The Effects of Temperature on Vegetative and Early Reproductive Growth of a Cold-Tolerant and, a Cold-Sensitive Line of Phaseolus vulgaris L. 1. Nodulation, Growth and Partitioning of Dry Matter, Carbon and Nitrogen

Nodulated plants of a cold-sensitive (Seafarer, SF) and tolerant(accession 194) line of Phaseolus vulgaris L. were grown underthree temperature regimes, 15/10, 20/15 and 25/15 C (light/dark).Dry matter, total C and N were measured in plant parts at threeharvests. Both lines produced functional nodules at a mean growthtemperature as low as 12.9 C (15/10) but 194 produced moreand larger nodules which fixed more N (total plant N) than SF.At the lowest temperature during early vegetative growth, 194accumulated greater amounts of d. wt than SF but had similarRGR and NAR. RLGR and RGR expressed in terms of N on the otherhand, were markedly greater in 194 than SF. 194 Partitionedmore d. wt and N into shoots vs roots and had a lower leaf:stem d. wt ratio than SF. Both lines showed similar increasesin leaf area, leaf area ratio and RGR with increasing temperature. The results suggest that the ability to nodulate well, increasenodule size in response to temperature stress and achieve maximumleaf expansion are important factors for the superior growthof 194 over SF. Phaseolus vulgaris, common bean, nodulation, growth, low temperature stress     

Cluster Bean—A Ureide- or Amide-Producing Legume?

Xylem sap of cluster bean (Cyamopsis tetragonoloba L. cv FS-277) and pigeonpea (Cajanus cajan cv UPAS-120) were analyzed for total nitrogen, amide nitrogen, and ureide nitrogen at flowering stage. Nitrogenase, uricase, and allantoinase were compared in nodules of cluster bean and pigeonpea. Xylem sap of cluster bean exhibited higher amounts of amides as compared to ureides, and the activities of uricase and allantoinase (ureide-producing enzymes) in nodules were also low, whereas the reverse was the case for pigeonpea. Based on these investigations, it has been concluded that cluster bean is an amide-producing legume rather than ureide-producing as had been reported earlier.     

Ureide Metabolism in Non-nodulated Phaseolus vulgaris L.

The distribution of ureide-N was studied throughout vegetativeand reproductive growth of non-nodulated Phaseolus vulgarisL. (bushbean) grown in nitrate nutrient solution. Largest increasesin ureide-N per plant were correlated with flowering and earlypod formation and with seed filling. Highest amounts of ureidesper organ were measured in stems and axillary trifoliates. Highestconcentrations (µmol ureide-N g^–1 fr. wt.) weremeasured in young developing organs and stems. Seeds did notaccumulate ureides until the ureide content of pods had reacheda maximum. Results obtained using the inhibitor of xanthine oxidase, allopurinol,are consistent with the origin of ureides via purine degradationbut alternative pathways cannot be discounted. Leaves and stems were shown to have the ability to degrade allantoatevia an enzymic process.     

Allantoin and Allantoic Acid in the Nitrogen Economy of the Cowpea (Vigna unguiculata [L.] Walp.)

The ureides, allantoin and allantoic acid, represented major fractions of the soluble nitrogen pool of nodulated plants of cowpea (Vigna unguiculata [L.] Walp. cv. Caloona) throughout vegetative and reproductive growth. Stem and petioles were the principal sites of ureide accumulation, especially in early fruiting.

Labeling studies using ¹⁴CO₂ and ¹⁵N₂ and incubation periods of 25 to 245 minutes indicated that synthesis of allantoin and allantoic acid in root nodules involved currently delivered photosynthate and recently fixed N, and that the ureides were exported from nodule to shoot via the xylem. From 60 to 80% of xylem-borne N consisted of ureides; the remainder was glutamine, asparagine, and amino acids. Allantoin predominated in the soluble N fraction of nodules and fruits, allantoin and allantoic acid were present in approximately equal proportions in xylem exudate, stems, and petioles.

Extracts of the plant tissue fraction of nitrogen-fixing cowpea nodules contained glutamate synthase (EC 2.6.1.53) and glutamine synthetase (EC 6.3.1.2), but little activity of glutamate dehydrogenase (EC 1.4.1.3). High levels of uricase (EC 1.7.3.3) and allantoinase (EC 3.5.2.5) were also detected. Allantoinase but little uricase was found in extracts of leaflets, pods, and seeds.

Balance sheets were constructed for production, storage, and utilization of ureide N during growth. Virtually all (average 92%) of the ureides exported from roots was metabolized on entering the shoot, the compounds being presumably used as N sources for protein synthesis.

     

Developmental effects on ureide levels are mediated by tissue-specific regulation of allantoinase in Phaseolus vulgaris L

The ureides allantoin and allantoate are key molecules in the transport and storage of nitrogen in ureide legumes. In shoots and leaves from Phaseolus vulgaris plants using symbiotically fixed nitrogen as the sole nitrogen source, ureide levels were roughly equivalent to those of nitrate-supported plants during the whole vegetative stage, but they exhibited a sudden increase at the onset of flowering. This rise in the level of ureides, mainly in the form of allantoate, was accompanied by increases in allantoinase gene expression and enzyme activity, consistent with developmental regulation of ureide levels mainly through the tissue-specific induction of allantoate synthesis catalysed by allantoinase. Moreover, surprisingly high levels of ureides were also found in non-nodulated plants fertilized with nitrate, at both early and late developmental stages. The results suggest that remobilized N from lower leaves is probably involved in the sharp rise in ureides in shoots and leaves during early pod filling in N(2)-fixing plants and in the significant amounts of ureides observed in non-nodulated plants.     

Translocation of nitrogen and expression of nodule-specific uricase (nodulin-35) in Robinia pseudoacacia

Uricase (urate oxidase, EC 1.7.3.3) activity and nodule-specific uricase II (nodulin-35) were detected in the nodules from a number of legume: Rhizobium symbioses ( Vigna unguiculata (L.) Walp., Phaseolus vulgaris L., and Kennedia coccinea Vent.) in the Phaseoleae, as well as in those of Robinia pseudoacacia L. which belongs to the tribe Robineae. Neither uricase activity nor nodulin-35 was detected in nodules from Lupinus angustifolius L., an amide-forming symbiosis of the tribe Genisteae. Nodules of R. pseudoacacia also showed high levels of allantoinase (EC 3.5.2.5) activity but activity of enzymes earlier in the pathway of ureide synthesis (xanthine dehydrogenase, EC 1.2.1.37; inosine monophosphate dehydrogenase, EC 1.2.1.14; and xanthosine nucleosidase, EC 3.2.2.1) could not be detected. Analysis of transport fluids (xylem, phloem and nodule exudates) from R. pseudoacacia found that asparagine, and, to a lesser extent, glutamine were the major translocated nitrogenous solutes. Ureides accounted for, at most, 2.6% of the N in transport fluids (tracheal xylem sap) and in nodule exudate, 0.1%. In common with nodules of the ureide-forming symbioses, those of R. pseudoacacia contained a high proportion of uninfected interstitial cells (53.7 ± 2.3%) in the central N₂-fixing tissue whereas in L. angustifolius only 2.5 ± 0.4% of cells in this tissue were uninfected. These data have been interpreted to indicate that expression of nodule-specific uricase is related to the differentiation of uninfected interstitial cells in nodules and not to the synthesis of ureides.     

Purine synthesis and catabolism in soybean seedlings : the biogenesis of ureides

The ureides, allantoin and allantoic acid, are the major nitrogenous substances transported within the xylem of N₂-fixing soybeans (Glycine max L. Merr. cv Amsoy 71). The ureides accumulated in the cotyledons, roots and shoots of soybean seedlings inoculated with Rhizobium or grown in the presence of 10 millimolar nitrate. The patterns of activity for uricase and allantoinase, enzymes involved in ureide synthesis, were positively correlated with the accumulation of ureides in the roots and cotyledons. Allopurinol and azaserine inhibited ureide production in 3-day-old cotyledons while no inhibition was observed in the roots. Incubation of 4-day-old seedlings with [¹⁴C]serine indicated that in the cotyledons ureides arose via de novo synthesis of purines. The source of ureides in both 3- and 4-day-old roots was probably the cotyledons. The inhibition of ureide accumulation by allopurinol but not azaserine in 8-day-old cotyledons suggested that ureides in these older cotyledons arose via nucleotide breakdown. Incubation of 8-day-old plants with [¹⁴C]serine suggested that the roots had acquired the capability to synthesize ureides via de novo synthesis of purines. These data indicate that both de novo purine synthesis and nucleotide breakdown are involved in the production of ureides in young soybean seedlings.     

Effects of applied nitrogen upon aspects of nitrogen metabolism and transport in developing nodulated winged bean plants

Nodulated winged bean [Psophocarpus tetragonolobus (L.) DC., cv. UPS 122] were grown under constant environmental conditions and supplied with mineral nutrient solution in which nitrogen was absent or was present as nitrate (12 mg N week^-1 plant^-1). Nitrate treatment dramatically promoted plant growth, increased fruit weight 1.6 fold, was necessary for tuberisation and enhanced nodulation. The in vitro accumulation of ¹⁴C into asparagine and aspartate components of excised nodules supplied with exogenous ¹⁴CO₂ and [¹⁴C]-D-glucose was greater for nitrate-treated plants, whilst accumulation into ureides was reduced by nitrate treatment. Levels of amino acids in xylem sap were greater for plants supplied with a complete nutrient solution, than those grown without applied nitrate, particularly for asparagine, glutamine and proline. Xylem ureide levels were greater for plants grown in the absence of supplementary nitrate. Nitrogen accumulated in leaf, stem and petiole, and root nodule tissues for utilisation during fruit development; peak nitrogen levels and time of anthesis were retarded for plants grown without applied nitrate. The shoot ureide content increased during fruiting, coincident with decreases in the total nitrogen content, indicating that ureide pools are not utilised during the early reproductive phase. However ureide reserves, particularly allantoin, were utilised during the later stages of pod fill. Enzyme activity which metabolised asparagine was found throughout the plant and was identified as K⁺-dependent asparaginase (EC 3.5.1.1) and an aminotransferase. Apart from temporal differences in developmental profiles of enzyme activity, the activity of these enzymes and of allantoinase (EC 3.5.2.5) in developing tissues were similar for both treatments. The main differences were greater asparaginase and asparagine:pyruvate aminotransferase activities in root tissues and fruit of nitrate-supplied plants; allantoinase activity in the primary roots of plants grown without nitrate decreased during development, whilst activity in developing tubers (nitrate-supplied plants) increased.     

Enzymes of ammonia assimilation and ureide biogenesis in developing pigeonpea (Cajanus cajan L.) nodules

Ammonia assimilatory and ureide biogenic enzymes were measured in the cytosol fraction of pigeonpea nodules during the period 15–120 days after sowing. The activity of enzymes involved in the initial assimilation of ammonia, i.e. glutamine synthetase, glutamate synthase, asparagine synthetase and aspartate aminotransferase, substantially increased activities during the period of plant growth and reached a maximum value around 105 days after sowing. These increases paralleled the increase in nodule mass, nitrogenase activity and ureide content in nodules. Though no regular pattern was obtained for their specific activities, yet these activities when expressed relative to the specific activity of nitrogenase were many fold higher at each stage of development. Similar increases were observed in the activities of enzymes associated with the formation of ureides from purines. In almost all cases, the activities were again maximum around 90–105 days after sowing. The specific activities of nucleotidase, nucleosidase, xanthine dehydrogenase, uricase and allantoinase, when expressed relative to the specific activity of nitrogenase at vegetative, flowering and podsetting stages were again many fold higher indicating the sufficiency of the levels of these enzymes for the biosynthesis of ureides. The data presented are consistent with the proposal that in ureide producing legumes, ammonia is initially assimilated into glutamine, aspartate, etc., which are metabolised for the denovo synthesis of purines. The purines are then utilised for the production of ureides by a group of enzymes investigated here     

Comparison of inhibition of N2 fixation and ureide accumulation under water deficit in four common bean genotypes of contrasting drought tolerance

Background and Aims

Drought is the principal constraint on world production of legume crops. There is considerable variability among genotypes in sensitivity of nitrogen fixation to drought, which has been related to accumulation of ureides in soybean. The aim of this study was to search for genotypic differences in drought sensitivity and ureide accumulation in common bean (Phaseolus vulgaris) germplasm that may be useful in the improvement of tolerance to water deficit in common bean.

Methods

Changes in response to water deficit of nitrogen fixation rates, ureide content and the expression and activity of key enzymes for ureide metabolism were measured in four P. vulgaris genotypes differing in drought tolerance.

Key Results

A variable degree of drought-induced nitrogen fixation inhibition was found among the bean genotypes. In addition to inhibition of nitrogen fixation, there was accumulation of ureides in stems and leaves of sensitive and tolerant genotypes, although this was higher in the leaves of the most sensitive ones. In contrast, there was no accumulation of ureides in the nodules or roots of stressed plants. In addition, the level of ureides in the most sensitive genotype increased after inhibition of nitrogen fixation, suggesting that ureides originate in vegetative tissues as a response to water stress, probably mediated by the induction of allantoinase.

Conclusions

Variability of drought-induced inhibition of nitrogen fixation among the P. vulgaris genotypes was accompanied by subsequent accumulation of ureides in stems and leaves, but not in nodules. The results indicate that shoot ureide accumulation after prolonged exposure to drought could not be the cause of inhibition of nitrogen fixation, as has been suggested in soybean. Instead, ureides seem to be produced as part of a general response to stress, and therefore higher accumulation might correspond to higher sensitivity to the stressful conditions.     

Influence of Soil and Air Temperature on I. Nucleotide Metabolism and Growth of Phaseolus vulgaris L. seedlings

Eight day old greenhouse grown Phaseolus vulgaris L. seedlingswere exposed to three different temperature regimes. The concentrationof the total free nucleotides, nucleoside triphosphates, RNAand protein was much more pronounced in seedlings exposed tothe interactive day/night temperature of 28 ?C (soil) and 15?C (air) of regime I. Seedlings treated to a low soil/air, day/nighttemperature of 15 ?C (regime II) had the lowest content of totalfree nucleotides, nucleoside triphosphates, RNA and protein.The nucleoside triphosphate content and energy charge valueof seedlings treated to a high soil/air, day/night temperatureof 28 ?C (regime III) declined much earlier than in the seedlingsexposed to temperature regimes I and II. The fresh and dry weightof seedlings exposed to temperature regime I was significantlyhigher than those seedlings exposed to the other two temperatureregimes. The slowest growth was observed in seedlings exposedto temperature regime II. The noticeably higher concentrationof ATP, pyridine nucleotides and root nodulation in seedlingsexposed to temperature regime I suggests that higher soil andlow air temperature enhances nitrogen metabolism in P. vulgarisseedlings.     

Evaluation of the Relative Ureide Content of Xylem Sap as an Indicator of N(2) Fixation in Soybeans: GREENHOUSE STUDIES

The use of the relative ureide content of xylem sap [(ureide-N/total N) × 100] as an indicator of N₂ fixation in soybeans (Merr.) was examined under greenhouse conditions. Acetylene treatments to inhibit N₂ fixation were imposed upon the root systems of plants totally dependent upon N₂ fixation as their source of N and of plants dependent upon both N₂ fixation and uptake of exogenous nitrate. Significant decreases in the total N concentration of xylem sap from plants of the former type were observed, but no significant decrease was observed in the total N concentration of sap from the latter type of plants. In both types of plants, acetylene treatment caused significant decreases in the relative ureide content of xylem sap. The results provided further support for a link between the presence of ureides in the xylem and the occurrence of N₂ fixation in soybeans. The relative ureide content of xylem sap from plants totally dependent upon N₂ fixation was shown to be insensitive to changes in the exudation rate and total N concentration of xylem sap brought about by diurnal changes in environmental factors. There was little evidence of soybean cultivars or nodulating strains affecting the relative ureide content of xylem sap. `Ransom' soybeans nodulated with Rhizobium japonicum strain USDA 110 were grown under conditions to obtain plants exhibiting a wide range of dependency upon N₂ fixation. The relative ureide content of xylem sap was shown to indicate reliably the N₂ fixation of these plants during vegetative growth using a ¹⁵N method to measure N₂ fixation activity. The use of the relative ureide content of xylem sap for quantification of N₂ fixation in soybeans should be evaluated further.     

Symbiotic nitrogen fixation and physiological performance of bean (Phaseolus vulgaris L.) plants as affected by Rhizobium inoculum position and bean rugose mosaic virus infection

Bean (Phaseolus vulgaris L. var. Tacarigua) plants were grownin sterilized Leonard jars under controlled conditions. Beforesowing, 1 g of gamma irradiated peat containing the Rhizobiumtropici strain CIAT899 was placed at either 2 or 10 cm belowthe sand surface. Mechanical infection of bean rugose mosaicvirus (BRMV) was carried out in 3-d-old seedlings. Thus, theearly events of nodulation occurred before the arrival of virusparticles to roots. Rhizobium inoculation at 2 cm deep resultedin the formation of nodule clusters close to the crown, in contrastto the homogeneous nodulation along the roots observed in plantsinoculated with Rhizobium at a depth of 10 cm. The uniform arrangementof nodules on the roots enhanced the plant shoot biomass, althoughthe total nodule mass per plant did not differ between Rhizobiuminoculation treatments. Nodules located on deeper roots resultedin higher ureide concentrations in shoots and leaves and inreduced carbohydrate concentrations in leaves. In healthy plants,nodules formed on deeper roots had higher allantoinase activityand a greater carbohydrate concentration when compared to thatof nodules located close to the crown. Deeper nodules had ureideconcentrations similar to those of upper nodules, probably asa consequence of increased translocation of N-compounds to aerialorgans. A similar pattern of nodule formation and response toinoculum position was observed in BRMV-infected plants at allharvests. However, virus infection resulted in reduced totalnodule mass, shoot biomass, total leaf area and induced transitoryalterations in the ureide, -amino-N and carbohydrate concentrationin the different plant compartments. The effect of BRMV infectionon plant parameters was more evident during the vegetative stagesof growth. Nevertheless, the magnitude of the effect was alwaysmore pronounced in plants inoculated with Rhizobium at a depthof 2 cm compared to those Inoculated at 10 cm due to a greateractivity of deeper nodules despite virus infection. Deeper nodulesin BRMV-infected plants showed higher carbohydrate concentrationas well as higher allantoinase and uricase activity than thosedeveloped close to the crown, at all harvests. This observationwas further supported by ultrastructural analysis of virus-infectednodules, since virus replication took place in cells containingbacteroids of upper and lower nodules, but only in the interstitialcells of the latter. BRMV infection did not hinder the allantoinaseactivity and the chlorophyll content of uppermost mature leavesregardless of inoculum position. At the flowering and fruitingstages, healthy and BRMV-infected plants did not differ withregard to any of the tested parameters. Only inoculum positionhad an effect. The nearly normal functioning of the symbioticprocess at these stages of growth was attributed to the formationof a new generation of nodules in BRMV-infected plants subjectedto each of the Rhlzobium inoculation treatments. Key words: Bean rugose mosaic virus, symbiotic nitrogen fixation, bean, Rhizobium inoculum position, nodule ultrastructure     

Composition of bleeding sap nitrogen from lines of field-grownPhaseolus vulgaris L.

Summary The nitrogenous compounds in the xylem (bleeding) sap of lines of field-grownPhaseolus vulgaris L., known to vary in N₂ fixation and yield, were measured during growth with and without N fertilizer. Forty nine-67% of the total sap N was in the form of nitrate in fertilized plants, with low amounts of the ureides, allantoin and allantoic acid (4–12%). Ureides contributed between 17 and 38% to the total sap N of non-fertilized plants, with nitrate generally comprising less than 40%. Among the nine lines grown without fertilizer there were significant differences in the % of the sap N as ureides and also in the total mol N ml^–1 sap.The ASN/GLN ratio (mol/mol) was greater in sap collected from the two parental lines given fertilizer compared with non-fertilized plants. However the actual ratio varied between the parental lines. Together the two amides generally comprised between 43–62% of the amino-N in sap samples from the two parental lines with or without N fertilizer.For each N treatment (fertilized or non-fertilized) there were no obvious differences in sap composition between the high N₂ fixing lines and the low N₂ fixing lines. However there was generally a positive relationship between the rate of N translocation (total N concn. ml^–1 sap x rate of exudation) and the ranking of the lines on the basis of higher N₂ fixation rates (acetylene reduction), which was to a large extent independent of the source of N available to the plant.     

Appearance of purine-catabolizing enzymes in fix and fix root nodules on soybean and effect of oxygen on the expression of the enzymes in callus tissue

The appearance of enzymes involved in the formation of ureides, allantoin, and allantoic acid, from inosine 5′-monophosphate was analyzed in developing root nodules of soybean (Glycine max). Concomitant with development of effective nodules, a substantial increase in specific activities of the enzymes 5′-nucleotidase (35-fold), purine nucleosidase (10-fold), xanthine dehydrogenase (25-fold), and uricase (200-fold), over root levels was observed. The specific activity of allantoinase remained constant during nodule development. With ineffective nodules the activities were generally lower than in effective nodules; however, the activities of 5′-nucleotidase and allantoinase were 2-fold higher in ineffective nodules unable to synthesize leghemoglobin than in effective nodules. Since the expression of uricase has been shown to be regulated by oxygen (K Larsen, BU Jochimsen 1986 EMBO J 5: 15-19), the expression of the remaining enzymes in the purine catabolic pathway were tested in response to variations in O₂ concentration in sterile soybean callus tissue. Purine nucleosidase responded to this treatment, exhibiting a 4-fold increase in activity around 2% O₂. 5′-Nucleotidase, xanthine dehydrogenase, and allantoinase remained unaffected by variations in the O₂ concentration. Hence, the expression of two enzymes involved in ureide formation, purine nucleosidase and uricase, has been demonstrated to be influenced by O₂ concentration.     

Nitrogen Fixation, Assimilation and Transport During the Initial Growth Stage of Phaseolus vulgaris L

In nodulated common bean (Phaseolus vulgaris L.), there is typicallya period of N stress between 15 and 20 d after emergence (DAE),due to a lack of synchronization between the depletion of Nin the cotyledons and the beginning of N² fixation and transport.Screening trials identified some Rhizobium leguminosarum bv.phaseoli strains with which symptoms of N deficiency were notvisible (‘precocious’ strains). Cultivar Negro Argelwas then inoculated with two ‘traditional’ strains(C-05 and CIAT 727) and two ‘precocious’ strains(CNPAF 146 and CNPAF 512), and plants were harvested from 8to 30 DAE. There were no differences between the two groupsof strains in nodule dry weight or in the acetylene reductionrates between 8 and 16 DAE. However, nodules induced by the‘precocious’ strains showed earlier onset of glutaminesynthetase (GS) (EC 6.3.1.2 [EC] ) and glutamate synthase (GOGAT)(EC 1.4.1.14 [EC] ) activities, and ureide synthesis. The N concentrationin the nodules formed by ‘precocious’ strains variedfrom 4.2 to 4.5%, whereas with the ‘traditional’strains, it increased from 3.2% at 8 DAE to 65% at 18 DAE, atwhich time plants exhibited N-deficiency symptoms. By 21 DAE,GS and GOGAT activities in ‘traditional’ noduleswere increased, as well as the ureide-N-concentration in thexylem sap, nodule N content declined to 4.5% and the leavesbecame green. These results suggest that the N stress with ‘traditional’strains is not a limitation in early N² fixation activity butrather in the rates of expression of the processes of N assimilationand transport. Key words: Glutamate synthase, glutamine synthetase, nitrogen fixation, Phaseolus vulgaris, Rhizobium     

Yield-Respiration Relationships at Different Bean (Phaseolus vulgaris) Plant Densities

Bean (Phaseolus vulgaris L.) plants were grown, one to fiveplants per pot, with a non-limiting supply of mineral nutrients.As plant density increased, seed and N yield per plant decreased,but those per pot remained fairly constant. The shoot: rootratio and the contribution of roots to total plant respirationwere also almost constant with changing density; the Q₁₀ forshoot respiration was higher at maximal densities. However,growth respiratory C losses per plant over the growth periodon a seed dry matter of N yield basis were not dependent onplant densities tested. Phaseolus vulgaris L., yield, respiration, plant density     

The Assimilation of Ureides in Shoot Tissues of Soybeans : 1. CHANGES IN ALLANTOINASE ACTIVITY AND UREIDE CONTENTS OF LEAVES AND FRUITS

The ureides, allantoin and allantoic acid, are major forms of N transported from nodules to shoots in soybeans (Merr.). Little is known about the occurrence, localization, or properties of the enzymes involved in the assimilation of ureides in shoot tissues. We have examined the capacity of the shoot tissues to assimilate allantoin via allantoinase (EC 3.5.2.5) during leaf and fruit development in nodulated soybeans. Specific activity of allantoinase in leaves peaked during pod formation and early seed filling. In developing fruits allantoinase activity in the seeds was 2 to 4 times that in the pods when expressed on a fresh weight or organ basis. In seeds, the embryos contained the highest specific allantoinase activity. Stems and petioles also had appreciable allantoinase activity. With development, peaks in the amounts of allantoic acid, but not allantoin, were measured in both leaves and fruits suggesting that the assimilation of allantoic acid may be a limiting factor in ureide assimilation. Highest amounts of ureides were measured in the pith and xylem of stem tissues and in developing pod walls.     

A Relationship between Membrane Permeability and Ethylene Production at High Temperature in Leaf Tissue of Phaseolus vulgaris L.

Leaf discs cut from primary leaves of Phaseolus vulgaris L cvMasterpiece were incubated at temperatures higher than the growthtemperature of 25 °C Both basal and wound ethylene productionincreased up to temperatures of 35–37 5 °C, thereafterdeclining rapidly There was no detectable ethylene productionat temperatures above 42 5 °C Exposure of leaf discs tohigh temperature for 60 mm resulted in a large production ofwound ethylene when they were returned to 25 °C The magnitudeof ethylene production was related to the initial incubationtemperature as was the length of the lag period before maximumproduction was achieved The results are discussed in relationto the requirement for continued membrane integrity for ethyleneproduction ethylene, temperature, membrane permeability, Phaseolus vulgaris L, dwarf bean