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Uptake and Utilization of Phosphate Associated With Respiratory Changes in Potato Tuber Slices

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... Smith (1966) has shown that in excess of 90% of the soluble phosphate-esters such as sugarphosphates are present in the cytoplasm. The terminal P-groups of ATP turn over with a half-life of 2-20 sec and most P-esters have half-lives of less than 30 min (Bieleski, 1968;Johnson and Bluff, 1967;Loughman, 1960;Weigl, 1963). In addition if as has been suggested, the greater proportion of phosphate is in the form of orthophosphate, it is not unreasonable to assume that the magnitude of P-esters would not limit the exchange of P_^ at the membrane level. ...
... It is possible that only a small fraction of the absorbed nutrient may have been available for translocation. This phenomenon has been observed in barley roots (Russell and Martin, 1953;Loughman, 1960;Crossett and Loughman, 1966). In our experiments with Najas minor most of the tracer absorbed remained at the site of absortion. ...
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Article
The translocation of phosphorus by the aquatic vascular plant Najas minor All. was examined using radiophosphorus (32P). Whole plants showed a lack of phosphorus translocation either from the root to the shoot or in the reciprocal direction. Autoradiographic experiments indicated that the lack of translocation may be due to a very slow movement of this nutrient in both the root and the shoot. Phosphorous was calculated to move 0.6 mm/hr in roots and 1.2 mm/hr in foliage presumably through cells rather than in the vascular system.
... Loughman (47) found that the capacity of potato slices to absorb phosphate into organic fractions was proportional to the respiration rise. Phosphate incorporated by aged slices was 30 per cent nucleotide, 50 per cent hexose phosphate, and 20 per cent inorganic phosphate. ...
Article
To evaluate the premise that Cl- and other anions might influence tuber quality by affecting the esterification of inorganic phosphorus and subsequent energy transformations involving metabolic processes of carbohydrate synthesis or degradation, the author studied the effects of Cl ~ in relation to cations and anions on nutrient uptake and inorganic phosphorus transformations.
... The earlier experiment was carried out using an indirect method of measuring sugar uptake, but it is unlikely that the inherent errors of the method can account for the complete difference of behaviour observed. In other tissues pretreatment conditions (Loughman 1960) and season of growth (Hanson and Kahn 1957) are known to affect accumulation behaviour. ...
Article
Radioisotope techniques were used to study kinetics of sucrose, glucose, and fructose accumulation in slices of immature sugar·cane tissue. For all three sugars, accumulation rate was P. hyperbolic function of sugar concentration, suggesting intermediate compound formation between the sugars and some receptor or "carrier" in the cell. Sucrose and glucose interacted competitively, implying that, these two sugars (and probably also fructose, fructose 6-phosphate, and glucose I-phosphate) shared the same carrier.
... It therefore appears that mixing of ^•^P with the root pool of phosphorus takes place before it enters the vascular system.^P entering plant tissues is rapidly incorporated into organic compounds (Loughman and Scott Russell, 1957;Loughman, i960;Bieleski and Laties, 1963). Paper ehromatography was used to separate ^•^P into organic and inorganic components, in order to determine the form in which ^^P was being accumulated by the root. ...
Article
Measurements were made of the absorption of 32P and its movement into the shoots of barley seedhngs growmg in millimolar phosphate nutrient solutions. The rate of movement of 32P into the shoot increased during the first 4–6 hours of absorption but thereafter remained constant. When an identical inactive nutrient solution was substituted for one labelled with 32P movement of radioactivity into the shoot continued for only 4–6 hours, the amount moving being independent of the length of the preceding absorption period and hence the amount of 32P in the root. The kinetics of 32P movement following such a change were examined. 32P was applied to the tips of roots growing in inactive nutrient solutions and radioactivity measured along the length of the root. An analysis was made of the chemical compounds in which 32P was found and a rough estimate made of their turnover rates. It was concluded that 32P entering the root is either accumulated in it, as orthophosphate, or mixes with a small part, called the root pool, of the phosphorus in the root before moving into the shoot. It wa suggested that the pool lies outside the outside the vascular system and that the acid-soluble organic phosphorus compounds of the root are in dynamic equihbrium with it.
... The data obtained with potato tuber slices (Loughman, i960;Bieleski and Laties, 1963) and beech mycorrhizal roots (Harley and Loughman, 1963) indicate that phosphate entering these tissues rapidly equilibrates with a small pool of orthophosphate which is closely associated with those metabolic reactions incorporating phosphate into bound form. This pool is about 5 % of the total orthophosphate in potato discs and for beech mycorrhizal roots contains about 0.017 ^E ^^ phosphorus per 100 mg dry weight. ...
Article
At concentrations of potassium dihydrogen phosphate in the external medium below 10−3 M, the greater proportion of phosphate which enters beech mycorrhizal roots is incorporated into bound form. Above 10−3 M, an increasing proportion is accumulated unchanged as orthophos-phate. Studies using 32P confirm, in greater detail, the observation of Harley and Loughman (1963) that phosphate in the external medium rapidly equilibrates with a small pool of ortho-phosphate within the fungal sheath, from which the ion is incorporated into bound form or transferred either to the host core or to a larger pool in the sheath itself. Ammonium chloride at 10−2 M increases the total uptake of phosphate through an increase in the rate of both the incorporation into bound form and the primary absorption process. Ammonium chloride over the range 10−4 to 10−1 M brings about an increase in the size of the small pool. However, ammonium chloride has no detectable effect on phosphate fractions in the absence of phosphate in the external medium. Sodium azide, on the other hand, causes a breakdown of bound phosphate, although it is only at high concentration that this inhibitor has any detectable effect on the level of orthophosphate within the roots. The results suggest that the size of the small pool may be an important determinant of phosphate uptake at low concentration and that the role of potassium in the primary absorption process must not be overlooked.
... In the potato tuber, as much as 92% of the Pi may be present in the vacuole as there are essentially no chloroplasts that normally contribute to the metabolic pool. Loughman (1960) examined respiratory changes in potato tuber slices and found that the larger part ofPi in the cell was in the vacuole and took no part in the steady-state metabolism of the cell. However, the Pi in the vacuole may become available for metabolism during cold-temperature storage. ...
Chapter
Introduction Starch Storage and Degradation Sucrose Metabolism Stress-Induced Membrane Changes Conclusions Literature Cited
Article
1. O2-uptake and initial orthophosphate saturation depending on temperature have been investigated in phosphate-deficient cells of Candida utilis.
Chapter
Respiration can be defined in the simplest of terms as the consumption of oxygen. In reality, it is a complex process involving chemical reactions in glycolysis and the Krebs cycle and electron transfer in the electron transport chains. The process of respiration is controlled by interactions at many levels, including organ, tissue, cell, organelle and pathway. In addition, there are many other causes of oxygen consumption. Despite these complexities, respiration is usually measured simply as oxygen consumption. The purpose of this chapter is to demonstrate how measurements of oxygen consumption can be used to study differences in respiration in plant roots throughout development. Techniques will be outlined for apportioning respiratory activity, determining the impact of tissue organization and accounting for the confounding effects of extramitochondrial oxygen consumption.
Chapter
In respiration all plants exchange gases with the surrounding medium, and with the exception of a few microorganisms this exchange consists of an absorption of oxygen by the plant from the medium and an evolution of carbon dioxide from the plant into the medium. With most vascular plants the medium is a double one, air and soil, exceptions being found in a few completely aerial plants and in water plants which may or may not be rooted in soil and which may be completely or only partially submerged. With most of the Bryophyta the bulk of the gaseous exchange takes place between the plant and air, the rhizoids attaching the plants to the soil forming only a very small portion of the plant. Apart from a comparatively small number of terrestrial forms the algae live in an aqueous medium which may be a weaker or stronger solution, mainly of inorganic salts, according to whether the plants live in fresh or salt water. The media with which gaseous exchange takes place are thus air, soil, fresh water and salt water, according to the species.
Chapter
Die pflanzliche Trockensubstanz setzt sich grob gesprochen zu etwa 80 % aus den Elementen Kohlenstoff, Sauerstoff und Wasserstoff zusammen. Wie aus der Zusammenstellung der zur Bildung von 100 bushels Mais erforderlichen Mengen der einzelnen Elemente oder N?hrstoffe hervorgeht (Tab. 61), haben davon Sauerstoff und Kohlenstoff dem Gewicht nach den h?chsten Anteil.
Chapter
The investigator of phosphorus and its role in the environment is well served by a large body of data covering all aspects of the subject and spanning the natural, earth and life sciences as well as the technologies of mining, manufacture and agriculture. There are two general texts devoted solely to phosphorus and the environment[1, 2] and a detailed chemistry of phosphorus, including its environmental and biochemical roles is also available [3].
Article
Excised primary roots of three days old maize seedlings were "washed" in aerated solution of 0.2 mM CaCl2, pH 6.0 at 30°C for various time intervals to study the relationship between ion uptake and inositol phospholipid metabolism. Time course of phosphate absorption in washed root showed that a lag period of 45 min. was required for the increase in phosphate uptake rate which continued to rise for about six hours before leveling off. However, phosphatidylinositol (PI) level exhibited a trend opposite to ion uptake (r=-0.815*). Four hour "washing" treatment was also provided in the presence of hormones: ABA (0.1 mM), IAA (0.1 mM), Kin (5 μM), Chloroethylphosphonic acid (0.1 mM), Gibberellic acid (0.1 mM) and other additives such as CoCl2 (1 mM), neomycin (10 μg mL-1), cycloheximide (10 μg mL-1), caffeine (10 μg mL-1) and cAMP (0.2 mM). Maximum augmentation of phosphate uptake was noted in 4 h washing in the presence of cAMP while the highest PI level was evident in the presence of neomycin. PI level had a significant negative correlation (r = -0.787**) with phosphate uptake. The findings indicate the involvement of PI metabolism in induced phosphate uptake.
Article
In detached leaves, GA3 and BAP exert an attractive effect on 32P phosphate and 35S sulphate, but not on 36C1 chloride. At the same dose the action of GA3 is stronger than that of BAP (200% against 150%) A comparative study has been conducted involving a pretreatment with the two hormones in order to better understand their effects both in relation to tissue absorption and also in relation to the spatial distribution of ions.
Article
31P nuclear magnetic resonance (NMR) spectra are described for a variety of plant tissues, including sections of mature potato tuber (Solanum tuberosum) and sections of maize seedling (Zea mays). The experimental procedures for obtaining such spectra, using a conventional high field spectrometer, are discussed in detail. Assignments are given for the observed resonances and the results are discussed in relation to the storage forms of plant phosphate. Attention is drawn to the power of the technique to distinguish the cytoplasm and vacuole in vivo, through the well-known pH dependence of the 31P chemical shifts.
Article
When plant storage tissue is cut into thin disks it rapidly develops a high capacity to absorb phosphate from dilute solutions. The recent trend has been to attribute the development of this ability to the increased metabolic activity of bacteria known to be containing the tissue. Data presented in this paper shows that bacterial contamination of the tissue does contribute to the apparent uptake of phosphate by the disks. However, during the ageing process the number of bacteria decrease and therefore contribute less to the total uptake in the aged tissue. If the tissue is prepared and maintained in a sterile condition it is still able to develop a high capacity for phosphate absorption during ageing.
Article
Prolonged washing of thin slices of Jerusalem artichoke (Helianthus tuberosus) did not result in any apparent increase in the activity of the phosphatase enzymes, although the washing process is known to stimulate the activity of many other enzymes. However, treatment of the tissue in either 3×10(-5)M 2,4-dichlorophenoxyacetic acid or 10(-4)M indole acetic acid resulted in a 3-fold increase in the phosphatase activity. Significant stimulations of activity were detectable one hour after placing the tissue in the auxin. Treatment of the tissue in either kinetin or gibberellic acid failed to stimulate the activity of the enzyme. The enhancement of phosphatase activity caused by auxins could not be prevented by adding cycloheximide to the treatment solution an it is concluded that the stimulation occurred as the result of the activation of enzyme already present in the tissue rather than by the de novo synthesis of new enzyme protein.
Article
The presence of a Pasteur effect in aged discs of carrot (Daucus carota L.) storage tissue and its apparent absence in fresh discs was confirmed. Changes in the concentration of glycolytic intermediates have been determined, following the transfer of fresh and aged discs from air to nitrogen. In addition the changes in glycolytic intermediates associated with the ageing of the discs have also been measured. The results are analysed and interpreted to indicate that in aged discs the enzyme phosphofructokinase plays an important role in controlling glycolysis. In fresh discs phosphofructokinase appears to exert little control of glycolysis. The results also suggest that glycolysis may be controlled at points other than phosphofructokinase.
Article
Phosphorylase was purified from young and senescent potato tubers. Antibodies raised against the enzyme from young tubers crossreacted with phosphorylase from old tissue, although the latter exhibited different physico-chemical properties. In polyacrylamide gel electrophoresis it migrated with higher mobility, its subunit molecular weight was determined in the range of 40,000 in contrast to 100,000 of the phosphorylase in young tubers. The enzyme of senescent tubers displayed an isoelectric point of 5.4 different from the one of young tubers with 5.0, and the diffusion coefficients of the two enzymes varied. The appearance of the phosphorylase form typical for senescent tissue is connected with changes in the intracellular localization as revealed by immunofluorescence. Before massive starch accumulation is initiated, non-vacuolated subepidermal cells contain antigenically active material in their cytoplasm. During starch accumulation in fully differentiated storage parenchyma, only amyloplasts fluoresce, indicating the presence of adsorbed phosphorylase protein. Cytoplasmic phosphorylase can be detected in the continuance of senescence and, finally, after 16 months of tuber storage, the particle-bound enzyme had mostly disappeared. Simultaneously, we observed membrane destruction and decomposition on the ultrastructural level. The phosphorylase from senescent potatoes is a converted molecule and seems to be formed by proteolytic cleavage. The location of phosphorylase in the amyloplasts during starch synthesis indicates that it also plays a role in starch synthesis and not only in its degradation.
Article
The incorporation of phosphate into disks of potato tubers treated with sodium fluoride was studied. Pretreatment of potato tuber disks, which had been aged in 0,5 mM CaCl2 for 24 hours, with 5 × 10−2 M NaF for 15 minutes resulted in an increase in the incorporation of 32P, compared to a control pretreated with NaCl. It was demonstrated that only the inorganic (32Pi) acid soluble fraction of the tissues was enhanced, whereas the organic acid soluble fraction was not modified. It was concluded that pretreatment with NaF, measured in terms of 32P-incorporation, did not affect the metabolism of the phosphorylated compounds. On the other hand, sodium fluoride added to the ageing solution for 24 hours brought about a consecutive decrease in 32P-incorporation at the level of the inorganic and organic acid soluble fractions. A possible action of fluoride on the metabolic changes due to the ageing process is discussed.
Article
Studies with specific metabolic inhibitors on 14CO2 fixation by potato tuber disks indicate that an active glycolysis pathway is essential for dark CO2 fixation. The effect of added substrates and of malonate confirmed that the TCA Cycle activity is suppressed in fresh tissue.
Article
Pea plants (Pisum sativum L.) were supplied with external phosphate for differing periods of time, so that their phosphorus status varied, and the intracellular distribution of inorganic phosphate (P1) in the roots was examined by 31P nuclear magnetic resonance. Over the range of phosphorus nutrition investigated, the quantity of vacuolar P1 per unit fresh weight of root tip changed considerably, whereas the quantity of cytoplasmic P1 per unit fresh weight of root tip did not alter. The relative volumes of the cytoplasm and the vacuole in pea root tips seemed to be little affected by differences in phosphorus nutrition, and this implied that the concentration of P1 in the cytoplasm was kept almost constant, at a level estimated to be ∼ 18 mM. The rate of absorption of 32P-labelled phosphate was negatively correlated with the vacuolar P1 concentration, but there was no clear correlation with the concentration of P1 in the cytoplasm.
Article
CHANGES IN THE ACTIVITY OF CHLOROGENIC ACID OXIDASE AND OTHER ENZYMES INVOLVED IN OXIDATION AND REDUCTION OF TPN IN AGEING POTATO TUBER SLICES. — The activation of respiration, and in particular of the pentose phosphate pathway, during incubation of potato tuber slices could depend on the increase of activity of oxidative enzymes mediating electron transfer from Gl. 6-P to oxygen.The present report deals with the activity changes, in the first period of incubation, of the following enzymes: Gl. 6-P-dehydrogenase, TPNH-glutathione reductase, gluta-thione-dehydroascorbate reductase, chlorogenic acid oxidase and a TPNH diaphorase utilizing tetrazolium salts as electron acceptors.The activity of all of these enzymes, with the exception of TPNH diaphorase, was found to bs, at all stages of incubation, in large excess respect that required to account for the estimated contribution of the pentose phosphate pathway to respiration.Gl. 6-P dehydrogenase, glutathione reductase and chlorogenic oxidase activities markedly incresed during incubation; but their increase appeared to be clearly delayed (of some hours) respect that of oxygen uptake. This seems to indicate that the increase in activity of these anzymes is rather a consequence than a cause of the respiratory activation.TPNH diaphorase showed a very low activity in the fresh slices, and it increased quite significantly already in the very first period (5 hours) of incubation. This behaviour suggests the possibility that this enzyme could limit TPNH oxidation, and thus the pentose phosphate pathway activity, and that its activation could be correlated with that of oxidative metabolism in the ageing slices. Further investigation of this hypothesis requires the identification of the natural electron acceptor of this enzyme.
Article
Phosphate absorbed from KH232PO4 solutions of low concentration by beech mycorrhizas is rapidly esterified. After periods of a few minutes about one-half of that absorbed is found in organic compounds. Both fungal and host tissues when exposed, after separation, to radioactive phosphate solutions show this ability for rapid esterification. Whole mycorrhizas which had been allowed to absorb KH232PO4 were rapidly dissected in the cold and the labelled phosphate fractions in their host and fungal tissues were separated. In the host tissue 90 % of the 32P was found in inorganic phosphate after half a minute and this percentage fell to a little under 80 % after 10 minutes. The curve of percentage labelling of inorganic phosphate in the host tissue appeared to extrapolate to 100% at zero time. It is concluded that inorganic phosphate passes into the host from the fungus. This result is discussed in relation to previous work on phosphate absorption by mycorrhizas.
Article
When excised epicotyl segments of Pisum are incubated for periods of up to 24 hours in 0.01 M potassium maleate they exhibit a considerable increase in their ability to absorb and esterify phosphate. In comparison, hypocotyl segments of Gossypium and Helianthus subjected to similar treatments show no change in their ability to absorb and esterify phosphate. The difference in response is attributed to differences between the species themselves rather than to their morphological nature. It is possible to reduce the magnitude of the increase in the rate of phosphate uptake occurring in segments of Pisum epicotyls by increasing the phosphate concentration of the outside medium. This reaction closely resembles that which occurs when slices of potato tuber are similarly treated. In contrast to potato slices, the rate of respiration of Pisum epicotyl segments decreased during the incubation period. The increase in the rate of phosphate uptake is accompanied by an increase in the rate of sulphate absorption and protein synthesis. Other results showed that the rate of phosphate absorption by fresh and incubated tissue is limited by different systems. It would appear that the rate of uptake of phosphate by fresh segments is limited by its rate of diffusion into the tissue, whilst that absorbed by incubated segments is limited by the metabolic activity of the segment.
Article
Movement of aluminium into excised root tips of sainfoin follows a normal curve which suggests little or no uptake into non-free space. Washing in water removes very little aluminium from the roots but washing in dilute buffer solution removes a considerable exchangeable fraction. The pattern of phosphate incorporation in roots pretreated with aluminium is different from that obtained with untreated roots in several respects. Both percentage esterification and the proportions of the esterified fractions differ suggesting both a Donnan free space and a metabolic interference. The small amount of aluminium removed by aqueous washing suggests a minimum of precipitation with aluminium either external to the root, or in the water-free space of the cortex. The importance of this aluminium-phosphate effect as a component of aluminium toxicity, its specific sites and rates of reaction, require further experimental assessment.
Article
Molybdate permeability increases during the leaf senescence; in the same order, ageing on distilled water leads to a subsequent increase of MoO4 uptake. This absorption evolution which is characteristic of the ageing process is prevented by a benzylaminopurine (BAP) pretreatment (20 mg/l) of the leaf discs. The first significant effect is observed after 5 h. This effect induced by the cytokinin during ageing (20°) appears even in the case of an absorption at 0°.RésuméLa perméabilité au molybdate s'accroît au cours de la sénescence foliaire; de même, la mise en survie sur eau distillée se traduit par une augmentation consécutive des quantités de MoO4 fixé. Cette évolution de l'absorption qui accompagne le vieillissement foliaire est prévenue par le prétraitement des disques de feuille avec la BAP (20 mg/l) dont l'effet inhibiteur apparaît significativement déjà après 5 h. Cet effect induit, par la BAP, au cours de la survie se manifeste même si l'absorption est faite à 0°.
Article
The distribution of phosphorus1 in the world, unlike that of all other elements but carbon, is dominated by the present and past activities of living organisms. Thus it was first isolated as an element from that preeminently biological fluid, urine, by the Arabian alchemists in the 12th century and then by H. Brand in 1669; while the next source to be discovered was bone, in 1770 (Corbridge 1978). It is widely distributed in the Earth’s crust, where it comprises 0.1% by weight of the elements present. Igneous deposits are known, but most of the phosphate used by man has been formed either as guano and its end-product, phosphatized coral, or as sedimentary deposits laid down under marine conditions in a combination of biological and physicochemical processes. In each case, the key event in formation of the deposit has been the ability of living organisms to scavenge phosphate from their surroundings, so that the concentration within the organism is increased one thousand fold or more (see Sect. 2). With guano-based products, phosphate has passed through a long food chain (marine microorganism → crustacean → fish → sea bird) and has finally been drawn into one place as excreta and as fish and bird remains.
Article
1. Der Phosphatgehalt von Bäckerhefe, die in Nährlösungen mit verschiedenem osmotischen Wert herangezogen worden war, wurde bestimmt. Als Osmotica wurden Sorbit (1,1 m) und Lutrol (20 Vol-%) verwendet. Die erhaltenen Meßergebnisse wurden auf das Trockengewicht bezogen. 2. Der Gesamtphosphatgehalt der Hefen ist bei erhöhter osmotischer Konzentration des Nährmediums herabgesetzt. 3. An der Erniedrigung des Gesamtphosphatgehalts der So- und Lu-Hefen gegenüber den Kontrollen sind alle drei bestimmten Phosphatfraktionen (Extraktionsmittel: 2,5%ige Trichloressigsäure) gleichermaßen beteiligt. 4. Errechnet man die prozentualen Anteile der Phosphatfraktionen am Gesamtphosphatgehalt, so zeigt sich, daß die an Sorbit oder Lutrol adaptierten Zellen einen relativ geringeren Gehalt an Orthophosphat gegenüber einem Anstieg des TCE-unlöslichen Phosphats besitzen als die Ko-Hefen. 5. Veränderungen in der Stoffwechselaktivität und damit der Phosphataufnahme sowie Veränderungen im Plasmavolumen und im freien lösenden Raum der Zellen wurden als die möglichen Ursachen für das differente Verhalten der unterschiedlich kultivierten Organismen diskutiert.
Article
3IP nuclear magnetic resonance (NMR) spectra are used to monitor intracellular changes in sections of potato tuber (Solarium tuberosum), maize root tips (Zea mays) and the roots of single maize seedlings. Intracellular changes that result from the uptake of inorganic phosphate, D-mannose, the spectroscopic broadening probe Mn2+ and 2, 4-dinitrophenol are described. It is concluded that NMR provides a powerful, direct method for following intracellular changes in plant tissues.
Article
During the climacteric rise in respiration of cantaloupe fruit (Cucumis melo L., var. reticulatus Naud.) the concentration per gramme fresh weight of adenosine triphosphate (ATP) increased and that of adenosine diphosphate (ADP) did not change; thus a net synthesis of adenosine pyrophosphate occurs during the respiratory climacteric. A net synthesis of protein which was observed was positively correlated with the concentration of ATP. Ethylene treatment stimulated a climacteric-like rise in the respiration and in the rate of ripening in fruit harvested at 9 to 32 days after anthesis. The ratio ATP/ADP increased in fruit ripened with ethylene only when harvested 20 days or more after anthesis.
Article
Respiration rate of foliarPelargonium discs was insensitive to ageing. The addition of BAP or GA3 to the ageing medium did not produce any effect. The presence of GA3 or BAP in the ageing medium induced an increase (27 %) or a decrease (45 %) of the phosphate uptake. The analysis of phosphorylated compound labelling showed that these two hormones decreased32P incorporation in the non-acid soluble fraction and increased32P incorporation in the acid soluble organic fraction. GA3 and BAP had little effect on the distribution of radioactivity between the different acid soluble compounds, but they increased the ATP level. These results suggest that both GA3 and BAP increase the basal metabolism, but they seem to act differently on the development of the uptake mechanism during ageing.
Article
This paper describes experiments that were undertaken in order to discover whether, in disks (1 x 10 mm) of storage tissue of carrot (Daucus carota L.), cycloheximide inhibited protein synthesis directly, or indirectly via an effect on respiration. Freshly cut disks, incubated in water for 4 hr and then transferred for 75 min to a medium that contained [14C]-leucine, incorporated [14C]-leucine into protein. Cycloheximide (10, gmg/ml) caused a 95 per cent inhibition of this incorporation. In comparable experiments, the effects of cycloheximide on the distribution of 14C from [6-14C]-glucose were determined. The results indicate very strongly that cycloheximide inhibited protein synthesis directly and not via any effect on respiration. Cycloheximide did not increase the rate of oxygen uptake. It is concluded that protein synthesis occurs when freshly cut dish of carrot are incubated in water and that cycloheximide inhibits this synthesis directly.
Article
(gIucose-6- phosphate ) and similar abbreviations for specific esters, P-lipid (phospholipid), P-choline (phosphatyl choline). 2 Throughout this article, solution concentrations will be given as molarities. The tissue content will usually be expressed as miIIimoles (mmoles), micromoles (I'moles) or nano­ moles (nmoles) per gram fresh weight (g fr wt); or else in terms of molarities, where the tissue is taken to be an equivalent volume of water. This should help in comparing solu­ tion and tissue concentrations and the results of different studies. I have made the neces­ sary conversions from other authors' data. Where values have been quoted in terms of dry weight alone, I have made the conversions by assuming dry wt/fresh wt ratios of 0.12, 0.14, and 0.17 for fleshy, normal, and woody tissues. They are sufficiently accurate for my comparisons. Unfortunately, authors do not always make clear the basis of their calculations. Calculations in terms of moles and molarities are free from ambiguity.
Article
ATPase activity in cell wall and microsomal fractions from fresh and washed potato tuber discs was measured. The activity was markedly stimulated by Ca(2+) whereas K(+) and Na(+) had little effect. The Ca(2+)-ATPase increased with washing, particularly in the cell wall fractions and in the low density fractions after discontinuous sucrose gradient centrifugation. The activities of succinic dehydrogenase and cytochrome-c-oxidase also increased with disc washing, although activity was highest in the denser regions of the gradient. A fine structural study of fresh and washed tissues revealed a pronounced increase in the membrane profile concentration of the endoplasmic reticulum and mitochondria after ageing for 24 hours.
Article
The effect of pretreatment with sufficient and deficient levels of phosphorus (P), applied for 16 days, on the subsequent P response of four populations of white clover (Trifolium repens L.) was studied in solution culture in a glasshouse. Inorganic‐P and total‐P levels of leaf tissue were measured at three harvest dates. Increasing the subsequent supply of P increased both inorganic‐p and total‐P levels of leaf tissue, especially if plants had previously been P‐stressed. The p content of leaves, and especially the ‘organic‐P’ content decreased with leaf age.Several white clover populations, collected from soils high in p and low in P, were grown at sufficient and deficient levels of p. populations collected from low‐P soils accumulated more inorganic‐P in their leaf tissue, especially when grown at high‐P, and were also able to reduce these inorganic‐p levels to lower concentrations when the P supply was deficient. This may be an important adaptive feature of white clover plants able to survive in low‐P soils.
Article
The effects of oxygen and of dinitrophenol on the respiratory activation of potato tuber slices. — It is well known that thin slices from storage organs show, in the first period following preparation and washing, a transition from a low to a high level of metabolic activity. In the potato tuber discs (and similar materials) this transition is characterized by: a) a several fold increase of oxygen uptake; b) an increase of the capacity of dissimilating to CO2 the carbon 1 of glucose; c) a decrease of the sensibility of oxygen uptake to the uncoupler 2,4 dinitrophenol (DNP); d) an increase of the capacity of ion and sugar uptake; e) the development of marked capacity of protein synthesis; f) and increase of the activity (as determined in homogenates) of several enzymes involved in the directs oxidation of glucose-6-P or — possibly — in the reoxidation of the TPN reduced by the pentose phosphate pathway reactions. The two latter responses appear with some delay respect the activation of oxygen uptake, which suggested (Marrè et al.) that they are probably rather a consequence than a primary cause of the activation of respiration.The present researches are aimed to a better understanding of the role played by the activity of oxidative enzymes and by high energy phosphate acceptor availability during the activation of metabolism in potato tuber slices.The importance of these factors was investigated by measuring the QO2 under different O2 pressure conditions, and by following the respiratory effects induced by DNP supplied at various concentration and at various incubation times. The results obtained can be summarized as follows:I. - Changes induced by varying O2 pressure.a) Lowering O2 pressure from 20% (air) to 5% does not affect the QO2 of freshly prepared slices, showing a low respiration rate, while it consistently depresses (by 40–50%) the QO2 of slices preincubated in air for periods longer than 8 hours, in which the process of respiratory activation is already well developped. At any stage of aging of the slices, no difference in QO2 is observed when air is substituted with pure oxygen. The rate of respiratory activation of the discs is highly sensitive to O2 partial pressure during incubation. At 20% O2 (air) the system involved in activation is practically satured, no further increase of the activation rate being observed at higher O2 (100%). With 5% O2, however, the rate of activation (measured after bringing again the slices in 20% oxygen) appears markedly depressed.b) The increase, upon incubation, of the dissimilation of carbon 1 of glucose to CO2 is also strongly depressed by 5% O2. This suggests that the progressive increase of the capacity of the oxidative system during aging makes limiting — at a given moment — the rate of diffusion of oxygen in the tissues.c) The increase during incubation of the capacity of active uptake of solutes such as the Rb+ ion and glucose is not significantly depressed by the low (5%) oxygen pressures. This seems to be in relation with the early development of this aspect of the activation process during the first period of activation, when the respiratory rate is low and lowering O2 pressure does not affect QO2. On the other hand, the lack of sensibility of ion and glucose uptake to low oxygen in the aged slices could indicate that the high energy phoshate level required for this process is lower than that for other processes, such as protein synthesis.d) Protein synthesis activation (measured as radioactivity incorporation into proteins in slices fed with glucose-6-C) is severely inhibited (by about 60%) by 5% O2. This suggests a close correlation between respiratory activity and protein synthesis, on one hand, and between protein synthesis and the activation process occurring during aging, on the other.II. - Changes induced by DNP at different O2 pressures.a) As already shown in other laboratories, DNP at an appropriate concentration (in our case around 3 × 10M, at pH 5) markedly stimulates O2 uptake in the fresh slices, and this effect gradually disappears, parallely with the respiratory activation, when DNP is supplied to slices preincubated in distilled water for increasing periods of time. When slices were incubated from the beginning with the DNP concentration giving maximal respiratory response (3 × 10M at pH 5), the respiratory increase due the incubation was completely suppressed and the control slices incubated in water reached, after a few hours (3–5), QO2 values, higher than those of the DNP treated slices. With DNP concentration between 10M and 3 × 10M the initial rate of respiration was still higher than in the controls; this positive difference very slowly disappeared with the increase of incubation time, until, after about 36 h (when respiratory activation in the controls approached its maximum) the two curves became practically identical.A large fraction of the DNP induced increase of QO2 can be readily reversed by washing the slices and removing the inhibitor. When this is done, the rate of respiration observed for the slices preincubated (up to 10 hours) in DNP concentration giving maximal positive respiratory response falled down to values close to those of the fresh slices; while in the case of lower DNP concentration the level of respiration is almost unaffected by washing off the inhibitor. These results confirm the hypothesis that lack of phosphate acceptors is strongly limiting respiration in the « fresh » slices, and that this type of control is slowly losing its importance during the « aging » process: which appears to be a consequence of both the increased activity of ATP utilizing systems and the appearance of some physiological (facultative) uncoupling mechanism.b) Immediately after preparation, when O2 uptake is very low, the respiration of both the slices in 20% and in 5% O2 is stimulated by DNP at approximately the same extent. However, when slices incubated in air for 7–8 hours, (still showing a significant, although reduced, respiratory response to DNP), are brought to 5% O2, the effect of DNP is completely suppressed. Conversely, the QO2 of slices incubated for the same period with 5% O2 (which inhibits respiratory activation, see I), do not respond to DNP when the O2 pressure is mainteined low, while they show a clear response when O2 in the gas phase is rised to 20%. The fact that in the « partially aged » (that is, incubated for a 7–9 h. period) slices lowering O2 to 5% simultaneously inhibits O2 uptake and completely suppresses the DNP effect, suggests that the respiratory fraction sensitive to O2 pressure is involved in (mitochondrial) oxidative phosphorylation. The simplest interpretation is in fact that in low O2 the ADP level rises, and that oxidative activity, instead of phosphate acceptor level, becomes the main factor limiting respiration.Conclusions. — When correleted with the previous data on the metabolic activation of potato tuber discs during incubation (cf also Romberger and Norton the present results suggest that the activation process in potato tuber slices comprehends two distinct phases. In the former, the rise of respiration appears to be a consequence of a release from lack of high energy phosphate acceptors. In the second (somewhat delayed) phase the increased activity of some key respiratory enzymes furtherly enlarges the oxidative capacity of the tissues. The inhibition of this phase of activation together with that of protein synthesis by both DNP or low oxygen tension suggests that enzyme synthesis, rather than enzyme activation, is responsible for the previously reported increase of respiratory enzyme activities.
Article
STUDIES ON MECHANISM OF COCHLIOBOLIN ACTIVITY. A: EFFECTS OF THE TOXIN ON FRESH POTATO TUBER SLICES. — Cochliobolin, a toxic compound produced by Helminthosporium oryzae, causes inorganic phosphorus leakage from fresh potato tuber slices, higher amounts being found in incubation media with higher toxin concentrations and for longer incubation periods. Organic compounds, also, are released by potato tuber slices, like phenolic products, large amounts of sugars, and some aminoacids, alanine, lysine, tyrosine, valine and γ-aminobutirric acid, which have never been observed in the incubation meida of untreated slices. Cochliobolin uptake by fresh potato tuber slices does not take place actively or, anyhow, at a metabolic level. Indeed, neither 2,4-dinitro-phenol (at concentration, pH, and incubations periods apt to reduce active uptake), nor low temperatures (0–2°C) prevent toxin uptake. Potato tuber slices are not affected by cochliobolin, unless kept at 25°C, and this fact suggests that while toxin uptake does not interest metabolic pathways, it might affect some phase, or structure, essential to cell metabolism. The locus of toxin activity seems therefore to be identified with its influence on cell absortion and retention activities, of products essential for metabolic processes. Thus the impairing of cell permeability, possibly affecting the processes or the structures which regulate the active uptake, seems to be, at the moment, the only evident interpretation of the phenomena observed.
Article
The time course of sulfate uptake in relation to respiration is shown for aging slices of potato, Solanum tuberosum L. cv. Russet. For comparative purposes, a time course for phosphate uptake is also shown. Malonic acid depressed both the respiratory rise and the sulfate accumulating ability of aging discs. A low dose of ultraviolet radiation given at the onset of aging reduced sulfate uptake by one-half without lowering respiration. We hypothesize that sulfate uptake is controlled by at least two mechanisms: one associated with oxidative metabolism and the other mediated by protein synthesis.
Article
When excised barley (Hodeum Vulgare L.) roots were aged, the rate of uptake of K and C1 increased raching a maximum in about 14 to 18 h. At its maximum the uptake rate was approxiamately twice that of the freshly excised root materila. Respiratory activity declined markedly during the aging period. Although excision was an essential requirement for uptake enhancement, washing was not. Both the uptake and aging processes were shown ot be unresponsive to the presence or absence of Ca in the tratment solutions. Because of cation exchange properties, the change in the total cation content of the root material was a more meaningful measure of the metabolically mediated cation uptake than was the change in content of the test cation itself. The pluggin of xylem vessels with protein and pectin-like substances was observed to increase with aging. It is proposed that the occlusion of the vessels may account for an apparent increaase in uptake since the obstruction could reduce a concurrent loss of ions through the cut ends of the root segments.
Article
The Influence of Benzylaminopurine on the Absorption of Phosphate by Potato Tubers Aging of disks of potato tuber in an aerated liquid medium induces a large increase of the rate of phosphate absorption. Experiments were performed with benzylaminopurine added to the aging solution at various times after slicing, and the rate of absorption was determined 24 h after slicing. The opposite experiment was also performed, with benzylaminopurine added at the beginning and withdrawn after different times. The addition of benzylaminopurine to the aging medium partially prevents the development of the phosphate uptake. The uptake mechanism is a metabolic phenomenon as shown by its sensitivity to temperature. The degree of inhibition depends on the benzylaminopurine concentration as well as on the time of aging. The results suggest that the cytokinin acts on a process which occurs all along the aging and underline the importance of the presence of benzylaminopurine during the first hours of aging.
Article
Rates of uptake of nitrate and chloride by excised beech mycorrhizas are much smaller than those of phosphate. With solutions containing 1 mM KCl or KH2PO4, about 45% of the chloride absorbed is found in the fungal sheath, compared with about 85% of the phosphate. The uptake of both chloride and phosphate is increased when the roots are cut into thin slices. The results show that direct uptake of chloride and phosphate into the host cells is limited by diffusion through the sheath, but in the case of chloride the diffusion gradient is not greatly affected by uptake into the sheath. It is suggested that, in the absence of nitrate reduction by the fungus, the processes controlling nitrate uptake and chloride uptake are likely to be similar. Effects of ageing excised mycorrhizas in dilute CaSO4 solutions are discussed.
Article
Glycine and catechol when added separately to both fresh and washed potato-tuber slices stimulated their oxygen uptake and CO2 production. Glycine and catechol added together produced an additive stimulation of the respiration of fresh tuber-slices but gave no stimulation of respiration by washed slices. The inhibitory effect of 3,4-dichlorophenyl serine on the oxidation of glycine by unwashed slices suggests that this step in the degradation was probably mediated by polyphenol oxidase.
Article
The transport and distribution of phosphate in Hydrodictyon africanum is reported, and discussed in relation to phosphate transport in other green algae and chloride transport in Hydrodictyon. The inorganic phosphate concentration in both vacuole and cytoplasm is 1–2 mM; the cytoplasm also contains 35 mM of phosphate as organic and polyphosphate, which are absent from the vacuole. Phosphate influx from 0.1 mM phosphate at pH 6.5 was much greater than the efflux, and was more stimulated by light and inhibited by low temperature than was the efflux. The phosphate influx is, on electrochemical criteria, active. The influx at the tonoplast was much higher than that at the plasmalemma. Na stimulated phosphate influx more than did K, in agreement with results for other green algae but in contrast to monovalent cation effects on active Cl influx. Both phosphate and chloride influxes show a simple hyperbolic relationship between anion concentration and influx, in the concentration range tested, but the kinetics for the two ions show different responses to changes in irradiance and Na concentration. pH effects on the influxes are also reported. The passive permeability of the plasmalemma to H2PO-4 is similar to that to Cl-.
Article
Organic phosphorus compounds have been extracted from the roots of intact plants which have absorbed radioactive phosphate. The distribution of phosphorus between different organic fractions of the root during a 24-hour absorption period is markedly influenced by the concentration of phosphorus supplied. Less than 1 minute after entry a significant proportion of the absorbed phosphorus is found to be in organic compounds. Incorporation into nucleotides is particularly rapid, whereas incorporation into hexose phosphates occurs more slowly. The pattern of esterification is influenced by the phosphate status of the plants. 2: 4-dinitrophenol (10 ⁻⁴ M.) reduces the uptake of phosphorus and also the extent of esterification, the latter effect being due solely to reduced incorporation into the nucleotide fraction. Although extensive esterification of phosphate occurs in roots, it appears to be transported to the shoot as inorganic phosphate accompanied by only a small amount of a single organic compound.
Article
SUMMARY Paper partition chromatography has been used for the separation of organic phosphorus compounds extracted from roots after short periods of absorption of radioactive phosphorus by whole barley plants. Methods of extraction, fractionation, and identification of the compounds are described. Equipment has been designed to record rapidly the activity along the length of the chromatograms. Salient features are congruence between chromatograms and record, high sensitivity and provision for automatic change of sensitivity.
Article
1.1. The respiratory increment which arises during the incubation of thin pieces of chicory root has been shown to be qualitatively distinct from the initial respiration. Whereas the initial respiration is almost entirely malonate resistant, the developed respiration is completely malonate sensitive.2.2. The respiration of fresh tissue may be increased several fold by the uncoupling agent 2,4-dinitrophenol (DNP), and the rise so induced is malonate sensitive. The respiration rate of incubated tissue is unaffected by DNP.3.3. The malonate-sensitive increment arising on aging, and the malonate-sensitive increment induced in fresh tissue by DNP have been shown to be different.4.4. Malonate-treated aged tissue readily oxidizes malate, thereby restoring the uninhibited respiration rate. By contrast, malate fails to affect malonate-inhibited, DNP-treated fresh tissue. Mitochondrial preparations from both types of tissue oxidize malate equally. Evidence has been presented that fresh tissue is permeable to malate.5.5. The nucleotide composition of fresh and incubated tissue was examined. Adenosine triphosphate (ATP) proved the predominant nucleotide in both cases, and no significant difference in nucleotide prevalence or composition was noted.6.6. The suggestion has been made that the respiratory rise attending aging is initiated by the removal of a restraint on the phosphorylative activity of the tissue.
Article
RESEARCH in several laboratories has clearly demonstrated that aerated potato disks develop an increased capacity for uptake of oxygen1–7. This additional respiratory capacity is not increased by 2,4-dinitrophenol7 and is relatively insensitive to inhibition by cyanide6 and carbon monoxide5,6. However, cyanide8, low temparature (0–5° C.)7 or absence of oxygen at normal temperature8 will prevent the development of the increased respiratory capacity.
Article
The uptake of phosphate-32P and its incorporation into TCA-precipitable material of the pea stem sections with time are reported. The data suggested that not all of the phosphate-32P taken up by the cells is readily available for incorporation into TCA-precipitable fraction.The incorporation of phosphate-32P into nuclear and cytoplasmic RNA of this plant tissue has been studied. The relative specific activity of cytoplasmic RNA was at most one-fifth that of the nuclear RNA in one hour incubation, one-half in 2 hours, and essentially equal to or higher than that of the nuclear RNA in 12 hours. The differences in the relative specific activities among fractions of mitochondria, microsome, and supernatant were small.
Respiratory mechanisms associated with inorganic phosphate uptake by potato tuber tissue
  • D P Hackett
GRIFFITHS, S. K. and D. P. HACKETT. 1957. Respiratory mechanisms associated with inorganic phosphate uptake by potato tuber tissue. Plant Physiol. suppl.: 32 xlvi.
Studies ol1 the "wound respiration" of potato tuber tissue
HACKETT, D. P. 1956. Studies ol1 the "wound respiration" of potato tuber tissue. Plant Physiol. suppl.: 31 xl.
The developmenit and centrol of coexisting respiratorv systems in slices of chicory root
LATIES. G. G. 1959. The developmenit and centrol of coexisting respiratorv systems in slices of chicory root. Arch. Biochem. Biophvs. 79: 378-391.
Studies on1 the dormancy and sprouting of potatoes. 1. The oxygen content of the potato tuber
BURTON, WV. G. 1950. Studies on1 the dormancy and sprouting of potatoes. 1. The oxygen content of the potato tuber. New Phytologist 49: 121-134.
The absorption and utilization of phosphate by young barley plants. IV. The initial stages of phosphate metabolism in roots
LOUGHMAN, B. C. and R. S. RE1SS L 1957. The absorption and utilization of phosphate by young barley plants. IV. The initial stages of phosphate metabolism in roots. Jour. Exp. Bot. 8: 280-293.