OSMOTIC ADJUSTMENT OF PLANTS TO SALINE MEDIA. II. DYNAMIC PHASE

Bernstein , Leon . (U. S. Salinity Lab., Riverside, Calif.) Osmotic adjustment of plants to saline media. II. Dynamic phase. Amer. Jour. Bot. 50(4): 360–370. Illus. 1963.—The time-course of osmotic adjustment in bean and pepper plants to increased salinity of the medium was determined by periodic sampling of plants following salt additions to the medium. Bean plants adjusted to increases of 1 atm OP within a day, the adjustment in roots occurring primarily at night following salt addition at 6 pm , whereas leaves and stems made most of their adjustment in the daytime. Pepper plants did not adjust completely to 1.5 atm NaCl additions in 48 hr, but OP increased by about the same amount in both species (0.5—1.0 atm per day). Diurnal fluctuations in OP of leaves and stems of both species and in roots of pepper were matched by parallel fluctuations in K concentrations. Added NaCl caused increased concentrations of K in leaves and stems which were more or less replaced by more slowly absorbed ions, Ca and Mg in bean leaves and Na in bean stems. Other salts produced comparable immediate effects on K level, but K was replaced more rapidly if the cation added was readily accumulated by the bean (Ca). In roots, Na uptake predominated if Na salts were added but K uptake was important on the CaCl₂ treatment. The K effects suggest a passive distribution of K between the cell and the medium.     

Effect of sodium in the nutrient medium on the incidence of potassium-deficiency symptoms in tomato plants

Summary Tomato plants (Lycopersicon esculentum cv. Amberley Cross) were grown in sand culture and were fed with four concentrations of potassium nitrate in combination with two levels of sodium nitrate. After six weeks the plants were scored for the presence and absence of a symptom of potassium deficiency, namely, marginal chlorosis and/or necrosis in the young, fully-expanded leaves. These leaves were also analysed for K and Na. Marginal chlorosis and/or necrosis occurred in plants given a nutrient solution containing 0.5 meq K/I or less and supplied with either of the sodium nitrate levels. However, the symptoms occurred more frequently in plants receiving the lower level of sodium nitrate. The laminae on plants receiving the lower concentration of sodium nitrate had a 50 per cent incidence of chlorisis and/or necrosis when the tissue potassium content was 0.74 per cent of the dry wt, while those laminae on plants receiving the higher level did not show a 50 per cent incidence until their potassium fell to 0.64 per cent of the dry wt.     

Uptake and distribution of potassium in tomato plants

Summary The uptake and distribution of potassium was examined in tomato plants, cv. Amberley Cross and Moneymaker, grown in peat/loam and given a nutrient feed either adequate or deficient in potassium.Detailed studies were also made of the distribution of potassium in various parts of tomato plants, cv. Amberley Cross, grown in sand and supplied with nutrient feeds containing four and seven concentrations of potassium. In these plants the concentration of potassium in stem, petiole and laminar tissue increased from the base to the apex of plants, irrespective of the potassium concentration in the nutrient feed. There was also a gradient of decreasing potassium concentration along leaves, from proximal to distal laminae. The concentration of potassium in all plant parts increased with increasing nutrient supply of potassium, petioles showing a greater response to nutrient potassium than laminar tissue.Marginal chlorosis and/or necrosis were observed when the potassium concentration in fully expanded leaves fell below 1.2 per cent of the dry weight for cv. Amberley Cross or 1.5 per cent for cv. Moneymaker. A 50 per cent incidence of chlorosis and/or necrosis occurred in leaf laminae containing 0.74 per cent potassium.Leaves rarely showed deficiency symptoms when the concentration of potassium in the petioles was higher than that in adjacent laminar tissue. However, chlorosis and/or necrosis occurred when the potassium concentration in petioles fell below that in laminae. In the diagnosis of the potassium status of tomato plants, the most suitable tissue for sampling for potassium analysis is considered to be the petioles of young fully expanded leaves.     

Transport of sodium into the xylem exudate of tobacco

When tobacco (Nicotiana tabacum L. var. Virginia Gold) plants were pretreated with Na (²²Na) several days before detopping, from 2.3 to 4.9% of Na previously accumulated in roots appeared in the xylem exudate in 7 days after detopping. Na from the external medium, however, was readily transported to the exudate. Moreover, the amount of the pretreatment Na that was transported to the exudate was not influenced by the presence of Na in the external medium. When Na was present in the external medium after detopping, about 4% (with an NaNO₃ post treatment) to 10% (with an NaCl post treatment) of the Na transported to the xylem in the 7 days following detopping originated in the vacuoles. Nitrate salts of K or Na in the external medium after detopping resulted in transport of large quantities of the respective cation to the exudate, but not in increased transport of the pretreatment Na. A much larger percentage of the K that was accumulated after detopping than of the Na similarly accumulated was transferred to the xylem exudate.     

Absorption and translocation of sodium in beans and cotton

At the end of a 4 hour absorption period approximately 95% of the sodium absorbed by bean plants was retained in the secondary roots. The sodium translocated to the shoot was retained in the stem.

2,4-Dinitrophenol decreased the amount retained in the secondary roots of bean plants and increased the amount translocated to the shoot. The stem retained most of the translocated sodium.

Bean plants without roots absorbed considerably more sodium than plants with roots and translocated a greater proportion of the sodium to the petioles and blades. 2,4-Dinitrophenol reduced the amount of sodium in the stem and petioles and increased the amount in the blades.

2,4-Dinitrophenol reduced the amount of sodium retained by the secondary roots of cotton plants but did not appreciably affect the amounts translocated to the shoot.

     

The growth of wheat plants in humic acid solutions under axenic conditions

Summary A technique is described for growing wheat plants in nutrient solutions containing C¹⁴-labelled humic acid under axenic conditions. The general appearance of axenic plants was indistinguishable from plants grown in association with microbes. C¹⁴-labelled humic acid enhanced the growth of both roots and shoots showing that by-products of microbial degradation of humic acid are unnecessary for this enhanced plant growth. Thus humic acid had a direct effect on the growth processes. The C¹⁴-labelled humic acid was taken up by the roots and virtually none was transported to the shoot. Only some 30 to 40 per cent of the incorporated radioactivity was associated with the root cell walls and thus more than 60 per cent was in the cytoplasm and may have influenced the biochemical processes involved in the regulation of plant growth.     

Sodium Absorption and Distribution in Forage Grasses of Different Potassium Status

The absorption and distribution of sodium were examined in threegrasses grown in flowing solution culture with different suppliesof potassium. There were marked differences between the speciesin the rate of absorption by their roots, timothy absorbingat a much slower rate than either ryegrass or cocksfoot. Inall species, the rate of Na absorption was greatest when therewas a maintained supply of K and/or when the K contents of theplants were high. Transport of Na from roots to shoots of timothywas restricted; it was less restricted in the other speciesand large proportions of the Na moved from roots to shoots whenK was not supplied to the plants. Sodium transported from theroots accumulated in old leaves and not in the younger leaves.When K was no longer supplied, the growth of ryegrass was maintainedin the plants previously grown with Na plus K; Na supplied insteadof K, however, did not maintain growth. Cocksfoot grown withNa grew less well than when grown without Na when plants wereno longer supplied with K; the growth of timothy was unaffectedby Na. Dactylis glomerata L., Lolium perenne L., Phleum pratense L., cocksfoot, ryegrass, timothy, absorption of ions, distribution of ions, potassium, sodium     

Calcium and Salt Toleration by Bean Plants

The role of calcium in the salt relations of the bean plant, Phaseolus vulgaris, was examined. Brittle wax bush bean plants were cultured in nutrient solutions containing 50 mM NaCl. In the absence of added calcium the plants showed a general breakdown of the roots. A low concentration of calcium in the nutrient solution (0.1 mM) prevented this. Without added calcium the plants absorbed and translocated sodium at such a rate that high concentrations of it built up in the leaves within two days. With increasing concentrations of calcium in the nutrient solution the leaves contained progressively less sodium, and at 3 mM CaSO₄ the concentrations of sodium in the leaves was equal to that of the control plants grown without addition of salt. Even after both roots and stems had reached a high concentration of sodium, the leaves of plants grown in the presence of adequate concentrations of calcium contained little sodium.     

The uptake of sodium by perennial ryegrass and its relationship to potassium supply in flowing solution culture

Summary The uptake of Na and K by perennial ryegrass from flowing solution culture with monitored concentrations of Na and K was followed in two experiments. In the first, when only 50 and 10 per cent of the K uptake by one set of plants, grown with K held constant at 2.5 μeq 1⁻¹, was supplied to two other linked sets of plants and the balance supplied as Na, there was a rapid decrease in K, and an increase in Na, concentration in the shoots over a 20-day period. However, when compared with the plants grown in K in solution held constant, there was not a complete replacement of Na for K. In the second experiment the concentration of K in the culture solution was held constant at 2 μeq 1⁻¹ and Na at 0, 5, 25, 50 and 100 μeq 1⁻¹. Although uptake of Na increased with increasing concentration in solution the contents in the plants were low,i.e. less than 0.19 per cent and decreased with time. There was an increase in the yield of both shoots and roots with increasing Na in the solution; it was suggested that, during the early stages of growth there may have been an inadequate supply of K and that Na may have substituted for K in some of the non-specific roles of K in the plants. There was evidence in both experiments that a flux of H-ions was involved in the uptake of Na.     

Effect of lipids on chloride and sodium transport in bean and cotton plants

This paper describes experiments on Cl transport into the roots, stem and leaves of bean plants, the roots of which have been exposed to lipids in the root solution. Monoand digalactose diglyceride strongly increased Cl transport into all plant parts, probably by transport of the glycolipids further into the plant. Phosphatidyl choline increased Cl absorption by the roots, but transport into the stem and leaves was not affected. This phospholipid was only absorbed by the root tissue. ³²P-glycerophosphoryl choline added to the root solution was readily transported and esterified as phospholipid in all plant parts. This chemical did increase Cl uptake by the roots but Cl accumulation in the leaves was reduced by as much as 40%. Phosphatidyl glycerol, phosphatidyl inositol, and sulfolipid increased Cl transport into roots, stem, and leaves, and a high mobility of ³²P-phosphatidyl glycerol was demonstrated. Generally no significant effect of the above lipids on Na transport in beans and cotton was noted except that monogalactose diglyceride did increase Na transport in cotton.     

Effect of calcium on transport of cations to the xylem exudate of tobacco

Summary Roots of detopped tobacco plants (Nicotiana tabacum var. Virginia Gold) were exposed to Na, K, and Ca salts or to water, and cation transfer to xylem vessels was measured. In some cases plants had been exposed to Na in addition to regular nutrient solutions before detopping. Calcium in the external medium greatly depressed the transport of Na from the external medium to the xylem vessels and it often stimulated the transfer of K from the external medium to the xylem vessels. The K/Na ratio in the exudate thus was dependent upon the Ca content of the external medium under these conditions. In contrast, externally applied Ca or Ca deficiency had very little effect on the transfer of preaccumulated K and Na from compartments within roots to the xylem vessels. The K/Na ratio in the exudate under these conditions was not related to Ca levels nor to mild Ca deficiency. The ratios decreased with time after detopping regardless of Ca level. Intact plants accumulated more Na than did root systems of detopped plants in a 6-day period.Riverside University of CaliforniaSoil Science and Agricultural Engineering     

Growth Adaptability and Salt Tolerance Osmoregulation of Aneurolepidium chinense Grown on Saline Grassland

The growth of Aneurolepidium chinense Kitag. grown on different saline soil of a Northeast grassland of China was studied and the K+,Na+proline and citric acid accumulated in plants or their organs were determined . The results showed that A. chinense had a strong adaptability to saline habitat and could grow on soil with a salt content of 0. 088%--1.63%,and pH ranging from 8.3 to 9.8. Sodium,proline and citric acid were accumulated by plants for osmotic adjustment when the salinity and Na+content of the soil increased. A. chinense absorbed Na+ rapidly from the soil and excluded K+ when the soil Na+ concentration was less than 20 μmol/g. Sodium was adsorbed slowly and K+ remained constant in plants when Na+ concentrations of soil were 20–80 μmol/g,and proline and citric acid contents were markedly increased. Sodium and K+ decreased slightly in plant tissue and organic solutes increased when Na+ concentrations exceeded 80 μmol/g in soil. Most K+ was distributed in young leaves which were metabolically active. The major sites of Na+ accumulation were in the roots and older mature leaves;whereas proline and citric acid accumulation occurred primarily in young leaves,mature leaves and stems. Tillering buds had strong ability to absord and accumulate K+,Na+ and Proline.     

Redistribution of Manganese in Maturing Lupin us angustifolius cv. Illyarrie in Relation to Levels of Previous Accumulation

The retranslocation of Mn from pools of pre-accumulation todeveloping seed of Lupinus angustifolius was examined in growthchamber and field experiments. In the growth chamber experiment, plants (cv. Illyarrie) weregrown in sand containing Mn at 18 levels of supply from low(15 fig Mn kg"1) to luxury (12800 fig Mn kg{small tilde}l).At 90 d, sand was washed from the roots and the plants weregrown to maturity in nutrient solution in the absence of Mn.At sequential harvests, the plants were divided into a numberof fractions and were analysed for Mn to determine changes inthe amount of Mn contained in each component. Plants (cv. Marri)were also grown in the field at a Mn deficient site with andwithout added Mn, and similar harvests and observations weremade. Manganese moved readily from roots, stems and petioles to developingsinks, including seeds via pods. Retranslocation of Mn preventedthe appearance of Mn deficient seed (‘split seed’)in plants which had accumulated sufficient Mn prior to the omissionof Mn supply. The mode of Mn transport is discussed, and itsconveyance to seed in phloem, mediated by transfer cells, issuggested. The identification of pools of Mn accumulation fromwhich Mn may retranslocate presents a basis on which tests prognosticof impending Mn deficiency in maturing lupins may be developed.Stem is favoured as the tissue on which to base such tests. No Mn translocated to developing seed sinks from mature, oreven senescing lupin leaves. The cause appears to be that Mnis poorly loaded into the phloem of leaves although much wasfound to be leachable. About 40 per cent of leaf Mn was extractablewith water, more (approx. 70 per cent) with dilute ethylenediamine tetraacen’c acid but little (approx. 14 per cent)with N7>Jdimethyl formamide along with other cell contents.The form of Mn in leaves is discussed.     

Sodium and rubidium as possible nutrients for sugar beet plants

This study concerned the degree to which Na or Rb could substitute for K in the growth of sugar beet plants when K in the culture solution was low (1 meq/liter) or high (12 meq/liter).

Sodium at high concentrations increased the growth of plants in a basal nutrient medium when either deficient in K or when adequately supplied with K alone. Redistribution of K from petioles to blades could not fully explain these results. Therefore, the essentiality of Na per se for growth of sugar beet plants may be inferred.

Rubidium increased the growth of plants significantly when supplied in small doses to a nutrient medium deficient or adequately supplied with K. The amount of K added and the mode of Rb addition to solution cultures should be carefully considered when studying the effect of Rb on growth. High Rb concentrations were toxic, especially to the growth of fibrous roots.

Sodium or Rb have been shown to enhance the growth of sugar beet plants under either low or high K conditions. Essentiality of either Na and/or Rb per se for growth of sugar beets may be inferred, but other criteria should be fulfilled also for conclusive proof.

     

The Effect of Sodium on Growth of Water-stressed Sugar beet

Sugar beet grown in solution culture, with or without a supplementof 16 millequivalents per litre of sodium, were subjected towater stress with polyethylene glycol solutions of –0.4,–3, and –8 bar osmotic potential. With the –0.4bar solution leaf water potential was between –6 and –8bar and leaf relative water content about 90 per cent. Decreasingthe solution osmotic potential to –8 bar decreased leafwater potential to about –15 bar and relative water contentto 75 per cent; leaves stopped expanding and transpiration andcarbon dioxide uptake were decreased by 80 and 50 per cent respectively.Net assimilation rates were only slightly decreased becauseleaf growth was decreased more than carbon dioxide assimilation.Relative growth rates of the plants were decreased by 8 percent at –3 bar and by 15 per cent at –8 bar. Sodium absorbed by the plant accumulated mainly in the leavesand petioles; it increased the water content of the leaves andstorage root and the plant fresh weight. Sodium decreased theleaf osmotic potential, slightly increased leaf water potential,and significantly increased turgor. It had no effect on carbondioxide uptake, transpiration, net assimilation rate, or relativegrowth rate. Sodium increased the rate at which the leaf areagrew and it is concluded that it did so by altering the leafwater balance.     

Translocation of potassium and sodium in intact maize seedlings

Summary The distribution of K and Na between root and shoot of intact maize seedlings after absorption periods of increasing length up to 24 hours was determined in three series of experiments. In two additional series the redistribution between root and shoot of K and Na absorbed previously during a period of 12 hours was followed up during the next 12 hours. Concentrations were such that either the specific or both the specific and non-specific mechanism of K-absorption present in this tissue were operative.A high degree of specificity in the transfer to the shoot became apparent, the amount of Na transported to the shoot within 24 hours being negligible in comparison to the amount of K transferred within the same period. For the most part this specificity appeared to be due to the fact that the specific mechanism of K-absorption is especially involved in the supply of K for transfer to the shoot. However, non-specifically absorbed K is also liable to transport to the aerial parts at a much higher rate than Na and, in contrast to Na, the translocation of K continues after the plants have been transferred to K- and Na-free media.A scheme is proposed to explain the phenomena described.     

Nonuniform Transport of Phosphorus from Single Roots to the Leaves of Zea mays

The postulate that single roots of Zea mays transport their absorbed phosphorus nonuniformly to the leaves was tested. Plants were grown under growth chamber conditions for three to four weeks in nutrient solution. At this stage of growth a series of plants was placed into a system in which two roots on each plant were allowed to absorb either ³³P or ³²P from uptake solutions for time intervals of up to 24 hours. Plants subsequently were harvested such that each leaf was partitioned into samples containing tissue from one side or the other of the midrib. All samples were assayed for ³³P and ³²P and the results were expressed as the amount of total P transported into different plant parts from a single root. Nonuniform P accumulation in the leaves occurred and different patterns of accumulation, dependent on the type of root chosen for uptake were observed. Nearly uniform P accumulation occurred between one side and the other of a given leaf when transport was from radicle roots. In marked contrast, transport from adventitious roots resulted in an alternating pattern of accumulation between one side and the other of each successive leaf up the stem. The seminal root system supplied more P to the older leaves than did the adventitious root system. The nature of these nonuniform P transport patterns is attributed to the vascular organization between roots and leaves.     

盐胁迫下盐地碱蓬体内无机离子含量分布特点的研究

用不同浓度NaCl溶液处理盐地碱蓬（Suaeda salsa)植株后,测定并比较老叶、幼叶及根部的无机离子含量和对K的选择性,叶片及根部的Na^ 、Cl^-含量随盐度的增加而升高,且累积趋势相似,盐胁迫下根部Na^ 、Cl^-及总离子含量（K^ 、Na^ 、Ca^2 ,NO3^-,Cl^-)明显低于叶片,说明盐地碱蓬地盐胁迫下,以叶片优先积累大量离子（如Na^ ,Cl^-) 为其适应特征。NaCl处理下,叶片的K^ ,Ca^2 含量低于对照,但随盐度的增加保持相对稳定,而根部K^ 含量,K/Na比、对K的选择性则高于叶片,这对盐胁迫下地上部的K^ 亏缺有一定补偿作用。低盐度处理（100mmol/LNaCl)促进NO3^-的吸收,另外随盐度的增加,叶片渗透势下降,渗透调节能力增强,幼叶渗透势低于老叶,但渗透调节能力相同。     

The effect of calcium bicarbonate on iron absorption and distribution byChrysanthemum morifolium, (Ram.)

Summary Plants grown for two weeks in high-bicarbonate nutrient solution with iron became chlorotic, absorbed less iron, and translocated a lower percentage of absorbed iron than did green plants grown under low bicarbonate with iron. Chlorotic plants, pretreated in low-bicarbonate solutions lacking iron, absorbed more iron and translocated a higher percentage to leaves than the green plants. Plants induced to chlorosis by high bicarbonate absorbed less iron after transfer to low-bicarbonate solution containing iron than did chlorotic plants pretreated with low-carbonate solution lacking iron. Initial localization of iron occurred in the roots. A considerable amount of the iron initially found on the roots was translocated to developing shoots over a nine-week period unless the plants were grown in high bicarbonate solutions. More iron was translocated from roots of plants in minus-iron solutions following initial absorption than when iron was supplied in the nutrient solutions. Journal Series Paper736. University of Georgia, College of Agriculture Experiment Stations, College Station, Athens, Ga. 30601.     

Salinity-calcium interactions on growth and ionic concentration of Citrus plants

Two-year-old Navel orange scions (Citrus sinensis (L.) Osbeck) budded to either Cleopatra mandarin (C. reticulata) and Troyer citrange (C. sinensis × P. trifoliata) rootstocks were used in this experiment. Cleopatra manda in rootstock was considered more tolerant to salinity than Troyer citrange, and this property was attributed to a greater capacity to exclude chloride ions.Plants were grown under glasshouse conditions and supplied with nutrient solution containing either no or 45 mM NaCl. Calcium concentration was increased from 3 to 30 mM. Sodium, potassium, calcium and chloride concentrations in plant organs were analyzed after 90 days of treatment.Supplemental Ca was found to mitigate the adverse effects of salinity on plant growth, defoliation or leaf injury.Chemical analysis indicated that in plants grafted on Troyer citrange Ca restricted uptake and subsequent translocation of Na to the leaves and increased K concentration in both roots and leaves. However, in Cleopatra mandarin-grafted plants increasing Ca levels seemed to reduce transport of Na from roots to leaves, and Na accumulation in roots was associated with reduced concentration of K in this rootstock.Organ chloride analysis showed that Cl accumulation in leaves of plants grafted on both rootstocks was reduced when external Ca concentration increased, whereas Cl concentration in roots remained constant or increased. The data of distribution of Cl in plants showed that a high external Ca level increased Cl accumulation in the basal stem and roots, and reduced the transport of Cl from roots to leaves.