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1.
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.  相似文献   

2.
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.  相似文献   

3.
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 NH4NO3. 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.  相似文献   

4.
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.  相似文献   

5.
《Journal of plant nutrition》2013,36(12):2413-2424
Abstract

Tomato and watermelon plants were grown in nutrient solutions in which nitrogen (N) was supplied as NO3 ? (6 mM‐N) or NH4 + (6 mM‐N). The experiments were conducted to evaluate the effect which different N sources exert on iron (Fe) uptake and accumulation, on the enzymatic activities of aconitase (Aco), chelate reductase (FeCH‐R), peroxidase (POD), catalase (CAT), and Fe‐superoxide dismutase (FeSOD), and on biomass production. For both species of plants, fertilization with NH4 + caused the total Fe concentration to be lower, in the roots and in the leaves in relation to the concentrations recorded in plants fertilized with NO3 ?. The response of the enzymes related to Fe correlated with their concentration. The plants treated with N?NO3 ? registered the highest activities in Aco, FeCH‐R, POD, and CAT for both tomato and watermelon. On the other hand, only in the tomato plants was the superoxide dismutase (SOD) activity appreciably influenced primarily by NH4 +, due possibly to the toxic effect of this N source. Finally, in relation to biomass production, fertilization with NH4 + drastically reduced growth in the tomato plants, while in watermelon plants, no significant alteration was detected in dry‐matter production, regardless of the N form used. It was concluded that the response of the parameters analyzed to NH4 + fertilization, in tomato and watermelon, compared to fertilization with NO3 ? was similar. By contrast, tomato plants, but not watermelon plants, were negatively influenced by NH4 +.  相似文献   

6.
Abstract

Nitrogen‐form effect on nutrient uptake and the subsequent concentration of nutrients in turfgrass plant tissue has not been thoroughly investigated. This study evaluated the effects of clipping regime and N‐form on the tissue concentration of macronutrients and micronutrients and macronutrient uptake in ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.). Turfgrass plugs were grown under greenhouse conditions in a modified Hoagland's solution with a combination of three nutrient solutions (100% NO3 ?, 100% NH4 +, and 50:50 ratio of NH4 +:NO3 ?) and two cutting regimes (cut and uncut). Concentrations of macronutrients and micronutrients were determined for shoot, root and verdure. Nutrient uptake was determined weekly. Uncut NO3 ?‐treated plants accumulated higher concentrations of K, Ca, Mg, B and Cu in the shoot tissue; P, K, Ca, Mg, B, Cu, Mn and Zn in the root tissue; and P, Ca, Mg, B, Fe and Mn in the verdure compared to uncut NN4 +‐treated plants. Nitrate uptake was greater with uncut NO3 ?‐treated plants than was NH4 + absorption with uncut NH4 +‐treated plants. Plants grown with the uncut 50:50 treatment adsorbed more NH4 + than NO3 ?. Plants grown with the uncut NO3 ? and 50:50 treatments adsorbed higher amounts of P, K, and Ca compared to the NH4 + treatment. The cut NO3 ?‐treated plants accumulated higher concentrations of K in the shoot tissue; P, Ca, Mg, B, Cu, Fe and Mn in the root tissue; and B in the verdure than did the cut NH4 +‐treated plants. Cut NO3 ?‐treated plants adsorbed less NO3 ? than did cut NH4 +‐treated plants adsorbed NH4 +. The cut 50:50 treatment adsorbed more NH4 + than NO3 ?. Plants grown with NO3 ? and 50:50 treatments, under both cutting regimes, resulted in higher concentrations of most macro‐ and micronutrients and greater nutrient uptake compared to the NH4 +‐treated plants.  相似文献   

7.
13 N-Iabelled experiments were carried out with barley and squash seedlings to analyse the effect of methionine sulphoximine (MSO), as an inhibitor of the ammonium assimilation, on NH4+ fluxes in the roots at the level (150 μM NH4+) of the high affinity uptake system (HATS). MSO pretreatment in the root medium significantly accelerated NH4+ influx and efflux in NH4+ -fed plants of both species. Concomitantly, the level of NH4+ extracted from the root and shoot tissues was strongly elevated whereas the translocation of13 N-Iabelled organic substances (presumably amino products) into the shoots was markedly reduced. The onset of the increased NH4+ influx did not occur immediately but was indicated about 1 h after the application of MSO to the nutrient solution. Also, MSO did not directly affect the uptake of13 NO3?. The reason why MSO treatment leads to an acceleration of the NH4+ influx against an increasing level in the cell tissue remains obscure. In squash, an intermediate of NO3? metabolism is thought to suppress NH4+ uptake since NH4+ influx was high in N-free- and NH4+ -grown seedlings but was reduced about threefold in NO3? -fed squash plants; the suppression was not eliminated by MSO treatment.  相似文献   

8.
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.  相似文献   

9.
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.  相似文献   

10.
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.  相似文献   

11.
High concentrations of bicarbonate (HCO? 3) cause alkalinity of irrigation water and are associated with suppression in plant growth and micronutrient deficiencies, such as iron (Fe) and zinc (Zn). Because reports indicate that the deleterious effects of alkalinity may be counteracted partially by supplementary potassium (K+) or ammonium (NH4 +) an experiment was designed to evaluate the response of bean plants (Phaseolus vulgaris L.) grown in high alkalinity conditions to varying proportions of NH4 +, K+, or sodium (Na+) (as a potential substitute for K+). Plants established in a growth chamber were grown in hydroponics for 21 days in solutions containing 5 mM HCO? 3 and a total of 5 mM of a mixture of NH4 +, K+, and Na+. The proportions of NH4 +, K+, and Na+ were designed according to mixture experiment methodology. Total N in all the mixture treatments was maintained at 10 mM by using nitrate (NO? 3)-N, thus the NH4 +:NO? 3 ratio varied according to the proportion of NH4 + in the mixtures. Alkalinity caused suppression in plant growth and chlorophyll concentration in the younger leaves, whereas excessive NH4 + was associated with leaf scorching and decreased leaf expansion. High proportions of K+ alleviated alkalinity symptoms and produced higher shoot and root dry mass provided that NH4 + was included in the mixture. However, a proportion of NH4 + higher than 0.333 in the mixture (>1.66 mM NH4 +) induced toxicity. The highest shoot dry mass occurred if the NH4 +:NO? 3 ratio was 0.19:0.81 and the NH4 +:K+:Na+ proportion was 0.38:0.38:0.24 (1.9 mM NH4 + + 1.9 mM K+ + 1.2 mM Na+). Thus, an improvement in plant growth is achieved when NH4 +, K+, and Na+ are blended together, in spite of the high alkalinity treatment imposed. Optimum NH4 + was associated with a decrease in solution pH and an increase in shoot Fe and Zn concentration.  相似文献   

12.
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 ?.  相似文献   

13.
ABSTRACT

This article presents the effects of nitrate/ammonium (NO3 ?/NH4 +), applied at different proportions to the root media with or without 5 mmol bicarbonate (HCO3 ?), on the yield and chemical composition of tomato fruit. Tomato plants were grown hydroponically (pH 6.9) in glasshouse conditions. The yield of fruit fresh matter from four clusters obtained from plants grown on the medium with NH4 + was about 25% lower than from the plants grown on the medium containing NO3 ? as the nitrogen (N) source. Supplying NO3 ?/NH4 + at a ratio of 4:1 increased the fruit yield by about 20% in comparison with the value recorded for NO3 ??plants. The enrichment of the medium with HCO3 ? stimulated the bearing, while the result depended on the ratio of NO3 ?/NH4 +. A combined treatment of HCO3 ? with NO3 ? or NH4 + in the medium increased yields by about 28% and 11%, respectively, in comparison to plants cultivated without HCO3 ?. The application of NO3 ?/NH4 + at ratios of 4:1 and 1:1 with HCO3 ? increased the respective yields by about 16% and 10% in comparison with plants grown without HCO3 ?. Modifications in the composition of the media affected the accumulation of organic solutions in the fruit. The NH4 + nutrition effected a 20% decrease in the accumulation of reducing sugars in the fruit in comparison to the fruit of plants grown in media with NO3 ?. In the cultivation of plants in media with various NO3 ?/NH4 + proportions the intermediate values of the reduced sugar concentrations were recorded in comparison with the values obtained for NO3 ??plants and NH4 +?plants. The enrichment of media with HCO3 ? increased the concentration of sugars in fruit from about 28% (for NO3 ??plants) to about 10% (for NH4 +?plants).

Malate and citrate are the main constituents of carboxylates in tomato fruit. The form of nitrogen applied to the medium did not significantly affect the concentration of carboxylates in fruit. Significant differences in carboxylate concentrations appeared in fruit grown on media enriched with HCO3 ? ions. In comparison with the cultivation without HCO3 ?, increases in the accumulation of carboxylates varied from about 22% to 30% depending on the form of the applied nitrogen. The concentration of amino acids in the fruit of plants grown with NH4 + exceeded that in NO3 ??plants by about 55%. In the plants grown on media of modified NO3 ?/NH4 + proportions, the concentration of amino acids in fruits were positively correlated with the level of NH4 + in the medium. The enrichment of media with HCO3 ? stimulated a further increase in amino acid concentration in fruit by about 9% in NO3 ? plants and about 21% in NH4 + plants compared with the respective control (without HCO3 ?).  相似文献   

14.
Abstract

Tomato plants were grown in sand culture with NH+ 4, and NO? 3, forms of N and three levels of light. Plants supplied with NH+ 4, nutrition under high light intensity had symptoms of stunting, leaf roll, wilting, interveinal chlorosis of the older leaves, and one third the dry weight of N03‐fed plants. In contrast, growth of plants receiving NH+ 4, nutrition under shade appeared normal although dry weight was reduced. NH4‐N nutrition suppressed K, Ca and Mg accumulation in tissues and increased P contents as compared to NO3‐N nutrition.  相似文献   

15.
ABSTRACT

An experiment was conducted to study the effects of nitrate (NO3 ?) and ammonium (NH4 +) ratios in nutrient solutions on the growth and production of fruits, runners, and daughter plants of strawberry Fragaria x ananassa Duch., grown in a hydroponic system. Five treatments were applied, consisting of different proportions of NH4 + and NO3 ? in the nutrient solution. The NH4 +:NO3 ? ratios were: T0 = 0:4, T1 = 1:3, T2 = 2:2, T3 = 3:1, and T4 = 4:0, at a constant nitrogen (N) concentration of 4 mol m?3. Growth and morphogenesis were characterized by monitoring leaf-area increase, number of flowers and fruits per plant, and number of daughter plants of first and second generations. Nitrogen and carbon (C) content were measured at the end of the experiment in the organs of both mother and daughter plants. None of the variables related to the growth of the mother plant was affected by the treatments. However, the number of fruits increased with the proportion of NH4 + in the nutrient solution. The number of daughter plants produced was affected only at high NH4 + proportions, and their size (dry matter per daughter plant) and fertility (number of second-generation plants per first-generation plants) were reduced. The N or C content of the plants was not significantly affected by the treatments, but the C/N ratio in the crowns of mother plants was higher in treatments with 25% and 50% NH4 + in the nutrient solution.  相似文献   

16.
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.  相似文献   

17.
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.  相似文献   

18.
ABSTRACT

A pot experiment was conducted to study the influence of four nitrogen (N) fertilizer forms [Urea; calcium nitrate, Ca(NO3)2; ammonium sulfate, (NH4)2SO4; and organic N] on growth, photosynthesis, and yield of rice under two cadmium (Cd) levels (0 and 100 mg Cd kg?1 soil). Cadmium addition significantly reduced photosynthetic rate, and the reduction varied with N fertilizer form, with ammonium (NH4 +)-N and urea treated plants having more reduction. Nitrogen form had a distinct effect on SPAD value, and the effect was also dependent on Cd level and growth stage. Cadmium-stress significantly reduced flag leaf area, but for the second leaf, only the plants supplied with organic N showed the reduction. There was a significant difference in plant height among four N forms, with NH4 +- and nitrate (NO3 ?)-treated plants having the highest and lowest height, respectively. Cadmium stress caused significant reduction in grains per panicle and total plant weight, and the reduction varied with N form, with organic N treatment showing more reduction. There were significant differences among N forms in N and Cd concentrations of the plants subjected to Cd stress, with NH4 +-N treated plants having highest N and lowest Cd concentrations and NO3 ?-treated plants having lowest N and highest Cd uptake. The results showed that the inhibition of Cd stress on growth and yield formation of rice is closely related to N fertilizer form.  相似文献   

19.
《Journal of plant nutrition》2013,36(10):1561-1573
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.  相似文献   

20.
Strawberry (Fragaria ananasa) plants were grown in hydroponics in a greenhouse, where the supply of different ammonium (NH4+): nitrate (NO3?) ratios, was investigated to reduce the negative effect of alkalinity in nutrient solutions. The experiment was arranged in factorial combination with two factors, NH4+:NO3? ratios (0%:100%, 25%:75%, 50%:50%, 75%:25%, and 100%:0%) and bicarbonate (0, 25, 50, and 75 mM; NaHCO3). Plants treated with increasing bicarbonate concentrations exhibited significantly inhibited growth. In plants treated with NH4+ and NO3? simultaneously, there was a counteraction of the bicarbonate-induced growth suppression. Sole NO3? application in the presence of high bicarbonate resulted in poor growth and plant death due to high alkalinity. The adverse effect of alkalinity on SPAD values and maximal quantum yield of PSII photochemistry (Fv/Fm) alleviated with increasing proportion of NH4+ in nutrient solutions. The results showed that fruit numbers and yield of strawberry increased with elevation of NH4+ in nutrient solutions.  相似文献   

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