不同铵硝比对菠菜生长、安全和营养品质的影响

通过水培试验,研究了等氮条件下5种不同铵硝比对菠菜生长和品质的影响。结果表明:(1)从铵硝比100∶0到0∶100,菠菜地上部鲜重不断增加,铵硝比为0∶100时,菠菜的鲜重达最大值;但铵硝比25∶75和0∶100两个处理菠菜的干物重没有显著差异(p<0.05)。(2)随着铵硝比的降低,菠菜茎叶中硝酸盐、亚硝酸盐的含量均表现为线性增加;菠菜茎叶中可溶性草酸的含量和营养液中铵硝比之间呈现出二次曲线相关,在铵硝比为25∶75时,菠菜茎叶中草酸含量最低。适当增施铵态氮有利于降低菠菜硝酸盐、亚硝酸盐及草酸的含量。(3)增铵可以提高菠菜Vc含量,铵硝比为50∶50的处理菠菜Vc含量最高;随着铵硝比的下降,菠菜茎叶中可溶性糖的含量逐渐降低,而粗蛋白的含量则以铵硝比25∶75处理最高。     

铵硝比和磷素营养对菠菜生长、氮素吸收和相关酶活性的影响

通过水培试验研究了不同铵硝比的氮素营养和磷素营养对菠菜生长、氮素吸收及硝酸还原酶活性（NRA）和谷氨酰胺合成酶活性（GSA）的影响。结果表明：在供磷水平相同时，菠菜的生物量随着铵硝比的降低而降低，但铵硝比为25：75与0：100两个处理之间没有显著差异；在铵硝比相同时，随着营养液中磷含量的增加，菠菜的生物量随之增加。菠菜茎叶中硝酸盐的含量随着铵硝比和磷水平的降低而升高。不同铵硝比处理，菠菜含氮量没有明显差异，随着磷水平的提高，菠菜植株含氮量有升高的趋势，但各处理之间差异不显著；受到生物量显著差异的影响，菠菜植株中氮素累积量随着铵硝比的降低和磷素水平的增加而增加。在铵硝混合营养条件下，缺磷会显著抑制菠菜对铵态氮和硝态氮的吸收，且磷索缺乏对菠菜吸收硝态氮的抑制作用要大于对铵态氮吸收的抑制作用。铵硝比相同时，随着营养液中磷索供应量的增加，菠菜茎叶中NRA显著增加；但是营养液中铵硝比较高时，会显著抑制菠菜茎叶中NRA，而铵硝比较低时，则有利于提高菠菜的NRA。缺磷会严重抑制GSA；在磷素水平相同时，随着营养液中铵比例的增加，菠菜茎叶中GSA显著增加。为此，在一些硝酸盐含量较高的土壤上栽培蔬菜时，可以采取增施适量磷肥的方法，以降低叶菜的硝酸盐含量。     

Role of Ammonium to Limit Nitrate Accumulation and to Increase Water Economy in Wild Swiss Chard

ABSTRACT

The present study was performed to characterize the interaction between nitrogen (N) form and availability with respect to growth, water relations, and mineral nutrition of wild swiss chard (Beta macrocarpa Guss). Plants were cultured hydroponically with two levels of N concentrations, high-N (2.5 mM) or low-N (0.5 mM), added as nitrate (NO^? ₃) or ammonium (NH⁺ ₄). At high N, growth was affected significantly by N form. If the NO^? ₃ medium was considered as control, the use of NH⁺ ₄ decreased dry matter production and leaf area by ca. 35%. Use of NH⁺ ₄ led to water economy and did not affect the nutrient content of the plant tissues. Compared to growth with high N, plants growth fell in either low- NO^? ₃ or low- NH⁺ ₄ medium. In this case, the difference between the two N sources was not significant. Our results showed that the replacement of NO^? ₃ by NH⁺ ₄ as the N source decreased the NO^? ₃ concentration in consumable leaves and increased the water use efficiency.     

Nitrogen partitioning in greenhouse‐grown broccoli in response to varying NH+ 4:NO− 3 ratios

Abstract

Broccoli (Brassica oleracea var. italica) plants were grown in the greenhouse and supplied continuously with 18 mM N in the following NH⁺ ₄:NO^? ₃ ratios: 100:0, 75:25, 50:50, 25:75, 0:100. At commercial maturity, the plant characteristics and partitioning of nitrogen in xylem and phloem saps and in plant tissue were determined. Plants fed solely with NH⁺ ₄ were stunted, exhibited signs of marginal necrosis on the lower leaves, and accumulated NH⁺ ₄ in the foliage. The maximum yield and shortest harvest time, together with minimal NO^? ₃ and NH⁺ ₄ accumulation were found at a ratio of 75:25. Ammonium concentrations in xylem sap decreased linearly with decreasing NH⁺ ₄ portion in the nutrient solution, whereas the NO^? ₃ concentrations reached a maximum when NO^? ₃ constituted 50% of the N supply. The glutamate family dominated the amino acid composition of both xylem and phloem saps, but did not vary much with NH⁺ ₄:NO^? ₃ ratio. It is suggested that the NH⁺ ₄ concentration in xylem sap may be used to assess NH⁺ ₄ vs NO^? ₃ utilization by broccoli grown under field conditions.     

氮素不同形态配比对菠菜体内游离氨基酸含量和相关酶活性的影响

采用溶液培养试验,研究了氮素不同形态配比对菠菜茎叶中游离氨基酸含量及3种主要氮代谢酶活性的影响。结果表明:1)随着营养液中铵硝比(NH4+-N/NO3--N)的降低,菠菜茎叶中游离氨基酸的总量呈下降趋势。在全硝营养下(NH4+-N/NO3--N=0∶100)下,菠菜茎叶中游离氨基酸的总量只有全铵营养(NH4+-N/NO3--N=100∶0)的34.4%。2)在全铵营养下,菠菜茎叶中游离氨基酸的主要组分是谷氨酰胺、精氨酸和谷氨酸,三者占游离氨基酸总量的百分比依次为39.8%、20.2%和8.9%;在全硝营养下,菠菜茎叶中游离氨基酸以谷氨酸、天冬氨酸和丝氨酸为主,三者占游离氨基酸总量的百分比分别为30.3%1、8.6%和8.5%。3)提高营养液中硝态氮的比例,可以显着提高菠菜茎叶中硝酸还原酶(NR)的活性,同时降低了谷氨酸脱氢酶(GDH)的活性,谷氨酰胺合成酶(GS)活性则呈现先升后降的抛物线状变化规律。4)菠菜茎叶中NR活性与谷胺酰胺含量之间存在着显著负相关关系(r=-0.968)。     

Influence of nitrogen forms and levels on the growth and nutrition of cacao

Ammonium and nitrate are the major forms of nitrogen (N) present in tropical soils. An experiment was conducted to assess the influence of nitrate and ammonium forms (NO₃^?, NH₄⁺, and mix of NO₃^? + NH₄⁺), and levels (1.5–12.0 mM) of N on the growth and nutrition of cacao (Theobroma cacao L). Growth parameters were significantly influenced by N forms, and nitrogen supplied as NH₄⁺ proved better for the growth of cacao compared with NO₃^? form and mixtures of these two forms. Irrespective of the forms of N, levels of N had no significant effect on plant growth parameters. Nutrient efficiency ratios (NERs) (shoot dry matter produced per unit of nutrient uptake) for macronutrients were sulfur>phosphorus>calcium>magnesium>nitrogen>potassium (S>P>Ca>Mg>N>K) and for micronutrients NERs were in the order of copper>boron>zinc>iron>manganese (Cu>B>Zn>Fe>Mn).     

Effect of Nitrate/Ammonium Ratios on Growth,Root Morphology and Nutrient Elements Uptake of Watermelon (Citrullus Lanatus) Seedlings

Nitrogen is taken up by most plant species in the form of nitrate and ammonium. The objective of this study was to investigate the effect of different nitrogen forms on the growth of watermelon seedlings. Plants were grown in hydroponic culture with five nitrate (NO₃^?)/ammonium (NH₄⁺) ratios (100/0, 75/25, 50/50, 25/75, 0/100). When the proportion of NH₄⁺ was increased, the leaf number, leaf area, shoot height, net photosynthesis, biomass, and root growth were significantly decreased. Higher concentrations of nitrogen (N) and phosphorus (P) were observed when plants were supplied with mixed NO₃^? and NH₄⁺ compared to NO₃^? or NH₄⁺ alone, whereas the concentrations of potassium (K), calcium (Ca), and magnesium (Mg) were decreased with increasing NH₄⁺. The microelements concentrations were generally increased with more NH₄⁺ added. In addition, plants fed with higher NO₃^?/NH₄⁺ ratios resulted in more minerals accumulation.     

Effects of Nitrate and Potassium on Ammonium Toxicity in Cucumber Plants

ABSTRACT

Interactions between nitrate (NO₃ ^?), potassium (K⁺), and ammonium (NH₄ ⁺) were investigated using hydroponically grown cucumber (Cucumis sativus L.) plants. Ammonium as the sole nitrogen (N) source at 10 mM was toxic and led to overall growth suppression, chlorosis, and necrosis of leaves. After 20 days, 50% of the plants were dead. However, when NO₃ ^? was supplied at very low concentration together with high NH₄ ⁺ (only 1% of total 10 mM N) all seedlings survived and their growth was improved. High K⁺ concentration (5 mM) also alleviated NH₄ ⁺ toxicity and increased plant growth several fold compared to intermediate concentration of K⁺ (0.6 mM). Leaf total N and ¹⁵N derived from ¹⁵N-labelled NH₄ ⁺ increased in the presence of NO₃ ^?, but decreased at high K⁺ concentration. High K⁺ supply enhanced total carbon (C) and δ ¹³C and stimulated GS and PEPCase activities in leaves and roots. Nitrate supplementation had no effect on GS or PEPCase activities. It is concluded that K⁺ may alleviate NH₄ ⁺ toxicity, partly by inhibiting NH₄ ⁺ uptake, partly by stimulating C and N assimilation in the roots.     

NITRATE/AMMONIUM RATIOS AFFECT RYEGRASS GROWTH AND NITROGEN ACCUMULATION IN A HYDROPONIC SYSTEM

Ryegrass has increasingly been used in constructed wetlands for treatment of eutrophic wastewater. To properly match plant species with the characteristics of wastewater being treated, it is important to know the performance of plant species under different nitrate/ammonium (NO₃ ^?/NH₄ ⁺) ratios. We investigated ryegrass (Lolium perenne L.) dry matter (DM) production and N accumulation under five NO₃ ^?/NH₄ ⁺ ratios (100/0, 75/25, 50/50, 25/75, 0/100) in a hydroponic system. The results showed that ryegrass total DM, shoot DM, root DM and nitrogen (N) accumulation were greater under NO₃ ^?/NH₄ ⁺ ratios of 50/50 and 75/25 than under other NO₃ ^?/NH₄ ⁺ ratios, indicating that ryegrass can be best used in constructed wetlands for treating wastewater with such NO₃ ^?/NH₄ ⁺ ratios to achieve high biomass production and efficient removal of N. On the other hand, for treating wastewater with either NO₃ ^? or NH₄ ⁺ dominate the inorganic N, other plant species that are more adapted to such conditions should be explored.     

Dry matter and nitrogen accumulation are not affected by superopt1mal concentration of ammonium in flowing solution culture with pH control

Abstract

While it is known that superoptimal concentrations of the nitrate (NO₃ ^?) ion in solution culture do not increase NO₃ ^? uptake or dry matter accumulation, the same is not known for the ammonium (NH₄ ⁺) ion. An experiment was conducted utilizing flowing solution culture with pH control to investigate the influence of superoptimal NH₄ ⁺ concentrations on dry matter, nitrogen (N), potassium (K), calcium (Ca), and magnesium (Mg) accumulation by nonnodulated soybean plants. Increasing the NH₄ ⁺ concentration in solution from 1 to 10 mM did not affect dry matter or N accumulation. Accumulations of K, Ca, and Mg were slightly decreased with the increased NH₄ ⁺ concentration. The NH₄ ⁺ uptake system, which is saturated at less than 1 mM NH₄ ⁺, is able to regulate uptake of NH₄ ⁺ at concentrations as high as 10 mM.     

Root Carbon Enrichment Alleviates Ammonium Toxicity in Cucumber Plants

ABSTRACT

The addition of carbonates to a nutrient solution to alleviate ammonium (NH₄ ⁺) toxicity in hydroponically-grown cucumber (Cucumis sativus L.) plants was investigated. Stable isotopes [nitrogen (¹⁵N) and carbon (¹³C)] were used to assess the uptake of nitrogen [NH₄ ⁺ or nitrate (NO₃ ^?)] as well as carbon [bicarbonate (HCO₃ ^?)/carbonate (CO₃ ^2?)] by the roots. Ammonium as the sole N source at 5 mM decreased plant fresh weights compared to NO₃ ^?. However, at lower concentrations of NH₄ ⁺ (25% of 5 mM total N), growth was increased compared to NO₃ ^? alone. Inorganic C enrichment [calcium carbonate (CaCO₃)] of the nutrient solution increased the fresh weight of NH₄ ⁺ grown plants with up to 150% relative to control plants receiving calcium hydroxide [Ca(OH)₂] for pH regulation. Root ¹⁵N enrichment was lower in ¹⁵NH₄ ⁺ supplied plants compared to ¹⁵NO₃ ^?, while the ¹³C enrichment in leaves was increased by NH₄ ⁺ nutrition compared to NO₃ ^? or NH₄NO_3. The enhanced C capture was associated with high PEPCase activity in the roots. It is concluded that inorganic carbon enrichment of the root medium may alleviate NH₄ ⁺ toxicity via increased synthesis of C skeletons and, accordingly, increased capacity for NH₄ ⁺ assimilation and N export to the shoots.     

Boron toxicity in kiwifruit plants (Actinidia deliciosa), treated with nitrate,ammonium, and a mixture of both

The objective of this research was to study the effects of nitrogen (N) forms (NO₃^–, 2.6 mM; NH₄⁺, 2.6 mM; NO₃^–, 1 mM + NH₄⁺, 1.6 mM) on the growth and mineral composition of kiwifruit plants exposed to three boron (B) levels (0.025, 0.1, 0.3 mM). The kiwifruit plants were grown in a 1:1 sand : perlite mixture and irrigated daily with nutrient solutions. Shoot height, mean shoot dry weight, the number of leaves, mean leaf dry weight, and N concentration of NH₄‐treated plants were significantly higher compared to the NO₃^– treatment at all B levels. The concentration of 0.3 mM B significantly reduced shoot height for all N treatments. Boron toxicity symptoms appeared 14 days after starting the experiment, when plants were treated with 0.1 and/or 0.3 mM B. The nitrate supply reduced the B concentration of roots, but B levels of different leaf parts were hardly affected by the N form. Furthermore, the NH₄‐N form significantly reduced the Mg concentration of the leaves.     

Changes in plant growth substances,contents and flower quality of rose cv. ‘Dolce Vita’ in response to nitrogen sources under soilless culture conditions

The aim of this study was to investigate the biochemical responses and vase life of rose cut flowers under different ratios of NO₃:NH₄:urea in soilless culture. In this study, urea was used as the source of nitrogen (N) in solution cultures. For this purpose, an experiment was conducted as completely randomized design with seven ratios of N forms and three replications. The rooted cuttings of rose cv Dolce Vita were supplied with seven different ratios of NO₃^?:NH₄⁺:urea (100:0:0, 70:15:15, 50:25:25, 50:0:50, 0:0:100, 50:50:0 and 0:100:0). Results showed that with the increase in urea and ammonium concentrations, the amounts of cuttings IAA, GA₃, zeatin, ABA and polyamines contents decreased significantly. Plants fertigated with nutrient solution containing NO₃^?:NH₄⁺:urea (50:25:25) had the highest concentrations of growth regulators, the highest stalk length and flower vase life. As the ammonium ratios in the nutrient solution increased, the flower vase life decreased significantly. It was concluded that using NO₃^?:NH₄⁺:urea at the ratio of 50:25:25 had the highest effects on improving the rose cut flowers quality by affecting plants growth regulators and can be recommended for cut rose production in soilless culture systems.     

Effects of different forms of nitrogen supply on the gas exchange of young pedunculate oaks (Quercus robur L.)

The effects of different forms and concentrations of N in the rooting medium on the CO₂/H₂O gas exchange of leaves of the pedunculate oak (Quercus robur L.) were investigated. Two-year-old seedlings were grown in nutrient solutions containing low (1.8 mM) or high (4.8 mM) concentrations of NH₄⁺, 3.6 mM NO₃^?, or both NH₄⁺ and NO₃^? (1.8 mM + 1.8 mM). In various sets of plants subjected to these N treatments, the following parameters were determined: biomasses of leaves and fine roots, leaf area-related net photosynthesis at light saturation (A) and leaf conductance (g), foliar concentrations of chlorophylls, N, Ca²⁺, Mg²⁺ and K⁺ and the ash alkalinity of the leaves (as a measure of the carboxylate content). In all treatments, the leaves were equally well supplied with nutrients. Oaks grown in high NH₄⁺ concentrations produced significantly smaller leaf and root biomasses. Compared to oaks cultivated with both N forms or with low NH₄⁺ concentration, oaks grown with high NH₄⁺ supply showed lower values of A and g, but no significant differences in ash alkalinity and leaf area-related chlorophyll concentrations. Oaks fed with NO₃^? as the only N form had an intermediate biomass production, but low values of A and g. The time courses of A in the different treatments closely followed the patterns of g. In all N treatments, the same linear relationship was found between A and g, indicating that, within a rather wide range, the variation in the form and amount of supplied N does not affect the instantaneous water use efficiency of young pedunculate oaks.     

Uptake,Transport, and Concentration of Chloride and Sodium in Three Citrus Rootstock Seedlings

ABSTRACT

Aspects of ammonium (NH₄ ⁺) toxicity in cucumber (Cucumis sativus L.) were investigated following growth with different N sources [nitrate (NO₃ ^?), NH₄ ⁺, or NH₄NO₃] supplied in concentrations of 1, 5, 10, or 15 mM. Plant dry weights and root: shoot ratios were lower with NH₄ ⁺-fed plants than with NO₃ ^?-fed plants. Ammonium accumulated strongly in leaves, stem, and roots when the concentration in the growth medium exceeded 1 mM. The increase in tissue NH₄ ⁺ coincided with saturation of glutamine synthetase activity and accumulation of glutamine and arginine. Low tissue levels of calcium and magnesium in the NH₄ ⁺-fed plants constituted part of the NH₄ ⁺-toxicity syndrome. Additions of small amounts of NH₄ ⁺ to NO₃ ^? -grown cucumber plants markedly increased the growth.     

Effect of N‐form on growth and nutrient content of creeping bentgrass 1

Abstract

The primary nitrogen forms utilized by plants are ammonium and nitrate. Although the importance of nutrients other than nitrogen for proper turfgrass growth is well established, the amounts of these nutrients in the plant tissue in relation to the use of different N‐forms has not been clearly documented. This study was conducted under greenhouse conditions to determine the effect of N‐form and cutting regime on growth, macronutrient, and micronutrient content of creeping bentgrass (Agrostis palustris Huds. ‘Penncross'). Treatments consisted of 100% NO3^? (calcium nitrate), 100% NH₄ ⁺ (ammonium sulfate), and a 50:50 ratio of NH₄ ⁺:NO₃ ^?. Half the turfgrass plants were maintained at a height of 1 cm (cut), while the other half of the plants were not cut until the end of the study (uncut). The uncut 50:50 treatment yielded the highest shoot, verdure, and total plant dry matter, while the uncut NO₃ ^? treatment produced the highest root dry matter. The uncut NH₄ ⁺ treatment yielded the least shoot, root, and total plant dry matter. Plants of the uncut NO₃ ^? treatment had greater accumulation of macronutrients in the shoot and root tissue compared to plants of the NH₄ ⁺ treatment. The uncut NO₃ ^? and 50:50 treatments had higher total accumulation of micronutrients compared to the uncut NH₄ ⁺‐treated plants. The cut NO₃ ^? treatment resulted in the highest macronutrient and micronutrient contents in the root tissue in comparison to other cut treatments. The cut treatments had the highest percentage accumulation of nutrients in the verdure tissue, while the uncut treatments had the highest percentage accumulation of nutrients in the shoot tissue.     

Rhizosphere effects of maize hybrids and N forms on Cd bioavailability in a limed soil

Replacing new corn genotypes in agricultural practices requires adequate information on the reaction of the selected hybrids to Cd uptake in Cd-polluted soil and an understanding of interactions with N fertilizers. A 2 × 2 × 3 factorial pot experiment with limed soil (pH 8), two maize (Zea mays) hybrids (Pioneer cultivar yellow and Pioneer cultivar white), two N fertilization forms (NH₄ ⁺ and NO₃ ^?) and three Cd exposures (0, 2 and 5 mg kg^?1 soil) was conducted under greenhouse conditions. Shoot dry mass increased significantly with NH₄ ⁺ nutrition compared with NO₃ ^? nutrition in both maize hybrids, with greater negative influence of Cd application combined with NH₄ ⁺ nutrition. The yellow cultivar had significantly greater shoot dry mass and lower Cd uptake than the white cultivar. Both hybrids exhibited similar N uptake in shoots and roots, with the exception of yellow cultivar with NH₄ ⁺ nutrition without Cd application. NO₃ ^? nutrition always decreased Cd uptake in both cultivars compared with NH₄ ⁺ nutrition. The N balance (mean across cultivars and Cd supply) after harvest showed most N uptake with NH₄ ⁺ nutrition (63.4%) and N_min remains in the soil with NO₃ ^? nutrition (48.7%). Soil pH decreased more with NH₄ ⁺ (?0.95 pH units) than NO₃ ^? nutrition (?0.21).     

Influence of Ammonium and Nitrate Nutrition on Plant Growth and Zinc Accumulation by Indian Mustard

ABSTRACT

The source of nitrogen (N) used in soil fertility practices affects plant growth, nutrient absorption, and the availability of nutrients. Consequently, the potential of plants to extract zinc (Zn) from soils may be increased by controlling the ratio of NH₄ ⁺ to NO₃ ^? to maximize growth and Zn accumulation. The objectives of this research were to determine the effects of Zn supply and different molar ratios of NH₄ ⁺ to NO₃ ^? on growth and Zn accumulation in Indian mustard (Brassica juncea Czern.). In a factorial experiment with solution culture, Indian mustard (accession 182921) was supplied with two concentrations of Zn (0.05 and 4.0 mg L^?1) in combination with six N treatments with different molar percentage ratios of NH₄ ⁺ to NO₃ ^? (0:100, 10:90, 20:80, 30:70, 40:60, and 50:50) for three weeks. Zinc supplied at 0.05 mg Zn L^?1 represented a common concentration of Zn in solution culture, whereas 4.0 mg Zn L^?1 was excessive for plant nutrition. If the supply of Zn in solution was excessive, plants developed symptoms of foliar chlorosis, which became severe if plants were supplied with 80% of N as NO₃ ^?. Supplying high proportions of NO₃ ^? in the nutrient medium stimulated Zn accumulation, whereas increasing proportions of NH₄ ⁺ (up to 50% of the total N) enhanced shoot growth. The pH of nutrient solutions generally decreased with increasing proportion of NH₄ ⁺ in solutions and with increased Zn supply. The Zn phytoextraction potential of Indian mustard was maximized, at about 15 mg Zn plant^?1, if plants received 10% of the total N as NH₄ ⁺ and 90% as NO₃ ^?.     

Ammonium Enables Aluminum-Induced Stimulation of Nitrogen Assimilation in Roots of Al-Tolerant Maize Genotypes

One aluminum (Al)-sensitive (B-73) and two Al-tolerant (F-2 and L-2039) maize genotypes were subjected to Al stress (100 μM Al) under two nitrogen (N) treatments [13.2 mM nitrate (NO₃^?) and 8.3 mM NO₃^? + 4.9 mM ammonium (NH₄⁺)]. Growth parameters, chlorophyll, root N and NO₃^? contents, root nicotinamide adenine dinucleotide (NADH-) and nicotinamide adenine dinucleotide phosphate (NADPH)-nitrate reductase, glutamine synthetase, and glutamate dehydrogenase activities were determined. Aluminum significantly decreased growth and chlorophyll content in Al-sensitive genotype. Nitrate accumulation in roots was increased by Al in tolerant plants. In the sensitive genotype, Al suppressed all enzymes in NO₃^? plants, while in NO₃^?/NH₄⁺ plants the suppression was less severe, and NADPH-nitrate reductase was even stimulated. In tolerant NO₃^?plants, glutamate dehydrogenase was stimulated in F-2 and glutamine synthetase suppressed in L-2039 genotype. In tolerant NO₃^?/NH₄⁺- plants, all enzymes were stimulated by Al, which may be attributed to their participation in defense mechanisms.     

SALINITY AND AMMONIUM/NITRATE INTERACTIONS ON TOMATO PLANT DEVELOPMENT,NUTRITION, AND METABOLITES

The interactions between NaCl and different NO₃ ^?NH₄ ⁺ ratios were investigated. Tomato plants (Lycopersicon esculentum Mill.) were grown in a greenhouse, in 120L capacity containers filled with continuously aerated Hoagland nutrient solution. Treatments were added to observe the combined effect of two NaCl levels (30 and 60 mM) and three millimolar ratios of nitrate: ammonium (14:0, 12:2, 10:4) on growth, nutrition, and contents of chlorophyll and sugars. Saline treatments decreased growth, which was partly restored by NH₄ ⁺ treatment. The leaf mineral composition showed a marked effect of nitrogen (N) source, while salinity only affected NO₃ ^? concentration. Changing the NO₃ ^?:NH₄ ⁺ ratio from 14:0 to 12:2 and 10:4 produced progressive increases in the concentrations of iron (Fe), chlorophyll, and reducing sugars in leaves. Therefore, the deleterious effect of salinity on biomass production can be minimized by the use of nutrient solutions containing higher NH₄ ⁺ concentrations, since this seemed to be correlated with increases in nitrogen assimilation and the levels of Fe and chlorophyll.