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1.
Growth and maintenance respiratory costs of cucumber fruits as affected by temperature, and ontogeny and size of the fruits 总被引:3,自引:0,他引:3
The rates of dry weight increase and respiration of fruits were measured throughout fruit ontogeny at 20, 25 and 30°C in cucumber ( Cucumis sativus L. cv. Corona). By maintaining one or five fruits per plant, which strongly affected fruit dry weight but not ontogeny, the effects of fruit size and ontogeny on respiration could be studied separately. The respiration rate per fruit followed a sigmoid curve during fruit ontogeny, while the specific respiration rate (respiration rate per unit dry weight) declined with time after anthesis. The specific respiration rate was almost linearly related to the relative growth rate. The specific respiratory costs for both growth and maintenance were highest in young fruits, but were not affected by fruit size. The average specific respiratory costs for growth and maintenance at 25°C were 3.3–3.9 mmol CO2 g−1 and 4.0 nmol CO2 g−1 s−1 , respectively. An increase in temperature had no effect on the specific respiratory costs for growth, while the costs for maintenance increased with a Q10 of about 2. The costs for growth agreed reasonably well with theoretical estimates based on the chemical composition of the fruits but not with estimates based on only the carbon and ash content. The respiratory losses as a fraction of the total carbon requirement of a fruit changed during fruit ontogeny, but were independent of temperature and were similar for slow- and fast-growing fruits. The cumulative respiratory losses accounted for 13–15% of the total carbon requirement. 相似文献
2.
Respiratory energy requirements of roots vary with the potential growth rate of a plant species 总被引:12,自引:0,他引:12
Hendrik Poorter Adrie Van der Werf Owen K. Atkin Hans Lambers 《Physiologia plantarum》1991,83(3):469-475
The rates of growth, net rate of nitrate uptake and root respiration of 24 wild species were compared under conditions of optimum nutrient supply. The relative growth rate (RGR)of the roots of these species varied between 110 and 370 mg g-1 day-1 and the net rate of nitrate uptake between 1 and 7 mmol (g root dry weight)-1 day-1 . The rate of root respiration was positively correlated with the RGR of the roots. Root respiration was also calculated from the measured rate of growth and nitrate uptake, using previously determined values for the costs of maintenance, growth and ion uptake of two slow-growing species. The calculated rate of respiration was slightly lower than the measured one for slow-growing species, but twice as high as measured rates for rapid-growing species. This discrepancy was not due to a relatively smaller electron flow through the alternative pathway and, consequently, a more efficient ATP production in the fast-growing species. Neither could variation in specific costs for root growth or maintenance explain these differences. Therefore, we conclude that fast-growing species have lower specific respiratory costs for ion uptake than slow-growing ones. Due partly to these lower specific costs of nutrient uptake, the fraction of respiration that rapid-growing species spend on anion uptake is lower than that of slow-growing species, in spite of the much higher rate of ion uptake of the fast-growing ones. 相似文献
3.
I. Scheurwater C. Cornelissen F. Dictus R. Welschen & H. Lambers 《Plant, cell & environment》1998,21(10):995-1005
Herbaceous plants grown with free access to nutrients exhibit inherent differences in maximum relative growth rate (RGR) and rate of nutrient uptake. Measured rates of root respiration are higher in fast-growing species than in slow-growing ones. Fast-growing herbaceous species, however, exhibit lower rates of respiration than would be expected from their high rates of growth and nitrate uptake. We investigated why the difference in root O2 uptake between fast- and slow-growing species is relatively small. Inhibition of respiration by the build-up of CO2 in closed cuvettes, diurnal variation in respiration rates or an increasing ratio of respiratory CO2 release to O2 uptake (RQ) with increasing RGR failed to explain the relatively low root respiration rates in fast-growing grasses. Furthermore, differences in alternative pathway activity can at most only partly explain why the difference in root respiration between fast- and slow-growing grasses is relatively small. Although specific respiratory costs for maintenance of biomass are slightly higher in the fast-growing Dactylis glomerata L. than those in the slow-growing Festuca ovina L., they account for 50% of total root respiration in both species. The specific respiratory costs for ion uptake in the fast-growing grass are one-third of those in the slow-growing grass [0·41 versus 1·22 mol O2 mol (NO3 – )–1 ]. We conclude that this is the major cause of the relatively low rates of root respiration in fast-growing grasses. 相似文献
4.
The validity of compartmental analysis of Rb+ efflux from roots of intact high-salt barley plants ( Hordeum vulgare L. cv. Salve) was examined. 86 Rb+ was used as a tracer. Rb+ (1 m M ) was included together with 3 m M K+ in the growth medium, and steady-state conditions were assumed to prevail during the experiment. Three phases of efflux were revealed with half-times of 23 min, 109 min and 12 h, respectively; and the time span of the experiment had to be at least 20 h to make determination of the slow phase possible. We cannot state what compartments in the root the 3 different slopes represent. A comparison of slopes was made between the plots of In efflux vs time and In content vs time. In spite of correction for tracer transport from the roots to the shoot, the slopes for the slow phase did not agree unless up to 85% of the root content of Rb+ is assumed not to participate in efflux. 相似文献
5.
SERGEY SHABALA JIAYIN PANG MEIXUE ZHOU LANA SHABALA TRACEY A. CUIN PETER NICK & LARS H. WEGNER 《Plant, cell & environment》2009,32(2):194-207
Nutrient acquisition in the mature root zone is under systemic control by the shoot and the root tip. In maize, exposure of the shoot to light induces short-term (within 1–2 min) effects on net K+ and H+ transport at the root surface. H+ efflux decreased (from −18 to −12 nmol m−2 s−1 ) and K+ uptake (∼2 nmol m−2 s−1 ) reverted to efflux (∼−3 nmol m−2 s−1 ). Xylem probing revealed that the trans-root (electrical) potential drop between xylem vessels and an external electrode responded within seconds to a stepwise increase in light intensity; xylem pressure started to decrease after a ∼3 min delay, favouring electrical as opposed to hydraulic signalling. Cutting of maize and barley roots at the base reduced H+ efflux and stopped K+ influx in low-salt medium; xylem pressure rapidly increased to atmospheric levels. With 100 m m NaCl added to the bath, the pressure jump upon cutting was more dramatic, but fluxes remained unaffected, providing further evidence against hydraulic regulation of ion uptake. Following excision of the apical part of barley roots, influx changed to large efflux (−50 nmol m−2 s−1 ). Kinetin (2–4 µ m ), a synthetic cytokinin, reversed this effect. Regulation of ion transport by root-tip-synthesized cytokinins is discussed. 相似文献
6.
Determination of the surface area of fine tomato roots via cation uptake experiments 总被引:1,自引:0,他引:1
H. T. Wolterbeek 《Physiologia plantarum》1987,69(4):704-708
A method is described by which the surface area of a root is estimated from cation uptake data. 24 Na+ was supplied to excised roots of tomato ( Lycopersicon esculentum Mill, cv. Tiny Tim) seedlings at 3 μ M in unstirred solution. Coarse roots, for which external surface area and specific gravity could be measured accurately, were used to estimate the thickness (dN ) of the Nernst boundary layer at the root surface. 24 Na+ uptake (J1 ) was measured by γ-ray spectroscopy. Jt and dN were used to calculate the total surface area for ion absorption in fine roots, assuming that Na uptake rate was diffusion-limited. The results were compared to data obtained by conventional methods and indicated the usefulness of the cation uptake technique for quantitative estimates of root surfaces. 相似文献
7.
Sune Pettersson 《Physiologia plantarum》1986,66(1):122-128
Plants of barley ( Hordeum vulgare L. cv. Salve) were grown with 6.5–35% relative increase of K+ supply per day (RKR) using a special computer-controlled culture unit. After a few days on the culture solution the plants adapted their relative growth rate (RGR) to the rate of nutrient supply. The roots of the plants remained in a low salt status irrespective of the rate of nutrient supply, whereas the concentration of K+ in shoots increased with RKR. Both Vmax and Km for K+ (86 Rb) influx increased with RKR. It is concluded that with a continuous and stable K+ stress, the K+ uptake system is adjusted to provide an effective K+ uptake at each given RKR. Allosteric regulation of K+ influx does not occur and efflux of K+ is very small. 相似文献
8.
Effects of nitrate on influx, efflux and translocation of potassium in young sunflower plants 总被引:3,自引:0,他引:3
Sune Pettersson 《Physiologia plantarum》1984,61(4):663-669
Influx, efflux and translocation of K+ (86 Rb) were studied in the roots of sunflower seedlings ( Helianthus annuus L. cv. Uniflorus) treated with 0–4.0 m M NO3 − during a 9 day growth period or a 24 h pretreatment period. Roots treated with high levels of NO3 − absorbed and translocated more K+ (86 Rb) than seedlings treated with low levels of NO3 − . The content of K+ in the shoots was, however, higher in seedlings treated with low levels of NO3 − , indicating a low rate of retranslocation of K+ in those plants. K+ (86 Rb) efflux was highest into the low-NO3 − solutions. All effects on K+ (86 Rb)-fluxes were more obvious in high-K plants than in low-K plants. The results are discussed in relation to the Dijkshoorn-Ben Zioni hypothesis for K+ + NO3 − -uptake and translocation in plants. 相似文献
9.
Flavia Navari-Izzo Riccardo Izzo Mike F. Quartacci Giacomo Lorenzini 《Physiologia plantarum》1989,76(3):445-450
Plants of three commercial cultivars of Hordeum vulgaris L. (Barberousse, Gerbel, Panda) were continuously exposed to two concentrations of SO2 (40±5 and 117±20 ppb) against a control (charcoal-filtered air). Experiments were performed in fumigation chambers. Fumigation was started 9 days after seeding and plant material was harvested after 48 days. In none of the three cultivars did visible symptoms of injury appear on the leaves after exposure to SO2 , while they all showed a reduction in plant height and dry matter of shoots and roots and a significant increase in the shoot/root dry weight ratios depending on the cultivars. The time course of conductivity, and K+ Ca2+ and sugar effluxes were determined for 24 h. Leaves from cvs Gerbel and Panda exposed to SO2 exhibited a progressive increase in conductivity, and in Ca2+ and sugar efflux (expressed as percentages of their total effluxes). Plusmn; efflux of the three cultivars and conductivity in cv. Barberousse increased only after 24 h incubation. A relative leakage ratio (RLR) was calculated from the UV absorption at 280 nm after 24 h incubation of the leaf strips and the total 280 nm UV absorption, obtained after liquid N2 killing of the tissues. The RLR was well correlated with the total amino acids and sugars found in the leachate and can be used as a test for determining the tissue response to SO2 . 相似文献
10.
Shading of maize plants ( Zea mays L. cv. Blizzard) reduced net H+ extrusion by roots and increased K+ release, whereas there was no significant effect on anion efflux in deionized water. With lower light intensity the concentrations of carbohydrates in the roots decreased, but ATP levels and energy charge remained unchanged. Also, shading raised the tissue pH of roots and made the cytoplasmic pH of root cells drop. There was a significant influence of light intensity on H+ uptake by roots from an acidified test solution and CCCP (carbonylcyanide-3-chlorophenylhydrazone)-in-duced H+ uptake was modified by shading.
It is concluded that low light intensity does not limit active H+ release by plasmalemma ATPase activity in the root cells, but that a reduced carbohydrate supply brings about a change in biochemical reactions which alter the membrane permeability for protons. An increased passive reflux of H+ into the cells rather than a reduced H+ ATPase activity explains the decrease of net H+ release by roots of intact maize plants under low light intensity. 相似文献
It is concluded that low light intensity does not limit active H
11.
Effect of phosphorus supply on the formation and function of proteoid roots of white lupin (Lupinus albus L.) 总被引:11,自引:1,他引:10
G. Keerthisinghe P. J. Hocking P. R. Ryan & E. Delhaize 《Plant, cell & environment》1998,21(5):467-478
We investigated (1) the effect of constant and altered inorganic phosphate (Pi ) supply (1–100 mmol m–3 ) on proteoid root production by white lupin ( Lupinus albus L.); and (2) the variation in citrate efflux, enzyme activity and phosphate uptake along the proteoid root axis in solution culture. Proteoid root formation was greatest at Pi solution concentrations of 1–10 mmol m–3 and was suppressed at 25 mmol m–3 Pi and higher. Except at 1 mmol m–3 Pi , the formation of proteoid roots did not affect plant dry matter yields or shoot to root dry matter ratios, indicating that proteoid roots can form under conditions of adequate P supply and not at the expense of dry matter production. Plants with over 50% of the root system as proteoid roots had tissue P concentrations considered adequate for maximum growth, providing additional evidence that proteoid roots can form on P-sufficient plants. There was an inverse relationship between the Pi concentration in the youngest mature leaf and proteoid root formation. Citrate efflux and the activities of enzymes associated with citric acid synthesis (phosphoenolpyruvate carboxylase and malate dehydrogenase) varied along the proteoid root axis, being greatest in young proteoid rootlets of the 1–3 cm region from the root tip. Citrate release from the 0–1 and 5–9 cm regions of the proteoid root was only 7% (per unit root length) of that from the 1–3 cm segment. Electrical potential and 32 Pi uptake measurements showed that Pi uptake was more uniform along the proteoid root than citrate efflux. 相似文献
12.
In vivo and in vitro effects of boron on the plasma membrane proton pump of sunflower roots 总被引:3,自引:0,他引:3
Marta Roldán rés Belver Pilar Rodríguez-Rosales Nuria Ferrol Juan Pedro Donaire 《Physiologia plantarum》1992,84(1):49-54
The effect of boron excess and deficiency on H+ efflux from excised roots from sunflower ( Heliarahus annuus L. cv. Enano) seedlings and on plasma membrane H+ -ATPase (EC 3.6.1.35) in isolated KI-washed microsomes has been investigated. When seedlings were grown in media with toxic levels of H3 BO3 (5 m M ) or without added boron and exposed to light conditions, an inhibition of the capacity for external acidification by excised roots was observed as compared to roots from seedlings grown with optimal H3 BO3 concentration (0.25 m M ). Toxic and deficient boron conditions also inhibited the vanadate-sensitive H+ -ATPase of microsomes isolated from the roots. The mechanism of boron toxicity was investigated in vitro with microsorne vesicles. A strong effect of boron on the vanadate-sensitive, ATP-dependent H+ transport was found, but the vanadate-sensitive phospho-bydrolase activity was not affected. These results suggest that boron could exert an effect on the plasma membrane properties, directly or indirectly regulating, proton transport. 相似文献
13.
The uptake of K+ ion was studied in the roots of wheat ( Triuicum aestivum L. cv. GK Szeged) and cucumber ( Cucumis sativus L. cv. Budai csemege) seedlings grown in nutrient solution under nitrogen and sulfate stress conditions. Seedlings pretreated with 1 or 10 m M NaNO3 , absorbed more K+ than those treated with 0.1 m M NaNO3 . However, the posteffect of NaNO3 was considerably influenced by the Na2 SO4 , treatment. The results suggest that, at least partly, a feed-back regulation of K+ uptake may occur. However, due to the high Na+ contents of the roots, a Na+ effect in this process cannot be excluded. The growth and dry matter yields of the roots and shoots were strongly influenced by the SO2− /4 and NO− /3 supply of the plants. Appreciable differences were experienced between wheat and cucumber seedlings. The optimum SO2− /4 concentration of the growth solution for maximal growth varied considerably between the species, and was also different for the roots and the shoots in a given species. 相似文献
14.
The long-term effect of tentoxin on K+; , Ca2+ and total phosphorus (P) concentrations in the roots and shoots of 7- and 14-day-old seedlings of winter wheat ( Triticum aestivum L. cv. Martonvásári-8) was studied. Growth (dry weight) and shoot to root ratios (dry weight and mineral concentrations) were also estimated. One p M tentoxin increased the shoot to root ratio for dry weight after a 14-day period of application. The concentration of Ca2+ slightly increased in the shoot. In roots, tentoxin caused a 30% higher accumulation of Ca2+ after 7 days, which did not change with treatment during the following 7 days. The accumulation of Ca2+ was enhanced by increasing concentrations of tentoxin. K+ and total P levels increased in roots but decreased in shoots after 7 days. However, they were redistributed between root and shoot during days 8–14 of tentoxin treatment. The effect of tentoxin is explained as a stimulation of ion transport mainly into the vacuoles of the immature metaxylem elements. It is suggested that tentoxin and other microbial products effective at very low concentrations may have a general significance in promoting plant infection or symbiosis via the modification of physiological or biochemical processes. 相似文献
15.
The surface charge density of wheat root membranes 总被引:1,自引:0,他引:1
Seedlings of winter wheat ( Triticum aestivum L. cv. Hildur) were grown at 18°C for 7 days in darkness in a complete growth medium in the presence or absence of 1 m M KCl to produce roots with different ion contents (high and low K+ respectively). The roots were homogenized, the 3 000 g, 10 000 g, 30 000 g (further fractionated by two phase partitioning) and 100 000 g pellets isolated, and their surface charge densities (σ) determined by the use of 9-aminoacridine fluorescence. The average σ for all membrane fractions weighted for protein content was the same (−18 mC m−2 ) for low and high K+ roots. The K+ , Na+ , Mg2+ and Ca2+ content of roots was determined and used to calculate an average σ following the procedure of Bérczi et al. [Physiol. Plant. 61: 529–534 (1984)]. The predicted value (−11 mC m−2 ) does not deviate much from the experimentally determined value. It is concluded as a useful working hypothesis that the average surface charge density is constant and that the ionic content of plant cells is regulated such that the average surface potential is constant. 相似文献
16.
CHUN-MEI WANG JIN-LIN ZHANG XUE-SONG LIU ZHAN LI GUO-QIANG WU JIAN-YI CAI TIMOTHY J. FLOWERS & SUO-MIN WANG 《Plant, cell & environment》2009,32(5):486-496
Puccinellia tenuiflora is a useful monocotyledonous halophyte that might be used for improving salt tolerance of cereals. This current work has shown that P. tenuiflora has stronger selectivity for K+ over Na+ allowing it to maintain significantly lower tissue Na+ and higher K+ concentration than that of wheat under short- or long-term NaCl treatments. To assess the relative contribution of Na+ efflux and influx to net Na+ accumulation, unidirectional 22 Na+ fluxes in roots were carried out. It was firstly found that unidirectional 22 Na+ influx into root of P. tenuiflora was significantly lower (by 31–37%) than in wheat under 100 and 150 m m NaCl. P. tenuiflora had lower unidirectional Na+ efflux than wheat; the ratio of efflux to influx was similar between the two species. Leaf secretion of P. tenuiflora was also estimated, and found the loss of Na+ content from leaves to account for only 0.0006% of the whole plant Na+ content over 33 d of NaCl treatments. Therefore, it is proposed that neither unidirectional Na+ efflux of roots nor salt secretion by leaves, but restricting unidirectional Na+ influx into roots with a strong selectivity for K+ over Na+ seems likely to contribute to the salt tolerance of P. tenuiflora . 相似文献
17.
T. J. Bouma R. De Visser J.H.J.A. Janssen M.J. De Kock P.H. Van Leeuwen H. Lambers 《Physiologia plantarum》1994,92(4):585-594
Protein turnover is generally regarded as a major maintenance process, but experimental evidence to support this contention is scarce. Here we quantify the component of dark respiration rate associated with overall protein turnover of tissues in vivo. The effect of an inhibitor of cytosolic protein synthesis (cycloheximide, CHM) on dark respiration was tested on a cell suspension from potato ( Solanum tuberosum L.) and quantified on leaf discs of expanding and full-grown primary leaves of bean ( Phaseolus vulgaris L.). The in vivo effect of CHM on protein biosynthesis was assessed by monitoring the inhibition of the induction of the ethylene-forming enzyme (EFE) activity. The present method yields the energy costs of turnover of the total pool of proteins irrespective of their individual turnover rates. Average turnover rates were derived from the respiratory costs and the specific costs for turnover.
Inhibition of respiration by CHM was readily detectable in growing-cell suspensions and discs of expanding leaves, The derived respiratory costs of protein turnover in expanding leaves were maximally 17–37% of total respiration. Turnover costs in full-grown primary leaves of bean amounted to 17–21% of total dark respiration. The maximum degradation constants (i.e. Kd -values) derived for growing and full-grown leaves were up to 2.42 × 10−6 and 1.12 × l0−6 s−1 , respectively. 相似文献
Inhibition of respiration by CHM was readily detectable in growing-cell suspensions and discs of expanding leaves, The derived respiratory costs of protein turnover in expanding leaves were maximally 17–37% of total respiration. Turnover costs in full-grown primary leaves of bean amounted to 17–21% of total dark respiration. The maximum degradation constants (i.e. K
18.
Abstract. Rates of proton extrusion and potassium (86 Rb) influx by intact roots of barley ( Hordeum vulgare cvs . Fergus, Conquest and Betzes) plants were simultaneously measured in short-term (15min) experiments. The nature and extent of apparent coupling between these ion fluxes was explored by manipulating conditions of temperature, pH and cation composition and concentration during flux determinations. In addition, the influence of salt status upon these fluxes was examined. At low K+ concentrations (0.01 to 1 mol m−3 ), H+ efflux and K+ influx were strongly correlated in both low- and high-K+ roots, although K+ : H+ exchange stoichiometries were almost consistently greater than 2:1. At higher concentrations (1 to 5 mol m−3 ), H+ efflux was either reduced or remained unchanged while K+ influxes increased. In the presence of Na2 SO4 , rates of H+ extrusion demonstrated similar cation dependence, although below 10 mol m−3 Na2 SO4 , H+ fluxes were generally 50% lower than in equivalent concentrations of K2 SO4 . These observations are considered in the context of current hypotheses regarding the mechanisms of k+ /H+ exchange. 相似文献
19.
Reinhard F. M. Van Steveninck Margaret E. Van Steveninck André Läuchli 《Physiologia plantarum》1988,72(1):1-7
External application of abscisic acid (ABA) induces a relatively high rate of xylem exudation in excised roots of Lupinus luteus L. cv. Weiko III. The response is relatively slow with a lag period of ca 1 h. It is also slowly, but reversibly, abolished by application of 3.6 or 36 μ M cycloheximide (CHX). Contrary to expectation, K+ is not a significant factor in maintaining flow rates in lupin roots as no response was measured after adding K+ to root systems, from which K+ had been withheld for periods ranging from 3 h to several days. In fact, excised roots obtained from seedlings raised in the absence of K+ failed to respond to added K+ . Total depletion of K+ is difficult to achieve, because of initial seed reserves, and prolonged exudation in lupins can be maintained utilising only a small proportion of the K+ originally present in the root tissue. Nevertheless, the data cast doubt on the general applicability of the concept that volume flow is maintained by an osmotic gradient with K+ as the principal mineral ion. 相似文献
20.
Paul Jensén 《Physiologia plantarum》1981,52(4):437-441
Uptake of Rb+ from a complete nutrient solution with 2.0 mM Rb+ was studied in roots of spring wheat seedlings ( Triticum aestivum L. cv. Svenno) with different K+ levels. The relationship between Rb+ uptake and concentration of K+ in the roots indicated a negative feedback mechanism operating through allosteric control. The Rb+ uptake process in root cells was divided into two steps: (1) binding of the ion in the free space, and (ii) transmembrane transport into the cytoplasm. Metabolic and non-metabolic components of uptake were separated by addition of the metabolic inhibitor 2,4-dinitrophenol (DNP) to the nutrient solution. It is suggested that metabolic Rb+ uptake requires energy in two uptake steps (for binding to the carrier entity in the free space and for transmembrane transport) or in one step only (for transmembrane transport), dependent on the K+ status of the roots. The change from metabolic to non-metabolic binding in the free space is accomplished by changing the conformational state of the carrier (slow/fast transitions). There may be a hysteretic effect on metabolic Rb+ uptake through a slow transition between carrier states. This is superimposed on the negative cooperativity, strengthening further cooperativity at intermediate K+ levels in the roots. Non-metabolic Rb+ uptake probably consists of two components, a carrier-mediated (facilitated diffusion) and a parallel diffusive component. 相似文献