Nitrogen transportation

Secondary compounds produced by plants may have other significant survival roles, such as signals to attract insects, birds, or other animals to enhance pollination or seed dispersal. In addition to any potential functions, secondary compounds may concomitantly serve a physiologic function, such as protection against ultraviolet (UV) light or frost, or provide a function in nitrogen transport and storage. In several instances, compounds can serve multiple functions in the same plant. Anthocyanins or monoterpenes can be... 

The biochemistry and physiology of quinolizidine alkaloids is reviewed with respect to their role in lupin meteibolism. Minor roles of the alkaloids may be nitrogen transport and nitrogen storage, but their main function is that of chemical defense. 

Since QA are readily metabolized by cells, the alkaloids could thus play a role as a minor means of nitrogen transport. 

Figure 25-18 Pathways of catabolism of purine nucleotides, nucleosides, and free bases. Spiders excrete xanthine while mammals and birds excrete uric acid. Spiders and birds convert all of their excess nitrogen via the de novo pathway of Fig. 25-15 into purines. Many animals excrete allantoin, urea, or NH4+. Some legumes utilize the pathway marked by green arrows in their nitrogen transport via ureides.

Plants also form the ureides allantoin and allantoic acid, and in some legumes, such as soy beans, these compounds account for 70-80% of the organic nitrogen in the xylem. They appear to function in nitrogen transport.337 As indicated in Fig. 25-18, the hydrolysis to glyoxylate, NH4+, and C02 follows a different pathway than in animals. See also Chapter 24, Section C. 

Figure 16.2 Model-predicted latitudinal distribution in the North Atlantic Basin (a) estuarine denitrification (b) total nitrogen transport by rivers. (Modified from Seitzinger, 2000.)...

Alberts, J.J., and Takacs, M. (1999) Importance of humic substances for carbon and nitrogen transport into southeastern United States estuaries. Qrg. Geochem. 30, 385-395. 

Alternatively, in skeletal muscle, pyruvate can be transaminated to alanine (which affords a route for nitrogen transport from muscle to liver) in the liver alanine is used to regenerate pyruvate, which can then be diverted into gluconeogenesis. This process is referred to as the glucose-alanine cycle. 

In some instances, additional functions are the attraction of pollinating or seed-dispersing animals, for example, by colored compounds such as betalains (within the Centrospermae), anthocyanins, carotenoids, and flavonoids or by fragrances such as terpenes, amines, and aldehydes 15,17). Physiological roles, such as UV protection [by fiavonoids or cou-marins 4,17)], nitrogen transport or storage 14,36,37), or photosynthesis (carotenoids), may be an additional function. 

Villareal, T. A., Altabet, M. A., and Culver-Rymsza, K. (1993). Nitrogen transport by vertically migrating diatom mats in the North Pacific ocean. Nature 363, 709—712. 

Piloso, S., Vallino, J., Hopkinson, C., Rastetter, E., and Claessens, L. (2004). Modeling nitrogen transport in the Ipswich River Basin, Massachusetts, using a hydrological simulation program in fortran (HSPF).J. Am. Water Resour. Assoc. 40, 1365-1384. 

Ittekkot, V., and Zhang, S. (1989). Pattern of particulate nitrogen transport in world rivers. Global Biogeochem. Cycles. 3, 383—391. 

Stalnacke, P., Grimvall, A., Sundblad, K., and Wilander, A. (1999). Trends in nitrogen transport in Swedish rivers. Environ. Monit. Assess. 59, 47—72. 

Priscu, J. C. (1989). Photon dependence of inorganic nitrogen transport by phytoplankton in perennialy ice-covered Antarctic lakes. In High Latitude Limnology (Vincent, W. F., and Elhs-Evans, J. C., eds.). Hydrobiologia 172, 173—182. 

Whalen, S. C., Alexander, V. (1986). Seasonal inorganic carbon and nitrogen transport by phytoplankton in an arctic lake. Can.J. Fish. Aquatic Sci. 43, 1177-1186. 

Graneli, E., and Graneli, W. (1999). Reducing nitrogen transport to Swedish coastal waters—A case study. In Marine Research and Policy Interface. Links, Interdisciplinary Co-operation, Availability of Results, Case Studies (Cornaert, M., and Lipiatou, E., eds.). Third European Marine Science and Technology Conference, Luxembourg, pp. 21—34. 

Wheeler, P. A. (1980). Use of methylammonium as an ammonium analog in nitrogen transport and assimUation studies with Cydotella cryptica (BacUlariophyceae). J. Phycol. 16, 328—334. 

Howes, B., Weiskel, P., Goehringer, D., and Teal, J. (1996). Interception of freshwater and nitrogen transport form uplands to coastal waters The role of saltmarshes. In Estuarine Shores Evolution, Environments and Human Alterations (Nordstrom, K., and Roman, C. T., eds.). Wiley, New York. pp. 287—310. 

Mousseau, L., Gosselin, M., Levasseur, M., Demers, S., Fauchot, J., Roy, S., Villegas, P. Z., and Mostajir, B. (2000). Effects of ultraviolet-B radiation on simultaneous carbon and nitrogen transport rates by estuarine phytoplankton during a week-long mesocosm study. Mar. Ecol. Prog. Ser. 199, 69-81. 

Important concentrations of aspartic add and asparagine are observed these amino acids are known to be the more common form of nitrogen transport or stocking for plants, alga, etc., [17 ]. 

Fleischer, S., Stibe, L. Leonardson, L. (1991) Restoration of wetlands as a means of reducing nitrogen transport to coastal waters. Ambio 20, 271-2. 

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