Growth of mycorrhizal tomato and mineral acquisition under salt stress

 High salt levels in soil and water can limit agricultural production and land development in arid and semiarid regions. Arbuscular mycorrhizal fungi (AMF) have been shown to decrease plant yield losses in saline soils. The objective of this study was to examine the growth and mineral acquisition responses of greenhouse-grown tomato to colonization by the AMF Glomus mosseae [(Nicol. And Gerd.) Gerd. and Trappe] under varied levels of salt. NaCl was added to soil in the irrigation water to give an EC_e of 1.4 (control), 4.7 (medium) and 7.4 dS m^–1 (high salt stress). Plants were grown in a sterilized, low P (silty clay) soil-sand mix. Mycorrhizal colonization was higher in the control than in saline soil conditions. Shoot and root dry matter yields and leaf area were higher in mycorrhizal than in nonmycorrhizal plants. Total accumulation of P, Zn, Cu, and Fe was higher in mycorrhizal than in nonmycorrhizal plants under both control and medium salt stress conditions. Shoot Na concentrations were lower in mycorrhizal than in nonmycorrhizal plants grown under saline soil conditions. The improved growth and nutrient acquisition in tomato demonstrate the potential of AMF colonization for protecting plants against salt stress in arid and semiarid areas. Accepted: 21 February 2000     

Response of two tomato cultivars differing in salt tolerance to inoculation with mycorrhizal fungi under salt stress

Effects of arbuscular mycorrhizal fungi (AMF) and salt stress on nutrient acquisition and growth of two tomato cultivars exhibiting differences in salt tolerance were investigated. Plants were grown in a sterilized, low-P (silty clay) soil-sand mix. Salt was applied at saturation extract (EC_e) values of 1.4 (control), 4.9 (medium) and 7.1 dS m^–1 (high salt stress). Mycorrhizal colonization occurred irrespective of salt stress in both cultivars, but AMF colonization was higher under control than under saline soil conditions. The salt-tolerant cultivar Pello showed higher mycorrhizal colonization than the salt-sensitive cultivar Marriha. Shoot dry matter (DM) yield and leaf area were higher in mycorrhizal than nonmycorrhizal plants of both cultivars. Shoot DM and leaf area but not root DM were higher in Pello than Marriha. The enhancement in shoot DM due to AMF inoculation was 22% and 21% under control, 31% and 58% under medium, and 18% and 59% under high salinity for Pello and Marriha, respectively. For both cultivars, the contents of P, K, Zn, Cu, and Fe were higher in mycorrhizal than nonmycorrhizal plants under control and medium saline soil conditions. The enhancement in P, K, Zn, Cu, and Fe acquisition due to AMF inoculation was more pronounced in Marriha than in the Pello cultivar under saline conditions. The results suggest that Marriha benefited more from AMF colonization than Pello under saline soil conditions, despite the fact that Pello roots were highly infected with the AMF. Thus, it appears that Marriha is more dependent on AMF symbiosis than Pello. Accepted: 22 January 2001     

Changes in water relations,photosynthetic activity and proline accumulation in one-year-old olive trees (<Emphasis Type="Italic">Olea europaea</Emphasis> L. cv. Chemlali) in response to NaCl salinity

The comparative responses of young olive trees (Olea europaea L. cv “Chemlali”) to different NaCl salinity levels were investigated over 11 months. One-year-old own rooted plants were grown in 10-L pots containing sand and perlite mixture (1:3 v/v). Trees were subjected to three irrigation treatments: CP (control plants that were irrigated with fresh water); SS1 (salt stressed plants irrigated with water containing 100 mM NaCl) and SS2 plants (salt stressed plants irrigated with water containing 200 mM NaCl). Shoot elongation rate, relative water content, leaf water potential and net carbon dioxide exchange rates decreased significantly with increased NaCl salinity level. Under stressed conditions, the increase of Na⁺ and Cl⁻ ions in both leaves and roots was accompanied with that of proline and soluble sugars. The above results show that the accumulation of proline and sugars under stressed conditions could play a role in salt tolerance. The absence of toxicity symptoms under both stress treatments and the superior photosynthetic activity recorded in SS1-treated plants suggest that cv Chemlali is better able to acclimatize to 100 mM NaCl than at 200 mM NaCl. Our findings indicate that saline water containing 100 mM NaCl, the most available water in arid region in Tunisia, can be recommended for the irrigation of cv Chemlali in the arid south of Tunisia.     

Long‐term effect of salinity on plant quality,water relations,photosynthetic parameters and ion distribution in Callistemon citrinus

The effect of saline stress on physiological and morphological parameters in Callistemon citrinus plants was studied to evaluate their adaptability to irrigation with saline water. C. citrinus plants, grown under greenhouse conditions, were subjected to two irrigation treatments lasting 56 weeks: control (0.8 dS·m^?1) and saline (4 dS·m^?1). The use of saline water in C. citrinus plants decreased aerial growth, increased the root/shoot ratio and improved the root system (increased root diameter and root density), but flowering and leaf colour were not affected. Salinity caused a decrease in stomatal conductance and evapotranspiration, which may prevent toxic levels being reached in the shoot. Net photosynthesis was reduced in plants subjected to salinity, although this response was evident much later than the decrease in stomatal conductance. Stem water potential was a good indicator of salt stress in C. citrinus. The relative salt tolerance of Callistemon was related to storage of higher levels of Na⁺ and Cl^? in the roots compared with the leaves, especially in the case of Na⁺, which could have helped to maintain the quality of plants. The results show that saline water (around 4 dS·m^?1) could be used for growing C. citrinus commercially. However, the cumulative effect of irrigating with saline water for 11 months was a decrease in photosynthesis and intrinsic water use efficiency, meaning that the interaction of the salinity level and the time of exposure to the salt stress should be considered important in this species.     

Boron and salinity effects on grafted and non-grafted melon plants

Production of melon (Cucumis melo) may be limited by excesses of boron and salinity, and it was hypothesized that melon grafted onto Cucurbita rootstock would be more tolerant to excessive boron concentrations than non-grafted plants. The objectives of this study were (i) to determine the effects of salinity and excessive boron concentrations in irrigation water on growth and yields of grafted and non-grafted melon plants; and (ii) to study the interaction between the effects of salinity and boron on the uptake of macroelements and boron by grafted and non-grafted melon plants. The plants were grown in pots of Perlite in a greenhouse. The combined effects of boron and salinity on growth and yield were investigated for five boron concentrations, ranging from 0.2 to 10 mg L^{− 1}, and two salinity levels, electrical conductivity (EC) 1.8 and 4.6 dS m^{− 1}, in the irrigation water. With low salinity the boron concentrations in old leaves of non-grafted and grafted plants ranged from 249 to 2827 and from 171 to 1651 mg kg^{− 1} dry weight, respectively; with high salinity the corresponding concentrations ranged from 192 to 2221 and from 200 to 1263 mg kg^{− 1} dry weight, respectively. These results indicate that the grafted plants accumulated less boron than the non-grafted plants when they were exposed to similar boron concentrations, and that both plant types absorbed less boron when irrigated with the more saline irrigation water. It is suggested that: (i) the Cucurbita rootstock excluded some boron and that this, in turn, decreased the boron concentration in the grafted plants; and (ii) the low boron uptake under high-salinity irrigation was mainly a result of reduced transpiration of the plants. Significant negative linear regressions were found between fruit yield and leaf boron concentration for grafted plants, under both low and high salinity levels, and for non-grafted plants under low salinity. The fruit yield of the grafted plants was less affected by boron accumulation in the leaves than that of non-grafted plants. Increasing the water salinity decreased the sensitivity of both plant types to increases in leaf boron concentration, which indicates that the effects of boron and salinity on melon plants were not additive.     

Arbuscular mycorrhiza influences carbon‐use efficiency and grain yield of wheat grown under pre‐ and post‐anthesis salinity stress

• Soil salinity severely affects and constrains crop production worldwide. Salinity causes osmotic and ionic stress, inhibiting gas exchange and photosynthesis, ultimately impairing plant growth and development. Arbuscular mycorrhiza (AM) have been shown to maintain light and carbon use efficiency under stress, possibly providing a tool to improve salinity tolerance of the host plants. Thus, it was hypothesized that AM will contribute to improved growth and yield under stress conditions.
• Wheat plants (Triticum aestivum L.) were grown with (AMF+) or without (AMF?) arbuscular mycorrhizal fungi (AMF) inoculation. Plants were subjected to salinity stress (200 mm NaCl) either at pre‐ or post‐anthesis or at both stages. Growth and yield components, leaf chlorophyll content as well as gas exchange parameters and AMF colonization were analysed.
• AM plants exhibited a higher rate of net photosynthesis and stomatal conductance and lower intrinsic water use efficiency. Furthermore, AM wheat plants subjected to salinity stress at both pre‐anthesis and post‐anthesis maintained higher grain yield than non‐AM salinity‐stressed plants.
• These results suggest that AMF inoculation mitigates the negative effects of salinity stress by influencing carbon use efficiency and maintaining higher grain yield under stress.

     

The impact of arbuscular mycorrhizal fungi in mitigating salt-induced adverse effects in sweet basil (Ocimum basilicum L.)

Salinity is one of the serious abiotic stresses adversely affecting the majority of arable lands worldwide, limiting the crop productivity of most of the economically important crops. Sweet basil (Osmium basilicum) plants were grown in a non-saline soil (EC = 0.64 dS m⁻¹), in low saline soil (EC = 5 dS m⁻¹), and in a high saline soil (EC = 10 dS m⁻¹). There were differences between arbuscular mycorrhizal (Glomus deserticola) colonized plants (+AMF) and non-colonized plants (−AMF). Mycorrhiza mitigated the reduction of K, P and Ca uptake due to salinity. The balance between K/Na and between Ca/Na was improved in +AMF plants. Growth enhancement by mycorrhiza was independent from plant phosphorus content under high salinity levels. Different growth parameters, salt stress tolerance and accumulation of proline content were investigated, these results showed that the use of mycorrhizal inoculum (AMF) was able to enhance the productivity of sweet basil plants under salinity conditions. Mycorrhizal inoculation significantly increased chlorophyll content and water use efficiency under salinity stress. The sweet basil plants appeared to have high dependency on AMF which improved plant growth, photosynthetic efficiency, gas exchange and water use efficiency under salinity stress. In this study, there was evidence that colonization with AMF can alleviate the detrimental salinity stress influence on the growth and productivity of sweet basil plants.     

Effect of AMF application on growth, productivity and susceptibility to Verticillium wilt of olives grown under desert conditions

The effect of arbuscular mycorrhizal fungi (AMF) on olive (Olea europaea) growth and development was followed for 4 years after transplanting in irrigated commercial orchards under arid conditions. Sites I and II were irrigated with saline water (EC?=?4.5 dS/m). In site I, the soil was infested with Verticillium dahliae and olive varieties ‘Picual’ (Verticillium susceptible) and ‘Barnea’ (relatively Verticillium tolerant) were tested. In site II, the soil was virgin soil (previously non-cultivated soil) and olive varieties ‘Souri’ and ‘Barnea’ were tested. Plants for all sites were inoculated in the nursery with Glomus intraradices alone or in a mixture with G. mosseae. Relative to non-inoculated trees, AMF colonization enhanced vegetative growth, expressed as tree height and trunk circumference, at all sites. At first commercial harvest, AMF-treated trees had higher fruit and oil yields than non-mycorrhitic controls. Under saline water irrigation, differences between inoculated and non-inoculated treatments were reduced in the slow-growing ‘Souri’ but remained apparent in the modern fast-growing ‘Barnea’. AMF colonization did not appear to improve tolerance of either ‘Picual’ or ‘Barnea’ to V. dahliae, and both were more susceptible than the non-inoculated controls. Thus inoculation of olive plants with AMF improves transplant growth and adaptation in arid areas during the first 3 years of growth and until the first commercial harvesting season.     

Characterization of salt-tolerance mechanisms in mycorrhizal (Claroideoglomus etunicatum) halophytic grass,Puccinellia distans

Responses of Puccinellia distans, a halophytic grass to low (50 mM) and high (200 mM) NaCl salinity, were studied in a sand culture experiment without or with inoculation by arbuscular mycorrhizal fungus (AMF), Claroideoglomus etunicatum isolated from its saline habitat. Plant biomass was not influenced by salinity levels, while a tendency to a higher biomass was observed in AMF plants under both control and saline conditions. Leaf photosynthesis increased by both salinity and AMF inoculation. Despite higher transpiration rate, AMF plants had higher water-use efficiency under sever saline conditions. AMF inoculation decreased proline concentration, but increased significantly leaf osmotic potential. Antioxidative enzymes responded differently to the salt and AMF treatments depending on the salt concentration and plant organ. Nonetheless, salt-induced malondialdehyde accumulation in the leaves diminished by AMF colonization. K and Ca contents were not affected by salt, while fungal colonization increased K in the roots and Ca in both leaves and roots. Our results indicated that enhancement of photosynthesis and ion homeostasis is involved in the tolerance of P. distans to both low and high salinity. AMF inoculation increased plants’ tolerance by augmentation of the above mechanisms accompanied by improvement of water relations and protection against oxidative damage in the leaves.     

不同强度盐胁迫下AM真菌对羊草生长的影响

不同浓度NaCl盐处理下,AM真菌对羊草(Leymus chinensis)的侵染能力和对植物生长的影响,从植物形态和离子含量角度探讨了AM真菌提高羊草耐盐性的作用机理。结果表明,在高盐胁迫下,AM真菌显著降低了盐胁迫效应,提高了羊草生物量,菌根效应明显。菌根化羊草的根茎比显著增加,并且N、P浓度较高,Na~+和Cl~-离子浓度较低,表明AM真菌即促进羊草对营养元素的吸收,又减少了离子毒害。菌根化羊草的Ca~(2+)和K~+离子浓度,以及P/Na~+和K~+/Na~+比高于非菌根化羊草,表明AM真菌可通过调节渗透势以避免或减缓盐胁迫造成的生理缺水。随着盐胁迫的增加,菌根化羊草对磷的依赖性逐渐转换为对钾的依赖性。研究结果有助于揭示AM真菌提高植物耐盐能力的作用机理,并对应用菌根技术修复盐化草地具有理论指导意义。     

Effects of NaCl salinity and water stress on growth and leaf water relations of Asteriscus maritimus plants

Potted plants of Asteriscus maritimus (L.) Less were submitted to water stress (during two consecutive cycles, irrigation water was withheld for 5 days followed by a recovery period of 25 days) and saline stress (150 days of exposure to 0, 70 and 140 mM NaCl daily irrigation) in order to assess the effect on leaf water relations and growth parameters. Plants under saline and water stress conditions showed lower biomass and an early reduction in leaf expansion growth. Both stresses promoted a substantial degree of stomatal regulation; but, in spite of this, the plants showed signs of leaf tissue dehydration, decreases in RWC and Ψ_pd values. However, salt-treated plants, developed a NaCl inclusion mechanisms, underwent osmotic adjustment, which was able to maintain leaf turgor. Under both stress conditions g_l was independent to plant water status in the range between –0.8 and 1.0 MPa. Under water stress conditions, midday leaf water potential showed a threshold value (around −1.1 MPa), below which leaf conductance remained constant. In the salt-treated plants, the gradual closure of the stomata over a wide range of Ψ_md may be important in maintaining some level of photosynthesis.     

Investigation of the effects of Vesicular Arbuscular Mycorrhiza on mineral nutrition and growth of <Emphasis Type="Italic">Carthamus tinctorius</Emphasis> under salt stress conditions

Salt stress is considered as one of the most important abiotic factors limiting plant growth and yield in many areas of the world. It has been shown that Vesicular Arbuscular Mycorrhizal Fungi (AMF) can alleviate this deficiency. The effects of AMF inoculation on growth variables and mineral nutrition of Carthamus tinctorius L. under salt stress condition were studied. Plants were grown in a sterilized, low-P sandy soil with Glomus etunicatum inoculum (10–12 spore/g soil) in a greenhouse. RLC (Root Length Colonized) percent was higher in control plants than treated ones with different salt concentrations. Shoot and root weights, height, the number of leaves, the number of lateral branches, and also leaf area of mycorrhizal (M) plants were higher than nonmycorrhizal (NM) ones in both controlled and salt-treated plants. P, Zn, Fe, Ca, K, Cu, and N contents in M plants were higher than in NM plants in control, low and medium salinity conditions, but Na content was lower in aerial parts of the M plants. The results showed a higher tolerance of inoculated M plants toward salt stress and their better growth.     

Improving growth, flower yield, and water relations of snapdragon (Antirhinum majus L.) plants grown under well-watered and water-stress conditions using arbuscular mycorrhizal fungi

The influence of arbuscular mycorrhizal (AM) fungus Glomus deserticola (Trappe and John) on plant growth, nutrition, flower yield, water relations, chlorophyll (Chl) contents and water-use efficiency (WUE) of snapdragon (Antirhinum majus cv. butterfly) plants were studied in potted culture under well-watered (WW) and water-stress (WS) conditions. The imposed water stress condition significantly reduced all growth parameters, nutrient contents, flower yield, water relations, and Chl pigment content and increased the electrolyte leakage of the plants comparing to those of nonstressed plants. Regardless of the WS level, the mycorrhizal snapdragon plants had significantly higher shoot and root dry mass (DM), WUE, flower yield, nutrient (P, N, K, Mg, and Ca) and Chl contents than those nonmycorrhizal plants grown both under WW or WS conditions. Under WS conditions, the AM colonization had greatly improved the leaf water potential (??_w), leaf relative water content (RWC) and reduced the leaf electrolyte leakage (EL) of the plants. Although the WS conditions had markedly increased the proline content of the leaves, this increase was significantly higher in nonmycorrhizal than in mycorrhizal plants. This suggests that AM colonization enhances the host plant WS tolerance. Values of benefit and potential dry matter for AM-root associations were highest when plants were stressed and reduced under WW conditions. As a result, the snapdragon plants showed a high degree of dependency on AM fungi which improve plant growth, flower yield, water relations particularly under WS conditions, and these improvements were increased as WS level had increased. This study confirms that AM colonization can mitigate the deleterious effect of water stress on growth and flower yield of the snapdragon ornamental plant.     

Exogenous proline effects on water relations and ions contents in leaves and roots of young olive

The ability of exogenous compatible solutes, such as proline, to counteract salt inhibitory effects was investigated in 2-year-old olive trees (Olea europaea L. cv. Chemlali) subjected to different saline water irrigation levels supplied or not with exogenous proline. Leaf water relations [relative water content (RWC), water potential], photosynthetic activity, leaf chlorophyll content, and starch contents were measured in young and old leaves. Salt ions (Na⁺, K⁺, and Ca²⁺), proline and soluble sugars contents were determined in leaf and root tissues. Supplementary proline significantly mitigated the adverse effects of salinity via the improvement of photosynthetic activity (Pn), RWC, chlorophyll and carotenoid, and starch contents. Pn of young leaves in the presence of 25 mM proline was at 1.18 and 1.38 times higher than the values recorded under moderate (SS1) and high salinity (SS2) treatments, respectively. Further, the proline supply seems to have a more important relaxing effect on the photosynthetic chain in young than in old leaves of salt-stressed olive plants. The differential pattern of proline content between young and old leaves suggests that there would be a difference between these tissues in distinguishing between the proline taken from the growing media and that produced as a result of salinity stress. Besides, the large reduction in Na⁺ accumulation in leaves and roots in the presence of proline could be due to its interference in osmotic adjustment process and/or its dilution by proline supply. Moreover, the lower accumulation of Na⁺ in proline-treated plants, compared to their corresponding salinity treatment, displayed the improved effect of proline on the ability of roots to exclude the salt ions from the xylem sap flowing to the shoot, and thus better growth rates.     

Carbon balance and water relations of sorghum exposed to salt and water stress

The daily (24 hour) changes in carbon balance, water loss, and leaf area of whole sorghum plants (Sorghum bicolor L. Moench, cv BTX616) were measured under controlled environment conditions typical of warm, humid, sunny days. Plants were either (a) irrigated frequently with nutrient solution (osmotic potential −0.08 kilojoules per kilogram = −0.8 bar), (b) not irrigated for 15 days, (c) irrigated frequently with moderately saline nutrient (80 millimoles NaCl + 20 millimoles CaCl₂·2H₂O per kilogram water, osmotic potential −0.56 kilojoules per kilogram), or (d) preirrigated with saline nutrient and then not irrigated for 22 days.

Under frequent irrigation, salt reduced leaf expansion and carbon gain, but water use efficiency was increased since the water loss rate was reduced more than the carbon gain. Water stress developed more slowly in the salinized plants and they were able to adjust osmotically by a greater amount. Leaf expansion and carbon gain continued down to lower leaf water potentials.

Some additional metabolic cost associated with salt stress was detected, but under water stress this was balanced by the reduced cost of storing photosynthate rather than converting it to new biomass. Reirrigation produced a burst of respiration associated with renewed synthesis of biomass from stored photosynthate.

It is concluded that although irrigation of sorghum with moderately saline water inhibits plant growth in comparison with irrigation with nonsaline water, it also inhibits water loss and allows a greater degree of osmotic adjustment, so that the plants are able to continue growing longer and reach lower leaf water potentials between irrigations.

     

Ornamental characters,ion accumulation and water status in Arbutus unedo seedlings irrigated with saline water and subsequent relief and transplanting

Arbutus unedo seedlings were grown in a greenhouse and submitted to three irrigation treatments (salinity period) using solutions with an EC of 0.85 dS m^?1 (control treatment), 5.45 dS m^?1 (S1) and 9.45 dS m^?1 (S2). After 16 weeks, growth and ornamental characters, leaf water potentials, gas exchange and ion concentrations were determined. After the salinity period, plants were exposed to a relief period for 1 month, whereby half of the plants were transplanted to field conditions and the other half into 24 cm diameter plastic pots. Salinity induced a significant decrease in shoot biomass and leaf area but root/shoot ratio was increased. Plant height was significantly inhibited by salinity. The ornamental characters were affected in the treated plants, with symptoms of salt injury, such as burning of leaf margin. Leaf water potentials decreased with increasing salinity, more significantly at predawn than at midday. The relationship between net photosynthesis (P_n) and leaf conductance (g_l) was linear for all treatments and the same values of P_n are associated with lower values of g_l for the saline treatments than for control treatment. The concentration of Cl^? in leaves increased with increasing salinity and was higher than the corresponding concentration of Na⁺. Na⁺ and Cl^? contents were higher in the leaves than in the roots in both saline treatments. The K⁺ and Ca²⁺ levels were lower in the treated plants than in control plants and applied salinity reduced the K⁺/Na⁺ ratio in leaves, stems and roots, the decrease being much greater for leaves than for roots. The Ca²⁺/Na⁺ ratio fell with salinity in all parts of the plants. At the end of the relief period leaf water potentials were recovered mainly in field conditions. S2 treatment showed lower values of P_n and g_l than control and S1 treatments in pot conditions and in field conditions S1 showed the lowest values for P_n and g_l.     

Alleviation of phosphorus deficiency stress by moderate salinity in the halophyte <Emphasis Type="Italic">Hordeum maritimum</Emphasis> L.

Hordeum maritimum (Poacea) is a facultative halophyte potentially useful for forage production in saline zones. Here, we assessed whether moderate NaCl-salinity can modify the plant response to phosphorus (P) shortage. Plants were cultivated for 55 days under low or sufficient P supply (5 or 60 μmol plant⁻¹ week⁻¹ KH₂PO₄, respectively), with or without 100 mM NaCl. When individually applied, salinity and P deficiency significantly restricted whole-plant growth, with a more marked effect of the latter stress. Plants subjected to P deficiency showed a significant increase in root growth (as length and dry weight) and root/shoot DW ratio. Enhanced root growth and elongation presumably correspond to the well-known root adaptive response to mineral deficiency. However, leaf relative water content, leaf P concentration, and leaf gas exchange parameters were significantly restricted. The interactive effects of salinity and P deficiency were not added one to another neither on whole plant biomass nor on plant nutrient uptake. Indeed, 100 mM NaCl-addition to P-deficient plants significantly restored the plant growth and improved CO₂ assimilation rate, root growth, K⁺/Na⁺ ratio and leaf proline and soluble sugar concentrations. It also significantly enhanced leaf total antioxidant capacity and leaf anthocyanin concentration. This was associated with significantly lower leaf osmotic potential, leaf Na⁺ and malondialdehyde (MDA) concentration. Taken together, these results suggest that mild salinity may mitigate the adverse effects of phosphorus deficiency on H. maritimum by notably improving the plant photosynthetic activity, the osmotic adjustment capacity, the selective absorption of K⁺ over Na⁺ and antioxidant defence.     

Salinity,water use and yield of maize: Testing of the mathematical model ecosys

There is a need to establish how root water uptake should be calculated under saline conditions, and to test calculated uptake against experimental data recorded under documented site conditions. In this study, the ecosystem simulation model ecosys was expanded to include an ion transfer-equilibrium-exchange model used to calculated electrical conductivity and osmotic potential. This expanded model was tested against experimental data for maize growth and water use reported under different irrigation and salinity levels at four different sites in the western U.S. to determine if salinity effects on crop growth and water use could be modelled from the effects of salinity on soil osmotic potential. The model was able to reproduce reductions in water use and phytomass yields on salinized (10 g total salts kg^–1 water) soils that ranged from 10 to 50% of those on non-salinized controls. In general, these reductions increased with increasing irrigation deficits. These reductions arose in the model from reduced canopy water potentials and conductances caused by reduced osmotic potentials in the saline soils. The hypothesis that salinity effects on crop growth and water use are caused by salinity effects on soil osmotic potential appear to be supported under the range of conditions included in this study. Models such as ecosys that are based on general hypotheses for the effects of salinity upon biological activity may be well adapted for general use in assessing the effects of salinity on crop growth and water use with different soils, managements and climates.     

Nondestructive leaf-area estimation and validation for green pepper (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.) grown under different stress conditions

Leaf area of a plant is essential to understand the interaction between plant growth and environment. This useful variable can be determined by using direct (some expensive instruments) and indirect (prediction models) methods. Leaf area of a plant can be predicted by accurate and simple leaf area models without damaging the plant, thus, provide researchers with many advantages in horticultural experiments. Several leaf-area prediction models have been produced for some plant species in optimum conditions, but not for a plant grown under stress conditions. This study was conducted to develop leaf area estimation models by using linear measurements such as lamina length and width by multiple regression analysis for green pepper grown under different stress conditions. For this purpose, two experiments were conducted in a greenhouse. The first experiment focused to determine leaf area of green pepper grown under six different levels of irrigation water salinity (0.65, 2.0, 3.0, 4.0, 5.0, and 7.0 dS m⁻¹) and the other under four different irrigation regime (amount of applied water was 1.43, 1.0, 0.75, and 0.50 times of required water). In addition to general models for each experiment, prediction models of green pepper for each treatment of irrigation water salinity and of irrigation regime experiments were obtained. Validations of the models for both experiments were realized by using the measurements belong to leaf samples allocated for validation purposes. As a result, the determined equations can simply and readily be used in prediction of leaf area of green pepper grown under salinity and water stress conditions. The use of such models enable researchers to measure leaf area on the same plants during the plant growth period and, at the same time, may reduce variability in experiments.     

Types of Irrigation Water and Soil Amendment Affect the Growth and Flowering of <i>Petunia x alkinsiana</i> ‘Bravo Pinc’

Water insufficiency is the hampering feature of crop sustainability, especially in arid and semi-arid regions. So, the effectual usage of all water resources especially underground brackish water represents the core priority in Saudi Arabia. The present study aimed to recognize the influence of different types of water irrigation (tap water as a control, salinized well water, and magnetized salinized well water) with or without soil amendments (soil without any amendment as a control, peat-moss, ferrous sulfate, and peat-moss plus ferrous sulfate) on petunia plant growth and flowering as well as ion content. Irrigating Petunia plants with saline well water adversely affected growth and flowering as compared to tap water and magnetized saline well water. Additionally, plants irrigated with magnetized water showed a significant enhancement in all the studied vegetative and flowering growth parameters as compared to those irrigated with salinized well water. Furthermore, mineral contents and survival of Petunia plants irrigated with magnetized well water were higher than those irrigated with tap water. Irrigation with magnetized well water significantly reduced levels of Na⁺ and Cl⁻ ions in leaves of Petunia plants indicating the role of magnetization in alleviating harmful effects of salinity. In conclusion, we recommend the utilization of magnetized saline well water for irrigating Petunia plants either alone or in combination with soil amendments (peat moss plus ferrous sulfate).