), the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) and the contents of ascorbate (ASC), reduced glutathione (GSH). The moderate water stress failed to further enhance the capacity of antioxidant defense systems, as compared to the mild water stress. The contents of catalytic Fe, which is critical for H 2 O 2 -dependent hydroxyl radical ( ” OH) production, and the oxidized forms of ascorbate and glutathione pools, dehydroascorbate (DHA) and oxidized glutathione (GSSG), markedly increased, a significant oxidative damage to lipids and proteins took place under the moderate water stress. Pretreatment with ABA caused an obvious reduction in the content of catalytic Fe and significant increases in the activities of antioxidant enzymes and the contents of non-enzymatic antioxidants, and then significantly reduced the contents of DHA and GSSG and the degrees of oxidative damage in leaves exposed to the moderate water stress. Pretreatment with an ABA biosynthesis inhibitor, tungstate, significantly suppressed the accumulation of ABA induced by water stress, reduced the enhancement in the capacity of antioxidant defense systems, and resulted in an increase in catalytic Fe, DHA and GSSG, and oxidative damage in the water-stressed leaves. These effects were completely prevented by addition of ABA, which raised the internal ABA content. Our data indicate that ABA plays an important role in water stress-induced antioxidant defense against oxidative stress.

This experiment aimed to assess the development, yield and chemical composition of Petroselinum crispum essential oil (EO), popularly known as parsley under different levels of water stress deficit: 30 to 40% (moderate stress), 50 to 60% (severe stress) and control 0 to 10%. The plants were kept in a greenhouse to complete the cycle, harvested and measured for their biomass (g), development (cm), yield (%) and chemical composition of EO of aerial parts and root. The EO was extracted by hydrodistillation and the chemical analysis done by gas chromatography/mass spectrometry (GC/MS). In the control and moderate stress, greater development of the aerial part occurred without showing difference in the root development. A yield increase of EO extracted from the roots was verified when it was submitted to moderate stress, but there was no difference in the aerial part yield. The EO chemical composition was influenced by the different conditions of water deficit, producing 100% of apiole in moderate stress and control of aerial parts and roots. A different behavior was observed for severe stress, which presented three compounds (89.98% apiole, 6.53% β-sesquiphellandrene and 3.49% myristicin) in aerial parts, but four compounds were found for the root (88.40% apiole, 5.83% β-sesquiphellandrene, 3.61% myristicin and 2.16% elemicin). These results indicated that under greater water deficit, the plant produced other compounds besides apiole, probably as a defense mechanism. The results showed that there was influence of the water stress on the plant development as well as on the essential oil yield and chemical composition. Key words: Apiole, gas chromatography/mass spectrometry (GC/MS), essential oil, water stress, parsley.