Marandu Palisadegrass Mineral Nutrition and Production Related to Nitrogen and Potassium Supply

Nitrogen (N) and potassium (K) fertilization play a key role in forage crops and can significantly increase yields of ‘Marandu’ palisadegrass [Brachiaria brizantha (Hochst. exA. Rich.) Stapf.], one of the most important forage crops in Brazil. This study aimed to identify the concentrations of total N and K, nitrate (NO₃^?), and ammonium (NH₄⁺), chlorophyll meter readings (SPAD), and nitrate reductase activity (At-RNA) required to maximize yield. Plants were grown in quartz substrate and treated with nutrient solutions that ranged from 2 to 33 mmol L^?1 for N and 0.5 to 11 mmol L^?1 for K. Dry matter production and At-RNA increased with increasing N and K supplies. SPAD readings correlated strongly with N leaf concentration and dry matter production and can be used to assess the N status of this species. The supply of N and K in the fertilization promoted high yield and adequate N and K concentration for plant metabolism.     

Significance of Nickel Supply for Growth and Chlorophyll Content of Wheat Supplied with Urea or Ammonium Nitrate

ABSTRACT

Nickel (Ni) is an essential element for activation of urease in higher plants. The effects of Ni as an essential micronutrient on growth and chlorophyll content of wheat plants grew in nutrient solutions supplied either with ammonium nitrate or urea as two different nitrogen (N) sources were investigated. Plants were allowed to grow for six weeks, then leaf chlorophyll content, shoot and root fresh and dry weights, and Ni concentration in shoots and roots were determined. Shoot and root Ni concentration in both urea and ammonium nitrate-fed plants increased significantly with the increase in Ni concentration. Growth and chlorophyll content in leaves of the urea-fed plants increased when Ni concentration in the solution was as high as 0.05 mg L^?1 and decreased at 0.1 mg Ni L^?1. In ammonium nitrate-fed plants, these parameters increased up to 0.01 mg Ni L^?1 and started to decrease with further increase in Ni concentration. Plants that grew in nutrient solutions containing urea had more shoots and roots fresh and dry weight at third and fourth Ni levels (0.05 and 0.1 mg L^?1) than those that grew in media containing ammonium nitrate with similar Ni levels. Total chlorophyll content was also higher in plants supplied with urea plus Ni. The amount of Ni required for optimum wheat growth was dependent on the forms of N used. When supplied with ammonium nitrate or urea, the amount of Ni needed was 0.01 and 0.05 mgL^?1 of nutrient solutions, respectively.     

Influence of the Modification of Nutritional Parameters in Aglaonema commutatum: K+, Ca2+, Mg2+ and Na+

Abstract

This trial was carried out to establish an appropriate nutrient solution for Aglaonema commutatum and to investigate the nutritional effects generated by modifications in the solution. Six treatments were tested: control (T₀; pH 6.5, E.C. 1.5 dS m^?1, 6 mmol L^?1 NO₃ ^?‐N, and 6 mmol L^?1 K⁺); high nitrogen (N) level (T₁; 9 mmol L^?1 6:3 NO₃ ^?–NH₄ ⁺); N form (T₂; 6 mmol L^?1 N‐NH₄ ⁺); high K⁺ level (T₃; 12 mmol L^?1 K⁺); high electrical conductivity (T₄; E.C. 4 dS m^?1, 25 mmol L^?1 NaCl), and basic pH (T₅; pH 8). At the end of the cultivation, leaf, shoot, and root dry weights and elemental concentrations were determined. Nutrient contents and total plant uptake were calculated from the dry weights and nutrient concentrations. Plant K⁺ uptake increased with application of K⁺ or basic nutrient solution. The uptake and transport of calcium (Ca) were enhanced by the use of NO₃ ^?‐N and inhibited by the presence of other cations in the medium (NH₄ ⁺, K⁺, Na⁺) and by basic pH. Magnesium (Mg) uptake increased with NO₃ ^?‐N application and with pH. Sodium (Na) uptake was the highest in the saline treatment (T₄), followed by the basic pH treatment. Sodium accumulation was detected in the roots (natrophobic plant), where the plant generated a physiological barrier to avoid damage. Dry weight did not differ significantly (p<0.05) among treatments except in the NaCl treatment. These results may help in the formulation of nutrient solutions that take into account the ionic composition of irrigation water and the physiological requirements of plants.     

硝酸盐反射仪和SPAD法对玉米氮素营养诊断的比较

精准的营养诊断是了解作物氮素营养及推荐施肥的基础。本文在田间滴灌条件下利用SPAD叶绿素仪(SPAD-502 Plus)和硝酸盐反射仪(RQ flex10)两种诊断方法对玉米关键生育时期的氮素营养诊断进行研究,旨在筛选出适宜的诊断方法,并依据诊断值建立滴灌玉米不同生育时期的施肥模型。试验设置0 kg(N)·hm~(-2)(N0)、225 kg(N)·hm~(-2)(N225)、330 kg(N)·hm~(-2)(N330)、435 kg(N)·hm~(-2)(N435)和540 kg(N)·hm~(-2)(N540)5个施氮水平,在不同生育时期测定了玉米叶片SPAD值和叶鞘NO_3~-含量,并分别与施氮量、植株全氮含量、产量进行方程拟合,比较两种诊断方法对玉米氮素营养的响应。研究结果表明:1)玉米叶片SPAD值和叶鞘NO_3~-含量均随施氮量的增加而显著升高,且在拔节期对施氮量的响应最敏感。叶鞘NO_3~-含量对施氮量变化的响应较SPAD值大,其与施氮量及玉米产量的拟合度均高于SPAD值,说明硝酸盐反射仪法对滴灌玉米氮素丰缺的反应更灵敏。2)玉米全氮含量与叶片SPAD值呈显著线性关系,而与叶鞘NO_3~-含量则以线性加平台表示。当叶鞘NO_3~-含量小于186 mg·L~(-1)时,植株全氮与NO_3~-间呈显著线性相关;当叶鞘NO_3~-含量大于186 mg·L~(-1)时,植株全氮随NO_3~-含量增加趋于不变。3)本农作区滴灌玉米最佳经济施氮量为402.5 kg·hm~(-2),对应的玉米产量为17 049 kg·hm~(-2)。玉米拔节期、抽雄吐丝期和灌浆期的临界叶鞘NO_3~-含量分别为729.3 mg·L~(-1)、536 mg·L~(-1)和81.2 mg·L~(-1)。SPAD叶绿素仪和硝酸盐反射仪均可对滴灌玉米进行氮素营养诊断,但硝酸盐速测值能更敏感地反映氮素丰缺状况,基于硝酸盐反射法进行作物氮素营养诊断及推荐施肥具有较好的准确性与适用性。     

Using Artificial Neural Network and Multiple Linear Regression for Predicting the Chlorophyll Concentration Index of Saint John’s Wort Leaves

This research investigates and compares artificial neural network and multiple linear regression for predicting the chlorophyll concentration index of Saint John’s wort leaves (Hypericum perforatum L.). Plants were fertilized with 0, 30, 60, 90, and 120 kg ha^?1 nitrogen [34% nitrogen ammonium nitrate (NH₄NO₃)]. Chlorophyll concentration index of each leaf was measured using SPAD meter. Afterwards, rgb (red, green, and blue color) values of all leaf images were determined by image processing. Values obtained were modeled using both multiple regression analysis and artificial neural networks. Using multiple regression analysis R² values were between 0.61 and 0.97. Coefficient of determination values (R²) using artificial neutral network values were found to be 0.99. Artificial neutral network modeling successfully described the relationship between actual chlorophyll concentration index values and predicted chlorophyll concentration index values.     

Effects of Foliar Spray of K on Mint,Radish, Parsley and Coriander Plants in Aquaponic System

An aquaponic system was designed to investigate the effects of foliar applications of potassium (K) on mint, radish, parsley, and coriander growth and physiological characteristics. Plants were sprayed with 100 mL pot^?1 of 0.5 g L^?1 potassium sulfate (K₂SO₄) twice a week. Fresh and dry masses of shoot in all species were higher in K-treated plants. Potassium concentration increased with K spray in the shoots of all species. K-sprayed parsley accumulated a greater amount of Fe and chlorophyll in shoots. Values of SPAD index in all species decreased significantly in untreated plants. The highest Quantum Photosynthetic Yield (F_v/F_m) values were observed in coriander plants treated with K, which was attributed to higher SPAD value in these plants. Potassium application had a negative effect on sodium (Na) and positive effect on magnesium (Mg), manganese (Mn), and zinc (Zn) concentrations in plants. These results indicated that foliar spray of K can effectively alleviate nutrient deficiencies in leafy and root vegetables grown in aquaponics.     

增铵对小白菜生长和叶绿素含量的影响

在营养液中添加一定量的铵态氮能提高作物生物量和叶绿素含量。为研究增铵对植物生长及叶绿素含量的影响机理,采用了6个NO3-∶NH4 浓度比为5·0∶0·0、5·0∶2·5、5·0∶5·0、5·0∶7·5、5·0∶10·0和0·0∶5·0的处理对小白菜进行培养试验。结果表明,在5mmolL-1硝态氮存在时,适当添加一定量的铵态氮(2·5mmolL-1)小白菜生物量和叶面积分别增加39·6%和16·3%,叶面积与生物量显著相关(r=0·941,p<0·01)。营养液中铵态氮浓度与叶片SPAD值、活性铁及叶绿体蛋白质含量均显著相关,相关系数r分别为0·914、0·954和0·964。适当提高铵态氮浓度增加小白菜产量的机制在于其促进了叶片扩展,提高了总光合面积,其原因可能是适当提高铵态氮浓度促进了叶片细胞分裂。进一步研究表明,提高铵态氮浓度提高叶绿素含量的原因,可能在于其促进了小白菜体内全铁的再利用,从而提高了叶片活性铁含量和叶绿体蛋白质含量。     

硝铵比例影响小白菜生长和叶绿素含量的原因探究

采用溶液培养试验研究了不同NO3-∶NH4+比例,分别为5.00∶0.00、3.75∶1.25、2.50∶2.50、1.25∶3.75和0.00∶5.00(mmol/L)对小白菜生长和叶绿素含量的影响及其原因。结果表明,1)与纯硝营养相比,NO3-∶NH4+为3.75∶1.25(mmol/L)时,小白菜具有最大的生物量、叶面积和叶片细胞分裂素含量;2)SPAD值、叶片可溶性蛋白质和活性铁含量均随着铵态氮比例的增加而增加;3)叶片细胞分裂素含量与叶面积、叶面积与生物量间的相关显著,相关系数(r)分别为0.97、0.95(P0.05);SPAD值与叶片可溶性蛋白质以及和活性铁含量之间的相关系数(r)分别为0.99和0.97(P0.05)。适当提高铵态氮比例可以增加小白菜叶面积可能是因提高了叶片细胞分裂素含量从而促进其扩展,进而影响生物量;提高铵态氮比例可以提高叶绿素含量,与提高了叶片蛋白质和活性铁的含量有关。     

Effects of Seasonal Nitrate Flush on Nitrogen Metabolism and Soluble Fractions Accumulation in Two Rice Varieties

ABSTRACT

Two rice varieties, ‘Piaui’ (a landrace) and ‘IAC-47’ (an improved variety), were grown in nutrient solution containing 20 mg nitrate (NO₃ ^?)-nitrogen (N) L^{? 1} up to 32 days after germination (DAG). After this, a group of plants received 200 mg NO₃ ^?NL^{? 1}, while the other was kept at 20 mg NO₃ ^?NL^{? 1} up to 42 DAG. From 42 until 56 DAG, all plants received 5 mg NO₃ ^?NL^{? 1}. Plants were collected at 42 and 56 DAG, soluble fractions, nitrate reductase (NR) and GS enzymatic activities were determined. The nutritional history of the plants affected significantly the uptake and use of nitrogen (N), and should be taken into consideration in the studies of N-use efficiency. The variety ‘Piaui’ was more efficient than ‘IAC-47’ in N-uptake use, accumulating more NO₃ ^? in its tissues at the initial phases of its cycle for subsequent utilization.     

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.     

Effect of Ammonium:Nitrate Ratios in the Response of Strawberry to Alkalinity in Hydroponics

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 (F_v/F_m) 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.     

Estimation of Leaf,Root, and Sap Nitrogen Status using the SPAD‐502 Chlorophyll Meter for Ornamental Shrubs

Abstract

The SPAD‐502 chlorophyll meter was evaluated as a rapid tool to predict plant nitrogen (N) concentration. The SPAD‐502 index utility, as a comparative tool with respect to N nutritional status, was evaluated for Laurustine (Viburnum tinus L.), tobir (Pittosporum tobira Thumb.), and strawberry tree (Arbutus unedo L.). The effect of sampling time on the SPAD‐502 index measures was also evaluated. Two sand culture experiments evaluating 1, 3, 5, and 7 mmol_c · L^?1 of total N concentration in nutrient solution and 70/30, 50/50, 40/60, and 30/70% nitrate/ammonium (NO₃ ^?/NH₄ ⁺) ratios were applied. In a media experiment, with similar conditions and fertilization, the accuracy of the SPAD‐502 regression data was evaluated. Leaf, root, and sap samples were taken in the middle and at the end of each experiment. Regression equations were established among leaf N, root N, of sap N analyzed concentrations and SPAD values with regard to global, as well as specific, data within each sampling time. Regression coefficients (b) among leaf N and SPAD were highly significant (P<0.05) for practically all sampling times. However, liner regression equations were different in all treatments among all the sampling dates. Determination coefficients (R²), in some cases, show that the SPAD‐502 index is not an adequate method for leaf, root, or sap N concentration fir Viburnum tinus L. and Pittosporum tobira Thumb. or for root or sap for Arbutus unedo L. in these experimental conditions. Nonetheless, the SPAD‐502 index could be a useful tool for relative comparison purposes and field operational nutrient management. However, the SPAD‐502 leaf greenness meter is a relatively good tool for leaf N and nutritional diagnosis for Arbutus unedo L. within the 38–66 SPAD‐502 index range.     

Nitrogen Source and Concentration Affect Growth and Performance of Bedding-Plant Impatiens

ABSTRACT

Impatiens (Impatiens wallerana Hook. f.) is the most important annual bedding plant in the United States, based on wholesale dollar volume. Production of high-quality plants requires optimization of the nutrition regimen during growth, especially the total nitrogen (N) concentration and the ratio of N sources. The objective was to determine the N concentration and the nitrate (NO₃ ^??N):ammonium (NH₄ ⁺?N) ratio of N source that optimized bedding-plant impatiens growth and flower development. Four N concentrations (3.5, 7, 10.5, and 14 mmol N · L^?1) were used in factorial combination with four ratios of NO₃ ^??N:NH₄ ⁺?N (4:0, 3:1, 1:1, and 1:3). Application of treatments was made for 30 d. Then for 10 d only deionized water was applied to reduce salt buildup. Substrate pH was lowest (4.9) with the NH₄ ⁺?N source and electrical conductivity (EC) highest, but never > 2.4 dS m^?1. Nitrogen concentration and N source displayed an interaction for most growth parameters. Shoot fresh and dry weights and flower bud number were maximized at the 1:3 NO₃ ^??N:NH₄ ⁺?N ratio with a N concentration of 10.5 mmol L^?1. However, plant diameter, leaf number, and leaf chlorophyll content responded quadratically to N form ratio, with the 1:1 ratio optimum at a concentration of 10.5 mmol N· L^?1.     

Nitrite and Ammonium Toxicity on Lettuce Grown under Hydroponics

Abstract

Nitrite (NO₂ ^?‐N) toxicity symptoms have been observed on lettuce (Lactuca sativa) at various locations in California. The objective was to evaluate the symptoms of ammonium (NH₄ ⁺‐N) and nitrite (NO₂ ^?‐N) toxicity on Sundevil iceberg lettuce and Paragon romaine lettuce and to determine lettuce growth and biomass production under different levels of NO₂ ^?‐N. Hydroponic studies under greenhouse conditions were conducted using nutrient solutions containing nitrate (NO₃ ^?‐N) and two other forms of nitrogen (NO₂ ^?‐N and NH₄ ⁺‐N) applied at a constant concentration (50 mg NL^?1) or using different NO₂ ^?‐N levels (0, 5, 10, 20, 30, and 40 mg N L^?1) and a constant NO₃ ^?‐N level (30 mg N L^?1). Crown discoloration (brownish color) was observed for lettuce grown in both NO₂ ^?‐N and NH₄ ⁺‐N solutions approximately 3 weeks after transplanting into the hydroponic systems. Lettuce grown in NO₃ ^?‐N solution produced larger biomass and greater number of leaves per plant than lettuce grown in NO₂ ^?‐N or NH₄ ⁺‐N solutions. Increasing the concentration of NO₂ ^?‐N suppressed plant height, fresh and dry biomass yield, and number of leaves and increased the root vascular discoloration. Lettuce growth was reduced more than 50% at NO₂ ^?‐N concentrations greater than 30 mg N L^?1. Even at 5 mg NO₂ ^?‐N L^?1, growth was reduced 14 and 24% for romaine and iceberg lettuce, respectively, relative to that obtained in nitrate solution. Although concentrations between 5 and 40 mg NO₂ ^?‐N L ^?1 reduced dry biomass similarly for both lettuce types, toxicity symptoms were more severe in iceberg lettuce than in romaine.     

Nutrients Accumulation,Biometric, Chlorophyll and Potassium Indexes and Production in Minituber Potato as Function of Potassium Doses in Organic and Hydroponic Conditions

ABSTRACT

Potato is one of the most economically important crops in Brazil. In this crop, potassium (K) is the most accumulated nutrient and has significant and positive effect on potato plant growth and tuber yield. Thus, the aim of this work was to determine the effects of K doses on nutrients accumulation, biometric, chlorophyll, and K indexes in potato plants grown. Two experiments were installed simultaneously in an unheated greenhouse with Agata cultivar. The experiment 1 was carried out in pot with commercial organic substrate with five K doses (0, 0.66, 1.32, 1.98, and 2.64 g dm^3?1). The experiment 2, nominated hydroponic system, with washed sand above a layer of expanded clay pebbles where the plants received daily nutrient solution application. The treatments were five K doses (0.0, 2.5, 5.0, 7.5 e 10.0 mmol L^?1). The biometrics data were collected 21 days after emergence and at harvest. Both experiments were set at a randomized block design with four replications. In both experiments, no visual symptoms of deficiency or excess were observed but only in plants at 0 mmol L^?1 of K. In both experiments, K doses interacted with some biometric and chlorophyll indexes measured in the fourth completely expanded leaf with portable SPAD and Dualex devices, commonly used as a guide to in-season fertilizer N management, leading to recommend their use only in plants properly nourished in K. K critical concentration in the fourth fully expanded leaf was 61.7 g kg^?1.     

Effects of Salinity and Nitrogen on Growth,Contents of Pigments,and Ion Accumulation of a Euhalophyte Suaeda Salsa in an Intertidal Zone and on Saline Inland

The different responses of two populations of Suaeda salsa (Linn.) Pall. (saline seepweed) from an intertidal zone and a saline inland zone to salinity [1 or 500 mM sodium chloride (NaCl)] and nitrogen [N; 0.05, 1, or 10 mM nitrate (NO₃ ^?)‐N] were investigated. Greater NO₃ ^?‐N supply (10 mM) increased shoot dry weight for the two populations of S. salsa, especially for S. salsa from the saline inland zone. Greater NO₃ ^?‐N supply (10 mM) increased the concentrations of chlorophyll and carotenoid in leaves and the NO₃ ^? and potassium (K⁺) concentrations in shoots for both populations. Greater NO₃ ^?‐N supply (10 mM) increased shoot Na⁺ in S. salsa from the intertidal zone. In conclusion, S. salsa from the saline inland zone is more responsive to NO₃ ^?‐N supply than the intertidal population. Greater NO₃ ^?‐N supply can help the species, especially the intertidal population, to grow and to mediate ion homeostasis under high salinity.     

Growth,Nutrition, and Photosynthetic Response of Black Walnut to Varying Nitrogen Sources and Rates

ABSTRACT

Black walnut (Juglans nigra L.) half-sib 1+0 seedlings were exponentially fertilized with ammonium (NH₄ ⁺) as ammonium sulfate [(NH₄)₂SO₄], nitrate (NO₃ ^?) as sodium nitrate (NaNO₃), or a mixed nitrogen (N) source as ammonium nitrate (NH₄NO₃) at the rate of 0, 800, or 1600 mg N plant^?1 and grown for three months. One month following the final fertilization, N concentration, growth, and photosynthetic characteristics were assessed. Compared with unfertilized seedlings, N addition increased plant component N content, chlorophyll content, and photosynthetic gas exchange. Net photosynthesis ranged from 2.45 to 4.84 μmol m^?2 s^?1 for lower leaves but varied from 5.95 to 9.06 μmol m^?2 s^?1 for upper leaves. Plants responded more favorably to NH₄NO₃ than sole NH₄ ⁺ or NO₃ ^? fertilizers. These results suggest that N fertilization can be used to promote net photosynthesis as well as increase N storage in black walnut seedlings. The NH₄NO₃ appears to be the preferred N source to promote black walnut growth and physiology.     

The Effect of Chloride on Yield and Nutrient Interaction in Greenhouse Tomato (Lycopersicon Esculentum Mill.) Grown in Rockwool

The effect of increasing chloride content in nutrient solution on nutrient composition in root environment, interaction of nutrients in leaves and yield of greenhouse tomato cv. ‘Grace F₁’ grown in rockwool were searched. In Experiment I (2004–2005) the levels of 15, 30, 60, and 90 mg Cl·L^?1 but in Experiment II (2006) 30, 60, 90 and 120 mg Cl·L^?1 of nutrient solution were tested. The sources of chloride were water (9.6–10.7 mg Cl·L^?1) and calcium chloride (CaCl₂·2H₂O) but the rest of nutrients and sodium in all treatments were on the same levels. It was found that increasing content of chloride from 15 to 60 mg Cl·L^?1 enhanced the total and marketable fruit yield. Within the range of 60 to 90 mg Cl·L^?1 the yield was on the optimum level but the content of 120 mg Cl·L^?1 declined it. Increasing chloride content in the nutrient solutions was reflected in rising of chlorine content in leaves. The concentration of chloride above 60 mg C·L^?1 reduced the content of nitrogen but above 90 mg C·L^?1 declined the content of calcium, sulfur and zinc in leaves. The antagonism between Cl:N, Cl:Ca: Cl:S and Cl:Zn was appeared. More variable interaction were between Cl:K and Cl:B. At the low levels of chloride, from 15 to 60 mg Cl·L^?1, potassium and boron content were decreased but at the higher ones, from 90 to 120 mg·L^?1, these nutrients had increasing course. It was not found out the effect of chloride contents on macro and microelement contents in nutrient solution emitted from drippers however their content upraising in root medium (rockwool). The highest increase was found out for Na 95.1 and 64.9 % (Exp. I and II - respectively), next for Ca (76.0, 70.1 %), Cu (62.5 and 71.0 %), Cl (43.6, 24.4), B (33.3, 21.0 %), N-NO₃ (30.4, 49.6 %), Zn (29.5, 32.8 %), S-SO₄ (25.9, 25.5 %), K (24.5, 24.1 %), Fe (19.8, 19.2 %), Mn (17.5, 21.3 %) and Mg (14.9, 11.7). Advantageous effect of chloride on tomato yield justified the need to introduce for the practice adequate chlorine nutrition, and recommend to maintain 60 to 90 mg Cl·L^?1 in nutrient solution. The best yield appeared when content of chlorine in leaves (8th or 9th leaf from the top) was in the range 0.48-0.60 % of Cl in d. m.     

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.     

Growth,Nitrate Accumulation,and Macronutrient Concentration of Pakchoi as Affected By External Nitrate-N: Amino Acid-N Ratio

ABSTRACT

A study was carried out to determine the influence of nitrogen (N) sources on the growth, nitrate (NO₃ ^?) accumulation, and macronutrient concentrations of pakchoi (Brassica chinensis L.) in hydroponics. Plants were supplied with NO₃ ^? and two amino acids (AA), glutamic acid (Glu), and glutamine (Gln), at six NO₃ ^?-N/AA-N molar ratios: (1) 100:0, (2) 80:20, (3) 60:40, (4) 40:60, (5) 20:80, (6) 0:100. The total N concentration was 12.5 mmol/L for all treatments in nutrient solutions. Both AAs reduced plant growth with decreasing NO₃ ^?-N/AA-N ratios, but the reduction was for Gln than for Glu. At 80:20 NO₃ ^?-N: Gln-N ratio, the Gln had no significant effect on pakchoi fresh weights. Decreasing NO₃ ^?-N/AA-N ratios reduced NO₃ ^? concentrations in the plant, regardless of AA sources. Adding an appropriate portion of AA-N to nutrient solutions for hydroponic culture increased concentrations of N, phosphorus (P), and potassium (K) in pakchoi shoots. Substituting 20% or less of NO₃ ^?-N with Gln-N in hydroponic culture will increase the pakchoi quality by reducing NO₃ ^? concentration and increasing mineral nutrient concentrations in shoots without significant reduction of crop yields.