Allantoin metabolism in soybean plants as influenced by grafts, a delayed inoculation with Rhizobium, and a late supply of nitrogen-compounds

Reciprocal grafts between A62-1 (nodulating variety) and A62-2(non-nodulating variety) of soybeans, delayed inoculation withRhizobium and a late supply of N-compounds to nodulated anddenodulated A62-1 plants were tested to study the regulationof allantoin production in soybeans. In the upper portions of stems of the A62-2 plants grafted ontoA62-1 plants, allantoin was accumulated in a significant quantity,but lower than the ungrafted intact A62-1 plants. The concentrationsof odier nitrogenous and sugar components were similar to thoseof the ungrafted A62-1 plants. On the other hand, in the upperstems of the A62-1 plants grafted onto A62-2 plants, littleallantoin was accumulated and the concentrations of variouscomponents were similar to those of the ungrafted intact A62-2plants. A62-1 and A62-2 plants not inoculated with Rhizobium showedapproximately the same levels of allantoin and of other componentswhen the same concentration of Ncompounds was supplied. Witha late inoculation, A62-1 plants showed a delayed accumulationof allantoin in accordance with the delayed development of nodules. When nodulated soygean plants were denodulated, the allantoinconcentration in the stems and roots rapidly decreased. Additionof ammonia, urea, or nitrate to the denodulated plants retardedthe decrease of allantoin concentration in the stems, but maintainedthe soluble Kjeldahl-N and amino-N concentrations at the samelevels as those in nodulated plants. In contrast, addition ofany one to nodulated plants did not increase the allantoin accumulation. (Received April 17, 1978; )     

Distribution and change in the contents of allantoin and allantoic acid in developing nodulating and non-nodulatng soybean plants

Distribution and change in contents of allantoin¹ in each organof nodulating variety, A62-1, and non-nodulating variety, A62-2,of soybean plants were measured over the growth period, andthe physiological significance of allantoin in soybean plantsis discussed. Allantoin in the cotyledons of both varieties increased andthen decreased in the germination stage. The allantoin levelin stems, roots and nodules of A62-1 was raised with the growthand attained a maximum at the green pod stage and then decreased.On the other hand, those organs of A62-2 accumulated littleallantoin over the growth period. The allantoin level in thestems of A62-1 was the highest compared with other organs. Inthe leaves of A62-1, the level was higher in the developingleaves than lower mature leaves. The level decreased just beforethe end of leaf development and became trace in the lower fullydeveloped leaves. The allantoin level in the pods of A62-1 duringthe young stage was fairly high; whereas that of A62-2 was lowbut significant, and then decreased with maturing. The dry seedsin both varieties showed low levels. Allantoin was concluded to be accumulated in roots and stemsof developing soybean plants bearing nodules and then decreasedin the stage of seed formation. ¹ In this article the sum of allantoin and allantoic acid ismeasured. Therefore, the expression "allantoin" in the textand abstract includes allantoic acid. (Received August 19, 1976; )     

Enzymes of purine catabolism in soybean plants

Remarkable formation and utilization of allantoin is observedin soybean (Glycine max variety A62-1). To study this, variousenzymes involved in purine catabolism (i.e., xanthine oxidase,uricase and allantoinase) were measured in different regionsof soybean plants during development. Uricase, which catalyzesthe direct formation of allantoin from uric acid, was studiedin detail. The activities of these three enzymes were highest in the rootnodules, indicating that the nodules are the major site of allantoinmetabolism. Radicles only showed appreciable activity about80 hr after the seeds were planted. Allantoinase activity wasdetected in all regions tested, showing that allantoin translocatedfrom the nodules can be metabolized in the roots, stem and leaves.In the nodules, xanthine oxidase was localized in the nuclearfraction, while uricase was mainly restricted to the mitochondrialfraction and allantoinase to the soluble fraction. Uricase was partially purified from the nodules and radicles,respectively. The pH optimum of enzyme from the nodules was9.5, whereas that of enzyme from the radicles was 7.0. The enzymefrom the nodules did not require a cofactor, while that fromthe radicles showed an absolute requirement for a cofactor,which was a low molecular substance easily separable from theapoprotein. Thus, the uricase in nodules differs in chemicalproperties from that in the host plant. The results are discussedin relation to change in the allantoin level in soybean tissues. (Received November 1, 1974; )     

A possible role of allantion and the influence of nodulation on its production in soybean plants

Summary To examine the influence of nodulation on the production of nitrogenous compounds, soybean plants (Glycine max var. Tamanishiki) were grown with or without N-fertilizer in the field, and the changes in amino-N and allantoin-N content in the different organs were determined throughout the growth period. In the stem allantoin-N markedly increased after the flowering period and then decreased during seed formation. Allantoin accumulated in the pod (up to 70 per cent of total alcohol soluble-N) during pod formation, while in the seed the main N-compounds were amino acids, the allantoin concentration being very low. In well-nodulated soybeans grown without N-fertilizer, allantoin content in every plant organ was always high compared to beans grown with N-fertilizer, but amino-N content was comparatively low.Another experiment, in which soybean plants were allowed to form nodules by growing on a N-free medium, and in which a fixed-N supply was then controlled by the addition of various levels of ammonium, was made in a greenhouse. When nodules were formed, the subsequent addition of high concentrations of ammonium caused the accumulation of allantoin as well as the accumulation of amides and arginine. A possible role for allantoin and some aspects of its production in soybeans are discussed. re]19760421     

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.

     

Nodule activity and allocation of photosynthate of soybean during recovery from water stress

Nodulated soybean plants (Glycine max [L.] Merr. cv Ransom) in a growth-chamber study were subjected to a leaf water potential (psi w) of -2.0 megapascal during vegetative growth. Changes in nonstructural carbohydrate contents of leaves, stems, roots, and nodules, allocation of dry matter among plant parts, in situ specific nodule activity, and in situ canopy apparent photosynthetic rate were measured in stressed and nonstressed plants during a 7-day period following rewatering. Leaf and nodule psi w also were determined. At the time of maximum stress, concentration of nonstructural carbohydrates had declined in leaves of stressed, relative to nonstressed, plants, and the concentration of nonstructural carbohydrates had increased in stems, roots, and nodules. Sucrose concentrations in roots and nodules of stressed plants were 1.5 and 3 times greater, respectively, than those of nonstressed plants. Within 12 hours after rewatering, leaf and nodule psi w of stressed plants had returned to values of nonstressed plants. Canopy apparent photosynthesis and specific nodule activity of stressed plants recovered to levels for nonstressed plants within 2 days after rewatering. The elevated sucrose concentrations in roots and nodules of stressed plants also declined rapidly upon rehydration. The increase in sucrose concentration in nodules, as well as the increase of carbohydrates in roots and stems, during water stress and the rapid disappearance upon rewatering indicates that inhibition of carbohydrate utilization within the nodule may be associated with loss of nodule activity. Availability of carbohydrates within the nodules and from photosynthetic activity following rehydration of nodules may mediate the rate of recovery of N2-fixation activity.     

Probable site of allantoin formation in nodulating soybean plants

Nodulated soybean plants contain high concentration of allantoin in all parts. Excision of nodules from the roots brought about a marked decrease in allantoin. To examine the function of nodules in allantoin production, nodulated and nodule-detached soybeans were fed with ¹⁵NH₃ for 1 week. High abundance of ¹⁵N was found in the amino acid-N fraction of both plants. In the root and stem of the nodulated plants, ca 80% of the nitrogen in this fraction was derived from the NH₃ added in the medium. Excess ¹⁵N was detected also in allantoin-N fraction, but the ¹⁵N content was very low in contrast to that in amino acid-N fraction. The site involved in the allantoin formation and the possible significance of its synthesis are discussed in relation to symbiotic nitrogen fixation.     

Incorporation of 15N into allantoin in nodulated soybean plants supplied with 15N2

Incorporation of ¹⁵N into allantoin and allantoic acid in noduleswas higher than that in roots. This confirms that nodules produceallantoin. The ¹⁵N concentration in allantoin was slightly higherthan that in allantoic acid, suggesting that allantoin decomposedto allantoic acid. Allantoin and allantoic acid in nodules weretranslocated rapidly to roots. (Received August 25, 1976; )     

Allantoin accumulation through overexpression of ureide permease1 improves rice growth under limited nitrogen conditions

In legumes, nitrogen (N) can be stored as ureide allantoin and transported by ureide permease (UPS) from nodules to leaves where it is catabolized to release ammonium and assimilation to amino acids. In non‐leguminous plants especially rice, information on its roles in N metabolism is scarce. Here, we show that OsUPS1 is localized in plasma membranes and are highly expressed in vascular tissues of rice. We further evaluated an activation tagging rice overexpressing OsUPS1 (OsUPS1^OX) under several N regimes. Under normal field conditions, panicles from OsUPS1^OX plants (14 days after flowering (DAF)) showed significant allantoin accumulation. Under hydroponic system at the vegetative stage, plants were exposed to N‐starvation and measured the ammonium in roots after resupplying with ammonium sulphate. OsUPS1^OX plants displayed higher ammonium uptake in roots compared to wild type (WT). When grown under low‐N soil supplemented with different N‐concentrations, OsUPS1^OX exhibited better growth at 50% N showing higher chlorophyll, tiller number and at least 20% increase in shoot and root biomass relative to WT. To further confirm the effects of regulating the expression of OsUPS1, we evaluated whole‐body‐overexpressing plants driven by the GOS2 promoter (OsUPS1^GOS2) as well as silencing plants (OsUPS1^RNAi). We found significant accumulation of allantoin in leaves, stems and roots of OsUPS1^GOS2 while in OsUPS1^RNAi allantoin was significantly accumulated in roots. We propose that OsUPS1 is responsible for allantoin partitioning in rice and its overexpression can support plant growth through accumulation of allantoin in sink tissues which can be utilized when N is limiting.     

Effects of Allopurinol [4-Hydroxypyrazolo(3,4-d)Pyrimidine] on the Metabolism of Allantoin in Soybean Plants

Some studies on the effects of xanthine oxidase inhibitor allopurinol [4-hydroxypyrazolo(3,4-d)pyrimidine] on allantoin metabolism of soybean plants (Glycine max cv. Tamanishiki) are reported. Soybean seedlings, aseptically germinated for 96 hours on agar containing 1 millimolar allopurinol, contained only slight amounts of allantoin, allantoic acid, and urea as compared with controls. Analysis of purines and pyrimidines of the allopurinol-treated seedlings showed marked accumulation of xanthine both in the cotyledons and seedling axes. No hypoxanthine accumulation was found. Xanthine accumulation due to allopurinol treatment was relatively low after the cotyledons had fallen. For nodulated plants, allopurinol caused a significant drop in allantoin (+allantoic acid) in the stems and nodules, accompanied by a striking accumulation of xanthine in the nodules. The xanthine concentration in the nodules far exceeded that in the germinated seedlings. Allopurinol at a concentration of 50 micromolar strongly inhibited xanthine oxidase prepared from soybean nodules.

The results suggested that the main pathway of allantoin formation in soybean plants was through purine decomposition, via xanthine-uric acid. It was specially noted that a very active purine-decomposing system existed in soybean nodules.

     

Metabolism and translocation of allantoin in ureide-producing grain legumes

Transfer of the nitrogen and carbon of allantoin to amino acids and protein of leaflets, stems and petioles, apices, peduncles, pods, and seeds of detached shoots of nodulated cowpea (Vigna unguiculata L. Walp. cv. Caloona) plants was demonstrated following supply of [2-¹⁴C], [1,3-¹⁵N]allantoin in the transpiration stream. Throughout vegetative and reproductive growth all plant organs showed significant ureolytic activity and readily metabolized [2-¹⁴C]allantoin to ¹⁴CO₂. A metabolic pathway for ureide nitrogen utilization via allantoic acid, urea, and ammonia was indicated. Levels of ureolytic activity in extracts from leaves and roots of nodulated cowpea were consistently maintained at higher levels than in non-nodulated, NO₃⁻ grown plants.

[¹⁴C]Ureides were recovered in extracts of aphids (Aphis craccivora and Macrosiphum euphorbieae) feeding at different sites on cowpea plants supplied with [2-¹⁴C]allantoin through the transpiration stream or to the upper surface of single leaflets. The data indicated that the ureides were effectively transferred from xylem or leaf mesophyll to phloem, and then translocated in phloem to fruits, apices, and roots.

     

Carbohydrate accumulation and partitioning in Pinus banksiana seedlings and seedling cuttings

Tests were conducted to identify possible relations between carbohydrates and callusing-rooting of Pinus banksiana Lamb, cuttings. Terminals, upper stems, and basal (1 cm) stems of 90-day-old untreated seedlings and seedling cuttings were analyzed for sucrose, total soluble reducing sugar, starch and total non-structural carbohydrate during propagation. Seedlings were evaluated in order to determine whether data for cuttings alone properly described carbohydrate-callusing-rooting relations under conditions where stock plants and cuttings were propagated in different environments. Results indicated that seedling terminals and upper stems, but not basal stems, accumulated the measured carbohydrates much like cuttings, though to lesser concentrations. Thus, carbohydrate accumulation by cutting terminals and upper stems would have been overestimated, based on cutting data alone. In terms of rooting, results indicated that: 1) Total carbohydrate accumulation in cutting basal stems was related to callusing-rooting, but a cause-effect relation was not established; 2) The positive relation between callusing-rooting and total carbohydrate accumulation was primarily due to accumulation of reducing sugar and starch, with reducing sugar predominant. 3) Reducing sugar/starch concentration ratios were the most sensitive and convenient indicators of specific carbohydrate differences within and between seedlings and cuttings.     

Concentration-dependent influence of quercetin on nodulation process and the main characteristics of soybean inoculated with Bradyrhizobium japonicum

Soybean plants cv. Corsoy were grown in greenhouse conditions on sterilized quartz sand. They were inoculated with Bradyrhizobium japonicum, strain 542. The plants were treated with different concentrations of quercetin (ranging from 10 nM to 1M) at regular intervals during the experiment. The experiment was terminated at flower development. The following parameters, important for symbiosis efficiency were determined: shoot, root and nodule weights, nodule number, total leghemoglobin in the nodules,total nitrogen and soluble protein concentrations in shoots and roots, as well as chlorophyll concentration in the leaves.The results obtained partly confirmed the earlier findings that quercetin inhibits nodulation since increasing quercetin concentration decreased the number of nodules. However, at very low concentrations, quercetin stimulated the number of nodules. Quercetin also exerted a stimulating influence on other characteristics of the plant and nodules which did not correlate with nodule number and quantity of N fixed. These are: nodule weight, leghemoglobin concentration, total soluble protein content in shoots and roots as well as shoot and root weight.     

三峡库区两种耐水淹植物的存活率和碳水化合物储备关系

野古草和秋花柳是三峡库区消落带两种强水淹耐受能力的植物物种。以往研究显示植物的水淹耐受性和体内碳水化合物储备有关。为了探明野古草和秋花柳水淹下的高存活率是否和碳水化合物储备有关, 研究了在室外6个月的模拟水淹条件下两个物种在不同水淹时间(40、90、120和180d)和不同水淹深度下(不水淹、根部水淹和完全淹没)的生物量积累、存活率和碳水化合物含量和分布。结果表明: (1)野古草和秋花柳对长期水淹具有很高的耐受性, 根部水淹植物6个月处理后完全存活; 而完全淹没条件下, 野古草仅在4个月, 秋花柳仅在6个月处理后才开始死亡; (2)碳水化合物主要储备在野古草的茎和秋花柳的茎与主根中, 野古草的根和秋华柳的细根中碳水化合物含量很低; (3)水淹深度和水淹时间对植物生物量积累和碳水化合物含量影响显著(P 0.05):与未水淹植株相比, 根部水淹仅略微降低了生物量积累以及可溶性糖和淀粉含量 (P 0.05), 且保持基本稳定或增加的趋势, 而完全淹没的植株生物量随水淹时间逐渐降低, 碳水化合物含量在前90天快速下降 (P 0.05), 之后缓慢下降或保持不变。研究结果表明, 野古草和秋花柳强的水淹耐受性是和它们高的碳水化合物储备以及水淹条件下对碳水化合物的动用能力有关, 后期的死亡率增加与碳水化合物储备消耗殆尽有关, 野古草和秋花柳对碳水化合物储备对水淹的响应的差异可能和它们的碳水化合物储备在不同组织中的分配模式有关。       

Nodule Activity and Allocation of Photosynthate of Soybean during Recovery from Water Stress

Nodulated soybean plants (Glycine max [L.] Merr. cv Ransom) in a growth-chamber study were subjected to a leaf water potential (Ψ_w) of −2.0 megapascal during vegetative growth. Changes in nonstructural carbohydrate contents of leaves, stems, roots, and nodules, allocation of dry matter among plant parts, in situ specific nodule activity, and in situ canopy apparent photosynthetic rate were measured in stressed and nonstressed plants during a 7-day period following rewatering. Leaf and nodule Ψ_w also were determined. At the time of maximum stress, concentration of nonstructural carbohydrates had declined in leaves of stressed, relative to nonstressed, plants, and the concentration of nonstructural carbohydrates had increased in stems, roots, and nodules. Sucrose concentrations in roots and nodules of stressed plants were 1.5 and 3 times greater, respectively, than those of nonstressed plants. Within 12 hours after rewatering, leaf and nodule Ψ_w of stressed plants had returned to values of nonstressed plants. Canopy apparent photosynthesis and specific nodule activity of stressed plants recovered to levels for nonstressed plants within 2 days after rewatering. The elevated sucrose concentrations in roots and nodules of stressed plants also declined rapidly upon rehydration. The increase in sucrose concentration in nodules, as well as the increase of carbohydrates in roots and stems, during water stress and the rapid disappearance upon rewatering indicates that inhibition of carbohydrate utilization within the nodule may be associated with loss of nodule activity. Availability of carbohydrates within the nodules and from photosynthetic activity following rehydration of nodules may mediate the rate of recovery of N₂-fixation activity.     

PvUPS1, an allantoin transporter in nodulated roots of French bean

Nodulated legumes receive their nitrogen via nitrogen-fixing rhizobia, which exist in a symbiotic relationship with the root system. In tropical legumes like French bean (Phaseolus vulgaris) or soybean (Glycine max), most of the fixed nitrogen is used for synthesis of the ureides allantoin and allantoic acid, the major long-distance transport forms of organic nitrogen in these species. The purpose of this investigation was to identify a ureide transporter that would allow us to further characterize the mechanisms regulating ureide partitioning in legume roots. A putative allantoin transporter (PvUPS1) was isolated from nodulated roots of French bean and was functionally characterized in an allantoin transport-deficient yeast mutant showing that PvUPS1 transports allantoin but also binds its precursors xanthine and uric acid. In beans, PvUPS1 was expressed throughout the plant body, with strongest expression in nodulated roots, source leaves, pods, and seed coats. In roots, PvUPS1 expression was dependent on the status of nodulation, with highest expression in nodules and roots of nodulated plants compared with non-nodulated roots supplied with ammonium nitrate or allantoin. In situ RNA hybridization localized PvUPS1 to the nodule endodermis and the endodermis and phloem of the nodule vasculature. These results strengthen our prediction that in bean nodules, PvUPS1 is involved in delivery of allantoin to the vascular bundle and loading into the nodule phloem.     

Allantoin and Allantoic Acid in Tissues and Stem Exudate from Field-grown Soybean Plants

Samples of stem exudate and plant tissue collected from field-grown soybean (Glycine max [L.] Merr.) plants were analyzed for allantoin and allantoic acid. Nitrogen in nitrate plus amino acids exceeded ureide N concentration in stem exudate prior to flowering. During all of reproductive development (from about 40 days after planting until maturity), ureide N concentration was two to six times greater than amino acid plus nitrate N concentration. Allantoin and allantoic acid, not asparagine, are the principal forms of nitrogen transported from nodulated roots to shoots of the soybean plant. During pod and seed development ureide N comprised as high as 2.3, 37.7, and 15.8% of total N in leaf blades, stems + petioles, and fruits, respectively. The concentration of ureide in stems and fruits declined to nearly zero at maturity.     

Increase in the Formation and Nitrogen Fixation of Soybean Nodules by Vesicular-Arbuscular Mycorrhiza

Symbiotic interactions of the tripartite association of soybeanplant, vesiculararbuscular (VA) mycorrhizal fungus and Rhizobiumjaponicum were shown. Mycorrhizal plants absorbed more P, Ca and Mg and had higherP, Ca and Mg contents in their stems or leaves than non-mycorrhizalplants. Phosphorus concentration was also higher in the nodulesof mycorrhizal plants. VA mycorrhizae increased nodule number, nodule weight and acetylenereduction activity of nodules. Concomitantly seed productionand N content of leaves were enhanced. Both nodulating (A62-1) and non-nodulating (A62-2) cultivarsof soybean plants [Glycine max (L.) Merr.] were colonized byVA mycorrhizal fungi, identified as belonging to the genus Glomus. (Received August 12, 1985; Accepted January 14, 1986)     

Effect of soil flooding on photosynthesis,carbohydrate partitioning and nutrient uptake in the invasive exotic Lepidium latifolium

Lepidium latifolium L. is an invasive exotic crucifer that has spread explosively in wetlands and riparian areas of the western United States. To understand the ecophysiological characteristics of L. latifolium that affect its ability to invade riparian areas and wetlands, we examined photosynthesis, chlorophyll concentration, carbohydrate partitioning and nutrient uptake in L. latifolium in response to soil flooding. Photosynthesis of flooded plants was about 60–70% of the rate of unflooded controls. Chlorophyll concentrations of flooded plants were about 60–70% of the unflooded plants during 15–50 days of flooding. Flooding resulted in an increase in leaf starch concentration, but root starch concentration was not significantly affected. However, concentrations of soluble sugar were significantly higher in both leaves and roots of flooded plants than unflooded controls. On day 50 after initial flooding, the concentrations of N, P, K and Zn in leaves of flooded plants were lower than in control plants. The concentrations of Mn and Fe in leaves of flooded plants were eight and two times those of control plants, respectively. In contrast, N, P, K and Zn concentrations of roots of flooded plants were slightly higher than in unflooded plants. The concentrations of Fe and Mn in roots of flooded plants were 15 and 150 times those of the control plants, respectively. The transport of P, K, and Zn to shoots decreased and that of Mn increased under flooding. The accumulation of N, K and Zn in roots decreased and that of Mn increased in response to flooding. The results suggested that the maintenance of relatively high photosynthesis and the accumulation of soluble sugar in roots of flooded plants are important adaptations for this species in flooded environments. Despite a reduction in photosynthesis and disruption in nutrient and photosynthate allocation in response to flooding, L. latifolium was able to survive 50 days of flooding stress. Overall, L. latifolium performed like a facultative hydrophyte species under flooding.     

Carbohydrate and Proline Contents in Leaves, Roots, and Apices of Salt-Tolerant and Salt-Sensitive Wheat Cultivars1

Intra-specific variations in nonstructural carbohydrates and free proline were determined in leaves, apices, roots, and maturing seeds of two salt-tolerant cultivars (CR and Kharchia-65) and one salt-sensitive cv. Ghods of spring wheat (Triticum aestivum L.) grown in sand culture at various levels of salinity (0, 100, 200, and 300 mM NaCl and CaCl₂ at 5 : 1 molar ratio) under controlled environmental conditions. The levels of leaf, apex, and root ethanol-soluble carbohydrates, fructans, starch, and proline increased in line with elevating level of salinity in all three cultivars under investigation. The contents of proline, soluble and insoluble carbohydrates in the apex increased to levels exceeding those in the leaves and roots. Soluble carbohydrate content of salt-sensitive cv. Ghods was higher in the leaves, apices, and roots and lower in the maturing seeds than in the other cultivars at all levels of salinity except at 300 mM. The results show considerable variation in the amount of soluble, insoluble sugars, and proline among plant tissues and wheat genotypes in response to salinity. Higher soluble carbohydrates and fructan in leaves, roots and maturing seeds of stressed plants indicate that their accumulation may help plant to tolerate salinity. Salt-sensitive cv. Ghods accumulated less soluble sugars in the maturing seeds and higher soluble sugars in the apices, which might be used as an indicator in screening wheat genotypes for salinity tolerance.