Arginase activity in the cotyledons of soybean seedlings

The influence of naphthylacetic acid, abscisic acid, gibberellic acid and kinetin on the formation of aerenchyma in seedling roots of Zea mays L. cv. Capella has been studied in relation to reported changes of their concentration in poorly aerated roots, which readily form aerenchyma, and to the effects of these hormones on the production of ethylene, a major factor promoting aerenchyma formation. Because the absence of nitrate accelerates aerenchyma formation in aerated roots, their influence on these roots was compared. The growth regulators were added to roots growing in non-aerated and aerated nutrient solutions, and aerenchyma formation and the production and endogenous concentration of ethylene were measured. Naphthylacetic acid prevented aerenchyma formation in both aerated roots without nitrate and in non-aerated roots although it enhanced the ethylene concentration of the roots. Abscisic acid also prevented aerenchyma formation, but without affecting the ethylene concentration. Gibberellic acid promoted aerenchyma formation in aerated roots only, but ethylene production in both aerated and non-aerated roots. Kinetin promoted aerenchyma formation in both aerated and non-aerated roots. It stimulated ethylene production in aerated roots, but slightly inhibited it in non-aerated roots. Co²⁺ and Ag⁺, which suppress ethylene production and action, respectively, reduced the promoting effects of gibberellic acid, but not those of kinetin. It is concluded that the effects of the plant growth regulators on aerenchyma formation in maize roots were, with a possible exception for gibberellic acid, not the result of altered ethylene concentrations in the roots. Their influence on aerenchyma formation is discussed in relation to their reported actions on cell membranes.     

Adaptation of barley roots to low oxygen supply and its relation to potassium and sodium uptake

The uptake of Na⁺ and K⁺ by barley seedlings grown on aerated or non-aerated solutions was studied. Plants growing in culture solution took up K⁺ with high selectivity whether the solution was aerated or not. Roots of plants grown on aerated CaSO₄ and transferred to a solution of KCl and NaCl had a lower preference for K⁺ than roots of plants grown on non-aerated CaSO₄. Both kinds of low-salt roots were much less able to discriminate between K⁺ and Na⁺ than high-salt roots grown on a culture solution. The different levels of K⁺ selectivity are suggested to be related to H⁺ release from the tissue.     

Inductive Responses of Alcohol and Malic Dehydrogenases in Relation to Flooding Tolerance in Roots

The levels of alcohol dehydrogenase and malic dehydrogenaseactivity were investigated in the roots of various species grownfor several days, in aerated and non-aerated culture solutions.The activity of these enzymes in non-aerated cultures increasedbut only in those species previously found to be intolerantof experimental flooding. The induction of alcohol dehydrogenasewas reversible. Physiological concentrations of acetaldehydeinduced alcohol dehydrogenase activity, this induction beinggreatest in the species intolerant of flooding. It is suggestedthat the ineffectiveness of the inductive stimulus in the plantstolerant of flooding contributes to their homeostatic survivalproperties under high water-table conditions.     

The effect of iron supply on the yield and composition of leaves of tomato plants

Summary This paper describes a factorial experiment which was designed to elucidate the effect of total iron supply and rate of iron supply on the yield of tomato plants. Information was also obtained on the effect of iron supply and leaf age on the concentration of a number of nutrient elements in the leaf tissue.Increasing the total iron supply increases the yield, and the iron concentration in the leaves, while the manganese, phosphorus, sodium, calcium and magnesium decrease in concentration. The young leaves have a lower concentration of iron, manganese, potassium, sodium, calcium and magnesium than the older leaves, while the reverse is true of nitrogen and phosphorus. A slow rate of iron supply decreases the yield and sodium concentration in the leaves but increases the manganese and phosphorus concentrations.Interaction between total iron supply and leaf position affects the manganese, potassium, calcium and magnesium concentrations in the leaves, while the interaction between total-iron level and rate of iron supply affects the phosphorus and calcium concentration in the leaves.     

A comparative study of the effects of natural and synthetic ligands on iron uptake by plants

Summary The uptake of iron by wheat seedlings was investigated using half-strength Hoagland's nutrient solution containing 2.0 M ferric chloride labelled with⁵⁹Fe. The iron content of root tissue, which includes adsorbed iron, was depressed by the presence in the solution of the synthetic ligands EDTA and polymaleic acid (PMA) and by the natural ligands, humate, fulvate and a water-extractable soil polycarboxylate. The patterns of change in iron content of the shoots were in all cases different from those of the roots and were of two types. EDTA and humate increased the iron content of the shoots to maximum values, at ligand concentrations of 5.0 M and 2.5 mg l^–1 respectively, and decreased it at higher concentrations. Fulvate, water-extractable soil polycarboxylate and PMA increased the iron content of the shoots up to the maximum ligand concentrations tested (25 mg l^–1). These results are discussed in the light of the likely solution chemistry of iron and the various ligands.     

TOXIC EFFECTS OF HEAVY METALS ON CROP PLANTS GROWN IN SOIL CULTURE

A number of pot experiments were made on various crops, to study the effects on the chemical composition of the plants of treating the soil with cobalt, copper or nickel sulphates, or with the cupric or ferric salts of ethylenediamine-tetraacetic acid (EDTA).
The tops of copper sulphate-treated plants usually contained higher concentrations of copper, manganese, calcium and magnesium and lower concentrations of potassium and phosphorus, than those of control plants.
The most marked effect of cobalt on oat was to increase the concentration of Ca+Mg in the tops; nickel had a profound effect on the composition of barley tops.
Total iron concentration was reduced in oat by cobalt and copper, and in barley by copper and nickel application. Symptoms of iron deficiency appeared only in the oat plants, their incidence being correlated with the reduction in iron concentration in the tops.
The ferric salt of EDTA tended to reduce the incidence of iron deficiency symptoms produced in oat by copper sulphate, but also gave rise to distinct toxic effects. Plants given the cupric salt of EDTA contained unusually large amounts of iron.     

Comparative Physiology of Apple Rootstocks: II. The Effect of pH and Aeration on the Growth of Malling Apple Rootstocks in Water Cultures

Three Malling apple rootstocks, M.IX, M.II, and M.XVI, weregrown in aerated and non-aerated nutrient solutions at pH 3·6,4·0, and 5·5, and their growth and survival comparedwith rootstocks grown in sand and in soil. No plants survivedin the non-aerated cultures due to severe bacterial and fungalattack on the roots. In the aerated series a marked differencein susceptibility of rootstocks to root infection was found,M.XVI being considerably more resistant than M.II or M.IX. Morerootstocks survived at the lower pH's (4·0 and 3·6)but among surviving plants of M.XVI growth was much less thanat pH 5·5. It would appear therefore that factors makingfor survival do not of necessity make for optimum growth. Insand and soil cultures all plants survived.     

Kinetic model for growth of Phaeodactylum tricornutum in intensive culture photobioreactor

A kinetic model has been developed to estimate the specific growth rate of Phaeodactylum tricornutum in batch cultures. The cultures were carried out in a laboratory scale photobioreactor. Some factors like pH, temperature and irradiance were studied. In the first case, an optimum pH of 7.8 and a specific growth rate of 0.064 h⁻¹ were achieved for certain nitrate conditions and illumination. The temperature influence has been modelled by a modified Sinclair model. The optimum temperature was achieved at 20.4 °C in aerated cultures and at 22.3 °C in non-aerated cultures. Better adaptation to low temperatures than high ones has been obtained. The experiments carried out with different irradiances drive to a simple Monod's equation for the irradiance influence on growth, with semi-saturation irradiance of 10.2 μEinstein⁻² s⁻¹ in aerated cultures and of 6.8 μEinstein m⁻² s⁻¹ in non-aerated cultures.     

Lipids in plant tissue cultures. V. Effect of environmental conditions on the lipids of Glycine soja and Brassica napus cultures.

The environmental conditions prevailing during growth of plant tissue cultures affect the concentration of certain lipid classes and the fatty acid patterns of the total lipids. Irrespective of whether the cultures are grown under continuous illumination or in the dark, aerated cultures contain larger proportions of sterols, steryl esters, steryl glycosides and various sterylglycolipids and lower concentrations of squalene than non-aerated cultures. The lipids of the latter contain larger proportions of saturated very long-chain fatty acids than those of the former cultures.     

Study of Zn,Cu and Pb content in plants and contaminated soils in Sardinia

Trace elements in soils exist as components of several different fractions. We have analyzed the correlation between total and extractable (EDTA, calcium chloride and deionized water) Zn, Pb and Cu concentrations in soils and the concentration of these elements in plant leaves. Soil and plant samples have been taken from Sulcis-Iglesiente (Sardinia), an area rich in mining tailings. This has made that the concentrations of the trace element under study in soils were varied. Three plants have been studied: Dittrichia viscosa, Cistus salviifolius, and Euphorbia pithyusa subsp. cupanii. Soil samples beneath each of them at depths of 0–30 and 30–60 cm have been considered. The highest concentration of trace elements in the leaves of the studied species has been found for Zn. The calcium carbonate content and the crystalline and amorphous forms of iron in the soil have determined the concentration of metal in plant leaves. The soil concentrations that have been found with the extraction methods are uncorrelated with Pb and Cu concentrations in plants, but Zn is correlated with the fraction extracted with EDTA and calcium chloride. The concentrations of trace metals in plants are most closely related to the soil contents of CaCO₃, electrical conductivity, Fe_ox, and Fe_dc.     

Improved methods for reducing calcium and magnesium concentrations in tissue culture medium: Application to studies of lymphoblast proliferation in vitro

Summary We have compared several methods for reducing calcium and magnesium concentrations in tissue culture medium, with the objective of producing selective deficiency effects on the growth of mouse (L5178Y) and human (P1R) lymphoblasts. In experiments in which calcium- and magnesium-“free” McCoy’s medium was supplemented with 15% horse or fetal calf serum, enough calcium and magnesium was provided by serum to support normal lymphoblast growth rate. Either dialysis or chelating-resin treatment of horse or fetal calf serum reduced calcium and magnesium contents approximately 100-fold. Use of dialyzed sera resulted in reduced growth rate, although in most cases the reduction in growth could be attributed to other effects of dialysis on serum, inasmuch as growth in those experiments was not restored to normal by the addition of calcium and magnesium to the medium. In contrast, the reduction of lymphoblast growth rate that occurred when resin-treated serum was used was always attributable to removal of calcium and magnesium, as normal growth always occurred in cultures to which calcium and magnesium were added. To demonstrate a growth-inhibiting effect on either mouse or human lymphoblasts by severe reduction of either calcium or magnesium in the presence of normal amounts of the alternative cation, it was necessary to (a) expose McCoy’s Ca−Mg-“free” medium to chelating-resin to reduce further the residual cation concentrations; (b) wash cells from stock cultures in a medium devoid of calcium and magnesium prior to inoculation into experimental cultures; (c) reduce the proportion of serum in the final medium from 15 to 5%; and (d) add 100 μM EGTA to cultures. Under these conditions, growth of both cell types was completely abolished in the presence of normal magnesium but in the absence of added calcium, and markedly reduced in the presence of normal calcium but in the absence of magnesium. These modifications did not compromise growth in cultures containing normal concentrations of both ions. This work has been supported by a Research Grant from the U.S. Public Health Service (CA 12790), from the Monroe County Cancer and Leukemia Association, and by a contract from the Atomic Energy Project at the University of Rochester, and has been assigned publication no. UR-3490-624.     

Ethylene-promoted formation of aerenchyma in seedling roots of Zea mays L. under aerated and non-aerated conditions

The role of ethylene in the formation of lysigenous cortical cavities (aerenchyma) in seedling roots of Zea mays L. cv. Capella, has been studied under aerated and non-aerated conditions. Passing roots from air to aerated water or from an aerated nutrient solution to a non-aerated solution, promoted cavity formation and was accompanied by an increase of the endogenous ethylene concentration. When the endogenous ethylene concentration of roots in aerated nutrient solutions, which otherwise would not produce much cavities, was enhanced by applying ethylene gas (0.1 and 1.0 μl 1^-1 in air) or the ethylene precursor 1-aminocyclopropane-1-car-boxylic acid, cavity formation was promoted. When, on the contrary, the endogenous ethylene concentration of the roots was reduced by adding the inhibitors of ethylene biosynthesis, cobalt ions and aminooxyacetic acid, or when the ethylene action was prevented by silver ions, cavity formation was prevented. It is concluded that endogenous ethylene controls the induction of cavity formation in the roots.     

Seasonal Variations and Aeration Effects on Water Quality Improvements and Physiological Responses of Nymphaea Tetragona Georgi

Seasonal variations and aeration effects on water quality improvements and the physiological responses of Nymphaea tetragona Georgi were investigated with mesocosm experiments. Plants were hydroponically cultivated in six purifying tanks (aerated, non-aerated) and the characteristics of the plants were measured. Water quality improvements in purifying tanks were evaluated by comparing to the control tanks. The results showed that continuous aeration affected the plant morphology and physiology. The lengths of the roots, petioles and leaf limbs in aeration conditions were shorter than in non-aeration conditions. Chlorophyll and soluble protein contents of the leaf limbs in aerated tanks decreased, while peroxidase and catalase activities of roots tissues increased. In spring and summer, effects of aeration on the plants were less than in autumn. Total nitrogen (TN) and ammonia nitrogen (NH₄ ⁺-N) in aerated tanks were lower than in non-aerated tanks, while total phosphorus (TP) and dissolved phosphorus (DP) increased in spring and summer. In autumn, effects of aeration on the plants became more significant. TN, NH₄ ⁺-N, TP and DP became higher in aerated tanks than in non-aerated tanks in autumn. This work provided evidences for regulating aeration techniques based on seasonal variations of the plant physiology in restoring polluted stagnant water.     

Mineral nutrition of cacao (Theobroma cacao L.)

Summary Two experiments on cacao seedlings grown in sand culture are described, the first of which was concerned with variations in the levels of nitrogen, phosphorus, potassium, calcium, magnesium and sulfur (the macronutrient experiment) and the second dealing with variations in the levels of iron, copper, zinc, boron, manganese, and molybdenum (the micronutrient experiment).Many of the deficiency symptoms obtained were similar to those reported in the literature and they have not been described again. However, additional information is provided for symptoms of phosphorus, potassium, calcium, iron, manganese, copper, boron, and molybdenum deficiencies.The effects of all treatments on the dry weights of leaves, stems, and roots are presented. The effects of the macronutrient treatments on the levels of nitrogen, phosphorus, potassium, calcium, and magnesium in the leaves of eight month old plants and the effects of micronutrient treatments on the levels of nitrogen, phosphorus, potassium, calcium, magnesium, iron, manganese, copper, zinc, boron, molybdenum, sodium, and aluminium in the leaves of eleven-month-old plants are presented and discussed.     

Improved methods for reducing calcium and magnesium concentrations in tissue culture medium: application to studies of lymphoblast proliferation in vitro.

We have compared several methods for reducing calcium and magnesium concentrations in tissue culture medium, with the objective of producing selective deficiency effects on the growth of mouse (L5178Y) and human (P1R) lymphoblasts. In experiments in which calcium- and magnesium- "free" McCoy's medium was supplemented with 15% horse or fetal calf serum, enough calcium and magnesium was provided by serum to support normal lymphoblast growth rate. Either dialysis or chelating-resin treatment of horse or fetal calf serum reduced calcium and magnesium contents approximately 100-fold. Use of dialyzed sera resulted in reduced growth rate, although in most cases the reduction in growth could be attributed to other effects of dialysis on serum, inasmuch as growth in those experiments was not restored to normal by the addition of calcium and magnesium to the medium. In contrast, the reduction of lymphoblast growth rate that occurred when resin-treated serum was used was always attributable to removal of calcium and magnesium, as normal growth always occurred in cultures to which calcium and magnesium were added. To demostrate a growth-inhibiting effect on either mouse or human lymphoblasts by severe reduction of either calcium or magnesium in the presence of normal amounts of the alternative cation, it was necessary to (a) expose McCoy's Ca-Mg-"free" medium to chelating-resin to reduce further the residual cation concentrations; (b) wash cells from stock cultures in a medium devoid of calcium and magnesium prior to inoculation into experimental cultures; (c) reduce the proportion of serum in the final medium from 15 to 5%; and (d) add 100 muM EGTA to cultures. Under these conditions, growth of both cell types was completely abolished in the presence of normal magnesium but in the absence of added calcium, and markedly reduced in the presence of normal calcium but in the absence of magnesium. These modifications did not compromise growth in cultures containing normal concentrations of both ions.     

亚适温条件下缺铁和硝酸盐胁迫对番茄幼苗生长及铁吸收的影响

研究亚适温(昼/夜18 ℃/12 ℃)条件下缺铁和硝酸盐胁迫对番茄幼苗生长及铁吸收的影响.结果表明: 与适温对照相比,亚适温条件下番茄幼苗生长受到明显的抑制,株高、叶面积显著变小,干物质积累下降;亚适温下缺铁对番茄幼苗生长的影响比适温下缺铁的影响大.亚适温条件下,缺铁、硝酸盐胁迫及二者同时胁迫的番茄幼苗株高与无胁迫处理差异不显著,但幼苗叶面积明显变小,电解质渗漏率、根系活力和三价铁还原酶活性明显增加,叶绿素含量降低;根总长、根表面积、根体积及根尖数明显减小;幼苗根、茎、叶中铁含量明显降低.亚适温下硝酸盐胁迫以及缺铁与硝酸盐二者同时胁迫加重了番茄幼苗干物质积累的减少、电解质渗漏率的增加,以及减少了对铁离子的吸收.Fe²⁺对K⁺和Ca²⁺吸收具有拮抗作用,不同器官中的表现有所差异;降低营养液中的Fe²⁺浓度可使番茄幼苗的缺铁症状更加严重.     

Stimulation of ethylene production and gas-space (aerenchyma) formation in adventitious roots of Zea mays L. by small partial pressures of oxygen

Adventitious roots of two to four-weekold intact plants of Zea mays L. (cv. LG11) were shorter but less dense after extending into stagnant, non-aerated nutrient solution than into solution continuously aerated with air. Dissolved oxygen in the non-aerated solutions decreased from 21 kPa to 3–9 kPa within 24 h. When oxygen partial pressures similar to those found in non-aerated solutions (3, 5 and 12 kPa) were applied for 7 d to root systems growing in vigorously bubbled solutions, the volume of gas-space in the cortex (aerenchyma) was increased several fold. This stimulation of aerenchyma was associated with faster ethylene production by 45-mm-long apical root segments. When ethylene production by roots exposed to 5 kPa oxygen was inhibited by aminoethoxyvinylglycine (AVG) dissolved in the nutrient solution, aerenchyma formation was also retarded. The effect of AVG was reversible by concomitant applications of 1-aminocyclopropane-1-carboxylic acid, an immediate precursor of ethylene. Addition of silver nitrate, an inhibitor of ethylene action, to the nutrient solution also prevented the development of aerenchyma in roots given 5 kPa oxygen. Treating roots with only 1 kPa oxygen stimulated ethylene production but failed to promote gas-space formation. These severely oxygen-deficient roots seemed insensitive to the ethylene produced since a supplement of exogeneous ethylene that promoted aerenchyma development in nutrient solution aerated with air (21 kPa oxygen) failed to do so in nutrient solution supplied with 1 kPa oxygen. Both ethylene production and aerenchyma formation were almost completely halted when roots were exposed to nutrient solutions devoid of oxygen. Thus both processes require oxygen and are stimulated by oxygen-deficient surroundings in the 3-to 12-kPa range of oxygen partial pressures when compared with rates observed in air (21 kPa oxygen).Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine     

Effects of the pO2 on swimming activity and food utilization in ophiocephalus striatus

The obligatory air-breathing fish Ophiocephalus striatus, fed on goat-liver, surfaced 906 times, swimming 270 m/day in aerated water (mean pO₂: 151 mm Hg) and 883 times, travelling 325 m/day in non-aerated water (92 mm Hg); surfacing and swimming activities increased below the pO₂ of 74 mm Hg. Hanging duration was more (8.4 hr/day) in the aerated series than that in the non-aerated series (5.9 hr/day). Rates of feeding, absorption and metabolism of either series averaged to 131,126 and 93 (= 0.8 ml O₂/g/hr) g cal/g live fish/day. Conversion rate and efficiency slightly increased from 22 g cal/g/day and 17% in the aerated series. Culturing O. striatus in aerated waters may not be advantageous. Starving groups in the aerated and non-aerated aquaria surfaced 317 times, hung for 14.7 hr, and swam 61 m/day, expending 15 g cal/ g/day (= 0.1 ml O₂/g/hr).     

THE EFFECT OF THE H ION CONCENTRATION ON THE AVAILABILITY OF IRON FOR CHLORELLA SP

The data obtained in these experiments indicate clearly that unless the necessary precautions are taken to keep the iron of the culture medium in solution the results obtained by varying the H ion concentration will not represent the true effect of this factor on growth. The availability of iron in nutrient solutions has been the subject of numerous recent investigations and it is now known that iron is precipitated at the lower hydrogen ion concentrations, that the iron of certain iron salts is less likely to be precipitated than that of others, and that certain salts of organic acids tend to keep the iron in solution. In general, ferric citrate seems to be the most favorable source of iron. In addition to chemical precipitation, however, it is also possible for the iron to be removed by adsorption on an amorphous precipitate such as calcium phosphate. As this precipitate is frequently formed when nutrient solutions are made alkaline, this may account for the discordant results reported in the literature as to the availability of certain forms of iron. By omitting calcium from the culture solution iron can be maintained in a form available for growth in alkaline solutions by the addition of sodium citrate. In such solutions the maximum growth of Chlorella occurred at pH 7.5. The alkaline limit for growth has not been established as yet. In investigating the availability of iron at varying concentrations of the hydrogen ion, changes in the pH value of the solution during the course of an experiment should also be taken into account. This is especially important in unbuffered solutions. The differential absorption of the ions of ammonium salts may cause a marked increase in the hydrogen ion concentration, which in turn will cause an increase in the solubility of iron. In strongly buffered solutions as used in these experiments this effect is slight.     

Induction of the mitochondrial permeability transition (MPT) by micromolar iron: Liberation of calcium is more important than NAD(P)H oxidation

The mitochondrial permeability transition (MPT) plays an important role in cell death. The MPT is triggered by calcium and promoted by oxidative stress, which is often catalyzed by iron. We investigated the induction of the MPT by physiological concentrations of iron. Isolated rat liver mitochondria were initially stabilized with EDTA and bovine serum albumin and energized by succinate or malate/pyruvate. The MPT was induced by 20μM calcium or ferrous chloride. We measured mitochondrial swelling, the inner membrane potential, NAD(P)H oxidation, iron and calcium in the recording medium. Iron effectively triggered the MPT; this effect differed from non-specific oxidative damage and required some residual EDTA in the recording medium. Evidence in the literature suggested two mechanisms of action for the iron: NAD(P)H oxidation due to loading of the mitochondrial antioxidant defense systems and uptake of iron to the mitochondrial matrix via a calcium uniporter. Both of these events occurred in our experiments but were only marginally involved in the MPT induced by iron. The primary mechanism observed in our experiments was the displacement of adventitious/endogenous calcium from the residual EDTA by iron. Although artificially created, this interplay between iron and calcium can well reflect conditions in vivo and could be considered as an important mechanism of iron toxicity in the cells.