Macronutrient Balance of Nickel-Stressed Lettuce Plants Grown under Different Sulfur Levels

This study investigated whether intensive nutrition with sulfur–sulfate (S-SO₄) (2, 6, or 9 mM S) of nickel-stressed (0, 0.0004, 0.04, or 0.08 mM Ni) butterhead lettuce cv. Justyna may improve macronutrient balance and reduce Ni bioaccumulation. Nickel exposure resulted in various unfavorable changes in the macronutrient content together with increase of Ni accumulation in the biomass. Intensive S nutrition of Ni-treated lettuce seems to have no beneficial effect on macronutrient balance. In general, it significantly reduced the root and foliar phosphorus (P), potassium (K), calcium (Ca), and S content and simultaneously did not affect the magnesium (Mg) content in the biomass. At the same time, the nitrogen (N) content was reduced in roots and elevated in shoots. Supplementation of Ni-exposed lettuce with high S doses raised in roots and reduced foliar Ni accumulation; however, Ni content in useable parts exceeded the acceptable limits established for consumption.     

不同阳离子组成微咸水灌溉对生菜光合和离子吸收特性的影响

为探究不同微咸水水质对土壤盐分和作物生长的影响,在日光温室条件下,以生菜为供试对象开展盆栽试验,以CaSO4的饱和溶液为对照(CK),向去离子水中添加氯化盐形成不同阳离子组成的微咸水处理(Na+,TNa;Na+/K+比为1 ∶ 1,TNa-K;K+,TK),各处理添加盐分总摩尔量相同,研究灌溉水中不同阳离子组成对土壤盐...     

Kinetics of Zinc Uptake and Anatomy of Roots and Leaves of Coffee Trees as Affected by Zinc Nutrition

Abstract

The influence of silicon (Si) (2.5 mM), sodium chloride (NaCl) (100 mM), and Si (2.5 mM) + NaCl (97.5 mM) supply on chlorophyll content, chlorophyll fluorescence, the concentration of malondialdehyde (MDA), H₂O₂ level, and activities of superoxide dismutase (SOD; E.C.1.15.1.1.), ascorbate peroxidase (APx; E.C.1.11.1.11.), catalase (CAT; E.C.1.11.1.6.), guaiacol peroxidase (G-POD; E.C.1.11.1.7.) enzymes, and protein content were studied in tomato (Lycopersicon esculentum Mill c.v.) leaves over 10-day and 27-day periods. The results indicated that silicon partially offset the negative impacts of NaCl stress with increased the tolerance of tomato plants to NaCl salinity by raising SOD and CAT activities, chlorophyll content, and photochemical efficiency of PSII. Salt stress decreased SOD and CAT activities and soluble protein content in the leaves. However, addition of silicon to the nutrient solution enhanced SOD and CAT activities and protein content in tomato leaves under salt stress. In contrast, salt stress slightly promoted APx activity and considerably increased H₂O₂ level and MDA concentration and Si addition slightly decreased APx activity and significantly reduced H₂O₂ level and MDA concentration in the leaves of salt-treated plants. G-POD activity was slightly decreased by addition of salt and Si. Enhanced activities of SOD and CAT by Si addition may protect the plant tissues from oxidative damage induced by salt, thus mitigating salt toxicity and improving the growth of tomato plants. These results confirm that the scavenging system forms the primary defense line in protecting oxidative damage under stress in crop plants.     

Derivation of a Dynamic Model of the Kinetics of Nitrogen Uptake Throughout the Growth of Lettuce: Calibration and Validation

A kinetic model of nitrogen (N) uptake throughout growth was developed for lettuce cultivated in nutrient solution under varying natural light conditions. The model couples nitrogen uptake with dry matter accumulation using a two-compartment mechanistic approach, incorporating structural and non-structural pools. Maximum nitrogen uptake rates are assumed to decline with shoot dry weight, to allow for the effects of plant age. The model was parameterized using data from the literature, and calibrated for differences in light intensity using an optimization algorithm utilizing data from three experiments in different growing seasons. The calibrated model was validated against the data from two independent experiments conducted under different light conditions. Results showed that the model made good predictions of nitrogen uptake by plants from seedlings to maturity under fluctuating light levels in a glasshouse. Plants grown at a higher light intensity showed larger maximum nitrogen uptake rates, but the effect of light intensity declined towards plant maturity.     

Interactions Between Sulfur and Selenium Uptake by Corn in Solution Culture

Interactions between sulfur (S) and selenium (Se) uptake and accumulation in corn (Zea mays) plants were investigated in solution culture. Two concentrations (5 and 10 μ M) of Se (as selenate) and three concentrations of S (as sulfate) (0.5, 1.5, and 2.5 mM) were used. Results showed that shoot and root biomass were affected significantly by different S concentrations in solution, but not affected by Se application when S concentrations in solution were lower than 1.5 mM. Selenium concentrations as well as Se accumulation in shoots and roots on a dry weight basis increased dramatically with increasing Se concentrations in solution. At a constant Se level, increasing S in solution reduced Se concentrations. Selenium accumulation in plants was not affected by S application, except in nutrient solution with Se at a concentration of 10 μ M. Sulfur concentrations and S accumulation in shoots increased significantly with increasing Se concentrations in solution, while those in roots were unaffected by Se addition. Solution-to-shoot transfer factors and shoot-root distribution coefficients of Se and S were also discussed. These data suggest that it is necessary to manage carefully both S and Se levels in solution or in soils for supplementation of Se in plants. Results from this study indicate that human Se nutrition can be improved by supplementation of Se in crops.     

Diurnal variations in absorption and translocation of a ferrated phytosiderophore in barley as affected by iron deficiency

The release of phytosiderophore (PS) from roots of Fe-deficient graminaceous plants follows a distinct diurnal rhythm with maximum release rates occurring usually 3 to 4 hours after the onset of light. However, it remains to be determined whether absorption of the PS-Fe³⁺ complex shows a diurnal rhythmicity similar to that of PS release, Barley plants grown with or without 10 µM FeEDTA for 7 days were fed with ferreted PS (10 µM labelled with ⁵⁹Fe) at 4-h intervals to study the diurnal variations in the absorption and transloca tion of ⁵⁹Fe, The absorption of ⁵⁹Fe, irrespective of the Fe nutritional status of the plants, was higher during the day and lower during the night but did not show any peak throughout the day-night cycle. On the other hand, the translocation of ⁵⁹Fe into shoots of Fe-deficient plants was lower than that of Fe-sufficient plants, while the Fe nutritional status of the plants did not affect the absorption of ⁵⁹Fe by roots, The formation of root apoplastic ⁵⁹Fe was lower during the day and higher during the night, regardless of the Fe nutritional status of plants. Our results showed that the absorption of the PS-Fe³⁺ complex by roots did not follow the PS release pattern.     

Uptake of Boron by Kiwifruit Plants Under Various Levels of Shading and Salinity

Abstract

Two experiments were conducted. In the first one, kiwifruit plants were grown in sand/perlite mixtures and irrigated with modified Hoagland's nutrient solutions containing two boron (B) concentrations (0.025 and 0.2 mM) combined with four levels of salinity (0.75, 2, 4, and 6 dS m^?1). Certain growth parameters and B concentration of the various plant parts were investigated. The highest level of salinity imposed was toxic for kiwifruit plants. Significant correlations (significance 0.000***) were found between B and salinity levels of the nutrient solutions and shoot height, mean shoot fresh weight, number of new leaves, mean leaf fresh weight, B concentration of upper leaves, basal leaves, 2-year old shoots and roots of kiwifruit plants. By increasing salinity level, the B concentration of leaves decreased when B concentration in solution was 0.2 mM. In another experiment, the nutrient solutions contained three B concentrations (0.025, 0.15, and 0.3 mM) and the plants were subjected to shading (100, 70, and 30% of full sunshine). Regression analysis indicated that significant correlations were found between B and shading (independent variables) and shoot height, mean shoot fresh weight, number of new leaves, B concentration of various plant organs (significance 0.000***) and mean leaf fresh weight (significance 0.018*).     

Growth and Heavy-Metal Uptake by Lettuce Grown in Soils Applied with Sewage Sludge Compost

A pot experiment was conducted to investigate the effect of sewage sludge compost (SSC) alone and applied with chemical fertilizer on growth and heavy-metal accumulations in lettuce grown on two soils, a Xanthi-Udic Ferralosol and a Typic Purpli-Udic Cambosol. The treatments included control; nitrogen–phosphorus–potassium (NPK) fertilizer; sewage sludge compost applied at the rates of 27.54 (SSC), 82.62 (3SSC), 165.24 (6SSC) t hm^–2; and coapplication treatment (1/2 SSC + 1/2 NPK), where the N, P, and K inputs from NPK fertilizer, SSC, and coapplication treatments were normalized to the local recommend rates. The SSC application increased the biomass; copper, zinc, and lead contents in lettuce; and soil total and diethylenetriaminepentaacetic acid (DTPA)–extractable metals. However, SSC alone at the recommended rate caused less plant biomass than NPK fertilizer alone. Coapplication treatment obtained greater or similar biomass to NPK fertilizer alone and did not increase heavy-metal accumulation in soils and plants. The results demonstrated that SSC should be applied to soils with chemical fertilizers.     

盐分胁迫条件下苜蓿根系吸水特性的模拟与分析

体文借鉴Ｈｏｍａｅｅ有关盐分胁迫的部分试验研究结果及一种新的数值迭代反求方法，对无水分、养分限制条件下，Ｈｏｍａｅｅ苜蓿盐分胁迫试验中苜蓿根系的吸水规律进行了数值模拟与分析，提出了一种计算相对根长密度分布函数的简便计算方法，建立了盐分胁迫条件下苜蓿根系的吸水模型．结果表明：盐分的存在会显著降低苜蓿的根系吸水速率，当土壤溶液的电导率达到约５ｄＳ／ｍ时，将极大地影响苜蓿的根系吸水；本文提出的计算相对根长密度分布函数的计算方法较为简便、可靠；基于相对根长密度分布函数的吸水模型可以较好地模拟根系的吸水规律．     

Light Intensity Effects on Growth and Micronutrient Uptake by Tropical Legume Cover Crops

ABSTRACT

Cover crops are important components of a sustainable crop-production system in plantation crops such as cacao (theobroma cacao), coffee (Coffee arabica), oil palm (Elaeis Spp.), and banana (Musa Spp.). Optimal growth of cover crops in plantation agriculture is determined by adaptability of crop species, light intensity reaching their leaf canopies, and their nutrient-use efficiencies, including those of micronutrients. An experiment was conducted in a climatically controlled growth chamber to evaluate the influence of levels of light intensity on growth and micronutrient [boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn)] uptake parameters in legume cover crops. Two photosynthetic photon flux density (PPFD, 200 and 400 μmol m^?2 s^?1) light treatments were imposed on nine legume species (joint vetch (Aeschynomene americana), sunhemp (Crotalaria juncea L.), Crotalaria rchroleuca, showy crotalaria (crotalaria spectabilis), hairy indigo (Indigofera hirsute L.), lab-lab (Lablab purpureus), sesbania (Sesbania microcarpa), Brazilian stylo (Stylosanthes guianensis), and cowpea (Vigna unguiculata)). Overall, light intensity significantly affected growth, micronutrient uptake, and use-efficiency ratios; with few exceptions, interactions between cover crop species and PPFD were also significant. Such PPFD × crop species interactions show that the cover crops used in this study differed in growth and nutrient-uptake parameters under the conditions imposed. Sunhemp, cowpea, sesbania, and lab-lab species were superior in producing shoot dry weight and in nutrient accumulation compared with other species at lower as well as at higher PPFD levels. Interspecific differences in nutrient influx and transport were observed. Influx and transport of micronutrients was in the order Mn > B > Fe > Zn > Cu. Overall, growth, nutrient uptake, and use-efficiency ratios were higher at higher PPFD than at lower PPFD. Results of this study indicate that the use of proper crop species at adequate light intensities is an important component of successful cultivation of cover crops in plantation agriculture.     

高温诱导叶用莴苣抽薹过程中碳氮的变化分析

为了明确叶用莴苣高温抽薹的生理学基础,以叶用莴苣易抽薹品种G-B30、G-B31和耐抽薹品种G-B4、G-B20为试材,研究叶用莴苣高温抽薹过程中各糖组分、可溶性总糖、淀粉、可溶性蛋白含量以及碳氮比的动态变化。结果表明,经高温处理后,除G-B20外,其他3个品种的葡萄糖、蔗糖和果糖含量均表现为抽薹临界期低于未抽薹时期。2个易抽薹品种均在抽薹临界期可溶性总糖含量达到最低,2个耐抽薹品种在花芽分化始期可溶性总糖含量最低。淀粉含量在花芽分化始期达到最大值,抽薹时期含量又迅速下降。2个易抽薹品种抽薹后期的半乳糖、可溶性蛋白质含量显著高于抽薹前,并有大量积累的趋势,而2个耐抽薹品种相反。2个易抽薹品种的C/N在抽薹期最低,2个耐抽薹品种在高温处理过程中C/N不断升高。综上,高温诱导叶用莴苣抽薹过程中可溶性蛋白、半乳糖、淀粉大量积累,而可溶性糖、葡萄糖、果糖、蔗糖含量及C/N降低。本研究结果为进一步探究叶用莴苣高温抽薹的分子机理提供了参考依据。     

矿物质调理剂对土壤养分含量及植物营养吸收的影响

通过室内培养和盆栽试验,研究了氮磷肥配施不同量(0、0.5、1.0、2.0 g/kg)矿物质调理剂对土壤pH和有效磷、钙、镁、硅等养分含量及作物产量和氮、磷、钾等营养元素吸收的影响。室内培养结果表明:施用1.0g/kg和2.0 g/kg调理剂,不仅增强了土壤抗酸化能力,使土壤pH从5.02提高到5.31和5.61,并且延缓了磷肥施入土壤后的固定速率,在施肥后第15天和第22天土壤有效磷含量得到明显增加,增幅分别为21.49%、24.17%和22.09%、23.84%。盆栽试验中,施用0.5～2.0 g/kg调理剂,土壤矿质养分得到有效补充,并能实现生菜增产10.47%～33.33%;同时,使生菜氮、磷、钾吸收量分别提高14.69%～44.26%、15.28%～52.89%和16.28%～42.43%。由此,施用矿物质调理剂是农业种植中改善土壤酸性、补充土壤有效养分、促进作物营养吸收并实现增产的有效途径。     

Macronutrients Composition of Lettuce Plants (Lactuca sativa L.) as Affected by Mineral Nutrition Level and ION Exchange Substrate Biona-312 Supplementation

The effect of ion exchange substrate Biona-312 addition (2 or 5%) on the macronutrients composition of butterhead lettuce cv. ‘Justyna’ plants under conditions of basic (1.5-times) and intensive (3-times concentrated Hoagland solution) mineral nutrition level was investigated. Both experimental doses of Biona-312 introduced into 1.5-times concentrated Hoagland nutrient solution [electrical conductivity (EC) 2.41–2.47 dS m^?1] dropped nitrogen (N) content in roots. Simultaneously statistically proven increase in foliar concentration of total sulfur (S) as well as a decrease in phosphorus (P) and potassium (K) contents in lettuce above- and underground organs were observed. The changes in calcium (Ca) and magnesium (Mg) content were insignificant. Ion exchange substrate supplementation into 3-times concentrated Hoagland nutrient solution (EC 6.85–7.30 dS m^?1), significantly elevated N and K contents in above- and underground organs, raised the foliar S content, decreased Ca and Mg contents in leaves, as well as dropped P concentration in roots and increased content in leaves.     

Nutrient Uptake,Water Relations,and Yield Performance lf Different Wheat Cultivars (Triticum aestivum L.) under Salinity Stress

A pot experiment was conducted in the wire house of Department of Crop Physiology, University of Agriculture, Faisalabad to evaluate the effect of salinity stress on water relations, nutrient uptake and yield of six local spring wheat cultivars. The seeds were sown in plastic pots (25 × 15 cm) and experiment was laid out in a randomized complete block design in factorial arrangement with three repeats. De-ionized water was used as control treatment while salinity stress was imposed by irrigating plants with sodium chloride (NaCl) solution of 10 mM at tillering, stem elongation, anthesis, and grain development stages. Results of the study demonstrated that salinity stress decreased water potential by 32%, osmotic potential by 12%, and relative water contents by 20% as compared to control treatment. The nitrogen (N) uptake was decreased by 36% under salinity stress, while phosphorous (P) and potassium (K) uptake were decreased by 56% and 42%, respectively. The yield of wheat plants was also significantly reduced under salinity stress. It reduced grain yield by 25% and grain weight by 7%. The response of different cultivars was also different to salinity stress as cultivars ‘Lasani-08’ and ‘FSD-08’ were found to be more tolerant as compared to other cultivars.     

Nodulation Productivity and Nutrient Uptake of Cowpea (Vigna unguiculata L. Walp) with Phosphorus and Potassium under Rainfed Conditions

Low availability of phosphorus (P) and potassium (K) in acidic soil is a major constraint for crop production. Therefore, a field study was conducted to determine the effects of K and P on nodulation, productivity, and nutrient uptake of cowpea (Vigna unguiculata L. Walp) under rainfed conditions. The K and P were subjected to main and subplots, respectively with 100, 75, and 50% of fertilizer application. The growth and yield attributes were better using 100% K with 100% P. However, 100% K resulted in 20.9 and 16.9% greater green pod and stover yield than 50% K. Similarly, 100% P recorded 20.2 and 15.6% greater green pod and stover yield than 50% P. Uptake of nutrients such as nitrogen (N), P, and K followed the trend of greater to lower, 100% > 75% > 50%, in order for K and P. Similarly, nutrient-use efficiencies and production efficiency followed the trend of nutrient uptake.     

Crop Productivity,Steviol Glycoside Yield,Nutrient Concentration and Uptake of Stevia rebaudiana Bert. under Mediterranean Field Conditions

Stevia rebaudiana Bertoni (Asteraceae Family), characterized by a high content of steviol glycosides (SG) in its leaves, represents an interesting source of non-sucrose and no-calorie sweeteners. Stevia, which is native to Paraguay, is a relatively new crop for the Mediterranean region, where it is grown as an annual or poly-annual crop. In order to assess the crop’s environmental requirements, productive performance and nutrient uptakes, a two-year field experiment was carried out in north-eastern Italy, where the species had never previously been cultivated. The aim was to evaluate the effects of important pre-harvest factors, such as cultivation site, harvest time and their reciprocal interaction, on productivity, leaf SG yield and nutrient requirements. Results showed that the timing of the harvest and the pedo-climatic conditions of the cultivation sites had a significant effect on the main biometric traits, total and leaf dry yield, SG production, macronutrient concentration and uptake.     

Various Types of Nitrogen and Light Levels on Brassica chinensis Yield and Quality Parameters under Water Stress

To evaluate the effect of nitrogen, light, and water interaction on the biomass of cabbage the experiment was performed at three light intensities, three water stresses, and four nitrogen levels for four replicates using hydroponic technique in green house. The results showed that the biomass of the edible parts of cabbage at H1L3 was significantly higher than in weak light intensity and water stress treatments under the same nitrogen supply. An optimal yield was reached at 60% of the traditional nitrogen application in the presence of adequate high light intensity and normal water content. Decreased nitrate reductase and low capacity of nitrogen assimilation were observed when the nitrate–nitrogen (NO₃-N) levels were increased from N2 to N4 with normal water content. Under severe water stress (H3), the plants have a high content of soluble sugars and a low content of amino acids in low NO₃^? levels (N1 to N3). Modulating the relationship between water stresses, light intensity, and nitrogen supply levels could increase the biomass and may promote the quality of a certain plant.     

Impact of Elevated Ozone on Nutrient Uptake and Utilization of Chinese Hybrid Indica Rice (Oryza Sativa) Cultivars under Free-Air Ozone Enrichment

To assess the effects of ozone (O₃) on uptake and utilization of nitrogen, phosphorus, and potassium nutrients in rice for planning rational fertilization under projected O₃ elevation. Two hybrid indica cultivars were exposed to ambient and elevated O₃ (E-O₃) under a free-air O₃ enrichment system. E-O₃ differently affected the accumulation and distribution of biomass, and the absorption and distribution of nutrients between cultivars. These effects were related to rice cultivar and nutrient type. E-O₃ led to significantly decreased partial factor productivity and grain production efficiency (GPE) of nitrogen in both cultivars; however, the effects of E-O₃ on GPEs of phosphorus and potassium varied with cultivar. Responses of nutrients harvest indices between cultivars to E-O₃ were adverse. Differences between cultivars and elements should be considered when examining E-O₃ potentially affecting the nutrient dynamics for the purpose of reducing the amount of fertilizer applied in paddy systems to decrease potential environmental pollution.     

Effects of Plant Growth-Promoting Rhizobacteria and N Source on Plant Growth and N and P Uptake by Tomato Grown on Calcareous Soils

Introducing specific microorganisms into the soil ecological system is an important strategy for improving nutrient use efficiency. Two pot experiments were conducted in the greenhouse from December 3, 2012 to January 25, 2013 (Experiment 1) and March 11 to April 23, 2013 (Experiment 2) to evaluate the effect of nitrogen (N) source and inoculation with plant growth-promoting rhizobacteria (PGPR) on plant growth and N and phosphorus (P) uptake in tomato (Lycopersicon esculentum Mill.) grown on calcareous soils from South Florida, USA. Treatments included urea, controlled release urea (a controlled release fertilizer, CRF) each at low and high N rates and with or without inoculation of PGPR. A mixture of PGPR strains Bacillus amyloliquefaciens IN937a and Bacillus pumilus T4 was applied to the soil during growing periods of tomato. Treatments with PGPR inoculation increased plant height compared to treatments without PGPR in both experiments. Inoculation with PGPR increased shoot dry weight and shoot N uptake for the same N rate and N source. In both experiments, only at high N rate, CRF and urea treatments with PGPR had significantly (P < 0.05) greater shoot biomass than those without PGPR. Only at high N rate, CRF treatment with PGPR significantly increased shoot N uptake by 39.0% and 10.3% compared to that without PGPR in Experiments 1 and 2, respectively. Meanwhile, presence of PGPR in the soil increased shoot P uptake for all treatments in Experiment 1 and for most treatments in Experiment 2. In Experiment 1, only at low N rate, CRF treatment with PGPR significantly increased shoot P uptake compared with that without PGPR. In Experiment 2, a significant increase in shoot P uptake by inoculation of PGPR was only observed in CRF treatment at high N rate. Results from this study indicate that inoculation with PGPR may increase plant growth and N and P uptake by tomato grown on calcareous soils. However, the effect of PGPR varied and was influenced by many factors such as N source, N rate, and soil fertility. Further investigations are warranted to confirm the effect of PGPR under different soil conditions.     

Aluminum-Enhanced Proton Release Associated with Plasma Membrane H+-Adenosine Triphosphatase Activity and Excess Cation Uptake in Tea (Camellia sinensis) Plant Roots

Cultivated tea (Camellia sinensis) plants acidify the rhizosphere, and Aluminum (Al) toxicity is recognized as a major limiting factor for plant growth in acidic soils. However, the mechanisms responsible for rhizosphere acidification associated with Al have not been fully elucidated. The present study examined the effect of Al on root-induced rhizosphere acidification, plasma membrane H⁺-adenosine triphosphatase (H⁺-ATPase) activity, and cation-anion balance in tea plant roots. The exudation of H⁺ from tea plant roots with or without Al treatment was visualized using an agar sheet with bromocresol purple. The H⁺-ATPase activity of plasma membranes isolated from the roots was measured after hydrolysis using the two-phase partition system. The Al treatment strongly enhanced the exudation of H⁺, and the acidification of tea plant roots by Al was closely associated with plasma membrane H⁺-ATPase activity. The root plasma membrane H⁺-ATPase activity increased with Al concentration. The Al content, amount of protons released, and H⁺-ATPase activity were significantly higher in roots treated with Al than in those untreated. The results of the cation-anion balance in roots showed an excess of cations relative to anions, with the amount of excess cation uptake increasing with increasing Al concentrations. These suggest that Al-enhanced proton release is associated with plasma membrane H⁺-ATPase activity and excess cation uptake. Findings of this study would provide insights into the contributing factors of soil acidification in tea plantations.