Effects of Aluminium on Honeylocust (Gleditsia triacanthos L.) Seedlings in Solution Culture

Honeylocust (Gleditsia triacanthos L.) seedlings were grownin solution culture at pH 4.0) with 50, 150, 600 and 1500 mmolm^–3 aluminium. All levels of aiuminium reduced the sizeand weight of roots, shoots and leaves with the exception ofroot elongation at 50 mmol m^–3 Al. Aluminium content ofroots was 50 to 100 times that of shoots. With increasing concentrationof aluminium, aluminium content of leaves and roots increasedexponentially while a linear increase was observed for stems.The nutrient content of seedlings was improved in 50 mmol m^–3where increases in shoot calcium, magnesium, and phosphorusconcentrations were observed. Aluminium concentrations greaterthan 50 mmol m^–3 reduced shoot nutrient content. Presenceof aluminium increased the root phosphorus and calcium levelsbut had no effect on potassium and magnesium concentrations.Results show that honeylocust is an aluminium sensitive treespecies whose growth may be reduced by high soil Al levels. Key words: Aluminium toxicity, Gleditsia triacanthos, nutrient solution     

Partitioning of shoot and root dry matter and carbohydrates in bean plants suffering from phosphorus, potassium and magnesium deficiency

The influence of varied supply of phosphorus (10 and 250 mmolP m^–3) potassium (50 and 2010 mmol K m^–3) and magnesium(20 and 1000 mmol Mg m^–3) on the partitioning of dry matterand carbohydrates (reducing sugars, sucrose and starch) betweenshoots and roots was studied in bean (Phaseolus vulgaris) plantsgrown in nutrient solution over a 12 d period. Shoot and rootgrowth were quite differently affected by low supply of P, K,and Mg. The shoot/root dry weight ratios were 4.9 in the control(sufficient plants), 1.8 in P-deficient, 6.9 in K-deficientand 10.2 in Mg-deficient plants. In primary (source) leaves,but not in trifoliate leaves, concentrations of reducing sugars,sucrose and starch were also differently affected by low nutrientsupply. In primary leaves under K deficiency and, particularlyMg deficiency, the concentrations of sucrose and reducing sugarswere much higher than in control and P-deficient plants. Magnesiumdeficiency also distinctly increased the starch concentrationin the primary leaves. In contrast, in roots, the lowest concenfrationsof sucrose, reducing sugars and starch were found in Mg-deficientplants, whereas the concentrations of sucrose and starch wereparticularly high in P-deficient plants. There was a close relationshipbetween shoot/root dry weight ratios and relative distributionof total carbohydrates (sugars and starch) in shoot and roots.Of the total amounts of carbohyd rates per plant, the followingproportions were parti tioned to the roots: 22.7% in P-deficient,15.7% in control, 3.4% in K-deficient and 0.8% in Mg-deficientplants. The results indicate a distinct role of Mg and K in the exportof photosynthates from leaves to roots and suggest that alterationin photosynthate partitioning plays a major role in the differencesin dry matter distribution between shoots and roots of plantssuffering from mineral nutrient deficiency. Key words: Bean, carbohydrates, magnesium nutrition, phosphorus nutrition, potassium nutrition, shoot/root growth     

Further Observations on Root--Shoot Equilibria in Perennial Ryegrass (Lolium perenne L.)

Plants of Lolium perenne L. (cv. S. 23) were grown in a heatedglasshouse. Two experiments were performed, both during earlysummer. One used a sand/solution rooting medium and includedlow-nitrogen (0.17 parts per 10⁶) and shade (20.2 per cent illumination)treatments; the other used aerated solution culture and involvedtwo levels of shading (20.2 and 6.1 per cent illumination),in addition to controls. In both experiments growth and ratesof potassium, magnesium and calcium uptake were studied throughthe calculation of various growth-functions from fitted curves. Despite the effects of treatment and environment, a constantinverse relationship was found between the mass ratio of rootsand shoots and their activity ratio. These new results wereadded to some previously published to form a combined model:mass ratio = 0.051 + 45.7 (1/activity ratio) where activityratio is expressed as specific absorption rate for potassium(in µg K mg root^–1 day^–1)/unit shoot rate(rate of increase of whole-plant dry weight per unit shoot weight,mg mg^–1 day^–1). The implications of this relationshipare discussed and a further model is put forward in which rootactivity is expressed in terms of the uptake of the sum of thepotassium, magnesium and calcium contents of the plant.     

FURTHER ASPECTS OF THE RELATIONSHIP BETWEEN NICKEL TOXICITY AND IRON SUPPLY

Absorption of nickel by oat plants increased with increasing pH for a fixed iron supply. Nickel uptake and toxicity symptoms (necrosis and chlorosis) were both reduced when the concentration of iron in the nutrient solution was high. Nickel-iron ratio in the nutrient solution. For solutions with the same nickel-iron ratio, toxicity symptoms increased with increase in the absolute amount of nickel. There was a linear relationship between the degree of necrotic symptoms and the nickel-iron ratio in the plant.
Nickel consistently reduced the iron content of roots and tops. In the absence of nickel, the iron content of the roots but not of the tops, increased with iron supply. In nickel-toxic plants, the magnesium, calcium and phosphorus contents of the tops and the potassium, calcium and phosphorus contents of the roots were higher than in healthy plants, but the potassium content of the tops and the magnesium content of the roots were lower.
Similar results were found with tomato.     

Nutrient Cycling in an Age Sequence of Western Washington Douglas-fir Stands

The cycling of nitrogen, phosphorus, calcium, magnesium andpotassium in a series of western Washington Douglas-fir [Pseudotsugamenziesii (Mirb.) Franco] stands ranging in age from 9 to 95years has been described. The stands were of relatively lowproductivity being limited by low nitrogen. The content of nitrogen,phosphorus, magnesium and potassium in tree foliage all tendedto stabilize at about 40 years whereas calcium continued toincrease. The content of all nutrients in the wood continuedto increase with stand age. Nitrogen in the forest floor accumulatedconstantly at about 5.7 kg ha^–1 year^–1 and thistogether with the above-ground tree accumulation meant about10.5 kg ha^–1 year^–1 nitrogen was immobilized. Calciumalso increased with time in the forest floor with age whereasthe other nutrients were fairly constant after about 30 years.Understorey nutrient content reached a peak at about 20 years,while understorey litter-fall was significant throughout theage sequence. Internal redistribution, especially of nitrogen,represented an increasingly greater proportion of stand requirementwith increasing stand maturity. Pseudotsuga menziesti (Mirb.) Franco, Douglas-fir, biomass, litter-fall, nutrient content, nutrient cycling     

Effect of Potassium Supply on the Acropetal Transport of Water, Inorganic Ions and Amino Acids in Young Decapitated Sunflower Plants (Helianthus annuus)

The effect of potassium supply on the exudation rate and the content of ions and amino acids in exudation sap was studied using young decapitated sunflower plants (Helianthus annuus L.). Plants were grown originally in a complete nutrient solution. After decapitation one set of plants was transferred to a nutrient solution without potassium and another set to a solution with potassium, all other nutrients remaining the same for both treatments. During an experimental period of 3 days the plants supplied with potassium showed exudation rates which were more than twice as high as plants in the nutrient medium without potassium. The potassium supply affected the potassium and nitrate contents of the exudation sap. Both were lower in the treatment without potassium. The calcium and magnesium contents of the exudation sap were not significantly influenced by the potassium treatment, whereas the phosphate content was higher in the treatment without potassium. At the beginning of the exudation period the potassium supply did not affect the content of amino acids in the exudate, but later the plants supplied with potassium showed higher contents of amino acids in the exudation sap. As the absence of potassium reduced the exudation rate considerably the acropetal transport of all exudation sap constituents analysed in this experiment was markedly reduced.     

Threshold environmental concentrations of cations determining the boundaries of survival of the filamentous alga <Emphasis Type="Italic">Spirogyra</Emphasis> sp. in freshwater reservoirs

The threshold concentrations of elements in fresh water necessary for the survival of Spirogira sp. were determined. The concentrations of sodium, potassium, calcium, and magnesium in the algae were maintained at a level of (84.3 ± 0.8), (23.9 ± 0.5), (3.5 ± 0.2), (8.5 ± 0.2) mmol/kg wet weight, respectively; the water content was (92.5 ± 0.21)%. It was shown that the threshold concentrations of sodium, potassium, calcium, and magnesium in water determining the boundaries of the range of Spirogyra sp. in freshwater reservoirs are 0.003–0.007, 0.002–0.003, 0.0017–0.0022, and 0.0012–0.0018 mmol/L, respectively. A decrease in water mineralization was accompanied by a substantial increase in the gradient of cation concentration between the algae and the environment, thus enhancing the load on the systems maintaining water-salt metabolism. It was shown on the basis of comparative analysis that Spirogyra sp., being the primary link of the trophic chain, possesses a more efficient ability to extract ions from water in comparison to freshwater animals.     

Effect of Soil pH on Growth and Cation Deposition in the Root Tip of <Emphasis Type="BoldItalic">Zea mays</Emphasis> L.

Abstract The effects of sandy soil pH on the distribution of growth velocities and on cation concentrations and deposition rates in root growth zones of Zea mays L. seedlings were investigated. The pH values of the rooting medium varied between 4.2 and 8.6 in sand culture (70% saturated) without external supply of nutrients. At all pH values, densities (in 7moles per g fresh weight) of potassium, magnesium, and calcium increased toward the root tip. Lower pH in the medium increased calcium tissue density fivefold and magnesium density 1.7-fold, whereas the density of potassium, the overall elongation rate, and the growth velocity distribution did not show any significant pH dependence. Throughout the growth zone the deposition rates of the divalent cations, as calculated on the basis of the continuity equation, increased with lower pH. The data are consistent with the hypothesis that the effects of pH on the cation deposition rates are due to the increase in the divalent cation concentration of the soil solution at low pH and that the abundant uronic acid residues of the young walls of the meristem provide a reservoir of storage capacity for Ca and Mg under conditions of low nutrient availability.     

磷素营养对降香黄檀幼苗生长及叶片养分状况的影响

设置0、15、30、60、100、150 mg P·株^-1等6个磷素处理开展降香黄檀幼苗盆栽试验,测定各处理幼苗的生长、生物量、叶片养分含量等指标,采用临界浓度法确定降香黄檀幼苗的适宜施磷量,从而探讨不同磷素水平对降香黄檀幼苗生长和叶片养分状况的影响,揭示其磷素需求规律以及适宜的磷供应范围。结果显示磷肥能促进幼苗生长和生物量的积累,而且随施磷量的增加,各指标呈现先升高后降低的趋势,最高值出现在60 mg P·株^-1处理,其苗高、地径、叶面积、生物量分别为对照的3.07、2.35、49.21和24.25倍。施磷显著降低幼苗叶片氮、钾含量,提高磷、镁含量,其中30、60、100 mg P·株^-13个处理间叶片磷含量差异不显著,约为对照的1.65倍。根据幼苗生物量与叶片磷含量、氮钾含量比、磷钾含量比的抛物线关系,确定叶片最适磷含量范围为1.35~2.32 g·kg^-1,由此推断降香黄檀幼苗最适宜的施磷量为60~100 mg P·株^-1。     

外源施钙对盐胁迫下花生营养元素吸收与分配的影响

为解决盐碱地花生养分吸收不畅及分配受阻等问题,研究外源施钙对盐胁迫下花生氮、磷、钾、钙、镁吸收积累、分配特性和产量的影响,为盐碱地花生生产合理、高效施肥提供理论依据.以‘花育25号’为材料,在0.3%盐胁迫浓度下,设置4个Ca浓度梯度[T₁(0)、T₂(75)、T₃(150)和T₄(225) kg·hm^-2 CaO]进行盆栽试验.结果表明: 花生植株内养分含量依次为氮>钾>钙>磷>镁,苗期植株对氮和钙素的吸收中心均在叶片,磷、钾、镁的吸收中心为茎,苗期近一半的营养积累分配在各元素相应的生长中心.成熟期氮、磷、钾吸收中心转移到荚果中,尤以氮、磷在籽仁中的积累量居多,达72.3%～78.9%;钙、镁的吸收中心仍为叶片和茎,其分配比例分别为49.8%、32.6%.盐胁迫明显抑制花生植株各器官对氮、磷、钾、钙和镁各元素的吸收积累与分配,尤以对叶片和籽仁中氮素积累的抑制较为显著,但盐胁迫对荚果中镁的积累有促进作用.外源钙对盐胁迫下花生植株各器官氮、磷、钙和镁的吸收累积有明显的促进作用,尤其对籽仁中磷素积累的调节最为显著,其在籽仁中的积累量提高50%以上.适宜的钙施用量可显著促进盐胁迫下花生养分吸收积累量,提高花生成熟期荚果中氮、磷、钾的分配比,最终提高产量.综合各养分吸收、积累分配和产量结果,在0.3%盐胁迫条件下钙肥适宜施用量为150 kg·hm^-2 CaO.     

Ion Transport to the Xylem in Aerenchymatous Roots of Zea mays L.

Aerenchyma was induced in the developing nodal (adventitious)roots of maize (Zea mays L. cv. LG11) in solution culture bytreatment with an atmosphere of 5% (v/v) oxygen (oxygen partialpressure 5.0 k Pa). Ion uptake by aerenchymatous and ordinary(non-aerenchymatous) roots was then compared to determine theeffect of degeneration of much of the cortex in aerenchymatousroots on radial ion movement to the xylem. Rates of uptake andtransport of phosphate, potassium and chloride were followedby labelling 4–12mm length segments of intact roots usingradioactive tracers. In some experiments, enhanced rates ofphosphate transport were induced by means of a divided rootsystem and nutrient deprivation. For all three nutrient ions,and over a range of concentration for phosphate (10–100mmol m^–3 and potassium (0·25–5·0 molm^–3 and with enhanced rates of transport, aerenchymatousroots were at least as effective as ordinary roots (per mm³of root) and sometimes more effective (per mm root length).These findings are discussed in relation to hypotheses concerningthe pathways for radial ion movement across the cortex in ordinaryand aerenchymatous roots. Correspondence to: Long Ashton Research Station, Long Ashton,Bristol BS18 9AF, U.K. Key words: Aerenchyma, ion transport, mineral nutrition, oxygen deficiency, radio-isotopic tracers, roots, structure, Zea mays     

Influence of potassium and manganese on growth and uptake of magnesium by soybeans (Glycine max (L.) Merr. cv. Bragg)

Summary Soybean (Glycine max (L) Merr. cv. Bragg) seedlings were grown in nutrient solutions to evaluate the response to manganese nutrition as affected by potassium supply. In solutions containing 275 M manganese, increasing the solution concentration of potassium from 1 mM to 10 mM alleviated symptoms of manganese toxicity, decreased manganese concentrations in the leaves and increased dry matter yields of the plants. The reduction in manganese toxicity was brought about by a reduced rate of root absorption of manganese at high potassium supply levels.Increasing the supply of either potassium or manganese decreased the leaf concentration of magnesium although there were no apparent symptoms of magnesium deficiency in any treatment. The reduced concentration of magnesium in the leaves was due to effects of potassium and manganese on the rate of root absorption of magnesium.Under manganese deficiency conditions, growth was reduced and manganese concentrations in plant parts were very low; there was no effect of potassium supply when manganese was absent from the nutrient solution.     

Content and deposition of major mineral elements in different tissues and empty body of growing bulls of the german simmental breed

54 bulls of the German Simmental breed were fed either on a high energy level (maize silage ad libitum and 1.8 kg concentrate) or on a low energy level (maize silage restrictively and 1.0 kg concentrate). In dependence on feeding intensity a mean daily weight gain of 870 or 1210 g was obtained. Animals were slaughtered with a live mass of 200 kg, 350 kg, 500 kg, 575 kg and 650 kg. Empty body was divided into 13 cuts and afterwards separated into lean, bone and adipose tissues and tendons. Major mineral element content was determined in these tissues as well as in the noncarcass parts.

In the lean tissue the mean content (200 kg) of 0.3 g calcium, 10 g phosphorus, 1 g magnesium, 2.3 g sodium and 14.8 g potassium/kg dry matter decreased slightly with rising live mass (200–650 kg). The contents of major mineral elements were much higher in bone tissue. For the fattening period from 200 to 650 kg of live mass mean contents of 151.5 g calcium, 71.3 g phosphorus, 3.2 g magnesium, 5.1 g sodium and 1.1 g potassium per kg DM were analysed. Mineral element content of bone tissue increased with rising live mass as well as animals on low feeding intensity showed a higher mineral content than on high energy level. In all, major mineral element content in fat tissue was very low. In noncarcass parts head and legs calcium and phosphorus had analogous to bone tissue the highest concentration. Hide showed a high content of sodium, whereas organs and digestive tract had a high content of potassium and phosphorus. Total mass of major mineral elements in the different tissues increased above all in the fattening period of 200 to 350 kg. In carcass as well as in empty body, mass of calcium and phosphorus was much higher than magnesium, sodium and potassium. Also animals on low feeding intensity showed a higher mass of major mineral elements in carcass and empty body than animals on high energy feeding intensity. The intensively fed bulls had a mean deposition of 12.7 g calcium, 6.9 g phosphorus, 0.37 g magnesium, 1.2 g sodium and 2.1 potassium per 1000 g of empty body weight gain, whereas restrictively fed bulls deposited in average 15.0 g calcium, 7.8 g phosphorus, 0.4 g magnesium, 1.2 g sodium and 2.4 g potassium per 1000 g of empty body weight gain.     

Hair Tissue Mineral Analysis and Metabolic Syndrome

Deficiency of minerals causes functional abnormality of enzymes, frequently resulting in metabolic disturbance. We investigated possible relationship between minerals and metabolic syndrome by analysis of hair tissue minerals. We selected 848 subjects older than 20 years of age at Ajou University Hospital from May 2004 to February 2007. We excluded the subjects who had cancers, steroid and thyroid medication, and incomplete record from the study. Finally, 343 subjects were eligible. We performed cross-sectional analysis for the relationship between minerals and metabolic syndrome. The contents of calcium, magnesium, and copper in the metabolic syndrome group were significantly lower than those of the normal group, whereas the amounts of sodium, potassium, and mercury in the metabolic syndrome group were significantly higher than those of the normal group. By dividing the subjects into quartile with the level of calcium, magnesium, and mercury concentrations, we carried out logistic regression analysis to study the subjects and found that the subjects in the third quartile of calcium and magnesium concentrations had significantly lower odds ratio (OR) of the metabolic syndrome compared with that of the lowest quartile group [OR = 0.30, confidence interval (CI) = 0.10–0.89; OR = 0.189, CI = 0.063–0.566] and that the subjects in the highest mercury quartile had significantly higher OR of the metabolic syndrome compared with that of the lowest mercury quartile group (OR = 7.35, CI = 1.73–31.1). As part of the metabolic syndrome, the optimal calcium and magnesium concentrations in hair tissue may reflect decreased risk of metabolic syndrome, whereas high mercury concentration in hair tissue may indicate increased risk of metabolic syndrome.     

Changes in phloem export of sucrose in leaves in response to phosphorus, potassium and magnesium deficiency in bean plants

The effect of varied phosphorus (10 and 250 mmol P m^–3potassium (50 and 2010 mmol K m^–3) and magnesium (20 and1000 mmol Mg m^–3 supply on sucrose, reducing sugars, aminoacids, P, K, and Mg in phloem exudate was studied in bean (Phaseolusvulgaris L.) plants over a 12 d growth period in nutrient solution.Phloem exudates were collected from detached primary leavesusing the EDTA-promoted exudation technique. Compared with controlnutrient-sufficient plants, sucrose export in the phloem exudatewas drastically decreased by K deficiency and, particularly,by Mg deficiency, whereas P deficiency either had no effector stimulated sucrose export. In Mg-deficient plants the rateof sucrose export was decreased to 10–20% of the controlplants. There was a close Inverse relationship between phloemexport and leaf concentration of sucrose: higher leaf concentrationsof sucrose were accompanied by lower phloem export of sucrose.In contrast to sucrose, reducing sugars in the exudates werevery low and not affected by P, K and Mg deficiency. The phloemexport of amino acids was strongly depressed by Mg deficiency,but only slightly by P and K deficiency. Resupplying Mg to Mg-deficientplants for 12 h during the dark or light periods rapidly stimulatedsucrose export. After resup ply of Mg for 24 h and 48 h therate of sucrose export was comparable with the rate in the controlplants. The results demonstrate a key role for Mg in phloem loadingand export of photosynthates from source leaves, especiallysucrose. Inhibition of root growth and development of visualsymptoms of chlorosis in Mg-deficient plants are suggested asconsequences of Impaired phloem loading. In agreement with thisin P-deficient plants where phloem loading was not impaired,chlorosis was absent and root growth was maintained at a highlevel. Key words: Bean, carbon partitioning, magnesium nutrition, phloem transport, phosphorus nutrition, potassium nutrition     

Carbonate crystal growth controlled by interfacial interactions of artificial cell membranes

Morphology of carbonate crystals grown on the surface of artificial cell membranes was controlled by changing the interfacial chemistry. For octadecyltriethoxysilane (OTE) films with terminal methyl groups interacting little with an aqueous calcium carbonate solution, calcite (104) crystals were formed. Polymerized pentacosadiynoic acid (PDA) films with terminal carboxylic acid groups induced deposition of calcite (012) crystals aligned along with each other within a polymer domain. On the other hand, stearyl alcohol (StOH) films with terminal hydroxyl groups induced deposition of aragonite crystals. When PDA was mixed with StOH, the 8∶1 PDA∶StOH (molar ratio) film produced dominating calcite (012) crystals without any crystal alignment, and the 4∶1 mixture film produced minor calcite (012) crystals and major aragonite crystals. For the 2∶1, 1∶1, 1∶2, and 1∶4 mixture films, aragonite crystals were dominating. Hence, it is found that the chemical composition at the interface plays a very important role in controlling the morphology of deposited carbonate crystals.     

The effect of air-borne ammonium sulphate onPinus nigra var.maritima in the Netherlands

Summary As a result of air pollution, considerable deposition of ammonium sulphate occurs on vegetation and soil in the vicinity of chicken farms and fields dressed with animal slurry. A clear relation exists between this ammonium sulphate deposition and the distance to certain agricultural activities. Field investigations and ecophysiological experiments both show that the needles ofPinus nigra var.maritima (Ait.) Melville take up ammonium and excrete potassium, magnesium and calcium. This often results in potassium and/or magnesium deficiencies and may lead to premature shedding of needles. The high levels of nitrogen in the needles are strongly correlated to fungal diseases.Whether the observed cation leaching will result in disturbed nutrient budgets depends mainly on soil conditions. Leaching of K, Mg and Ca from the soil, caused by ammonium sulphate, may further inhibit nutrient uptake.Field investigations show a clear correlation between increased ratios of NH₄ to K, Mg and Ca in the soil solution and the damage to pine forests.     

湖南烟区土壤交换性钙、镁含量及对烤烟品质的影响

分析了湖南烟区主要土壤类型交换性钙、镁元素含量状况及其对烟叶品质的影响,结果表明:(1)土壤交换性钙、镁含量在不同土壤类型间存在显著性差异,交换性钙含量平均为8.87cmol/kg,以红壤含量最高;交换性镁含量平均为1.16cmol/kg,以黄棕壤含量最高;交换性钙镁比值大小依次为:红壤(11.74)>水稻土(10.25)>黄壤(6.84)>黄棕壤(6.14),在烟叶实际生产中,应重视镁肥在红壤和水稻土中的施用;(2)烟叶钙含量偏高(21.93g/kg±4.37g/kg),烟叶镁含量偏低(2.52g/kg±1.26g/kg),两者均存在广泛的变异性;(3)整体来看,烟叶钙含量随土壤中交换性钙含量的升高和镁含量的降低而显著升高;烟叶镁含量随土壤交换性镁含量的升高而升高,与土壤交换性钙含量的相关性不显著;(4)典型相关分析表明,土壤中交换性镁含量的降低可能引起烟叶钾含量的提高,从而使得烟叶钾素和镁素含量达到较好的平衡;(5)土壤交换性钙、镁含量与烟叶其它化学成分指标的相关分析表明,土壤交换性钙有利于烟株对硼和氯素的吸收,对氮、锌和锰素的吸收则有显著的抑制作用;而土壤交换性镁有利于烟叶总糖、硼素和锰素的积累,对氮、磷、铁和锌素的吸收具有显著的抑制作用。     

The Influence of the Plant Growth-regulator, 2-Methyl-4-Chlorophenoxyacetic Acid, on the Metabolism of Carbohydrate, Nitrogen and Minerals in Solanum lycopersicum (Tomato)

The effects of the foliar application of phytocidal concentrationsof 2-methyl-4-chlorophenoxyacetic acid (MCPA) on change in totaldry weight, and in ‘available carbohydrate’ (starch,‘total’ and ‘reducing’ sugars), totalnitrogen, phosphorus, potassium, calcium, and magnesium of ‘tops’and roots of tomato plants have been followed over a periodof 14 days following spraying. There were two main treatments—‘nutrient’(nutrient supply to roots continued after spraying) and ‘water’(distilled water only supplied to roots after spraying) and‘water’ (distilled water only supplied to rootsafter spraying)—the sub-treatments consisting of ‘MCPA’versus ‘no-MCPA’ for each of the main treatments.Twelve different times of sampling were used. In analysing the present data, the quantity ‘residualdry weight’ (total dry weight less ‘available carbohydrate’),which was originally introduced by Mason and Maskell as a basisof reference for analyses of plant organs in short-period experimentsnot involving appreciable growth, has been used as an estimateof the permanent structure of plant growth. This new use ofthe ‘residual dry weight’ basis has brought outimportant features which were obscured when the data were leftin their primary form (as percentages of total dry weight oramounts per plant). Growth, as measured by increase in ‘residual dry weight’,was greatly inhibited by 2-methyl-4-chlorophenoxyacetic acidshortly after spraying, in both the presence and the absenceof nutrient. In the presence of 2-methyl-4-chlorophenoxyacetic acid, netassimilation rate (estimated as rate of increase in total dryweight per gram ‘residual dry weight’ of the ‘tops’)was greatly diminished while uptake of total nitrogen and ofP₂O₅ (estimated as increase in total nitrogen or of P₂O₅ ofthe whole plant per day per 1 g. ‘residual dry weight’of the roots) appeared to undergo a similar but much smallerdiminution. It seemed probable, however, that in the presenceof MCPA a larger proportion of the carbohydrate actually formedwas utilized for synthesis of aminoacids and protein. In the plant as a whole there was no evidence of actual depletionof ‘available carbohydrate’ as a result of MCPAtreatment, this fraction showing a steady increase in all treatmentsthroughout the experiment. The rate of increase was, however,much reduced by MCPA treatment. The ‘tops’ presentedmuch the same picture as the whole plant, but for the rootsthe situation was quite different. While the roots of the ‘no-MCPA’plants and also of the ‘MCPA-water’ plants showeda steady increase in available carbohydrate, those of the ‘MCPA-nutrient’plants rose only very slightly (from the initial value of 8mg. per plant to about 10 mg.) during the first 2 days, andthen in the next 2 days declined to a value (about 6 mg.) belowthe initial and remained at this low level for the rest of theexperiment. It is suggested that the phytocidal effect of 2-methyl-4-chlorophenoxyaceticacid in the presence of nutrient may be due to depletion ofthe ‘available carbohydrate’ supplies in the roots,which is shown to be brought about, in part, by reduced transportfrom the tops, and partly by the relatively greater utilizationof the carbohydrate present. These results offer an explanationfor the facts that plants showing vigorous growth are more easilykilled by MCPA and that perennial plants, particularly thosewith storage tissues in their roots, are more resistant. Further,they suggest the useful practical application that MCPA treatmentshould be given when the carbohydrate reserves of the rootsare at a minimum. For perennial plants, conditions might beexpected to be optimal for the application of MCPA in late spring,at a time when the first ‘flush’ of growth is slowingdown and before any appreciable new reserves of carbohydratehave been accumulated. It was also shown that 2-methyl-4-chlorophenoxyacetic acid preventedthe net synthesis of starch, but still permitted an appreciablenet formation of sucrose. 2-methyl-4-chlorophenoxyacetic acid appeared to have no effecton the uptake of potassium, calcium, or of magnesium. The lackof effect on potassium is contrasted with the previous observationby Rhodes, Templeman, and Thruston (1950) that sub-lethal concentrationsof MCPA, applied over a relatively long period to the rootsof tomato plants, specifically depressed the uptake of potassium.     

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.