Ureide metabolism in higher plants
TL;DR: The evidence that light appears to be involved in ureide assimilation in green tissues suggests that different regulatory mechanisms may exist in plants compared with micro-organisms.
About: This article is published in Phytochemistry.The article was published on 1981-03-13. It has received 125 citations till now. The article focuses on the topics: Assimilation (biology) & Allantoic acid.
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TL;DR: This review integrates the current knowledge regarding inorganic and organic nitrogen management at the whole-plant level, spanning from nitrogen uptake to remobilization and utilization in source and sink organs, demonstrating that nitrogen transporters are effective targets to improve crop productivity and nitrogen use efficiency.
Abstract: Contents Summary 35 I. Introduction 35 II. Nitrogen acquisition and assimilation 36 III. Root-to-shoot transport of nitrogen 38 IV. Nitrogen storage pools in vegetative tissues 39 V. Nitrogen transport from source leaf to sink 40 VI. Nitrogen import into sinks 42 VII. Relationship between source and sink nitrogen transport processes and metabolism 43 VIII. Regulation of nitrogen transport 43 IX. Strategies for crop improvement 44 X. Conclusions 46 Acknowledgements 47 References 47 SUMMARY: Nitrogen is an essential nutrient for plant growth. World-wide, large quantities of nitrogenous fertilizer are applied to ensure maximum crop productivity. However, nitrogen fertilizer application is expensive and negatively affects the environment, and subsequently human health. A strategy to address this problem is the development of crops that are efficient in acquiring and using nitrogen and that can achieve high seed yields with reduced nitrogen input. This review integrates the current knowledge regarding inorganic and organic nitrogen management at the whole-plant level, spanning from nitrogen uptake to remobilization and utilization in source and sink organs. Plant partitioning and transient storage of inorganic and organic nitrogen forms are evaluated, as is how they affect nitrogen availability, metabolism and mobilization. Essential functions of nitrogen transporters in source and sink organs and their importance in regulating nitrogen movement in support of metabolism, and vegetative and reproductive growth are assessed. Finally, we discuss recent advances in plant engineering, demonstrating that nitrogen transporters are effective targets to improve crop productivity and nitrogen use efficiency. While inorganic and organic nitrogen transporters were examined separately in these studies, they provide valuable clues about how to successfully combine approaches for future crop engineering.
413 citations
TL;DR: The use of nanofiltration membranes for the recovery of phosphorous with a second type of technology for recovery of nitrogen is suggested to be a viable process.
Abstract: INTRODUCTION 539 THE EXCHANGE OF REDUCED CARBON AND NITROGEN: AN OVERVIEW. ... 540 MAJOR PRODUCTS OF RECENTLY FIXED N2 EXPORTED FROM NODULES.... 542 SYNTHESIS OF AMIDES AND UREIDES 546 Ammonium Assimilation .... 546 Asparagine Synthesis . 547 Synthesis of 4-Methyleneglutamine 548 Synthesis of Citrulline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 Biogenesis of Allantoin and Allantoic Acid 551 METABOLISM OF AMIDES AND UREIDES . ......... . . ... . . ........ .... . . .. ..... . 558 ENERGETICS OF SYNTHESIS AND METABOLISM OF THE PRODUCTS OF Nz FIXATION 564 SUMMARy......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567
405 citations
TL;DR: Evidence suggests that nickel is essential for soybeans and possibly for higher plants in general and that addition of nickel to the nutrient media prevented urea accumulation, necrosis, and growth reductions.
Abstract: Soybean plants deprived of nickel accumulated toxic concentrations of urea (2.5 percent) in necrotic lesions on their leaflet tips. This occurred regardless of whether the plants were supplied with inorganic nitrogen or were dependent on nitrogen fixation. Nickel deprivation resulted in delayed nodulation and in a reduction of early growth. Addition of nickel (1 microgram per liter) to the nutrient media prevented urea accumulation, necrosis, and growth reductions. This evidence suggests that nickel is essential for soybeans and possibly for higher plants in general.
309 citations
TL;DR: The biosynthesis, interconversion and degradation of purine and pyrimidine nucleotides in higher plants are reviewed and physiological aspects of nucleotide metabolism in various areas of growth and organized development in plants are examined.
291 citations
TL;DR: In this paper, the inorganic N species nitrate (NO3 ), nitrite (NO2 ), and ammonium (NH4 ) were analyzed and the results suggest that biomass burning is a source of WSON, yet poorly understood.
Abstract: acids. In addition to total WSON the inorganic N species nitrate (NO3 ), nitrite (NO2 ), and ammonium (NH4 ) were also analyzed. WSON was found to represent � 45% (mean concentration � 3.5 nmol N/m 3 ) and � 43% (mean concentration � 61 nmol N/m 3 )o f the total N in wet and dry season aerosol samples, respectively. Urea and amino N made up � 19% of the total organic N in dry season aerosols and � 2.5% of the total organic N in wet season aerosols; the majority of WSON, � 80% in the dry season and � 97% in the wet season, remained uncharacterized. The results suggest that biomass burning is a source of WSON, yet poorly understood (since this data set represents the first study of WSON in the context of biomass burning). Future studies aimed at determining the magnitude of WSON released from biomass burning globally, its species composition, and its biogeochemical significance are needed. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0365 Atmospheric Composition and Structure: Troposphere— composition and chemistry; 1615 Global Change: Biogeochemical processes (4805); KEYWORDS: nitrogen cycling, biomass burning, organic nitrogen
184 citations
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TL;DR: Seed biochemical composition was the basis for segregating 24 crops into four distinct groups because sustained seed growth demanded continued nitrogen translocation from vegetative tissues.
Abstract: Seed biochemical composition was the basis for segregating 24 crops into four distinct groups. Nitrogen requirements of pulses and soybeans were so great that sustained seed growth demanded continued nitrogen translocation from vegetative tissues. This translocation must eventually induce senescence in these tissues, restrict the duration of the seed-fill period, and limit seed yield.
593 citations
TL;DR: This article corrects the article on p. 403 in vol.
Abstract: [This corrects the article on p. 403 in vol. 40.].
514 citations
406 citations
TL;DR: The role of the root system in the upward transport of nitrogen from the xylem to the shoot is discussed in this paper, where it is shown that the root can produce organic compounds from the nitrate or other forms of inorganic nitrogen.
Abstract: This paper reviews current knowledge and presents some new information on the metabolism of nitrogen in various species of higher plants. The role of the root system is considered. It is shown that the roots of many herbaceous and woody plants can manufacture organic compounds of nitrogen from the nitrate or other forms of inorganic nitrogen they absorb from the medium. The extent to which they do this varies greatly with the age and nutrition of the plant and with the environmental conditions under which it is growing. The relationship is examined between the synthetic activities of the root and its activity in upward transport of nitrogen to the shoot. The latter process takes place predominantly, if not exclusively, in the xylem, and in each species one or more nitrogen-rich compounds, e.g., amides, ureides and amino acids, carry the bulk of the nitrogen leaving the root. A second group of plants is described in which roots do not function to any extent in the reduction of nitrate. Consideration is given to the fate of recently absorbed nitrogen once it reaches the shoot system. An inorganic source such as nitrate, or molecules such as amides containing surplus amino groupings, are shown to serve as nitrogen sources for synthesis of amino acids required for protein synthesis. Some of these amino acids arise directly from the photosynthetic apparatus. Alternatively, surplus nitrogen arriving from the root may be stored in the shoot, from where it is drawn upon extensively if uptake by the root fails to keep pace with the shoot's demands for nitrogen. The transport system for nitrogen is examined for the whole plant. The classes of sources and sinks for nitrogen are described, and information presented on the types of nitrogenous solutes they receive from the xylem and phloem.
362 citations
TL;DR: It is demonstrated that ureides play a dominant role in N transport in nodulated soybeans and that the synthesis of ureide is largely dependent upon nodulation and N(2) fixation.
Abstract: Experiments were conducted to characterize the distribution of N compounds in the xylem sap of nodulated and nonnodulated soybean plants through development and to determine the effects of exogenous N on the distribution of N compounds in the xylem. Xylem sap was collected from nodulated and nonnodulated greenhouse-grown soybean plants (Glycine max [L.] Merr. “Ransom”) from the vegetative phase to the pod-filling phase. The sum of the nitrogen in the amino acid, nitrate, ureide (allantoic acid and allantoin), and ammonium fractions of the sap from both types of plants agreed closely with total N as assayed by a Kjeldahl technique. Sap from nodulated plants supplied with N-free nutrient solution contained seasonal averages of 78 and 20% of the total N as ureide-N and amino acid-N, respectively. Sap from nonnodulated plants supplied with a 20 millimolar KNO3 nutrient solution contained seasonal averages of 6, 36, and 58% of total N as ureide-N, amino acid-N, and nitrate-N, respectively. Allantoic acid was the predominant ureide in the xylem sap and asparagine was the predominant amino acid. When well nodulated plants were supplied with 20 millimolar KNO3, beginning at 65 days, C2H2 reduction (N2 fixation) decreased relative to nontreated plants and there was a concomitant decrease in the ureide content of the sap. A positive correlation (r = 0.89) was found between the ureide levels in xylem sap and nodule dry weights when either exogenous nitrate-N or urea-N was supplied at 10 and 20 millimolar concentrations to inoculated plants. The results demonstrate that ureides play a dominant role in N transport in nodulated soybeans and that the synthesis of ureides is largely dependent upon nodulation and N2 fixation.
314 citations