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Effects of manganese deficiency on the nitrogen metabolism of Lupinus angustifolius cultivar Unicrop

Mahmood, Marziah (1984) Effects of manganese deficiency on the nitrogen metabolism of Lupinus angustifolius cultivar Unicrop. PhD thesis, Murdoch University.

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Manganese deficiency in developing lupin seeds of Lupinus angustifolius cultivar UniCrop causes the accumulation of ethanol-soluble nitrogenous compounds accompanied by a decrease in protein content. The most marked changes were in the aspartate/glutamate balance. While glutamate + glutamine were greater than aspartate + asparagine in normal seeds, they were lower in manganese-deficient seeds. Arginine levels were also decreased by manganese deficiency.

NADP-dependent isocitrate dehydrogenase activity was higher in manganese-deficient seeds when extracts were assayed with added manganese. In the early stages of seed development the total enzyme activity was initially lower than that found in manganese-sufficient seeds but the activity continued to rise to almost as high as that from manganese-sufficient seeds, although somewhat delayed. Its activity remined higher in manganese-deficient maturing seeds. There was no change in isozyme pattern or the number of isozymes present in the leaves. or in any stage of seed development for either treatments.

Glutamate dehydrogenase activity was significantly lowered in manganese-deficient seed extracts. The NADH-dependent glutamate dehydrogenase was more affected than the NADPH-dependent enzyme. The isozyme patterns of NADH-dependent glutamate dehydrogenase in manganese-deficient and manganese-sufficient seeds differed considerably. Manganese-deficient seed extracts showed a decrease in NADH-dependent glutamate dehydrogenase isozymes activated by manganese. The situation could be explained by the synthesis or modification of other metal-requiring isozymes.

While manganese deficiency effects on glutamate synthesis appeared unlikely to involve isocitrate dehydrogenase, changes in the total activity of glutamate dehydrogenase, its isozyme pattern and the isozyme response to Mn all suggest that glutamate dehydrogenase activity is affected.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Environmental and Life Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Dilworth, Michael and Loneragan, Jack
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