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The use of desalinated seawater (DSW) for irrigation in semi-arid regions is taking hold. Citrus tolerance to ions that predominate in DSW and water stress depends on the rootstock. Deficit irrigation was applied to DSW-irrigated lemon trees and grafted on rootstocks with different tolerance (Citrus macrophylla (CM) and sour orange (SO)). Plants were irrigated with DSW or Control treatment (distilled water), and, 140 days later, irrigation treatments were started: full irrigation (FI) or DI (50% of the volume applied to FI). After 75 days, differences between CM and SO plants irrigated with DSW and under DI were found. The higher concentrations of Cl− and Na+ in CM and B in SO were the main causes of shoot growth reduction. The osmotic adjustment of CM plants was made possible by the accumulation of Na+, Cl−, and proline, but SO failed to adjust osmotically. In CM and SO plants, photosynthesis reduction was due to lower chlorophyll levels, but also to stomatal factors (CM plants) or alterations of the photochemical machinery (SO plants). Finally, unlike CM, SO had a good antioxidant system. In the future, knowing the different responses of CM and SO under these stressful conditions could be useful in citrus-growing areas.

An experiment was conducted with seedlings of Citrus macrophylla Wester to study the effects of P nutrition on plants inoculated with a mixture (Rhizophagus irregularis and Funneliformis mosseae) of arbuscular mycorrhizal (AM) fungi. The treatments consisted of factorial combinations of two factors: mycorrhization (-AM: non-inoculated plants, and +AM: inoculated plants) and P nutrition (0, 0.1, 1, and 5 mM P). After the P treatments had been applied for 165 days, the AM fungi showed an important effect on plant growth and P uptake, but this effect depended on the P fertilization. In the absence of P fertilization, inoculation with the AM fungi had little impact on P nutrition and plant growth. However, when 0.1 or 1 mM P was supplied, inoculation had a clear beneficial effect on plant growth, since P nutrition was significantly improved, the maximum growth of the +AM plants occurring at 1 mM P. The supply of 5 mM P did not increase plant growth with regard to 1 mM P due to a lack of improvement in leaf P nutrition and photosynthesis. The higher demand of the AM fungi in the roots of the +AM plants for sucrose reduced the concentration of sucrose in the leaves of plants receiving 5 mM P, and of fructose and glucose in the roots of plants supplied with 0.1 or 1 mM P, relative to the –AM plants. The inoculated plants grown with 5 mM P had a decreased starch concentration in their roots, in order to supply the high sugar demand of the AM fungi. The C drain towards the AM fungi in the +AM plants may have been compensated by a higher photosynthetic rate and improved mineral nutrition. Inoculation improved plant P nutrition in the 0.1 and 1 mM P treatments but had a lesser effect at 5 mM P. The tissue levels of certain nutrients, such as Mg, improved with inoculation regardless of the P treatment, but those of other nutrients - such as Zn or Fe - increased more in the +AM plants with lower P supply. So, in general, the +AM C. macrophylla plants receiving the highest P supply did not show improved mineral nutrition relative to the –AM plants. Overall, the results indicate that when the availability of P to C. macrophylla plants is high, the lower benefits received by the plants from the C-for-P trade can convert a mutualistic relationship between the host plant and AM fungi into a parasitic one since colonization can persist even when the availability of P in the soil is high.

Water deficit and increasing pressure on water resources in semi-arid regions has led to the spread of irrigation with non-conventional water resources, such as desalinated seawater (DSW). The few existent studies to date, mainly carried out in Israel and Spain, have shown that suitable management of irrigation with DSW must be performed to avoid agronomic problems and reductions in crop productivity and fruit quality in the mid-long term. To the best of our knowledge, in the case of citrus, fruit production, and quality, information on the effects of DSW irrigation is not available. In this study, we evaluated the short-term agronomic and economic effects of irrigating a mandarin orchard during two crop cycles (2017&ndash, 2019) with (i) fresh water (FW), (ii) desalinated seawater (DSW), and (iii) a mix of water composed of 50% FW and 50% DSW. Stem water potential (&Psi, s &lt, &minus, 1 MPa) and gas exchange parameters (net photosynthesis, A &gt, 6.5 &micro, mol/m2/s and stomatal conductance, gs &gt, 65 mmol/m2/s) indicated that trees were well irrigated throughout the experiment. The concentration of Na+ and B3+ in the DSW always exceeded the maximum thresholds for irrigation water proposed in the literature for citrus, and the concentration of Na+ in the leaves exceeded the maximum threshold in summer 2018. Nonetheless, symptoms of toxicity were not observed. Significant differences among treatments were not observed for &Psi, stem, A, gs, Na+, Cl&minus, and B3+ in leaves (except in the summer months), yield components, fruit quality, or the economic assessment. The lack of such differences was explained by the large standard deviations caused by the youth of the trees, with figures that on occasion could represent more than 100% of the mean value. These results may justify the agronomic and economic viability of the irrigation of young trees with DSW in the short-term, but further research, considering the effects on adult trees in the long term is still needed.

In this study we review the state of the art of different physiologically-based water-saving irrigation strategies and methods used to improve productive water use efficiency (WUEyield) and berry and wine quality in vineyards. We also show how these irrigation practices, combined with more sustainable soil management and other agroecological practices, can help to mitigate the negative effects of climate change on wine grapes cultivation and make irrigated Mediterranean vineyards more resilient and sustainable. We analyse the deficit irrigation (DI) strategies used most often for different varieties and edaphoclimatic conditions. We review the latest advances in the application of regulated deficit irrigation (RDI) and partial root zone drying irrigation (PRI) strategies in grapevines (red and white grapes), as well as other irrigation methods used less frequently in vineyards to improve WUEyield, berry quality and irrigation efficiency, such as subsurface drip irrigation. We also analyze recent findings concerning the physiological response of the vine to water stress with more holistic approaches such as, hydraulic safety marging and stress distance, and discuss how to translate these physiological approaches into the practical application of RDI management in field conditions, according to the genotypic characteristics and degree of drought tolerance of the variety/rootstock combination. We review optimum vine water status ranges and the thresholds proposed for better deficit irrigation scheduling in vineyards. In addition, we consider sustainable soil management practices - such as cover crops, mulching, composting, reduced tillage, mutualistic plant-microorganisms interactions, and agroforestry - and their potential as beneficial agroecological practices to improve WUE, soil/vine performance, and other ecological services in RDI vineyards within a more sustainable farming system (organic farming). The idea is to design sustainable and climate-change-resilient agricultural systems (e.g. vineyards) in Mediterranean semi-arid areas.

Regulated deficit irrigation (RDI) and partial root zone irrigation (PRI) were compared for five years, in field-grown mature Monastrell grapevines grafted on five different rootstocks (140Ru, 1103 P, 41B, 110R, and 161-49C), in the semiarid winegrowing region of D.O. Bullas, South Eastern Spain. Vines grafted on invigorating rootstocks (140Ru or 1103 P) showed the highest vigor, water productivity, and productive water use efficiency (WUEyield), but at the expense of berry quality (lower berry quality indices, QI), compared to those on rootstocks of medium-low vigor (41B, 110R, and 161-49C). Vines grafted on 41B showed a moderate vigor-yield-efficiency-quality response, and this did not improve substantially the final berry quality. The least vigorous rootstocks (161-49C and 110R) gave lower yield, WUEyield, and productivity ratios, but a significant improvement in long-term final berry quality. The PRI increased the yield and/or berry quality attributes, especially in low vigor rootstocks (161-49C, 110R) and high vigor rootstocks (140Ru, 1103 P), but not in the medium vigor rootstock 41B. In addition, PRI produced a beneficial increase in the nutraceutical potential for practically all rootstocks. The PRI vines grafted on 161-49C gave the lowest yield and WUEyield, but the highest QI scores and the highest nutraceutical value, while PRI vines grafted on 110R had enhanced long-term yield, WUEyield, and amino acid and resveratrol contents, with similar berry quality (QI) indices, compared to RDI vines. Both 161-49C and 110R seem good options to achieve a compromise between long-term yield-quality-efficiency and returns for the grower. The application of low water volumes (85-90 mm year−1) with well-designed DI strategies was enough to maintain the vines in an optimum physiological state, obtaining moderate yields (7,400–9,900 kg ha−1, for 161-49C and 110R) with high berry quality and nutraceutical potential for premium red wine production. Such an approach can serve as an adaptation measure in the face of climate change, to improve vine performance and enhance Monastrell vineyard sustainability under semiarid and water limiting conditions.

Skin diseases can be the cause of a significant psychosocial burden for those who suffer them. A number of studies have considered issues such as a lower quality of life, increased anxiety, depression, suicidal ideation and other psychological disorders1-3. However, adequate means for evaluating social interaction difficulties, diminished social networks, and the impoverished conversational exchanges that affect the wellbeing and mental health of the individual have not been sufficiently developed. This article is protected by copyright. All rights reserved.

Partial rootzone drying (PRD) establishes discrete wet and dry parts of the rootzone (for example using parallel drip lines on either side of the crop row), and alternates them to stimulate root growth and root-to-shoot ABA signalling. To assess whether alternation frequency affects plant physiological responses, Citrus macrophylla Wester seedlings were grown with the root system split between two pots and 5 irrigation treatments applied: Control, PRD-Fixed (where wet and dry parts of the rootzone were not alternated) and three alternate PRD treatments where the wet and dry parts were swapped at 3 (PRD1), 6 (PRD2) and 12 (PRD3) days intervals, to dry the soil to different degrees before alternating the irrigation. Water was equally distributed between both pots in Control plants, whereas only one pot was watered and the other allowed to dry in PRD plants, with all plants receiving the same irrigation volume. After 24 days, soil water content (θv), leaf water potential (Ψleaf), root water potential (Ψroot), abscisic acid (ABA) concentration in roots ([ABA]root), leaves ([ABA]leaf) and shoot xylem sap ([X-ABA]shoot), biomass allocation and leaf area were measured. Higher soil water availability of the dry side (PRD1 and PRD2) had no significant effects on leaf water relations, ABA status and plant biomass allocation. However, increasing the duration of exposure of part of the root system to dry soil (PRD3 and PRD-Fixed) further decreased Ψroot and stimulated root ABA accumulation, while decreasing Ψleaf and increasing [ABA]leaf of PRD3 plants compared to the other treatments. Differences in physiological response between PRD3 and PRD-Fixed plants were attributed to differences in the proportion of root mass exposed to drying soil: PRD3 plants had a lower Ψleaf and a higher [ABA]leaf with a smaller proportion of their root mass in wet soil. Since long drying cycles were required to alter plant biomass allocation and physiological responses in PRD plants, these should be implemented in designing suitable PRD strategies for field application.

The irrigation necessities for grapefruit production are very high. Due to the scarcity of water resources, growers use deficit irrigation (DI) – which could affect the fruit quality. Different DI strategies were studied: Control (irrigated at 100% ETc) and T1, T2 and T3 (50% ETc at phases I, II and III of fruit growth, respectively). Strategy T1 only delayed external maturation depending on the duration of the water stress. High water stress in T2 delayed fruit maturation, increased acidity and reduced the sugar concentration. Under T2, trees suffering moderate water stress showed increased flavonoid and phenolic contents but decreased lycopene levels. External maturation was delayed in T3 when severe stress occurred during the first part of phase III. Strategy T3 advanced internal ripening when moderate water stress occurred during the first 40 days of phase III, increasing sugar accumulation, promoted by the high acidity of the fruits. Moderate water stress also increased β-carotene, flavonoids and phenolics levels.

Laughter, one of the most intriguing reactions of individuals, is an important emotional component of intelligence’s adaptive processes. Laughter spontaneously appears as an instinctive “gut” reaction; but it is also a cognitive phenomenon (humour), it is social, it has positive-negative valence, and it may wrap itself onto other emotional contents. Laughter becomes one of the most interesting instances to discuss the common information processing that underlies emotions and intelligence. In this article a new core hypothesis on the neurodynamics of laughter and its behavioural repercussions is discussed. The “sentic forms” hypothesis developed by Manfred Clynes for sensory-motor tactile com-munication is generalized neurodynamically in order to understand the problem-solving characteristics of laughter and the unusual sound features that it presents in our species. Laughter, far from being a curious evolutionary relic or a trivial innate behaviour, should be considered as a highly efficient tool for cognitive-emotional-social problem solving. Explaining laughter becomes a first-class neurodynamic and neurocomputational challenge.

Field-grown mature Monastrell grapevines grafted on five different rootstocks (140Ru, 1103 P, 41B, 110R, 161-49C) were subjected to regulated deficit irrigation (RDI) and partial root zone irrigation (PRI) in a semiarid region in SE Spain (D.O. Bullas, Region of Murcia). The main goal was to analyse the effects of the rootstock (R), irrigation method (IM), and their interaction (R x IM) on the final wine composition, volatile aromatic profile, and wine sensory attributes. The application of low annual water volumes (85–90 mm year−1) to low vigorous rootstocks (161-49C, 110R) was reflected in wines with higher contents of polyphenolics and alcohol, a higher wine quality index (QIwine), enhanced levels of health-promoting bioactive compounds (flavonols, malvidins), and better organoleptic perception compared to other rootstocks. These wines also had lower concentration of aromatic compounds (alcohols and esters). The 140Ru wines, although having a lower polyphenolic concentration and worse color, were among those rated most highly and preferred by the tasters. These wines had a high content of lactic acid and amino acids, higher tartaric/malic and anthocyanins/tannins ratios and a low concentration of aromatic compounds. In contrast, 1103 P and 41B wines had lower polyphenolic content-nutraceutical value, lower QIwine, tartaric/malic and anthocyanins/tannins ratios, more aromatic compounds, abundant green-vegetable/astringent notes, and more defect-causing compounds. In addition, these wines were also the worst rated in the sensory analysis. Significant positive correlations between the polyphenolic content and alcoholic degree and the score in the wine sensory analysis indicated that the greater the polyphenolic and alcohol contents in the wine, the better valued and more preferred by the tasters it was. PRI method improved wine quality and organoleptic perception for low vigor rootstocks (especially 161-49C), compared to RDI. These wines showed darker color, higher sugar content and nutraceutical potential as well as better sensory perception compared to other rootstock-IM combinations. In contrast, for high vigor rootstocks (1103 P, 140Ru), RDI was more beneficial for wine composition, global quality, and sensory perception. Overall, the PRI method also increased the presence of some volatile unpleasant alcohols in the wines. We recommend the use of low vigor rootstocks and DI techniques with small water volumes to improve Monastrell wine quality, and as a measure to adapt vineyards to climate change under semiarid and water limiting conditions.

‘Clemenules’ mandarin citrus trees, grafted on Cleopatra and Carrizo rootstocks, were subjected to three irrigation treatments: the control (100% ETc), and phases II and III treatments (non-irrigation during phases II and III, respectively). The two deficit irrigation (DI) treatments affected in different ways some fruit quality parameters and these effects were also dependent on the rootstock. Although phase II treatment increased total soluble solids (TSS) and titratable acidity (TA), it delayed the maturation process. Phase II-stressed fruits on Carrizo had more fructose and glucose but less sucrose in relation to control fruits, thus increasing the reducing sugars. Phase II-stressed fruits on Cleopatra had more glucose, fructose and sucrose, for osmotic adjustment, also increasing the reducing sugars in these fruits. Phase III-stressed fruits had greater acidity, TSS, total phenolics, lycopene, glucose and sucrose than control fruits, but the same maturation state. In conclusion, DI in phase III improved fruit quality, by increasing the values of important quality parameters related to taste, flavour and nutritional benefits, but DI in phase II produced a drastic delay in the maturation process that made fruits non-commercial.

The influence of a deficit-irrigation (DI) strategy on soil–plant water relations and gas exchange activity was analysed during a 3-year period in mature ‘Lane late’ (Citrus sinensis (L.) Osb.) citrus trees grafted on two different rootstocks, ‘Cleopatra’ mandarin (Citrus reshni Hort. ex Tanaka ) and ‘Carrizo’ citrange (C. sinensis L., Osbeck × Poncirus trifoliata L.). Two treatments were applied for each rootstock: a control treatment, irrigated at 100% ETc (crop evapotranspiration) during the entire season, and a DI treatment, irrigated at 100% ETc, except during Phase I (cell division) and Phase III (ripening and harvest) of fruit growth, when complete irrigation cut-off was applied. Under soil water deficit, the seasonal variations of soil water content suggested that ‘Cleopatra’ mandarin had a better root efficiency for soil water extraction than ‘Carrizo’ citrange. Moreover, in all years, trees on ‘Cleopatra’ reached a lower water-stress level (midday xylem water potential values (Ψmd) > −2 MPa), maintaining a better plant water status during the water-stress periods than trees on ‘Carrizo’ (Ψmd

Sufficient nutrient application is one of the most important factors in producing quality citrus fruits. One of the main guides in planning citrus fertilizer programs is by directly monitoring the plant nutrient content. However, this requires analysis of a large number of leaf samples using expensive and time-consuming chemical techniques. Over the last 5 years, it has been demonstrated that it is possible to quantitatively estimate certain nutritional elements in citrus leaves by using the spectral reflectance values, obtained by using near infrared reflectance spectroscopy (NIRS). This technique is rapid, non-destructive, cost-effective and environmentally friendly. Therefore, the estimation of macro and micronutrients in citrus leaves by this method would be beneficial in identifying the mineral status of the trees. However, to be used effectively NIRS must be evaluated against the standard techniques across different cultivars. In this study, NIRS spectral analysis, and subsequent nutrient estimations for N, K, Ca, Mg, B, Fe, Cu, Mn, and Zn concentration, were performed using 217 leaf samples from different citrus trees species. Partial least square regression and different pre-processing signal treatments were used to generate the best estimation against the current best practice techniques. It was verified a high proficiency in the estimation of N (Rv = 0.99) and Ca (Rv = 0.98) as well as achieving acceptable estimation for K, Mg, Fe, and Zn. However, no successful calibrations were obtained for the estimation of B, Cu, and Mn., Funding for this research came from the Ministry of Education and Science, government of Spain (Project Plan National AGL2011-24795).

The interest in the consumption of pepper fruits (Capsicum annuum L.) is, to a large extent, due to its content of bioactive nutrients and their importance as dietary antioxidants. A greenhouse experiment was carried out to determine the effects of salinity and different ripening states of pepper fruits on several compounds with antioxidant properties. Fruits from plants grown under three saline treatments (0, 15, and 30 mM NaCl) were collected at three maturity states (green, turning, and red). Antioxidant activity in the hydrophilic (HAA) and lipophilic (LAA) fractions, lycopene, β-carotene, ascorbic acid, total phenolic compounds and reducing sugars were determined. From the nutritional point of view, the red state was the most appropriate state of maturation, since red peppers had the highest levels of lycopene, β-carotene, and sugars and the highest antioxidant activity for both hydrophilic and lipophilic fractions. The effect of salinity depended on the maturity state of the peppers: it had no effect on HAA, β-carotene or sugars, but decreased ascorbic acid and total phenolic compounds, and increased LAA and lycopene. The use of a moderately-saline water was beneficial when peppers were harvested in the red state, by increasing HAA and LAA in fruits, with no significant effects on other parameters.

The response of two cultivars of melon (Cucumis melo L.) (Galia and Amarillo Oro) to irrigation with saline water at different stages of development has been studied under field conditions. Two levels of salinity (1.3 and 6.1 dS m−1) were used for irrigation water. Four treatments, differing with respect to the time of application of saline water, were used. These treatments were: control water (1.3 dS m−1) throughout the experiment, saline water (6.1 dS m−1) from transplanting to harvest, control water until flowering and then saline water until harvest, and control water from transplanting to fruiting and then saline water until harvest. Salinity had similar effects on vegetative growth in both cultivars. However, Galia exhibited higher salt tolerance than Amarillo Oro on the basis of fruit yield since marketable yield was reduced by 12% and 39%, respectively, when salinity was applied throughout the experiment. Salinity reduced flower number of Amarillo Oro and delayed flowering in Galia. Application of saline water from fruiting onward did not reduce marketable fruit yield (28.8 and 20.6 t ha−1 for Galia and Amarillo Oro, respectively) and increased fruit quality (TSS and maturity index) in both cultivars. Melon plants accumulated Na+ and Cl− in the stem, avoiding high concentrations of these ions in the leaves., This work was supported by the Comisión Interministerial de Ciencia y Tecnología, Project No. AGF95-0135.

SummaryTomato plants were grown in hydroponic culture in a greenhouse. The effect of supplying bicarbonate, ammonium and calcium to saline nutrient solutions was investigated. High salinity (60 mM NaCl) decreased total and marketable yields of tomato fruit, mainly by reducing size fruit. Applications of ammonium produced the lowest marketable yield, by reducing the size and number of marketable fruit compared to the control treatment. This reduction was due to an increase in the number of fruits with blossom-end rot, probably caused by low Ca2+ concentration in the fruits.Although no significant effect on yield was produced by adding Ca2+, HCO3– or NH4+ to the saline treatment, some quality parameters, such as firmness, pH, total soluble solids (TSS), TSS/acidity ratio and glucose content, were affected.

6 pages, 3 figures, 2 tables., A study was conducted in order to assess the effect of different fertilisation levels of Ca2+, K+ and NO3- on the bioactive nutrient content in red pepper (Capsicum annuum L) fruits. The experiment was carried out in a greenhouse, under hydroponic culture. Lycopene, -carotene, vitamin C, total phenolic compound, sugar, nitrate and potassium contents and antioxidant activity were determined. Increasing Ca2+ and NO3- concentrations in the root medium increased the lycopene and -carotene contents in pepper. Antioxidant activity was determined in the hydrophilic (HAA) and lipophilic (LAA) fractions. HAA was increased by intermediate and high Ca2+ concentrations in the culture medium. However, LAA was raised only by NO3- treatments. Vitamin C, sugar and total phenolic acid contents were not affected by Ca2+ or NO3- treatments. K+ treatments had no effect on nutritional quality of pepper. An increased supply of Ca2+ and NO3- in the culture medium could constitute a useful practice for improving the nutritional attributes of pepper as well as its commercial quality. Copyright © 2004 Society of Chemical Industry, This work was funded by CICYT, Spain (project AGF 1999-1110).

The effects of Ca 2+ , K + and cGMP on Na + influx in pepper plants ( Capsicum annum L.) were studied. Calcium and K + inhibited Na + net uptake and had no effect on Na + efflux. The inhibition of Na + uptake by Ca 2+ showed a K i of 0.46 mM and micromolar concentrations of the membrane permeable cyclic nucleotide 8-bromo-cGMP inhibited Na + uptake. These results suggest that transporters with low discrimination between K + and Na + , sensitive to Ca 2+ and to cyclic nucleotides, may constitute important pathways for Na + influx. As suggested for other plant species, non-selective voltage-independent cation channels may mediate a large amount of Na + influx into pepper plants.

Des plants de tomates cv. Daniela ont ete cultives dans une solution nutritive contenant 0, 30, et 60 mM NaCl et fertilises avec 14/0, 12/2 et 10/4 mM NO 3 -/NH 4 + dans le but d'etudier l'effet de la salinite et de la source d'azote apportee. Dans tous les cas, sauf pour les plantes fertilisees avec du nitrate en presence de 30 mM NaCl, la salinite entraine une diminution du rendement total, quelle que soit la source d'azote. L'augmentation de la concentration en NH 4 + dans la solution nutritive entraine une diminution du rendement. Le rendement le plus eleve a ete observe dans les premieres grappes pour tous les traitements, sauf pour les plantes cultivees dans une solution contenant un rapport NO 3 -/NH 4 + de 12/2 jusqu'a l'apparition de la troisieme grappe puis transferees dans une solution nutritive avec NO 3 - comme seule source d'azote. L'augmentation de la salinite et de la concentration en NH 4 + dans la solution nutritive entraine une meilleure qualite des tomates. Ceci est du a l'augmentation du taux de sucres et d'acides organiques dans les fruits. Cependant, cette amelioration de la qualite est accompagnee par une chute de rendement.

Melon (Cucumis melo L.) plants were grown hydroponically in a greenhouse to investigate the interaction of phosphorus (P) and calcium (Ca) under saline conditions on vegetative biomass and cation balance. Three levels of Ca (0.4, 2, and 8 mM) were combined factorially with two levels of phosphate (0.1 and 1 mM) under two regimes of NaCl salinity (10 and 80 mM). An increase of phosphate and salinity level decreased shoot and root growth. A strong antagonism between Ca and magnesium (Mg) was observed regardless of the salinity level. Calcium effect on growth depended on the salinity level. At low salinity, an increase of Ca reduced sodium (Na) concentration in all plant fractions. At high salinity, this effect was only significant in young and medium leaves. At low salinity and low Ca the reduction of growth could be due to Na toxicity and an unbalanced Ca/Mg ratio. In addition to that, at high salinity, the restoration of growth by increasing Ca concentration in the root medium could be due to an effect on water relation and by increasing potassium K/Na selectivity.

Seedlings of Cleopatra mandarin (Citrus reshni Hort. ex Tan.) and Alemow (Citrus macrophylla Wester) were inoculated with a mixture of AM fungi (Rhizophagus irregularis and Funneliformis mosseae) (+AM), or left non-inoculated (-AM). From forty-five days after fungal inoculation onwards, half of +AM or -AM plants were irrigated with nutrient solution containing 50 mM NaCl. Three months later, AM significantly increased plant growth in both Cleopatra mandarin and Alemow rootstocks. Plant growth was higher in salinized +AM plants than in non-salinized -AM plants, demonstrating that AM compensates the growth limitations imposed by salinity. Whereas AM-inoculated Cleopatra mandarin seedlings had a very good response under saline treatment, inoculation in Alemow did not alleviate the negative effect of salinity. The beneficial effect of mycorrhization is unrelated with protection against the uptake of Na or Cl and the effect of AM on these ions did not explain the different response of rootstocks. This response was related with the nutritional status since our findings confirm that AM fungi can alter host responses to salinity stress, improving more the P, K, Fe and Cu plant nutrition in Cleopatra mandarin than in Alemow plants. AM inoculation under saline treatments also increased root Mg concentration but it was higher in Cleopatra mandarin than in Alemow. This could explain why AM fungus did not completely recovered chlorophyll concentrations in Alemow and consequently it had lower photosynthesis rate than control plants. AM fungi play an essential role in citrus rootstock growth and biomass production although the intensity of this response depends on the rootstock salinity tolerance.

Salinity is one of the major abiotic stresses affecting arable crops worldwide, and is the most stringent factor limiting plant distribution and productivity. In the present study, the possible use of in vitro culture to evaluate the growth and physiological responses to salt-induced stress in cultivated explants of Citrus macrophylla was analyzed. For this purpose, micropropagated adult explants were grown in proliferation and rooting media supplemented with different concentrations of NaCl. All growth parameters were decreased significantly by these NaCl treatments; this was accompanied by visible symptoms of salt injury in the proliferated shoots from 60mM NaCl and in the rooted shoots from 40mM NaCl. Malondialdehyde (MDA) increased with increasing salinity in proliferated shoots, indicating a rising degree of membrane damage. The concentration of total chlorophyll significantly decreased in the presence of NaCl, and this effect was more pronounced in the rooted explants. The Na(+) and Cl(-) concentrations in the explants increased significantly with the salinity level, but Cl(-) levels were higher in the proliferated explants than in the rooted explants. For osmotic adjustment, high concentrations of compatible solutes (proline and quaternary ammonium compounds-QAC) accumulated in salt-stressed plants in proliferation, but differences were not observed in rooted explants. In proliferation, proline and QAC were highly correlated with the sodium and chloride concentrations in the explants, indicating a possible role of these compounds in osmotic adjustment. The plant concentrations of NO(3)(-), K(+), Mg(2+), Ca(+) and Fe were also affected by the NaCl concentration of the medium. We suggest that the important deleterious effects in the in vitro explants of Citrus macrophylla grown at increasing NaCl concentrations were due mainly to toxic effects of saline ions, particularly Cl(-), at the cellular level.

Two iso-osmotic concentrations of NaCl and Na2SO4 were used for discriminating between the effects of specific ion toxicities of salt stress on pepper plants (Capsicum annuum L.) grown in hydroponic conditions, in a controlled-environment greenhouse. The two salts were applied to plants at different electrical conductivities, and leaf water relations, osmotic adjustment and root hydraulic conductance were measured. Leaf water potential (Ψw), leaf osmotic potential (Ψo) and leaf turgor potential (Ψp) decreased significantly when EC increased, but the decrease was less for NaCl- than for Na2SO4-treated plants. The reduction in stomatal conductance was higher for NaCl-treated plants. There were no differences in the effect of both treatments on the osmotic adjustment, and a reduction in root hydraulic conductance and the flux of solutes into the xylem was observed, except for the saline ions (Na+, Cl− and SO4 2−). Therefore, pepper growth decreased with increasing salinity because the plants were unable to adjust osmotically or because of the toxic effects of Cl−, SO4 2− and/or Na+. However, turgor of NaCl-treated plants was maintained at low EC (3 and 4 dS m−1) probably due to the maintenance of water transport into the plant (decrease of stomatal conductance), which, together with the lower concentration of Na+ in the plant tissues compared with the Na2SO4 treatment, could be the cause of the smaller decrease in growth.

Differences between rootstocks, 'Cleopatra' mandarin and 'Carrizo' citrange, in soil-plant water relations and the influence of these factors on vigor, crop yield, fruit quality and mineral nutrition were evaluated in field-grown Clemenules mandarin trees irrigated at 100% of potential seasonal evaporation (ET(c)) (control treatment), or irrigated at 100% ET(c), except during Phases I and III of fruit growth and post-harvest when no irrigation was applied (deficit irrigation (DI) treatment), for 3 years. Differences between rootstocks in plant-soil water relations were the primary cause of differences among trees in vegetative development and fruit yield. After 3 years of DI treatment, trees on 'Cleopatra' showed more efficient soil water extraction than trees on 'Carrizo', and maintained a higher plant water status, a higher gas exchange rate during periods of water stress and achieved faster recovery in gas exchange following irrigation after water stress. The DI treatment reduced vegetative development more in trees on 'Carrizo' than in trees on 'Cleopatra'. Cumulative fruit yield decreased more in DI trees on 'Carrizo' (40%) than on 'Cleopatra' (27%). The yield component most affected by DI in 'Cleopatra' was the number of fruit, whereas in 'Carrizo' it depended on the severity of water stress reached in each phase (severe water stress in Phase I affected mainly the number of fruit, whereas it affected fruit size the most in Phase III). In the third year of DI treatment, water-use efficiency decreased sharply in trees on 'Carrizo' (70%) compared to trees on 'Cleopatra' (30%). Thus, trees on 'Cleopatra' were able to tolerate moderate water stress, whereas trees on 'Carrizo' were more sensitive to changes in soil water content.

SummarySweet pepper (Capsicum annuum L.) plants were grown hydroponically inside a greenhouse, to investigate the effect of salinity (produced by Cl– or SO42– ions) on yield and fruit quality. The electrical conductivity (EC) levels of 2, 3, 4, 6, and 8 dS m–1 were achieved by adding concentrated NaCl or Na2SO4 solutions to the basic nutrient solution, maintained at 2 dS m–1. High conductivity treatments strongly decreased fruit yield and fruit size. High blossom-end rot (BER) incidence with increasing EC resulted in fewer marketable fruits. In general, saline treatments decreased the quality of pepper fruits. Although salinity reduced yield and fruit quality, sulphate treatments were less deleterious than chloride treatments, particularly for moderate EC levels.

Summary Melon seedlings ( Cucumis melo L. cv.Galia) were grown hydroponically to study the effect of salinity (80 mmol/LNaCl) on phosphate (Pi) uptake and translocation at two levels of Pi (25 μmol/L and 1 mmol/L). Net uptake rates of Pi were determined by depletionof the medium and by plant content. Salinity decreased Pi uptake at low Pi (high affinity uptake mechanism), 25 μmol/L, although no specific competitive inhibition of Pi uptake by Cl − was observed. When plants were grown with high Pi (1 mmol/L), the uptake of Pi through the low affinity system was increased by 80 mmol/L NaCl. Salinity also reduced the phosphorus flux, as Pi, through the xylem. It is hypothesised that high levels of NaCl decrease the mobility of Pi stored in vacuoles, and as a result, inhibit export from this storage compartment to other parts of the plant.

We investigated the effects of regulated deficit irrigation (RDI) during the pre-harvest period (kernel-filling stage) on water relations, leaf development and crop yield in mature almond (Prunus dulcis (Mill.) D.A. Webb cv. Cartagenera) trees during a 2-year field experiment. Trees were either irrigated at full-crop evapotranspiration (ETc=100%) (well-irrigated control treatment) or subjected to an RDI treatment that consisted of full irrigation for the full season, except from early June to early August (kernel-filling stage), when 20% ETc was applied. The severity of water stress was characterized by measurements of soil water content, predawn leaf water potential (Psipd) and relative water content (RWC). Stomatal conductance (gs), net CO2 assimilation rate (A), transpiration rate (E), leaf abscission, leaf expansion rate and crop yield were also measured. In both years, Psipd and RWC of well-irrigated trees were maintained above -1.0 MPa and 92%, respectively, whereas the corresponding values for trees in the RDI treatment were -2.37 MPa and 82%. Long-term water stress led to a progressive decline in gs, A and E, with significant reductions after 21 days in the RDI treatment. At the time of maximum stress (48 days after commencement of RDI), A, gs and E were 64, 67 and 56% lower than control values, respectively. High correlations between A, E and gs were observed. Plant water status recovered within 15 days after the resumption of irrigation and was associated with recovery of soil water content. A relatively rapid and complete recovery of A and gs was also observed, although the recovery was slower than for Psipd and RWC. Severe water stress during the kernel-filling stage resulted in premature defoliation (caused by increased leaf abscission) and a reduction in leaf growth rate, which decreased tree leaf area. Although kernel yield was correlated with leaf water potential, RDI caused a nonsignificant 7% reduction in kernel yield and had no effect on kernel size. The RDI treatment also improved water-use efficiency because about 30% less irrigation water was applied in the RDI treatment than in the control treatment. We conclude that high-cropping almonds can be successfully grown in semiarid regions in an RDI regime provided that Psipd is maintained above a threshold value of -2 MPa.

SummaryMelon plants were grown hydroponically in a greenhouse to investigate the interaction of phosphorus and Ca21 under saline conditions on vegetative biomass production, yield and fruit quality. Two levels of Ca21 (2 and 8 mM) were combined factorially with two levels of phosphate (0.2 and 1 mM) under two regimens of NaCl salinity (10 and 80 mM). The increase of Ca21 concentration in the nutrient solution under saline conditions improved to the same extent vegetative growth and fruit yield. Parameters of fruit quality were affected by salinity, phosphorus and Ca21 nutrition. Salinity increased fruit quality by increasing firmness, total sugars and total soluble solids (TSS). High Ca21 treatment increased sucrose, fructose and glucose, this effect being greater under low salinity conditions than under high. In the two saline treatments, the highest concentration of sucrose in flesh was found at 0.2 mM of phosphate in the nutrient solution.