Wirkung einer Abscisinsäure-Applikation auf die Cl−Translokation in Sojabohnen bei niedriger und hoher Besalzung des Nährmediums

Effect of abscisic acid in the root medium on Cl^? translocation in soybeans under low and high salt conditions With soybeans of the varieties ?Lee”? and ?Jackson”? the effect of abscisic acid (ABA) applied to the root medium in different concentrations (10^?4, 10^?5 and 10^?6M) on Cl^? translocation was investigated. Under low salt conditions (0,5 mM NaCl) ABA, depending on its concentration, strongly decreased Cl^? translocation to the shoot. At the highest ABA concentration, within 24 h the Cl^? content of the shoots was reduced to about 40 % of the control, the Cl^? accumulation within the roots was reduced about 25 %. However, the 10^?5 and the 10^?6M ABA treatment increased Cl^? accumulation in the roots but decreased Cl^? translocation to the shoot. Under high salt conditions (75 mM NaCI) ABA had no measureable effect on CI- translocation to the shoot. It was found that the genetic mechanism responsible for high CI- accumulation within the roots of ?Lee”? and high CI- translocation to the shoot of ?Jackson”? was not affected by ABA. ABA strongly inhibited transpiration. High ABA concentration in combination with low salt treatment decreased the transpiration rate up to 50 % of the control. ABA also inhibited transpiration under high salt conditions. This result is discussed considering the fact, that ABA added to the highly saline nutrient solution did not decrease the CI- translocation to the shoot. An investigation using ¹⁴C-ABA showed, the radioactive substance was taken up by the roots and translocated to the shoot independently from the salt treatment. The metabolism of the radioactive substance was different for roots and leaves. However, no difference could be observed by comparing the two soybeans varieties with or without salt treatment.     

Short-term studies on the uptake and transport of Cl− by soybean cultivars differing in salt tolerance

Short-term tracer experiments (³⁶Cl) were conducted with the differentially salt susceptible soybean cultivars “Lee” (moderately tolerant) and “Jackson” (sensitive) to elucidate the pattern of Cl^? uptake and translocation in relation to the physiology of salt tolerance. Rates of Cl^? uptake by excised roots of “Jackson” were much greater in the lower (0.1–0.5 mM NaCl) and particularly in the higher concentration range than by the more tolerant cultivar. The transfer rate to the shoot was significantly higher in “Jackson” than in “Lee” and increased with time of treatment. The cultivar “Lee” translocated a relatively high amount of Cl^? during the onset of salt treatment, but in contrast to “Jackson” was then able to slow down Cl^? translocation into the shoot to a degree about proportional to the increment of dry matter. In experiments on secondary translocation both cultivars extruded substantial amounts of ³⁶Cl^? to the nutrient solution during the period in inactive solution with constant salinity following labeling. Possibly, some Cl^? that had moved into the leaves during labeling was retranslocated and extruded via the roots. The absolute efflux rate was presumably greater for “Jackson” than for “Lee” although it appeared not efficient enough to compensate for the high rate of influx into the root. After 5–6 days of secondary translocation a lesser amount of Cl^? was shifted from the root to the shoot in “Lee” as compared with “Jackson”. Chloride accumulation in the upper root and lower stem, similar to that reported for Na⁺ in several Na⁺ excluding species, was not observed. From the results it may be concluded that the cultivar “Jackson” cannot sufficiently control the uptake of Cl^? and its translocation, particularly into the mature leaves; this contributes causally to the development of severe injury under continuous salt stress.     

Studies on growth and distribution of Na+, K+ and Cl− in soybean varieties differing in salt tolerance

Soybean plants, varieties “Lee”, “Jackson” and “Bragg” were grown in solution culture at various salinity levels. A NaCl concentration of 10 mM was already inhibitory to growth of “Jackson”; growth of “Lee”, however, was only reduced at a salt concentration of 50 mM or higher. The moderately salt tolerant variety “Lee” efficiently excluded Cl^? from the leaves up to about 50 mM NaCl in the medium, but showed high Cl^? contents in the root; exclusion of Na⁺ from the leaves was also apparent in this variety. On the other hand, the salt sensitive variety “Jackson” did not have the capacity for exclusion of Cl^? and Na⁺. The physiological behaviour of the variety “Bragg” resembled that of “Jackson”. It is suggested that the exclusion of Cl^? and Na⁺ from the leaves in the soybean variety “Lee” is regulated by the root.     

Influence of extreme K:Na ratios and high substrate salinity on plant metabolism of crops differing in salt tolerance

Mineral regulation of two soybean varieties Jackson and Lee was investigated in long term water culture experiments using saline solutions. The effects of extreme K:Na ratios using chloride and sulfate as counterions were studied in the early stages of salinity.

The growth rates of both varieties were not affected by salinization. A K⁺ stimulated, intensive acropetal Cl^‐ translocation was observed in the salt sensitive variety Jackson. The varieties did not differ in Na⁺ translocation and in the suppression of Ca²⁺ and Mg²⁺ in the leaves. But the effect of the nature of salinization indicates already differences in Na uptake and translocation of the cultivars.

The avoidance of Cl^‐, but also of Ha⁺, in connection with influences of the resulting ionic imbalance on metabolic pathways are probably the most causative factors for the different tolerance to salinity of the two soybean varieties.     

Effects of salt stress on distribution of Na+ and some other cations in two soybean varieties differing in salt tolerance

In the course of investigations on the impact of salinity on mineral ion transport in differentially salt susceptible soybeans (“Lee” and “Jackson”) short-term experiments were conducted to elucidate the distribution pattern of Na⁺ and some other cations. The results showed that low salinity (7.5 mM NaCl) did not induce varietal differences in Na⁺ content during a 30 hrs uptake period. At 66.5 mM NaCl, however, the Na⁺ contents increased more in the leaves of the salt sensitive variety “Jackson” than in “Lee”. Both soybean varieties retained Na⁺ in the proximal root and stem. Furthermore, they extruded considerable amounts of Na⁺ from the roots to the medium. Increasing the level of salinity in the solution substantially reduced the Ca²⁺ uptake of both soybean varieties. In an experiment with the salt sensitive variety under constant salinity but increasing Ca²⁺ concentration in the medium, the plants showed a reduction in Na⁺ uptake and translocation to stem and leaves and an enhanced Ca²⁺ uptake and translocation to the shoots. It is suggested that the injury observed in “Jackson” after salt treatment is not only related to the insufficient control of Cl^? transport. At higher salinity levels the increasing accumulation of Na⁺ in the leaves and the varietally independant depression of Ca²⁺ uptake and translocation may enhance the development of leaf necrosis.     

Influence of extreme K:Na ratios and high substrate salinity on plant metabolism of crops differing in salt tolerance

Abstract

Ion‐specific initial salt effects due to supply of extreme K⁺, Na⁺, Cl or SO₄ ^2‐ combinations were studied on the carbohydrate pattern as well as on the activity of amylases, phosphorylase and invertase of two soybean varieties, Jackson and the more tolerant Lee.

Reducing sugars were little affected. Salinity increased leaf sucrose more in Jackson than in Lee, and more due to Cl^? than to SO₄ ^2‐ supply. Salinity increased the higher level of root sucrose in Lee less than the lower sucrose level in Jackson, independent of the nature of salination. Salinity increased leaf starch more in Jackson than in Lee. KCl increased leaf starch of Jackson most, Na₂SO₄. least. KCl increased leaf starch of Lee more than NaCl, while K₂SO₄ and Na₂SO₄ tended to decrease leaf starch. Only KCl stimulated amylases and phosphorylase in leaves of Jackson. Salinity changed amylases according to the starch content in leaves of Lee, while phosphorylase decreased independent of the ion combination supplied. Salinity decreased invertase in leaves of Jackson, it affected invertase in Lee only little.

It is suggested that the carbohydrate metabolism dependent and independent of ionic regulation contribute to physiological salt tolerance mechanisms of soybean varieties.     

Protective role of proline against salt stress is partially related to the improvement of water status and peroxidase enzyme activity in cucumber

Abstract

A salt-sensitive cucumber cultivar “Jinchun No. 2” (Cucumis sativus L.) was used to investigate the role of proline in alleviating salt stress in cucumber. Proline was applied twice (day 0 and day 4 after salt treatment) as a foliar spray, with a volume of 25?mL per plant at each time. Plant dry weight, leaf relative water content, proline, malondialdehyde (MDA), Na⁺, K⁺ and Cl^? contents, as well as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) activities in the plants were determined at day 8 after salt treatment. The results showed that 100?mmol?L^–1 NaCl stress significantly decreased plant dry weight, leaf relative water and K⁺ contents, and increased leaf MDA, Na⁺ and Cl^? contents and SOD, POD, CAT and APX activities. However, leaf proline accumulation was not affected by salinity. The exogenous application of proline significantly alleviated the growth inhibition of plants induced by NaCl, and was accompanied by higher leaf relative water content and POD activity, higher proline and Cl^? contents, and lower MDA content and SOD activity. However, there was no significant difference in Na⁺ and K⁺ contents or in CAT and APX activities between proline-treated and untreated plants under salt stress. Taken together, these results suggested that the foliar application of proline was an effective way to improve the salt tolerance of cucumber. The enhanced salt tolerance could be partially attributed to the improved water status and peroxidase enzyme activity in the leaf.     

COMPARISON OF OSMOTIC REGULATION IN DEHYDRATION- AND SALINITY-STRESSED SUNFLOWER SEEDLINGS

Plant dry matter accumulation rate (DMAR), relative water content (RWC), electrolyte leakage percentage (ELP), chlorophyll content, osmotic adjustment ability (OAA), and osmotica accumulation in leaves of sunflower (Helianthus annuus L.) seedlings under different levels of dehydration and salinity stress induced by iso-osmotic PEG (polyethylene glycol) or sodium chloride (NaCl) were evaluated. Plants were subjected to four stress treatments for 10 days: ?0.44 MPa PEG6000, ?0.44 MPa NaCl, ?0.88 MPa PEG6000, ?0.88 MPa NaCl. Results showed that PEG and NaCl treatments decreased the plant's DMAR and RWC, and NaCl treatments had more severe inhibitory effect on the plants than PEG treatments. Leaf ELP in sunflower seedlings increased after NaCl and PEG treatments. However, leaf ELP under salt stress was higher than that under dehydration stress (PEG treatment). All stress treatments increased OAA in plant leaves. Leaf OAA was enhanced significantly as PEG concentration increases, while leaf OAA was less enhanced at higher concentration of NaCl. OAA of sunflower leaves under dehydration stress was due to an increase in potassium (K⁺), calcium (Ca²⁺), amino acid, organic acid, magnesium (Mg²⁺), and proline content. OAA of sunflower leaves under moderate salt stress was owing to an increase in K⁺, chlorine (Cl^?), amino acid, organic acid, sodium (Na⁺), and proline content, and was mainly due to an accumulation of K⁺, Cl^?, Na⁺, and proline under severe salt stress.     

CONTRIBUTION OF PROLINE AND INORGANIC SOLUTES TO OSMOTIC ADJUSTMENT IN COTTON UNDER SALT STRESS

Physiological responses to salt stress were investigated in two cotton (Gossypium hirsutum L.) cultivars (Pora and Guazuncho) grown hydroponically under various concentrations of NaCl. Dry matter partitioning, plant water relations, mineral composition and proline content were studied. Proline and inorganic solutes were measured to determine their relative contribution to osmotic adjustment. Both leaf water potential (Ψ_w) and osmotic potential (Ψ_s)decreased in response to NaCl levels. Although Ψ_wand Ψ_s decreased during salt stress, pressure potential Ψ_p remained between 0.5 to 0.7 MPa in control and all NaCl treatments, even under 200 mol m^?3 NaCl. Increased NaCl levels resulted in a significant decrease in root, shoot and leaf growth biomass. Root / shoot ratio increased in response to salt stress. The responses of both cultivars to NaCl stress were similar. Increasing salinity levels increased plant Na⁺ and Cl^?. Potassium level remained stable in the leaves and decreased in the roots with increasing salinity. Salinity decreased Ca²⁺ and Mg²⁺ concentrations in leaves but did not affect the root levels of these nutrients. The K/Na selectivity ratio was much greater in the saline treated plants than in the control plants. Osmotic adjustment of roots and leaves was predominantly due to Na⁺ and Cl^? accumulation; the contribution of proline to the osmotic adjustment seemed to be less important in these cotton cultivars.     

Water deficit and abscisic acid production of Salicornia bigelovii under salinity stress

We investigated the mechanism of growth reduction of dicotyledonous halophyte Salicornia bigelovii under salinity stress by growing it at 0.005 to 500?mol?m^?3 sodium chloride (NaCl). The optimal range for growth of S. bigelovii was between 50 and 200?mol?m^?3 NaCl. A significant correlation was found between growth and water content, which indicated that water deficit was an important factor in growth reduction at both suboptimal and supraoptimal salinities. Abscisic acid (ABA) concentration of the shoot was negatively related to growth and water content, which suggested that ABA induced by water deficit may inhibit growth at both the suboptimal and supraoptimal salinities. The cause of water deficit at supraoptimal salinity might be caused by nutritional imbalance and osmotic stress due to the low osmotic potential of the external solution. However, limited salt uptake may be one of the causes of water deficit under suboptimal salinity. We discuss a sodium ion (Na⁺) specific deficit rather than salt deficit as another possible cause of water deficit.     

The influence of high salt stress on starch,sucrose and degradative enzymes of two glycine max varieties that differ in salt tolerance

Salt stress effects were investigated on growth, the carbohydrate levels and the activity of degradative enzymes amylases, phosphorylase and invertase of two soybean varieties, Jackson and the more salt tolerant Lee.

Stress depressed growth of Jackson more than of Lee. Salt stress increased leaf and root sucrose more in Jackson than it did in Lee. Root sucrose was higher in Lee. Stress reduced leaf starch in both. It decreased spec. invertase activity in close negative correlation with the sucrose. Independent from salt tolerance, increased spec. amylase activity was in some correlation with the declined starch level. Stress changed phosphorylase little in both varieties. It is concluded that salt stress‐induced restricted utilization of leaf sucrose, but not foliar starch, could partly be a result of ionic affected degradation, which may diminish survival value of soybean varieties.     

Physiological responses and adaptive strategies of wheat seedlings to salt and alkali stresses

Abstract

Effects of salt (NaCl?:?Na₂SO₄) and alkali (NaHCO₃?:?Na₂CO₃) stresses on the contents of inorganic ions and organic solutes in wheat shoots were compared to explore the physiological responses and adaptive strategies of wheat to these stresses. Wheat significantly accumulated Na⁺ and simultaneously accumulated Cl^?, soluble sugars and proline to maintain osmotic and ionic balance under salt stress. Compared with salt stress, the high pH from alkali stress enhanced Na⁺ accumulation and affected the absorption of inorganic anions. To maintain ionic and osmotic balance, wheat accumulated organic acids, soluble sugars and proline. The accumulation of Cl^? and organic acids was the main difference in the physiological responses and adaptive mechanisms to salt and alkali stresses, respectively.     

Einfluß von Stickstoffernährung und Wuchsstoffapplikation auf die Knolleninduktion bei Kartoffelpflanzen

Influence of nitrogen nutrition and application of growth regulators on tuber initiation in potato plants In water culture the effect of continuous and discontinuous N-nutrition on tuber initiation was investigated. Additional applications of growth regulators on growing stolon tips were carried out. Continuous supply of nitrate or ammonium inhibited completely the tuber initiation in S. tuberosum varieties ?Ostara”? and ?Clivia”?, The inhibition was compensated by application of CCC and ABA on the stolon tip. In contrast to this stolon application of kinetin and root application of CCC were ineffective. Temporarily damaging of the root system led to tuber initiation even when nitrogen was supplied continuously. In S. andigena grown under short day continuous N supply only delayed the tuber initiation but could not prevent it. Discontinuous N supply promotes tuber initiation in S. tuberosum. A sudden increase in N supply caused ?re-growth”? of the tuber, i.e. a stolon was formed on the tuber apex. GA₃ application on the growing tuber had the same effect. The effect of N nutrition on tuber initiation can be explained via changing the balance of endogenous growth regulators in general and the physiological aging of the leaves in particular. Discontinuous N supply seems to reduce cytokinin production in roots and therefore accelerates the aging of the leaves. This in turn favours the formation of inhibitors and/or presumably reduces the GA production in the shoot, which will change the balance of the growth regulators in the stolon tip in favour to tuber initiation.     

INTERACTIVE EFFECTS OF SALINITY AND PHOSPHORUS NUTRITION ON PHYSIOLOGICAL RESPONSES OF TWO BARLEY SPECIES

Salinity is one of the most important agricultural problems in Iran. The effect of different levels of salinity and phosphorus on shoot length, root and shoot fresh and dry weight, nutrient elements (sodium (Na⁺), potassium (K⁺), phosphorus (P) and chloride (Cl^?), proline and soluble sugar contents of barley were investigated. Two cultivars of barley, Hordeum murinum (wild resistant germplasm) and Hordeum vulgar, variety Afzal were treated in vegetative stage under hydroponics condition in a factorial arrangement based on completely randomized block (CRB) design with four levels of salinity [0, 100, 200 and 300 mM sodium chloride (NaCl)] and three levels of phosphorus (15, 30 and 55 μm L^?1) with three replications. By increasing salinity, all the measured parameters, except sodium (Na⁺) content were reduced. Furthermore, with increased in phosphorus levels from 15 to 55 μm, Na⁺ content of the plant shoots decreased, but length, fresh and dry weights of roots and shoots and K⁺, P, Cl^?, proline, and soluble sugars content of the shoots increased. The results indicated that accumulation of mineral ions for osmotic adjustment and restriction of Na⁺ accumulation in shoots were involved in phosphorus enhancement of the salt tolerance of barley. Thus, it seems that in saline soils, where there is no possibility for soil leaching and amending, application of phosphorus fertilizers can lead to a satisfactory growth and production in barely yield.     

Growth,Mineral Composition,and Biochemical Changes of Broad Bean as Affected by Sodium Chloride and Zinc Levels and Sources

Plants grown in salt‐affected soils may suffer from limited available water, ion toxicity, and essential plant nutrient deficiency, leading to reduced growth. The present experiment was initiated to evaluate how salinity and soil zinc (Zn) fertilization would affects growth and chemical and biochemical composition of broad bean grown in a calcareous soil low in available Zn. The broad bean was subjected to five sodium chloride (NaCl) levels (0, 10, 20, 30, and 40 m mol kg^?1 soil) and three Zn rates [0, 5, and 10 mg kg^?1 as Zn sulfate (ZnSO₄) or Zn ethylenediaminetetraaceticacid (EDTA)] under greenhouse conditions. The experiment was arranged in a factorial manner in a completely randomized design with three replications. Sodium chloride significantly decreased shoot dry weight, leaf area, and chlorophyll concentration, whereas Zn treatment strongly increased these plant growth parameters. The suppressing effect of soil salinity on the shoot dry weight and leaf area were alleviated by soil Zn fertilization, but the stimulating effect became less pronounced at higher NaCl levels. Moreover, rice seedlings treated with ZnSO₄ produced more shoot dry weight and had greater leaf area and chlorophyll concentration than those treated with Zn EDTA. In the present study, plant chloride and sodium accumulations were significantly increased and those of potassium (K), calcium (Ca), and magnesium (Mg) strongly decreased as NaCl concentrations in the soil were increased. Moreover, changes in rice shoot Cl^?, Na⁺, and K⁺ concentrations were primarily affected by the changes in NaCl rate and to a lesser degree were related to Zn levels. The concentrations of Cl^? and Na⁺ associated with 50% shoot growth suppression were greater with Zn‐treated plants than untreated ones, suggesting that Zn fertilization might increase the plant tolerance to high Cl^? and Na⁺ accumulations in rice shoot. Zinc application markedly increased Zn concentration of broad bean shoots, whereas plants grown on NaCl‐treated soil contained significantly less Zn than those grown on NaCl‐untreated soil. Our study showed a consistent increase in praline content and a significant decrease in reducing sugar concentration with increasing salinity and Zn rates. However, Zn‐treated broad bean contained less proline and reducing sugars than Zn‐untreated plants, and the depressing impact of applied Zn as Zn EDTA on reducing sugar concentration was greater than that of ZnSO₄. In conclusion, it appears that when broad bean is to be grown in salt‐affected soils, it is highly advisable to supply plants with adequate available Zn.     

Wheat response to combined application of nitrogen and phosphorus in a saline sandy loam soil

Fertilization with nitrogen (N) or phosphorus (P) can improve plant growth in saline soils. This study was undertaken to determine wheat (Triticum aestivum L; cv Krichauff) response to the combined application of N and P fertilizers in the sandy loam under saline conditions. Salinity was induced using sodium (Na⁺) and calcium (Ca²⁺) salts to achieve four levels of electrical conductivity in the extract of the saturated soil paste (EC_e), 2.2, 6.7, 9.2 and 11.8?dS?m^?1, while maintaining a low sodium adsorption ratio (SAR; ≤1). Nitrogen was applied as Ca(NO₃)₂?·?4H₂O at 50 (N50), 100 (N100) and 200 (N200)?mg?N?kg^?1 soil. Phosphorus was applied at 0 (P0), 30 (P30) and 60 (P60)?mg?kg^?1?soil in the form of KH₂PO₄. Results showed that increasing soil salinity had no effect on shoot N or P concentrations, but increased shoot Na⁺ and chlorine ion (Cl^?) concentrations and reduced dry weights of shoot and root in all treatments of N and P. At each salinity and P level, increasing application of N reduced dry weight of shoot. At each salinity and N level P fertilization increased dry weights of shoot and root and shoot P concentration. Addition of greater than N50 contributed to the soil salinity limiting plant growth, but increasing P addition up to 60?mg?P?kg^?1 soil reduced Cl^? absorption and enhanced the plant salt tolerance and thus plant growth. The positive effect of the combined addition of N and P on wheat growth in the saline sandy loam is noticeable, but only to a certain level of soil salinity beyond which salinity effect is dominant.     

Effects of zinc activity in nutrient solution on uptake,translocation, and root export of cadmium and zinc in three wheat genotypes with different zinc efficiencies

The interactions of zinc (Zn) and cadmium (Cd) in uptake and translocation are common but not consistent. We hypothesized that Cd²⁺ and Zn²⁺ activity in the apoplasmic solution bathing root-cells could affect Zn accumulation in plants dependent on the wheat genotype. This hypothesis was tested using seedlings of two bread wheat genotypes (Triticum aestivum L. cvs. Rushan and Cross) and one durum wheat genotype (Triticum durum L. cv. Arya) with different Zn efficiencies grown in chelate-buffered nutrient solutions with three Zn²⁺ (10^?11.11, 10^?9.11, and 10^?8.81?µM) and two Cd²⁺ (10^?11.21 and 10^?10.2?µM) activity levels. Increasing Zn²⁺ activity in the nutrient solution significantly increased Zn concentration in root and shoots of all three wheat genotypes, although the magnitude of this increase was dependent on the genotype. Cadmium decreased Zn concentration in roots of “Cross” while it had no significant effect on root Zn concentration in “Rushan.” At Zn^2+?=?10^?11.11?µM, Cd decreased shoot Zn concentration in “Arya” whereas it increased shoot Zn concentration at Zn^2+?=?10^?8.81?µM. Cadmium increased shoot Zn concentration of “Rushan” and “Cross” at Zn^2+?=?10^?8.81?µM but it had no significant effect on shoot Zn concentration of these genotypes at Zn^2+?=?10^?11.11?µM. The zinc-inefficient genotype “Arya” accumulated significantly more Cd in its root in comparison with “Cross” and “Rushan.” Cadmium concentration in roots of “Arya” was decreased significantly with increasing Zn activity. The effect of Zn on accumulation of Cd in roots of “Cross” and “Rushan” was dependent on the dose provided, and therefore, both synergistic (at Zn^2+?=?10^?9.11?µM) and antagonistic (at Zn^2+?=?10^?8.81?µM) interactive effects were found in these genotypes. Zinc supply increased the Zn concentration of xylem sap in “Cross” and “Rushan” whereas Zn content in xylem sap of “Arya” was decreased at Zn^2+?=?10^?9.11?µM and thereafter increased at Zn^2+?=?10^?8.81?µM. Cadmium treatment reduced Zn concentration in xylem sap of “Arya,” while it tended to increase Zn content in xylem sap of “Cross.” At Zn-deficient conditions, greater retention of Zn in root cell walls of Zn-inefficient “Arya” resulted in lower root-to-shoot transport of Zn in this genotype. Results revealed that the effect of Cd on the root-to-shoot translocation of Zn via the xylem is dependent on wheat genotype and Zn activity in the nutrient solution.     

Effect of salinity and arbuscular mycorrhizal fungi on growth and some physiological parameters of Citrus jambheri

Arbuscular mycorrhizal (AM) fungi alleviate the unfavorable effects of salinity stress on plant growth. A pot study was conducted to determine the effects of AM fungi and salt on growth and some physiological parameters of Citrus jambheri rootstock. Four levels of salinity (2, 4, 6, and 8 dS m^?1 as NaCl) and three mycorrhizal treatments (Glomus etunicatum, Glomus intraradices and non-mycorrhizal (NM) control) were used. As salinity increased, all measured characteristics of plants after 4.5-month growth except Na uptake, proline content, and electrolyte leakage decreased. Shoot dry weight and K uptake were significantly higher in G. intraradices-colonized seedlings than NM controls at all salinity levels. Root dry weight and shoot P uptake were significantly higher in G. etunicatum-colonized seedlings than NM controls at all salinity levels. G. intraradices-colonized seedlings had significantly higher proline content than NM controls and G. etunicatum-colonized seedlings at salinity levels of 4, 6 and 8 dS m^?1. The electrolyte leakage percentage was significantly lower in G. intraradices-colonized seedlings than NM controls at all salinity levels. The data demonstrated that mycorrhizal citrus seedlings exhibited greater tolerance to salt stress than NM seedlings and the enhanced proline content seems to be one of the mechanisms involved.     

Effect of salinity and soil temperature on the growth and physiology of drip-irrigated rice seedlings

Drip irrigation offers potential for rice (Oryza sativa L.) production in regions where water resources are limited. However, farmers in China’s Xinjiang Province report that drip-irrigated rice seedlings sometimes suffer salt damage. The objective of this study was to learn more about the effects of soil salinity and soil temperature on the growth of drip-irrigated rice seedlings. The study consisted of a two-factor design with two soil salinity treatments (0 and 1.8 g kg^?1 NaCl) and three soil temperature treatments (18°C, 28°C and 36°C). The results showed that shoot biomass, root biomass and root vigor were greatest when seedlings were grown with no salt stress (0 g kg^?1 NaCl) at 28°C. Moderate salt stress (1.8 g kg^?1 NaCl) combined with high temperature (36°C) significantly reduced root and shoot biomass by 39–53%. Moderate salt stress and high temperature also increased root proline concentration by 77%, root malonyldialdehyde concentration by 60% and seedling mortality by 60%. Shoot and root Na⁺ concentrations, shoot and root Na⁺ uptake and the Na⁺ distribution ratio in shoots were all the greatest when moderate salt stress was combined with high temperature. In conclusion, high soil temperature aggravates salt damage to drip-irrigated rice seedlings. Therefore, soil salinity should be considered before adopting drip-irrigation for rice production.