EFFECTS OF SALINITY AND CALCIUM ON THE GROWTH AND CHEMICAL COMPOSITION OF PISTACHIO SEEDLINGS

Poor quality of irrigation water (high salinity) has reduced the yields of pistachio over recent years, especially in Kerman. The effects of four salinity levels [0, 30, 60, and 90 mM sodium chloride (NaCl)] and three calcium (Ca) levels [0, 0.5, and 1 mM Ca as calcium nitrate (Ca(NO₃)₂.4H₂O)] on growth and chemical composition of pistachio seedlings cv. ‘Badami’ were studied in sand culture under greenhouse conditions in completely randomized design (CRD) with four replications. After 170 days, leaf area, leaf number, shoot and root dry weights were determined. Also shoot and root sodium (Na), potassium (K), Ca, and magnesium (Mg) concentrations were measured. Results showed salinity decreased all growth parameters. Ca application increased shoot and root Ca concentrations and root K concentration, while Ca application decreased shoot K concentration and shoot and root Mg concentrations. Salinity decreased shoot Ca, root K, and root Mg concentrations, while salinity increased shoot and root total sodium uptake, and shoot and root Cl concentrations.     

Effects of Zinc Application on Growth,Absorption and Distribution of Mineral Nutrients Under Salinity Stress in Soybean (Glycine Max L.)

The purpose of the present work was to evaluate effects of zinc application on growth and uptake and distribution of mineral nutrients under salinity stress [0, 33, 66, and 99 mM sodium chloride (NaCl)] in soybean plants. Results showed that, salinity levels caused a significant decrease in shoot dry and fresh weight in non-zinc application plants. Whereas, zinc application on plants exposed to salinity stress improved the shoot dry and fresh weight. Potassium (K) concentration, K/sodium (Na) and calcium (Ca)/Na ratios significantly decreased, while sodium (Na) concentration increased in root, shoot, and seed as soil salinity increased. Phosphorus (P) concentration significantly decreased in shoot under salinity stress. Moreover, calcium (Ca) significantly decreased in root, but increased in seed with increased salinization. Iron (Fe) concentration significantly decreased in all organs of plant (root, shoot, and seed) in response to salinity levels. Zinc (Zn) concentration of plant was not significantly affected by salinity stress. Copper (Cu) concentration significantly decreased by salinity in root. Nonetheless, manganese (Mn) concentration of root, shoot, and seed was not affected by experimental treatments. Zinc application increased Ca/Na (shoot and seed) ratio and K (shoot and seed), P (shoot), Ca (root and seed), Zn (root, shoot, and seed) and Fe (root and shoot) concentration in soybean plants under salinity stress. Zinc application decreased Na concentration in shoot tissue.     

Interactive Effect of Soil Salinity and Copper Application on Growth and Chemical Composition of Pistachio Seedlings (cv. Badami)

The effects of five salinity levels and four Cu levels on growth and chemical composition of Badami pistachio seedlings were studied under greenhouse conditions in a completely randomized design with three replications. Growth parameters were determined on the 24th week after planting. Total elemental uptake amounts in shoot and root of plant were measured. Results showed that salinity decreased leaf area, stem height, and shoot and root dry weights. Application of 2.5 and 5 mg copper (Cu) kg^?1 soil significantly increased root dry weight, whereas it had no significant effects on shoot dry weight and leaf area. Application of 7.5 mg Cu kg^?1 soil had a negative effect on stem height. Salinity declined shoot and root total Cu and phosphorus (P) uptake amounts but increased shoot and root total sodium (Na) and chlorine (Cl) uptake amounts. Copper increased shoot and root total Cu uptake amounts, root total P uptake, and shoot total Na uptake but decreased shoot total Cl uptake.     

Effects of Salinity and Copper on Growth and Chemical Composition of Pistachio Seedlings

The effects of five salinity levels and four copper levels on growth and chemical composition of ‘Ghazvini, pistachio seedlings were studied under greenhouse conditions in a completely randomized design with three replications. Leaf area, stem height, shoot and root dry weights were determined on 24th week after planting. Copper (Cu), phosphorus (P), sodium (Na), and chlorine (Cl) total uptake in shoot and root of plant were measured. The results showed that salinity decreased growth parameters. Low levels of Cu application had no significant effect on leaf area, shoot and root dry weights while decreased stem height. The highest level of Cu (7.5 mg Cu kg^?1 soil) significantly increased leaf area and shoot dry weight but decreased stem height. Salinity decreased Cu and P uptake in the shoot and root, but increased total sodium and chloride uptake. Cu application increased shoot total P uptake and decreased root total Na uptake.     

Comparative Study of Substrate-Based and Commercial Formulations of Arbuscular Mycorrhizal Fungi in Romaine Lettuce Subjected to Salt Stress

To compare the effect of substrate-based and commercial arbuscular mycorrhizal fungi (AMF) in salt stress tolerance of Romaine lettuce a bifactorial analysis was carried out. Under non-saline conditions, only plants inoculated with formulation 1 stimulated shoot weight but not related with greater root AMF colonization. Phosphorus and potassium concentrations in leaves were improved by mycorrhizal association. Irrigation with 100 mM sodium chloride (NaCl) did not affect leaf relative water content and we observed no osmotic adjustment in leaves from non-mycorrhizal plants. However, root dry biomass and its starch content decreased, while leaf starch and root soluble sugar concentrations were enhanced. Lettuce inoculated with formulation 2 and substrate-based Glomus intraradices showed the highest root colonization percentages. Nevertheless, none of the mycorrhizal treatments induced a significant improvement on growth of lettuce subjected to salt stress. Romaine lettuce seems to be a moderately tolerant variety to salinity and therefore, the contribution of AMF was minimized.     

WHEAT RESPONSE TO NITROGEN SOURCE UNDER SALINE CONDITIONS

ABSTRACT

The influence of nitrogen (N) sources on biomass yield and nutrient uptake of wheat (Triticum aestivum L.) under saline conditions was studied in a greenhouse experiment. Six different forms of N {nitrate-N as Ca(NO₃)₂, urea-N [CO(NH₂)₂], ammonium-N as (NH₄)₂SO₄, nitrate-N+urea-N, nitrate-N+ammonium-N and a control (no N fertilizer)} were factorially combined with three levels of salinity to give a total of 18 treatments that were replicated three times. Each of the five levels of applied N was at the rate of 100?kg?ha^?1. The salinity levels (ECe) were 6.2 and 12.1?dSm^?1, denoted as S ₁ and S ₂ and untreated soil (S ₀), respectively. A basal dose of phosphorus (P) and potassium (K) was also applied. Five wheat plants were grown in each pot for six weeks. Data were collected for shoot and root biomass and shoot samples were analyzed for N, P, K, calcium (Ca), magnesium (Mg), sodium (Na), chloride (Cl), and micronutrients contents. Plant growth and nutrient uptake were influenced by both salinity and source of N. As expected, increasing salinity decreased dry matter production of shoot and root, whereas N application increased plant growth across all levels of salinity. The total dry biomass (shoot and root) of wheat was significantly higher in combined N treatments than in single sources. Irrespective of N forms most of the nutrient concentrations in the shoot was increased with increasing level of salinity. Among the fertilizers the concentration of cation was higher in nitrate-treated plants than in other forms of N. Ammonium-N and urea-N tended to inhibit the uptake of cations compared to nitrate-N under saline conditions. The trend for P and Cl concentration was almost opposite to that of cations concentration in the shoot. The uptake of nutrients seemed to be influenced by cation–anion balance in soil-plant system. Nitrogen concentration of shoot was greatly enhanced by all forms of N in the following order: Ni>NiAm>Am>NiUr>Ur>control. The interactive effect of salinity and fertilizer on iron (Fe), manganese (Mn), and zinc (Zn) contents was not consistent. Among the fertilizers the concentration of trace elements in the shoot was also not significantly different. It was concluded that the plant growth and nutrient concentration of shoot could depend upon N source and level of salinity. The mixed application of both ammoniacal and nitrate forms of N could possibly be conducive to plant growth in salt affected soils.     

Interaction Between Salinity Stress and Verticillium Wilt Disease in Three Pistachio Rootstocks in a Calcareous Soil

ABSTRACT

The interaction between soil salinity and infection caused by Verticillium dahliae was studied in pistachio (Pistacia vera) in a greenhouse experiment. Treatments consisted of 0, 1400, 2800, and 4200 mg sodium chloride (NaCl) kg^{? 1} soil and three rootstocks (Sarakhs, Badami, and Qazvini cultivars). They were gradually exposed to salinity stress before and/or after root inoculation with a water suspension of 10⁷ conidia/mL of a pistachio isolate of V. dahliae. Salt stress significantly increased rootstock shoot and root colonization by V. dahliae. All rootstocks were susceptible to V. dahliae, but symptoms of the disease appeared earlier in Sarakhs, a salt sensitive cultivar. Moreover, salinity and V. dahliae interaction increased the concentrations of sodium (Na), potassium (K) and chloride (Cl), but decreased the K/Na ratio in all rootstocks. Shoot and root tissues of inoculated Sarakhs and Qazvini (a salt tolerant) contained the highest and the lowest concentrations of Na, K,and Cl, respectively. In salinity treatments, shoot and root dry weight of all rootstocks decreased as compared with controls. Sarakhs showed smaller shoot and root dry weight than Qazvini and Badami. Also, increasing the NaCl level increased accumulation of Na, K, and Cl in shoot and root of the rootstocks. Sarakhs showed higher concentrations of ions in the shoot and root. Based on shoot and root dry weights and ion accumulation, Sarakhs and Qazvini were susceptible and tolerant to salinity, respectively.     

Effects of Salinity and Water Stress on Echophysiological Parameters and Micronutrients Concentration of Pomegranate (Punica granatum L.)

In order to study the effects of salinity and drought stress on echophysiological parameters and micronutrients concentration of pomegranate leaves, a factorial experiment was conducted based on completely randomized design with 0, 30, and 60 mM of salinity levels of sodium chloride and calcium chloride (1:1) and three irrigation intervals (2, 4, and 6 days) with three replications on ‘Rabab’ and ‘Shishegap’ cultivars of pomegranate. The results analysis of shoot and root indicated that the water salinity and drought affected the concentration of iron (Fe²⁺), zinc (Zn²⁺), copper (Cu²⁺) and manganese (Mn²⁺) in pomegranate leaves and roots. Mineral concentration of zinc (Zn²⁺), copper (Cu²⁺) and manganese (Mn²⁺) in roots and manganese (Mn²⁺) in shoot was increased with increasing salinity. Drought treatments decreased the concentration of Zn²⁺ in the shoot and increased Zn²⁺ in roots. Both cultivars showed significant differences in the Fe²⁺ concentrations of shoot, however the most accumulation of Fe²⁺ was observed in ‘Shishegap’ cultivar.     

Specific flavonoids as interconnecting signals in the tripartite symbiosis formed by arbuscular mycorrhizal fungi, Bradyrhizobium japonicum (Kirchner) Jordan and soybean (Glycine max (L.) Merr.)

Many legume plants benefit from the tripartite symbiosis of arbuscular mycorrhizal fungi (AMF) and rhizobia. Beneficial effects for the plant have been assumed to rely on increased P supply through the mycorrhizas. Recently, we demonstrated that P does not regulate the establishment of the tripartite symbiosis. Flavonoids appear to play a role as early signals for both rhizobia and AMF. Four soybean lines known to express different concentrations of the isoflavones genistein, daidzein and glycitein in the seed were used to test three hypotheses: (i) The establishment of the tripartite symbiosis is not dependent of a nutrient mediated effect; (ii) There is a positive correlation between seed isoflavone concentrations of different soybean lines and the progress of the tripartite symbiosis; (iii) Specific flavonoids control the establishment of the tripartite symbiosis in that a change in flavonoid root accumulation resulting from the development of one microbial partner can stimulate colonization of soybean roots by the other. Disturbed versus undisturbed soil treatments were produced to vary the potential for indigenous AMF colonization of soybean. In contrast, the potential for Bradyrhizobium was kept identical in both soil disturbance treatments. The uptake of P and Zn and the concentration of flavonoids in mycorrhizal soybean roots at 10 d after emergence were analysed either separately of Bradyrhizobium or in context of the tripartite symbiosis. Zinc nutrition did not differ between AMF treatments which supports the first hypothesis. The concentration of daidzein was at least four times greater in the root than in the seed reaching 3958±249 μg g⁻¹ dry across soybean lines. Coumestrol, which was absent in the seed, was synthesized to reach 2154±64 μg g⁻¹ dry. Conversely, the concentration of genistein was approximately three times smaller in the root that in the seed (301±15 μg g⁻¹ dry), while glycitein and formononetin were never detected. The establishment of the tripartite symbiosis was identical across soybean lines which does not support the second hypothesis. Concentrations of flavonoids were significantly greater in roots under disturbed soil, for which both symbioses were not as developed as in plants from undisturbed soil. This clearly supports the third hypothesis. This research provides the first data linking the function of different flavonoids to the establishment of the tripartite symbiosis, and suggests that these compounds are produced and released into the rhizosphere as a function of the colonization process.     

土壤中芦笋生长最大需磷量对接种丛枝菌根真菌的响应特征

Fertilizer application efficiently increases crop yield, but may result in phosphorus（P） accumulation in soil, which increases the risk of aquatic eutrophication. Arbuscular mycorrhizal fungi（AMF） inoculation is a potential method to enhance P uptake by plant and to reduce fertilizer input requirements. However, there has been limited research on how much P application could be reduced by AMF inoculation. In this study, a pot experiment growing asparagus（Asparagus officinalis L.） was designed to investigate the effects of AMF inoculation and six levels of soil Olsen-P（10.4, 17.1, 30.9, 40.0, 62.1, and 95.5 mg kg^-1for P0, P1, P2, P3, P4 and P5treatments, respectively） on root colonization, soil spore density, and the growth and P uptake of asparagus. The highest root colonization and soil spore density were both obtained in the P1treatment（76% and 26.3 spores g^-1 soil, respectively）. Mycorrhizal dependency significantly（P 〈 0.05） decreased with increasing soil Olsen-P. A significant correlation（P 〈 0.01） was observed between mycorrhizal P uptake and root colonization, indicating that AMF contributed to increased P uptake and subsequent plant growth.The quadratic equations of shoot dry weight and soil Olsen-P showed that AMF decreased the P concentration of soil required for maximum plant growth by 14.5% from 67.9 to 59.3 mg Olsen-P kg^-1. Our results suggested that AMF improved P efficiency via increased P uptake and optimal growth by adding AMF to the suitable P fertilization.     

Response of a wild-type and modern cowpea cultivars to arbuscular mycorrhizal inoculation in sterilized and non-sterilized soil

Cowpea is an important crop that serves as a legume and vegetable source to many smallholder farmers in sub-Saharan Africa. Soil fertility is a significant limitation to its production thus; inoculation with beneficial soil biota such as arbuscular mycorrhizal fungi (AMF) could improve its performance. However, plant–AMF interaction could vary based on crop cultivar hence affecting overall crop production. The present study aimed at determining the effect of AMF inoculation and soil sterilization on root colonization and growth of a wild-type and three modern cowpea cultivars grown by smallholder farmers in Kenya. Potted cowpea plants were inoculated with a commercial AMF inoculum comprising of Rhizophagus irregularis, Funneliformis mosseae, Glomus aggregatum and Glomus etunicatum and maintained in a greenhouse for 40 days. After harvesting, mycorrhizal colonization, nodule number and dry weight, root and shoot dry weights, nitrogen (N,) phosphorus (P) and potassium (K) content were determined. Interestingly, the modern cultivars showed significantly (p < 0.001) higher root colonization, nodulation, shoot P and N compared to the wild-type cultivar. Moreover, a strong positive correlation between AMF root colonization and shoot P (r² = 0.73, 0.90, p < 0.001), AMF root colonization and shoot N (r² = 0.78; 0.89, p < 0.001) was observed in both sterilized and non-sterilized soil, respectively. Soil sterilization affected root colonization and growth parameters with plants grown in non-sterilized soil performing better than those grown in sterilized soil. This study provides major evidence that modern cowpea cultivars are still responsive to mycorrhizal inoculation suggesting that modern breeding programs are not deleterious AMF symbiosis.     

Interactive Effect of Soil Salinity and Water Stress on Growth and Chemical Compositions of Pistachio Nut Tree

ABSTRACT

The effects of three sodium chloride (NaCl) levels (0, 1200, and 2400 mg kg^{? 1} soil) and three irrigation intervals (3, 7, and 14 d) on the growth and chemical composition of two Pistacia vera rootstocks (‘Sarakhs’ and ‘Qazvini’) were investigated under greenhouse conditions. Eight-week-old pistachio seedlings were gradually exposed to salt stress which afterward, water stress was initiated. At any irrigation interval, plant height and shoot and root dry weights of both rootstocks were reduced with increasing salinity. However, increasing irrigation intervals alleviated the adverse effects of soil salinity. A negative relationship observed between relative shoot growth and electrical conductivity of soil saturation extract (EC_e) confirmed the above findings. Under 3-d irrigation interval, the EC_e required to cause a 50% growth reduction was lower than those under 7- and/or 14-d irrigation intervals. Shoot and root chemical analyses indicated that the salinity as well as irrigation regime affected the concentration and distribution of sodium (Na⁺), potassium (K⁺), and chloride (Cl^?) in pistachio. The concentration of Na⁺, K⁺ and C1^? ions increased with a rise in NaCl level, and was generally declined with increasing irrigation interval. Based on plant height, shoot and root dry weights and the concentrations of Na⁺, K⁺, and C1^? in the plant tissues, at lowest irrigation intervals ‘Sarakhs’ shows a higher sensitivity to soil salinity than ‘Qazvini’, but with increasing irrigation interval, ‘Sarakhs’ and ‘Qazvini’ can be classified as resistant and sensitive to salinity, respectively.     

TREATED EFFLUENT AND SALINE WATER IRRIGATION INFLUENCES SOIL PROPERTIES,YIELD, WATER PRODUCTIVITY AND SODIUM CONTENT OF SNOW PEAS AND CELERY

To determine the effects of irrigation water quality, plants were irrigated with normal potable water [0.25 dS m^?1 electrical conductivity (EC), 25 mg L^?1 sodium (Na), 55 mg L^?1 chloride (Cl)], treated effluent (0.94 dS m^?1 EC, 122 mg L^?1 Na, 143 mg L^?1 Cl) and saline water with low salinity (1.24 dS m^?1 EC, 144 mg L^?1 Na and 358 mg L^?1 Cl) and high salinity (2.19 dS m^?1 EC, 264 mg L ^?1Na and 662 mg L^?1 Cl) for snow peas, and high salinity (3.07 dS m^?1 EC, 383 mg L^?1 Na and 965 mg L^?1 Cl) and very high salinity (5.83 dS m^?1 EC, 741 mg L^?1 Na and 1876 mg L^?1 Cl) for celery. The greater salts build up in the soil and ion toxicity (Cl and Na) with saline water irrigation contributed to significantly greater reduction in root and shoot biomass, water use, yield and water productivity (yield kg kL^?1 of water used) of snow peas and celery compared with treated effluent and potable water irrigation. There was 8%, 56% and 74% reduction in celery yield respectively with treated effluent, high salinity and very high salinity saline water irrigation compared with potable water irrigation. The Na concentration in snow peas shoots increased by 54%, 234% and 501% with treated effluent, low and high salinity saline water irrigation. Similarly, the increases in Na concentration in celery shoots were 19%, 35% and 82%. The treated effluent irrigation also resulted in a significant increase in soil EC, nitrogen (N) and phosphorus (P) content compared with potable water irrigation. The heavy metals besides salts build up appears to have contributed to yield reductions with treated effluent irrigation. The study reveals strong implications for the use of saline water and treated effluent for irrigation of snow peas and celery. The salt build up within the root zone and soil environment would be critical in the long-run with the use of saline water and treated effluent for irrigation of crops. To minimize the salinity level in rhizosphere, an alternate irrigation of potable water with treated effluent or low salinity level water may be better option.     

Partitioning of Chlorine,Sodium, and Potassium and Shoot Growth of Three Pomegranate Cultivars Under Different Levels of Salinity

Salinity is a major problem in a wide pomegranate-growing area of central Iran. Effects of four levels of salinity on leaf and root chlorine (Cl), sodium (Na), and potassium (K) partitioning and shoot growth in three major commercial cultivars of pomegranate (Punica granatum), namely ‘Alak Torsh,’ ‘Malas Torsh,’ and ‘Malas Shirin,’ under climatic conditions of central Iran were investigated. Pomegranate cuttings were rooted and planted in plastic pots containing 1:1 sand:perlite medium and irrigated immediately with complete Hoagland's solution immediately. Four salinity levels of irrigation water (0, 40, 80, and 120 mM NaCl) were used. Final concentrations of NaCl were achieved after three weeks and continued for 80 d. Growth characteristics (i.e., length of the main stem, length and number of internodes, and leaf surface) were measured during the experiment. At harvest, concentrations of Na, K, and Cl in root and apical and basal leaves of the three cultivars were determined separately. In ‘Malas Torsh’ and ‘Alak Torsh’ cultivars, increasing salinity was proportional to NaCl concentration and reduced the length of stem, the length and number of the internodes, and leaf surface. There was an increase in the growth rate of the ‘Malas Shirin’ cultivar with increasing salinity up to 40 mM, but a decline in growth rate occurred at salinity levels higher than 40 mM. With increasing salinity level, the tissue concentration of Na and Cl increased while the K/Na ratio decreased. No significant differences were observed among the three cultivars in Na, Cl, and K concentrations of roots or apical or basal leaves. These results show that ‘Malas Shirin’ grew better under saline conditions compared with the ‘Malas Torsh’ and ‘Alak Torsh’ cultivars.     

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.     

Effect of Phosphorus Additions and Arbuscular Mycorrhizal Fungal Inoculation on the Growth,Physiology, and Phosphorus Uptake of Wheat Under Two Water Regimes

Drought stress greatly affected the growth and development of wheat in the world, while wheat growth could benefit through improvement of water status and nutrient uptake by mycorrhizal symbiosis or addition of phosphorus (P). Experimental treatments were (a) phosphorus addition (0 and 90 kg/ha), (b) soil water condition (40% field capacity and 95% field capacity), and (c) arbuscular mycorrhizal fungi (AMF, Glomus intraradices) (noninoculation and inoculation) which were conducted in a growth chamber. The results showed that addition of phosphorus and AMF inoculation significantly increased the relative water content and specific leaf area of flag leaves especially under 40% field capacity (water deficit (WD)). The leaf gas exchange parameters were all decreased under WD. The water use efficiency (WUE) and instantaneous WUE (WUEi) was enhanced by WD, AMF inoculation, and phosphorus addition. AMF inoculation and WD significantly decreased the carbon isotope discrimination (CID) of leaf. The P concentrations in stem, grain, and leaf were significantly increased by phosphorus addition, WD, and AMF inoculation. Significant correlations were found between WUE and grain P, stem P, and leaf P concentrations. Leaf CID was significantly negatively correlated with WUE and stem P concentrations. Inoculation of AMF or phosphorus addition could improve the growth, physiology, and phosphorus uptake in spring wheat under drought conditions.     

Is the salt tolerance of maize related to sodium exclusion? I. Preliminary screening of seven cultivars

Maize (Zea mays L.) plants in the early stage of development were treated with 80 mM sodium chloride (NaCl) with or without supplemental calcium (Ca²⁺) (8.75 mM) for a seven day period. The effects of salinity on dry matter production and shoot and root concentrations of sodium (Na⁺), Ca²⁺, and potassium (K⁺) were measured for seven Pioneer maize cultivars. Salinity significantly reduced total dry weight, leaf area, and shoot and root dry weight below control levels. For all seven cultivars, Na⁺concentrations were reduced and leaf area was significantly increased by supplementing salinized nutrient solutions with 8.75 mM calcium chloride (CaCl₂). The two cultivars with the lowest shoot and root Na⁺ concentrations under NaCl‐salinity showed the greatest increases in total, shoot and root dry weights with the addition of supplemental Ca. Shoot fresh weight/dry weight ratios for all cultivars were decreased significantly by both salinity treatments, but supplemental Ca²⁺ increased the ratio relative to salinity treatments without supplemental Ca. Root fresh weight/dry weight ratios were decreased only by salinity treatments with supplemental Ca. With NaCl‐salinity, cultivars which had lower shoot and root Na⁺ concentrations were found to be more salt sensitive and had significantly lower amounts of dry matter production than those cultivars which had higher shoot and root Na⁺ concentrations. It was concluded that Na⁺ exclusion from the shoot was not correlated with and was an unreliable indicator of salt tolerance for maize.     

Earthworm (Aporrectodea trapezoides)–mycorrhiza (Glomus intraradices) interaction and nitrogen and phosphorus uptake by maize

The interactive impacts of arbuscular mycorrhizal fungi (AMF, Glomus intraradices) and earthworms (Aporrectodea trapezoides) on maize (Zea mays L.) growth and nutrient uptake were studied under near natural conditions with pots buried in the soil of a maize field. Treatments included maize plants inoculated vs. not inoculated with AMF, treated or not treated with earthworms, at low (25 mg kg⁻¹) or high (175 mg kg⁻¹) P fertilization rate. Wheat straw was added as feed for earthworms. Root colonization, mycorrhiza structure, plant biomass and N and P contents of shoots and roots, soil available P and NO₃⁻–N concentrations, and soil microbial biomass C and N were measured at harvest. Results indicated that mycorrhizal colonization increased markedly in maize inoculated with AMF especially at low P rate, which was further enhanced by the addition of earthworms. AMF and earthworms interactively increased maize shoot and root biomass as well as N and P uptake but decreased soil NO₃⁻–N and available P concentrations at harvest. Earthworm and AMF interaction also increased soil microbial biomass C, which probably improved root N and P contents and indirectly increased the shoot N and P uptake. At low P rate, soil N mobilization by earthworms might have reduced potential N competition by arbuscular mycorrhizal hyphae, resulting in greater plant shoot and root biomass. Earthworms and AMF interactively enhanced soil N and P availability, leading to greater nutrient uptake and plant growth.     

蚯蚓与菌根提高玉米生长和氮磷吸收的互补效应

【目的】蚯蚓和丛枝菌根真菌处于不同的营养级,但在促进植物生长和提高土壤肥力等方面却都发挥着积极作用。研究蚯蚓菌根互作及其对玉米吸收土壤中的氮、磷养分的影响,可为提升土壤生物肥力及促进农业的可持续发展提供理论依据。【方法】本研究采用田间盆栽方式,以玉米为供试作物,研究蚯蚓(Eisenia fetida)与丛枝菌根真菌(Glomus intraradices)互作及其对玉米养分吸收的影响。试验设置P 25和175 mg/kg两个水平。每个磷水平进行接种与不接种菌根真菌以及添加与不添加蚯蚓,共8个处理。调查了玉米生长、养分吸收以及真菌浸染和土壤养分的有效性。【结果】两个磷水平下,蚯蚓和菌根在增加玉米地上部和根系生物量方面有显著正交互作用(P0.05)。接种菌根真菌的各处理显著增加了玉米的侵染率及泡囊丰度、根内菌丝丰度等菌根指标。同时添加蚯蚓和接种菌根真菌的处理(AM+E)显著提高了菌根的侵染率、菌丝密度、丛枝丰度和根内菌丝丰度但是泡囊丰度有所下降。两种磷水平下,AM+E处理玉米地上部和地下部含氮量和含磷量均显著高于其他三个处理。在低磷条件下,地上部氮磷总量的增加分别是添加蚯蚓和接菌的作用;而地下部磷总量的增加主要是菌根真菌的作用。在高磷条件下,单加蚯蚓显著增加玉米氮磷的总量,而接种菌根真菌对玉米氮磷吸收的影响未达显著性水平。在高磷条件下,单加蚯蚓的处理显著提高玉米地上地下部生物量(P0.05),而单接菌的处理效应不显著,蚯蚓菌根互作通过提高土壤微生物量碳、氮实现对玉米生长和养分吸收的调控。在低磷条件下,单接菌显著提高了玉米的生物量(P0.05),单加蚯蚓的处理具有增加玉米生物量的趋势。菌根真菌主要促进玉米对磷的吸收,蚯蚓主要矿化秸秆和土壤中的氮磷养分增加土壤养分的有效性,蚯蚓菌根互作促进了玉米根系对土壤养分的吸收并形成氮磷互补效应。【结论】无论在高磷还是低磷水平下,蚯蚓菌根相互作用都提高了玉米地上地下部生物量、氮磷吸收量同时提高了土壤微生物量碳、氮。蚯蚓菌根相互作用对植物生长的影响取决于土壤养分条件。在高磷条件下(氮相对不足),蚯蚓菌根互作通过调控土壤微生物量碳、氮调控玉米生长和养分吸收。低磷条件下,菌根主要发挥解磷作用,蚯蚓主要矿化秸秆和土壤中的氮素,蚯蚓和菌根互补调控土壤中氮、磷,从而促进植物的生长和养分吸收。     

Effect of Salinity and Nitrogen Application on Growth,Chemical Composition and Some Biochemical Indices of Pistachio Seedlings (Pistacia Vera L.)

To study the effect of nitrogen and salinity on growth and chemical composition of pistachio seedlings (cv. ‘Badami’), a greenhouse experiment was conducted. Treatments consisted of four salinity levels [0, 800, 1600, and 2400 mg sodium chloride (NaCl) kg^?1 soil], and four nitrogen (N) levels (0, 60, 120, and 180 mg kg^?1 soil as urea). Treatments were arranged in a factorial manner in a completely randomized design with three replications. The highest level of nitrogen and salinity decreased leaf and root dry weights. Nitrogen application significantly increased the concentration of shoot N and salinity suppressed shoot N concentration. Salinity and nitrogen fertilization increased shoot and root sodium (Na), calcium (Ca), and magnesium (Mg) concentrations. Nitrogen application increased proline concentration and reducing sugar content. Although salinity levels increased proline concentration a specific trend on reducing sugars content was not observed.