EFFECT OF NITRATE NUTRITION ON GROWTH AND NITROGEN ASSIMILATION OF PEARL MILLET EXPOSED TO SODIUM CHLORIDE STRESS

Influence of nitrate concentration on growth and nitrogen assimilation in salinity-stressed pearl millet (Pennisetum typhoids L.) was studied. The plants were grown in perlite and irrigated with nutrient solution containing 0, 25, 50, or 100 mM sodium chloride (NaCl) in the presence of 2 or 10 mM NO₃ ^?. Salinity decreased leaf dry weight and soluble proteins, as well as total chlorophyll. Free amino acid content, including proline, was higher in salt-stressed plants compared to controls. The activities of nitrate reductase, nitrite reductase, and glutamate synthase were reduced, but the glutamine synthetase activity was less affected. High nitrate (10 mM) in the irrigation solution partially restored activities of the above enzymes and increased the soluble protein content despite the high NaCl concentration. The retarded growth of pearl millet due to salinity stress was partially restored in the presence of high nitrate concentration in the irrigation solution.     

The potential of glauconitic sandstone as a potassium fertilizer for olive plants

This study evaluated the potential of glauconitic sandstone as a fertilizer for supplying potassium to plants. The glauconite sandstone (Maraveh, Iran), as analyzed by X-ray fluorescence, was composed of 2.24% potassium oxide plus high contents of silicon, aluminum and ferric oxide. One-year old olive trees, Olea europaea L., were grown in sand or hydroponic culture in a greenhouse under three potassium treatments. Modified Hoagland nutrient solutions based on potassium treatments including 0.5 mM K⁺, 5 mM K⁺ and 400 g glauconitic sandstone powders (per 10 L in hydroponics and per 2.5 L in sand instead of K⁺ supply) were used in both cultures. Plants grown under the three different potassium treatments did not show any potassium deficiency symptoms. In the sand culture, growth and potassium content were higher in plants fed with 5 mM potassium than with the other two potassium treatments. Growth retardation and decreased potassium content in plants fed with 0.5 mM potassium were more severe in the hydroponic culture than in the sand culture. However, plants fed with 400 g glauconitic sandstone showed higher growth in the hydroponic culture than the sand culture. Thus, glauconitic sandstone has the ability to release potassium and can be utilized in combination with other potassium fertilizers.     

Induction of high affinity nitrate and ammonium uptake systems in wheat

Abstract

The ability of 7 day old wheat seedlings to take up nitrate or ammonium from hydroponic solution was measured. Seedlings were grown under fully aerated hydroponic conditions. The growth solution consisted of either 0.5 mM CaSO₄ alone or in combination with high nitrate (5 mM NO₃ ^‐ ), high ammonium (2 mM NH₄ ⁺) or modified 1/10 Hoaglands solution with nitrate N only (14 mM) or ammonium N only (2 mM). After washing the roots for one hour in CaSO₄, nitrate or ammonium uptake was measured with an ion selective electrode. Plants grown in high nitrate were unable to take up nitrate from a 0.1 mM external solution. Those grown in CaSO₄ were able to take up nitrate at the same external concentration (flux = 10.2 +/‐ 3.0 μmol nitrate/g dry wtlbh). The same result was seen for plants grown in high ammonium vs those grown in CaSO₄ (flux = 21.0 +/‐ 10.0 μmol/g dry wtlbh). Similar results were obtained when modified Hoagland's solution was substituted for the high N solutions. These data indicate that wheat roots possess both high and low affinity nitrate and ammonium uptake systems. The data further indicate that, for a given ion, the high and low affinity systems do not operate simultaneously under high N conditions. The high affinity system is switched off in the range of 1 mM for both ionic forms of N. Developmental studies show that the expression of the high affinity trait is reversible and may be induced (repressed) by conditioning for 24 h in low (high) N media. Plants grown in high N solutions showed efflux of the ion under assay conditions. Neither ion interfered with the induction/repression of the high affinity trait for the other under the conditions used in this study.     

Silicon modulates the activity of antioxidant enzymes and nitrogen compounds in sunflower plants under salt stress

Sunflower (Helianthus annuus L.) is an important oilseed crop with clear sensibility to salt stress. In this study, we evaluated silicon (Si) effect on the nitrogen metabolism and antioxidant enzyme activity in sunflower plants subjected to salinity. A 4 × 4 factorial arrangement of treatments in a completely randomized design with four replicates was used, consisting of four concentrations of Si (0.0; 1.0; 1.5; and 2.0 mM) and four concentrations of NaCl (0; 50; 100; and 150 mM) in the nutrient solution. The salinity reduced the nitrate content, but the increasing Si concentration in the medium improved the nitrate uptake, leading this ion to accumulate in salt-stressed plants, particularly in the roots. The nitrate reductase activity and the proline and soluble N-amino contents were also significantly increased by Si in salt conditions. The salinity increased electrolyte leakage and reduced the activity of enzymes superoxide dismutase, ascorbate peroxidase and catalase in sunflower plants, but these decreases were reversed by Si at 2 mM, thus alleviating the effects of salinity on these variables. We conclude that Si is able to positively modulate nitrogen metabolism and antioxidant enzyme activities in sunflower plants in order to alleviate the harmful effects of salinity.     

The effect of chloride and sulphate salts on the nitrate content in lettuce plants (Lactuca sativa L.)

The effect of chloride and sulphate on the nitrate accumulated in lettuce plants (Lactuca sativa L., cv. deci minor) under low light conditions was examined. The plants were grown on a complete nutrient solution for circa 45 days and then chloride was substituted for the nitrate in the nutrient solution. In another experiment, sulphate was substituted for the nitrate in the nutrient solution. Approximately 5 days later a reduction in growth occurred. The nitrate in the plants was not completely exhausted and was very slowly available for reduction both in the leaf blades and midribs. It was immaterial whether sulphate or chloride was substituted for nitrate in the nutrient solution. Chloride was taken up from the solution but sulphate was not. In plants in both treatments, sugars accumulated concomitantly with the decrease in nitrate content.

The actual nitrate reductase activity in the leaf blades decreased several days after the chloride and sulphate treatments began and was negligible on day 12. Nevertheless, the potential nitrate reductase activity of the treated plants was still 50% of the control.

It is suggested that the availability of nitrate from the storage pool is the limiting process for nitrate reductase activity, and is independent of the metabolic demand. For commercial growers it may be of advantage to use hydroponics in which the nitrate can be removed easily several days before harvest, to reduce high nitrate contents in vegetables, particularly under low light conditions.     

ROOT FERRIC CHELATE REDUCTASE IS REGULATED BY IRON AND COPPER IN STRAWBERRY PLANTS

In the present experiment, we studied the interaction between copper (Cu) and iron (Fe) in strawberry plants grown in nutrient solutions containing different concentrations of Fe. Plants grown in the absence of iron (Fe0) had the characteristic symptoms of Fe deficiency, with smaller chlorotic leaves, less biomass, acidification of the nutrient solution, and roots that were smaller and less ramified, while no symptoms of Fe deficiency were observed in plants grown with Fe. A greater amount of Cu was found in roots of chlorotic plants than in those grown with Fe, while plants grown with 20 μM of Fe (Fe20) in the nutrient solution had a greater amount of Fe compared with plants from the other treatments. Chlorotic plants (Fe0) and plants grown with the greatest level of Fe (Fe20) had a greater root ferric chelate reductase (FC-R; EC 1.16.1.17) activity compared with the other treatments with 5 or 10 μM Fe in the nutrient solution. The same pattern was obtained for relative FC-R mRNA concentration and for the sum of Fe and Cu contents in shoots (leaves plus crowns). The DNA obtained from amplification of the FC-R mRNA was cloned and several of the inserts analysed by single strand confirmation polymorphism (SSCP). Although there were different SSCP patterns in the Fe20 treatment, all the inserts that were sequenced were very similar, excluding the hypothesis of more than one FC-R mRNA species being present. The results suggest that Cu as well as Fe is involved in FC-R expression and activity, although the mechanism involved in this regulation is unknown so far. Both small contents of Fe and Cu in plants led to an over-expression of the FC-R gene and enhanced FC-R activity in strawberry roots.     

The effect of N and NaCl on growth,yield, and nitrate content of salad rocket (Eruca sativa Mill.)

Hydroponic production of rocket as a salad vegetable has become increasingly important in recent years. Rocket is known to be a high nitrate (NO₃^–)-accumulating vegetable, which can be grown throughout the year. In the present study, rocket was grown in a floating hydroponic system at three levels of nitrogen (N) and sodium chloride (NaCl). The highest yield was obtained at 14 mM N, whereas the yield was lower at 20 mM and 40 Mm NaCl. Leaf elongation was more sensitive to salinity than leaf differentiation. Adding NaCl to the nutrient solution increased the relative chlorophyll content. Na⁺ and Cl^– concentrations increased as salinity increased. NO₃^? levels in fresh biomass increased with increased amounts of NO₃^? in the nutrient solution, and plants at 18 mM N were able to maintain a higher NO₃^? : Cl^? ratio than those at 10 mM N.     

Nitrogen‐use efficiency traits of mini‐watermelon in response to grafting and nitrogen‐fertilization doses

Two experiments were conducted to study the effect of grafting on nitrogen‐use efficiency (NUE) in mini‐watermelon plants. In the first study, mini‐watermelon plants (Citrullus lanatus [Thumb.] Matsum. and Nakai cv. Minirossa) either ungrafted or grafted onto Macis, Vita (Lagenaria siceraria [Mol.] Standl.), PS1313, and RP15 (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne) rootstocks grown in hydroponics were compared in terms of shoot dry biomass, leaf area, root‐to‐shoot ratio, SPAD index, shoot N uptake, and nitrate reductase (NR) activity 40 d after transplantation in response to nitrate concentration in the nutrient solution (0.5, 2.5, 5, 10, 15, or 20 mM of NO$ _3^- $ ). In the second experiment, the suitability of a selected rootstock with high NUE (Vita) to improve crop performance and NUE of grafted mini‐watermelon plants was evaluated under field conditions. In the hydroponic experiment mini‐watermelon grafted onto Vita rootstock needed the lowest nitrate concentration (1.31 mM of NO₃) in the nutrient solution to reach half maximum shoot dry weight. Total leaf area, SPAD index, and shoot N uptake increased in response to an increase of N concentration in the nutrient solution. At 2.5 mM NO$ _3^- $ , mini‐watermelon grafted on either Vita or RP15 had the highest NR activity whereas no significant difference was observed at 10 mM NO$ _3^- $ . The open‐field study indicated that increasing N‐fertilization rates from 0 to 100 kg ha^–1 improved total and marketable yields of mini‐watermelon plants while decreasing NUE. When averaged over N levels, the marketable yield, NUE, N‐uptake efficiency, and N‐utilization efficiency were significantly higher by 39%, 38%, 21%, and 17%, respectively, in Minirossa grafted onto Vita compared to ungrafted Minirossa plants. Therefore, grafting mini‐watermelon plants onto selected rootstocks can be used as a quick and effective method for improving productivity and NUE.     

Nitrogen nutritional status of young maize plants (Zea mays) is not limited by NaCl stress

Maize plants (Zea mays L. cv. Pioneer 3906) were grown in hydroponics with four different NaCl treatments (control, 50, 100, 150 mM NaCl). Nitrogen (N) was supplied as 2 mM Ca(NO₃)₂ in the fully concentrated nutrient solution. Plants of half of the pots were treated with additional 1 mM NH₄NO₃ 2 d after start of the NaCl application. After 23 d, the maize plants were harvested and contents and concentrations of nitrate, reduced N as well as chloride were determined in shoots and roots. With increasing NaCl stress net nitrate uptake and net root‐to‐shoot translocation of total N decreased significantly. Under salt stress, decreased nitrate concentrations in shoots probably caused substrate limitation of nitrate reductase. However, the concentrations of reduced N in shoots were not affected by salt stress and no N deficiency was observed. Additional N application to the 100 and 150 mM NaCl treatments did not improve plant growth. A Cl^?/NO antagonism was only weakly pronounced, probably because of the Cl^? exclusion ability of maize. Thus, although net uptake and net translocation of total N were markedly decreased by NaCl application, the smaller maize plants nevertheless took up enough N to meet their demand pointing to other growth‐limiting factors than N nutrition.     

Lettuce (Lactuca sativa L.) growth,yield and quality response to nitrogen fertilization in a non-circulating hydroponic system

The objective of this study was to determine the effect of nitrogen fertilization rate on growth and quality of leafy lettuce grown during the winter season in non-circulating hydroponic system. Plants were subjected to seven nitrogen (N) concentrations, i.e. 0, 30, 60, 90, 120, 150 and 180 mg L^?1 N using ammonium nitrate. Nitrogen treatments did not have a significant effect on leaf fresh and dry mass, root fresh and dry mass, number leaves and leaf area. Leaf ascorbic acid and total phenolic content, and antioxidant capacity peaked at 100 and 120 mg L^?1 N, whereas leaf chlorophyll concentration linearly increased with increasing N application. The results indicate that a solution N concentration of 100 and 120 mg L^?1 may be sufficient to improve growth, yield and quality parameters of leafy lettuce grown in non-circulating hydroponic system.     

Differences in Response to Iron Deficiency Among Some Lines of Common Bean

Abstract

Five dry bean cultivars (Coco blanc, Striker, ARA14, SVM29‐21, and BAT477) were evaluated for their resistance to iron deficiency on the basis of chlorosis symptoms, plant growth, capacity to acidify the external medium and the root‐associated Fe³⁺‐reduction activity. Plants were grown in nutrient solution supplied or not with iron, 45 µM Fe(III)EDTA. For all cultivars, plants subjected to iron starvation exhibited Fe‐chlorosis. These symptoms were more severe and more precocious in BAT477 and Coco blanc than in the others cultivars. An important acidification of the culture medium was observed between the 4th and the 8th days of iron starvation in Striker, SVM29‐21 and, particularly, ARA14 plants. However, all Fe‐sufficient plants increased the nutrient solution pH. This capacity of acidification appeared more clearly when protons extrusion was measured in 10 mM KCl + 1 mM CaCl₂. The above genotypic differences were maintained: ARA14 showed the higher acidification followed by Coco blanc and BAT477. Iron deficiency led also to an increase of the root‐associated Fe(III)‐reductase activity in all lines. However, genotypic differences were observed: Striker shows the highest capacity of iron reduction under Fe deficiency condition.     

Effect of sulfur and molybdenum levels on growth,nitrate‐assimilation,and nutrient con‐tent of Phalaris

An experiment was conducted with Phalaris aquatica L. cv. Sirolan under hydroponic conditions in the glasshouse at constant temperature of 25°C and natural sunlight. Plants were grown in double pot system with four sulfur and three molybdenum levels along with all the major‐ and micro‐nutrient elements. There was increase in growth, nitrate‐reductase activity and contents of most of the nutrient elements at all levels of sulfur and 1.68 μ/L molybdenum. Molybdenum at 3.36 μg/L level inhibited growth and nitrate‐reductase activity and decreased concentration of nutrient elements in plant. The inhibitory effect of higher level of molybdenum is perhaps mediated through its role in the nitrate‐reductase.     

Effects of a nitrification inhibitor on efficiency of nitrogen utilization by wheat and millet

Abstract

Preliminary soil incubation studies established that the nitrification inhibitor, Dicyandiamide (DCD), could maintain the ratio of NH.‐N to NO₃‐N at predetermined levels. When one part DCD was mixed with 10 parts of the ammonium fertilizer prior to incorporation with the soil, nitrification was inhibited for at least six weeks. In a greenhouse experiment, wheat was grown to maturity and millet to the flowering stage in pots containing nitrate and ammonium fertilizers treated with DCD. Soil analyses during the plant growth period indicated that ammonium oxidation in soil was effectively inhibited. Plants of both species exposed to ammonium only with DCD produced lower yields than those exposed to a mixture of nitrate and ammonium nitrogen with DCD. Plants supplied with nitrate‐only gave somewhat lower yields than the mixtures. The nitrate‐only treatments resulted in the lowest accumulation of reduced nitrogen compounds in shoots of both species. Magnesium uptake by millet and calcium and magnesium uptake by wheat were reduced as the proportion of ammonium in soil was increased.     

Optimum Phosphorus Concentration for Growth of Catharanthus roseus (L.) G. Don ‘Pacifica White’ in a Subirrigation and Top Watering System

The objective of this study was to quantify the optimum rates of water-soluble phosphorus (P) on the growth of Catharanthus roseus (L.) G. Don ‘Pacifica White’ in soilless media in a recirculating subirrigation and top watering system. The experiment was designed so that only P varied between treatments; nitrogen (N), ammoniacal N to nitrate N ratio, and potassium (K) content were held constant. Media pH decreased with increasing P concentration in the nutrient solution in both the subirrigated and top-watered plants. Shoot N, P, K, magnesium, manganese, zinc, and copper were in general greater in the subirrigated plants when compared to top-watered plants. Shoot calcium, sulfur, iron, aluminum, and boron were greater in top-watered plants when compared to subirrigated plants. Optimal plant growth was achieved at ≥0.5 mM P in the subirrigated and top-watered plants, which is lower than what is usually commercially applied. Subirrigated plants were of greater quality and dry mass regardless of P concentration in the nutrient solution, when compared to top-watered plants.     

Influence of foliar application of manganese on growth,pigment content,and nitrate reductase activity of Vigna radiata (L.) R. Wilczek under salinity

The effect of the micronutrient manganese (Mn) on the physiological performance of green gram [Vigna radiata (L.) R. Wilczek] under saline condition was studied in the present work. Green gram was grown under controlled conditions and treated with different concentrations of sodium chloride (NaCl): 100, 200, and 300 mM. The plant samples were analyzed from 25 to 65 days of plant growth at every 10-day interval. Significant difference was observed in leaf area index, membrane stability index, nitrate reductase enzyme activity, total chlorophyll, and carotenoid content in treated plants. A drastic reduction was recorded at 200 and 300 mM NaCl treated plants in the parameters. The concentration 100 mM resulted in a slight increase of the parameters. Foliar application of Mn as manganese chloride (MnCl₂) was found to improve the physiological parameters in green gram at 200 and 300 mM salinity level and was useful in alleviating the detrimental effects of NaCl.     

硝酸还原酶基因启动子NRE2元件缺失对烟草氮代谢的影响

为了探究硝酸还原酶基因启动子中硝酸盐响应元件NRE2缺失对烟草植株氮代谢的影响,以烤烟品种K326为材料,采用CRISPR/Cas9基因编辑技术获得了烟草NIA11和NIA2基因启动子中NRE2元件缺失的突变体材料,并于同一氮素营养条件下培养,测定烟草植株氮代谢相关生理指标.结果表明,与野生型相比,单突变体和双突变体叶...     

Effects of Molybdenum,Nickel, and Nitrogen Sources on the Mineral Nutrition and Growth of Rice Plants

Upland rice plants, cultivar ‘IAC 202,’ were grown in nutrient solution until full tillering. Treatments consisted of ammonium nitrate (AN) or urea (UR) as nitrogen (N) source plus molybdenum (Mo) and/or nickel (Ni): AN + Mo + Ni, AN + Mo ? Ni, AN ? Mo + Ni, UR + Mo + Ni, UR + Mo ? Ni, and UR ? Mo + Ni. The experiment was carried out to better understand the effect of these treatments on dry‐matter yield, chlorophyll, net photosynthesis rate, nitrate (NO₃ ^?‐N), total N, in vitro activities of urease and nitrate reductase (NR), and Mo and Ni concentrations. In UR‐grown plants, Mo and Ni addition increased yield of dry matter. Regardless of the N source, chlorophyll concentration and net photosynthesis rate were reduced when Mo or Ni were omitted, although not always significantly. The omission of either Mo or Ni led to a decrease in urease activity, independent of N source. Nitrate reductase activity increased in nutrient solutions without Mo, although NO₃ ^?‐N increased. There was not a consistent variation in total N concentration. Molybdenum and Ni concentration in roots and shoots were influenced by their supply in the nutrient solution. Molybdenum concentration was not influenced by N sources, whereas Ni content in both root and shoots was greater in ammonium nitrate–grown plants. In conclusion, it can be hypothesized that there is a relationship between Mo and Ni acting on photosynthesis, although is an indirect one. This is the first evidence for a beneficial effect of Mo and Ni interaction on plant growth.     

Effect of MES [2(N‐morpholino)ethanesulfonic acid] and amberlite IRC‐50 resin on nutrient pH control and soybean growth

The relative effectiveness of Amberlite IRC‐50 resin, in a recirculating ion exchange column, and several concentrations of MES [2(N‐mor‐pholino)ethanesulfonic acid] were evaluated for control of nutrient solution pH of hydroponically cultured soybean (Glycine max [L.] Merr. cv Williams). A low buffering capacity, urea‐based nutrient solution was used. MES buffer, at the concentrations evaluated (1,2, 4, and 10 mM), was less effective at maintaining desired pH than the IRC‐50 resin system. The pH of the 4.0 mM MES buffered nutrient solution decreased from 6.5 to below 4.0 in five days with 25 to 30 day old plants. By comparison, the pH of the IRC‐50 resin buffered nutrient solution dropped from 6.5 to 5.9 during the same period. Nitrate uptake by 27 to 29 day‐old plants was significantly slower when solutions were buffered with MES than with IRC‐50 resin. Rate of nitrate uptake decreased with increasing MES buffer concentrations and decreasing pH in short‐term studies on plants previously grown on IRC‐50 resin buffered nutrient solution. Mass of the plants grown on IRC‐50 resin buffered nutrient solution equaled or exceeded that of plants grown on 1, 2, or 4 mM MES. Total elemental uptake (mg/plant) by plants grown on nutrient solution buffered by IRC‐50 resin, for the ten elements tested, was equal to or greater than uptake by plants grown on nutrient solution buffered by 1, 2, or 4 mM MES. It is concluded that IRC‐50 resin in recirculating columns provides better pH control than does MES buffer for hydroponically grown soybean.     

Growth and nitrate consumption of sunflowers in the rhizostat,a device for continuous nutrient supply to plants

A hydroponic system was designed in which the replenishment of nutrients is proportional to the consumption of nitrate or ammonium by higher plants. Further characteristics of this ‘rhizostat’ are on‐line measurement of nitrate or ammonium, bubble‐free aeration of the culture solution with pure oxygen, and auxostatic pH control at 6.00±0.1. Young sunflowers were grown in the rhizostat for up to 16 days. Leaf area, total fresh weight, root fresh weight, and nutrient demand per day increased exponentially. The rate of nitrate consumption per plant followed a characteristic diurnal pattern with maximal values at the end of the 12‐h photoperiod. After two weeks of growth, about 95% of the inorganic bound nitrogen removed from the nutrient solution was recovered in the biomass of the plants. Growth of sunflower seedlings over two weeks led only to slight but tolerable deviations of macronutrient and trace element concentrations from the formula of the nutrient solution. As expected, nitrate‐grown plants lowered potassium concentration, whereas growth with ammonium resulted in an accumulation of this ion. Other plants successfully grown in the rhizostat have been corn, soybean, sugarcane, tobacco, and spinach.     

Mineral nitrogen effect on nodulation and nitrogen fixation of the stem-nodulating legume Aeschynomene afraspera

The effect of increasing amounts of nitrogen (nitrate or urea) on the nitrogen fixing capacity (acetylene reduction assay = ARA), growth (fresh and dry weight) and the number of stem- and root-nodules of the tropical legume Aeschynomene afraspera was studied in hydroponic cultures (in growth cabinet) as well as in pot experiments (field conditions). The experiments were carried out at Dakar in the rainy season of 1985. Plants were grown in the presence of 6 nitrate concentrations (0,3,6,9,12 and 15 mM N/l) in hydroponic solution and with 4 urea concentrations (0,50,100 and 200 kg N/ha) in pots. In both types of experiments, root nodulation and ARA were strongly inhibited by increasing amounts of mineral nitrogen. Stem nodulation and potential nitrogen fixation of stems, however, remained unaffected. Lower amounts of mineral nitrogen even enhanced growth as well as nitrogen fixation. The possible future of this remarkable plant as green manure or fodder in low input countries of the tropics is discussed.