Showing papers in "Journal of Experimental Botany in 1985"
411 citations
TL;DR: The roots of plants which were watered well throughout the 18 d experimental period penetrated the soil profile to a depth of 60 cm while the greatest percentage of total root length was between 20-40 cm and high soil water depletion rates corresponded with these high root densities.
Abstract: Sharp, R. E and Da vies, W. J. 1985. Root growth and water uptake by maize plants in drying soil.— J. exp. Bot. 36: 1441-1456. The influence of soil drying on maize (Zea mays L.) root distribution and use of soil water was examined using plants growing in the greenhouse in soil columns. The roots of plants which were watered well throughout the 18 d experimental period penetrated the soil profile to a depth of 60 cm while the greatest percentage of total root length was between 20-40 cm. High soil water depletion rates corresponded with these high root densities. Withholding water greatly restricted root proliferation in the upper part of the profile, but resulted in deeper penetration and higher soil water depletion rates at depth, compared with the well watered columns. The deep roots of the unwatered plants exhibited very high soil water depletion rates per unit root length.
284 citations
TL;DR: Schulte and Hinckley as discussed by the authors compared various computer algorithms with respect to estimates of osmotic potential, turgor loss point, symplastic fraction, and bulk modulus of elasticity.
Abstract: Schulte, P. J. and Hinckley, T. M. 1985. A comparison of pressure-volume curve data analysis techniques.—J. exp. Bot. 36: 1590-1602. Computer assisted analysis of data derived with the pressure-volume technique is currently feasible. In this study, various computer algorithms were used to analyse a variety of pressure-volume curve data sets. Comparisons were made with respect to estimates of osmotic potential, turgor loss point, symplastic fraction, and bulk modulus of elasticity. While osmotic potential estimation was fairly insensitive to the model used, estimates of the bulk modulus of elasticity appear to be highly dependent on the model used for analysis of the data.
253 citations
TL;DR: Analysis of the course of events in leaf four following salinization of the medium showed that net photosynthesis was inversely correlated with the sodium concentration in the leaf tissue, and the relationship between transpiration rate and leaf sodium concentration closely paralleled that for photosynthesis.
Abstract: The effect of salinity upon net photosynthesis and transpiration by individual leaves of rice has been investigated by gas exchange measurements in seedlings at the five to six leaf stage. Salinity did not, initially, reduce net photosynthesis in the whole plant but only in the older leaves in which sodium accumulated. Analysis of the course of events in leaf four following salinization of the medium showed that net photosynthesis was inversely correlated with the sodium concentration in the leaf tissue. There was no evidence of a threshold effect; net photosynthesis declined linearly with increasing leaf sodium concentration and was reduced by 50% at only 05 mmol sodium per gram dry weight. The relationship between transpiration rate and leaf sodium concentration closely paralleled that for photosynthesis; there was no effect of leaf sodium concentration on the carbon dioxide concentration in the intercellular spaces, showing that sodium accumulation in the leaf affected stomatal aperture and carbon dioxide fixation simultaneously. Photosynthesis was reduced by half at a sodium concentration in the leaf which did not reduce the concentration of chlorophyll. The nature of the effect of salinity upon leaf gas exchange is discussed.
232 citations
TL;DR: It is supported that nitrate may serve as osmoticum at low light conditions to compensate for the shortage of carbohydrates resulting from suboptimal photosynthesis.
Abstract: Blom-Zandstra, M. and Lampe, J. E. M., 1985. The role of nitrate in the osmoregulation of lettuce (Lactuca sativa L.) grown at different light intensities.—J. exp. Bot. 36: 1043-1052. The effect of different light intensities on the nitrate accumulation vis-a-vis the concentration of other solutes in plant sap expressed from lettuce leaves was studied. After growing lettuce plants under constant environmental conditions for 52 d, they were transferred to different light intensities and harvested periodically. A quantitative analysis of components in solution in the expressed plant sap showed a decrease in nitrate concentration and an increase in the organic acids (mainly malate) and sugars (mainly glucose) with increasing light intensity. The light intensity only slightly increased the osmolarity of the expressed plant sap. The measured osmolarity corresponded very well with the value estimated from the quantitative analyses implying that all osmotically active compounds had been accounted for. The decrease in nitrate concentration in the expressed plant sap was fully compensated for by an increase in the dissociated organic acids that partly dissociate twofold to sustain electroneutrality and by an increase in both organic acids and sugars to maintain the osmolarity. The suggestion is supported that nitrate may serve as osmoticum at low light conditions to compensate for the shortage of carbohydrates resulting from suboptimal photosynthesis.
161 citations
TL;DR: Time-course studies showed levels of inorganic cations were not altered in the growing areas during the first few h of PEG-induced stress, but glucose increased as i/<„ decreased, and the results showed that proline increase is not the cause but could be a consequence of osmotic adjustment, and its increase was not due to cell death.
Abstract: Riazi, A., Matsuda, K. and Arslan, A. 1985. Water-stress induced changes in concentrations of proline and other solutes in growing regions of young barley leaves.—J. exp. Bot. 36: 1716-1725. Young, intact barley Hordeum vulgare L. cv. 'Arivat' seedlings stressed with PEG or NaCl were measured for water status and levels of proline, sugars and inorganic cations in growing (basal 1 0 cm) and other areas of leaves. In growing regions, reductions in ipn were found within 1 h in seedlings stressed with PEG ( — 0-8 MPa) but 4 h were required before proline increased and proline accounted for less than 5% of the osmotic adjustment after 24 h. Increases in proline occurred to a lesser extent in expanded mid-blade regions where osmotic adjustment was less. After one or more days stress, proline levels in basal tissues were 10 x higher than in mid-blade tissues, and proline increases in these and intervening tissues occurred without loss of turgor. When seedlings were stressed for extended periods with mild to moderate concentrations of PEG, proline elevations in basal to mid-blade areas were proportional to reductions in tissue ii/ and ii/„. NaCl-stress led to similar responses except proline increases per unit decrease in ip* were 2-3 x greater than in PEG-stressed tissues. Time-course studies showed levels of inorganic cations were not altered in the growing areas during the first few h of PEG-induced stress, but glucose increased as i/<„ decreased. The results showed that proline increase is not the cause but could be a consequence of osmotic adjustment, and its increase is not due to cell death. They also provided independent evidence that stress responses of growing tissues differ substantially from expanded areas in young barley leaves.
160 citations
159 citations
140 citations
TL;DR: A large amount of awns in the ear is therefore a drought adaptive attribute in these cereals, for which tetraploid wheat exceeded hexaploid Wheat and six-rowed barley exceeded two-rowing barley.
Abstract: Carbon exchange rate (CER) and transpiration were measured in flag leaves, whole ears, glumes (referring to the total area of glumes and lemmas) and awns, in six hexaploid spring wheats (Triticum aestivum L.), three cultivated tetraploid spring wheats (T. turgidum L.), four wild tetraploid wheats (T. dicoccoides\ eight six-rowed barleys (Hordeum vulgare L.) and five two-rowed barleys (H. vulgare L.). Differences between varieties and between species in total ear CER and transpiration were associated largely with differences in ear surface area rather than with rates per unit area. Rates of CER and transpiration per unit area of ears were 40-80% of those of flag leaves, depending on the species. However, since ear surface area was greater than flag leaf area by a factor of 1-1, 3-9, 5-5 and 4-4, in hexaploid wheat, tetraploid wheat, six-rowed barley, and two-rowed barley, respectively, total ear CER reached up to 90% of that of the flag leaf. The contribution of awns to total ear CER depended largely on total awn surface area per ear, rather than on CER per unit awn area. Awns contributed about 40-80% of total spike CER, depending on the species, but only 10-20% of spike transpiration. The disproportionately small contribution of awns to ear transpiration was caused by the very low rate of transpiration per unit area of awns. Thus, while transpiration ratio (C£.R/transpiration) was about the same in flag leaves and glumes, it was higher by several orders of magnitude in the awns. A large amount of awns in the ear is therefore a drought adaptive attribute in these cereals, for which tetraploid wheat exceeded hexaploid wheat and six-rowed barley exceeded two-rowed barley.
139 citations
TL;DR: Both slower shoot initiation and reduced leaf length contributed to the reduced growth rates at higher salinities, and increasing salinity resulted in increases in leaf concentrations of phosphate, glycinebetaine, sucrose and proline, and in decreases in the concentrations of nitrate, sulphate, magnesium, calcium, total amino acids and organic acids.
Abstract: Gorham, J., McDonnell, E., Budrewicz, E. and Wyn Jones, R. G. 1985. Salt tolerance in the Triticeae: growth and solute accumulation in leaves of Thinopyrum bessarabicum.—]. exp. Bot. 36:1021-1031. The diploid wheatgrass Thinopyrum bessarabicum was found to withstand prolonged exposure to 350 mol m "3 NaCl in hydroponic culture. During the gradual addition of salt to the external medium, osmotic adjustment was rapidly achieved by the accumulation of Na and CI. Following osmotic adjustment constant leaf Na and CI concentrations were maintained, and K was retained at a high level. Thinopyrum bessarabicum may be described as an osmoconformer, adjusting its internal osmotic pressure to 400-500 mOsmol kg"1 above that of the external medium in hydroponic culture. Both slower shoot initiation and reduced leaf length contributed to the reduced growth rates at higher salinities. Leaf width was not affected. Increasing salinity resulted in increases in leaf concentrations of phosphate, glycinebetaine, sucrose and proline, and in decreases in the concentrations of nitrate, sulphate, magnesium, calcium, total amino acids and organic acids. Thinopyrum bessarabicum exhibits salt tolerance characters which may be useful in wheat breeding.
126 citations
TL;DR: In this paper, the seeds of pearl millet were germinated on wet filter paper at temperatures up to 50 °C, where the temperature was held at 50°C during imbibition and was then lowered to 32°C or 25°C.
Abstract: Seeds of pearl millet were germinated on wet filter paper at temperatures up to 50 °C. In one experiment, the temperature was held at 50 °C during imbibition and was then lowered to 32 °C or 25 °C. Germination rate and the maximum fraction of seeds germinating (Gm) both decreased as the time of exposure to 50 °C increased. In contrast, exposure to 50 °C after imbibition for 8 h slowed germination but did not significantly reduce Gm. When the 'high' temperature imposed after imbibition was reduced from 50 °C to 45 °C, there was a small reduction in the rate of germination but not in Gm. The responses have implications for the optimum time of sowing in the tropics when maximum daytime soil temperature at the depth of sowing is in the range of 45-50 °C.
TL;DR: It is concluded that in rice, aerenchyma forms speedily even in well-aerated environments as an integral part of ordinary root development, and there seems to be little or no requirement for ethylene as a stimulus in stagnant root-environments where aerenchema is likely to increase the probability of survival.
Abstract: Jackson, M. B., Fenning, T. M., and Jenkins, W. 1985. Aerenchyma (gas-space) formation in adventitious roots of rice (Oryza sativa L.) is not controlled by ethylene or small partial pressures of oxygen.—J. exp. Bot. 36: 1566-1572. The extent of gas-filled voids (aerenchyma) within the cortex of adventitious roots of vegetative rice plants (Oryza sativa L. cv. RB3) was estimated microscopically from transverse sections with the aid of a computer-linked digitizer drawing board. Gas-space was detectable in 1-d-old tissue and increased in extent with age. After 7 d, approximately 70% of the cortex had degenerated to form aerenchyma. The extent of the voids in 1-4-d-old tissue was not increased by stagnant, poorly-aerated external environments characterized by sub-ambient oxygen partial pressures and accumulations of carbon dioxide and ethylene. Treatment with small oxygen partial pressures, or with carbon dioxide or ethylene applied in vigorously stirred nutrient solution also failed to promote the formation of cortical gas-space. Furthermore, ethylene production by rice roots was slowed by small oxygen partial pressures typical of stagnant conditions. Silver nitrate, an inhibitor of ethylene action, did not retard gas-space formation; similarly when endogenous ethylene production was inhibited by the application of aminoethoxyvinylglycine (AVG), aerenchyma development continued unabated. Cobalt chloride, another presumed inhibitor of ethylene biosynthesis, did not impair formation of the gas in rice roots nor did it decrease the extent of aerenchyma even if AVG was supplied simultaneously. These results contrast with those obtained earlier using roots of Zea mays L. We conclude that in rice, aerenchyma forms speedily even in well-aerated environments as an integral part of ordinary root development. There seems to be little or no requirement for ethylene as a stimulus in stagnant root-environments where aerenchyma is likely to increase the probability of survival.
TL;DR: The proton pump thus appears to be non-operative, while the cell is in the K.+ state, and recovers slowly as thecell is returned to a low K+ medium, if the cells are kept in K + state for some hours.
Abstract: Exposure to high K+ medium transforms Chara plasmalemma into [K+]o—sensitive state (K+ state). The current-voltage (I/V) characteristics under such conditions display a negative conductance region. This feature results from the complex time and voltage dependence of K+ channel opening At potentials more negative than a threshold p.d. the channels are closed and the I/V characteristics become linear with a low slope conductance of ~ 08 S m2 and only a weak dependence on [K + ] o. Such behaviour is usually associated with a non-specific leak current The threshold level for K+ channel closing depends on [K + ] o. In 2-0 mol m~3 and 5-0 mol irT3 K+ medium the membrane resting p.d. follows £K, but hyperpolarizes gradually if the [K + ]o is lowered. The proton pump thus appears to be non-operative, while the cell is in the K.+ state, and recovers slowly as the cell is returned to a low K.+ medium. Excitation currents decline if the cells are kept in K + state for some hours.
TL;DR: The effects of three ranges of C02 concentration on growth, carbon distribution and loss of carbon from the roots of maize grown for 14 d and 28 d with shoots in constant specific activity 14C02 are described in this article.
Abstract: The effects of three ranges of C02 concentration on growth, carbon distribution and loss of carbon from the roots of maize grown for 14 d and 28 d with shoots in constant specific activity 14C02 are described Increasing concentrations of C02 led to enhancement of plant growth with the relative growth rate (RGR) of the roots affected more than the RGR of the shoots Between 16% and 21% of total net fixed carbon (defined as 14C retained in the plant plus 14C lost from the root) was lost from the roots at all C02 concentrations at all times but the amounts of carbon lost per unit weight of plant decreased with time Possible mechanisms to account for these observations are discussed
TL;DR: Cell walls were able, in vitro as well as in vivo, to oxidize guaiacol in the absence of H202 when NADH was present in the incubation medium together with p-coumarate and MnCl2 as cofactors.
Abstract: Cell wall activities which are related to the final stages of lignin biosynthesis, that is the generation of hydrogen peroxide and peroxidase activity, were investigated using biochemical and histochemical methods. Peroxidases involved in both reactions appeared to be restricted to lignifying tissues. Isolated cell walls exhibited a very high affinity for syringaldazine. Cell walls were able, in vitro as well as in vivo, to oxidize guaiacol in the absence of H202 when NADH was present in the incubation medium together with p-coumarate and MnCl2 as cofactors. The origin of the NADH used to form H202 is discussed.
TL;DR: Mycorrhizal infection was shown to have no effect on the intrinsic hydraulic properties of the soil/plant system over a wide range oftranspiration rates in either soil, and elevated transpiration rates exhibited by M plants were attributed to an enhanced phosphorus status.
Abstract: Koide, R. 1985. The effect of VA mycorrhizal infection and phosphorus status on sunflower hydraulicand stomatal properties.—J. exp. Bot. 36: 1087-1098.Mycorrhizal (M) and non-mycorrhizal (NM) sunflower plants were grown in a soil of low phosphorusavailability (with and without phosphorus amendment) and in a soil of moderate phosphorusavailability (without phosphorus amendment). Using the Ohm's law analogy and measured leaf waterpotentials, stem water potentials, and transpiration rates, hydraulic resistances were calculated for thewhole plant, leaf, and below leaf components. Mycorrhizal infection (as high as 89%) was shown tohave no effect on the intrinsic hydraulic properties of the soil/plant system over a wide range oftranspiration rates in either soil when M and NM plants of equivalent root length were compared.When grown in the soil of moderate phosphorus availability, calculated hydraulic resistances undergiven environmental conditions were the same for M and NM plants, as were stomatal resistances andtranspiration rates. When grown in the soil of low phosphorus availability, calculated values ofhydraulic resistance were lower for M plants than for NM plants under given sets of environmentalconditions. These differences in calculated hydraulic resistance were not due to a difference in theintrinsic hydraulic properties of M and NM plants. The differences were evident because stomatalresistances were lower and transpiration rates higher for M plants and because hydraulic resistancevaried inversely with transpiration rate. When plants of significantly greater root length werecompared to plants of lesser root length, the calculated hydraulic resistances under givenenvironmental conditions were much lower for the plants of greater root length. This difference waslargely due to a difference in the intrinsic hydraulic properties between large and small plants, and notbecause of differences in transpiration rate. The elevated transpiration rates exhibited by M plantswere attributed to an enhanced phosphorus status. Short term phosphorus amendments made tophosphorus-deficient NM plants improved transpiration; transpiration rates were similar for M andNM plants before NM plants became phosphorus-deficient, and phosphorus-amended M and NMplants had similar transpiration rates. The data are discussed in relation to other reports ofmycorrhizal influence on hydraulic and stomatal resistances. Possible mechanisms for the influence ofinfection on stomatal resistance are also briefly discussed.Key words—Hydraulic resistance, stomatal resistance, mycorrhizas.Correspondence to: Department of Biological Sciences, Stanford University, Stanford, CA 94305, U.S.A.
TL;DR: It is concluded that cytoplasmic acidification stimulates the electrogenic proton pump in Sinapis root hairs, and it is suggested that the FC-induced effects, viz. hyperpolarization and external acidification, can also be interpreted in this way.
Abstract: Bertl, A. and Felle, H. 1985. Cytoplasmic pH of root hair cells of Sinapsis alba recorded by a pH-sensitive micro-electrode. Does fusicoccin stimulate the proton pump by cytoplasmic acidifica tion?—J. exp. Bot. 36: 1142-1149. pH-sensitive micro-electrodes, filled with ion-exchanger resin have been fabricated with a turgor insensitive tip and have been applied to test the intracellular pH and changes thereof in root hair cells of Sinapis alba. (1) The cytoplasmic pH of Sinapis root hairs was determined to be 7-3 ± 0-2 (at neutral external pH). (2) 10 mol m ~3 sodium azide depolarizes the membrane potential by about 100 m V and acidifies the cytoplasm by 0 8 pH-units. (3) The change from 10 mol m~3 to 10 mol m~3 external potassium causes a depolarization of about 45 mV, but no change in internal pH. (4) At an external pH of 5 0, sodium acetate hyperpolarizes the plasmalemma by about 60 mV and acidifies the cytoplasmic pH by 0-2 to 0-3 units. (5) 2 0 mmol m-3 fusicoccin (FC) hyperpolarizes the plasmalemma by 20-25 mV, acidifies the cytoplasm by 01 to 0-2 pH-units, and acidifies the external medium by about 0-3 pH-units. It is concluded that cytoplasmic acidification stimulates the electrogenic proton pump in Sinapis root hairs, and it is suggested that the FC-induced effects, viz. hyperpolarization and external acidification, can also be interpreted in this way.
TL;DR: Kermode et al. as mentioned in this paper showed that the role of maturation drying in the transition from seed development to germination is mirrored by a change in the pattern of insoluble protein synthesis within the endosperm storage tissue.
Abstract: Kermode, A. R., Gilford, D. J. and Bewley, J. D. 1985. The role of maturation drying in the transition from seed development to germination. III. Insoluble protein synthetic pattern changes within the endosperm of Ricinus communis L. seeds.—J. exp. Bot. 36: 1928-1936. Immature seeds of Ricinus communis L. cv. Hale (castor bean) removed from the capsule at 30 or 40 days after pollination (DAP) can be induced to germinate by being subjected to drying. This desiccation-induced switch from development to germination is mirrored by a change, upon subsequent rehydration, in the pattern of insoluble protein synthesis within the endosperm storage tissue. During normal development from 25-40 DAP there is rapid synthesis of the insoluble (1 IS) crystalloid storage protein. At later stages of development (45 and 50 DAP), crystalloid protein synthesis declines markedly and synthesis of new insoluble proteins commences. Following premature drying at 30 or 40 DAP, the pattern of insoluble protein synthesis upon rehydration is virtually identical to that following imbibition of the mature seed. Proteins synthesized during normal late development (at 45 and 50 DAP) are produced up to 48 h after imbibition; a subsequent change in the pattern of insoluble protein synthesis occurs between 48 and 72 h. Thus, in contrast to the rapid switch in the pattern of soluble protein synthesis induced by drying, insoluble protein syntheses within the endosperm are redirected towards those uniquely associated with a germination/growth programme only after a considerable delay following mature seed imbibition, or following rehydration of the prematurely dried seed. Nevertheless, these results support our contention that drying plays a role in the suppression of the developmental metabolic programme and in the permanent induction of a germination/growth programme.
TL;DR: The results showed first that bud pretreatment completely inhibited induction and secondly that anthers of all genotypes had an absolute requirement for a 35 °C treatment in order to induce embryoid formation, confirming the importance of genotypic control for some components of embryo yield.
Abstract: Eleven Fx hybrid genotypes of winter rape (Brassica napus ssp oleifera) were used in a study of induction and growth of microspore-derived embryos Plants of each genotype were grown in controlled environments at either a constant 15 CC or a constant 20 °C, both with a 16 h photoperiod Equal numbers of buds, approximately 2-5 mm in length, containing uninucleate microspores were harvested from each genotype and either pretreated (14 d at 4°C) or dissected immediately after harvest Anthers were cultured on liquid medium based upon that of Murashige and Skoog (1962) and
containing 8% sucrose, 0-5 mg dm-3 naphthylacetic acid and 0-05 mg dm-3 benzylaminopurine Anthers from equal samples of buds were incubated at 35 °C for 0,1, 2 or 3 d before transfer to 30 °C (21 d) and then 25 °C After a total of 42 d incubation, cultures were scored for the presence of
macroscopic embryos (1-2 mm in length) and for the presence of anthers containing aborted embryoids which had not developed further
The results showed first that bud pretreatment completely inhibited induction and secondly that anthers of all genotypes had an absolute requirement for a 35 °C treatment (optimal duration 2 d) in order to induce embryoid formation In the great majority of genotypes plants grown at 15 °C provided ore productive anthers than plants grown at 20 °C However, within each treatment there were great
differences both in the frequency of anthers showing induced embryoids and of the final yield of embryos There was evidence that hybrids with a common parent responded similarly under certain treatments This confirmed the importance of genotypic control for some components of embryo yield
TL;DR: In this paper, the role of acid invertase in the provision of carbon substrates for cell growth was discussed in relation to the effect of light-growing plants on the development of Phaseolus vulgaris.
Abstract: In the stem of Phaseolus vulgaris L. the specific activity of acid invertase was highest in the most rapidly elongating internode. Activity of the enzyme was very low in internodes which had completed their elongation, in young internodes before the onset of rapid elongation, and in the apical bud. From shortly after its emergence from the apical bud the elongation of internode 3 was attributable mainly to cell expansion. Total and specific activities of acid invertase in this internode rose to a maximum at the time of most rapid elongation and then declined. Transfer of plants to complete darkness, or treatment of plants with gibberellic acid (GA3), increased the rate of internode elongation and final internode length by stimulating cell expansion. Both treatments rapidly increased the total and specific activities of acid invertase in the responding internodes; peak activities of the enzyme occurred at the time of most rapid cell expansion. In light-grown plants, including those treated with GA3, rapid cell and internode elongation and high specific activities of acid invertase were associated with high concentrations of hexose sugar and low concentrations of sucrose. As cell growth rates and invertase activities declined, the concentration of hexose fell and that of sucrose rose. In plants transferred to darkness, stimulated cell elongation was accompanied by a rapid decrease in hexose concentration and the disappearance of sucrose, indicating rapid utilization of hexose. No sucrose was detected in the apical tissues of light-grown plants. The results are discussed in relation to the role of acid invertase in the provision of carbon substrates for cell growth.
TL;DR: The role of ureides in the nitrogen partitioning and grain yield was confirmed by the significant correlation between mean ureide content in xylem sap and nitrogen partitionsing or yield and the possible significance of this is discussed.
Abstract: Neves, M. C. P., Didonet, A. D., Duque, F. F. and Dobereiner, J. 1985. Rhizobium strain effects on nitrogen transport and distribution in soybeans.—J. exp. Bot. 36: 1179-1192. The role of six Rhizobium strains in the nitrogen metabolism of soybeans (Glycine max Merril) was studied under glasshouse and field conditions. The strains could be divided into two groups, group I which produced a large nodule mass with relatively low efficiency and group II which produced less nodule mass but which fixed the same amount of nitrogen. Plants inoculated with group I strains remobilized nitrogen faster from leaves but also lost more nitrogen in senesced leaves. Although the total nitrogen transported in the xylem was similar for all strains, plants inoculated with group I strains contained less nitrogen in ureides in the xylem sap during the whole growth cycle. This difference was reflected in the nitrogen partitioning within the shoot, and smaller nitrogen harvest indexes were observed in these plants than in those inoculated with strains of group II. The role of ureides in the nitrogen partitioning and grain yield was confirmed by the significant correlation between mean ureide content in xylem sap and nitrogen partitioning or yield. Further, nodules formed with group I strains evolved more hydrogen than those formed with group II strains and the possible significance of this is discussed.