Carbohydrate Oxidation in Developing Barley Endosperm

Duffus, C. M.; Rosie, Roberta

doi:10.1111/j.1469-8137.1977.tb04843.x

Cited by 12 publications

(5 citation statements)

References 21 publications

(20 reference statements)

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“…These reducing equivalents may be utilized as such or oxidized to produce energy. Again the observed coincidence of peaks of mitochondrial enzyme activities (Figure 4) with the rate of respiration and the active phase of starch synthesis (Sangwan, 1981;Kumar and Singh, 1981) strongly supports the view that active respiratory processes yielding energy in the form of ATP from oxidative phosphorylation, etc., accompany grain development in cereals, as inferred earlier from biochemical (Duffus, 1970;Duffus and Rosie, 1977) and ultrastructural (Buttrose, 1960(Buttrose, ,1963 Williams and Duffus, 1978) studies. Low levels of mitochondrial enzymes observed at early and later stages of grain maturation may reflect the biogenesis (Williams and Duffus, 1978) and disintegration (Kolloffel, 1970) of mitochondria at these stages, respectively.…”

Section: Discussionmentioning

confidence: 61%

Enzymes of carbohydrate oxidation in developing wheat grains

Sangwan¹,

Popli²,

Singh³

1983

J. Agric. Food Chem.

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Section: Discussionmentioning

confidence: 61%

Enzymes of carbohydrate oxidation in developing wheat grains

Sangwan¹,

Popli²,

Singh³

1983

J. Agric. Food Chem.

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“…In the present study, Downloaded by [King Mongkuts University of Technology Thonburi] at 11:31 19 October 2014 and non-donnant varieties of wheat. Apparently, G6PDH is synthesized and stored during seed development, as was demonstrated for barley endosperin (Duffus and Rosie, 1977), castor beans (Simcox et aZ., 1979) and wild oats (Upadhyaya et aZ., 1981). However, during the first 24 h of incubation (gennination phase), the G6PDH activity increased almost two fold in the preharvest sprouting susceptible Tugela-DN seeds while remaining at the same rate as was measured in dry seeds ofthe resistant cultivar, Betta-DN (HR).…”

Section: Discussionmentioning

confidence: 89%

The possible role of the oxidative pentose phosphate pathway in seed dormancy in winter wheat cultivars

Pretorius

2005

South African Journal of Plant and Soil

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Seed dormancy is an important characteristic in small grain cultivars, because of its potential to prevent preharvest sprouting and the subsequent loss of quality. In this study the oxidative pentose pathway (OPP) activity in seeds of a preharvest sprouting susceptible winter wheat cultivar, Tugela-DN and that of a preharvest sprouting resistant cultivar, Betta-DN, were compared. Carbon flux through the OPP pathway was determined both indirectly (total in vitro activity of the first regulatory enzyme, Glucose-6-phosphate dehydrogenase (G6PDH) and directly ( 14 C0 2 evolution from metabolized D-[1 J4C]_ and D-[6-14 C]_glucose, including C6/C1 ratios). G6PDH activity increased twofold in both the harvest ripe (HR) and after ripened (AR) seeds of the susceptible cultivar during the germination phase (first 24 h of incubation) and threefold during the post germinative phase up to 72 h of incubation. The latter coincided with a high germination percentage. However, the G6PDH activity remained constant in both the HR and AR seeds of the resistant cultivar during the first 24 h of incubation and increased only slightly in the HR seeds over the remaining incubation time. Moreover, a C6/C1 ratio of below unity in seeds of Tugela-DN during the germination phase, confirmed that the OPP pathway was far more active in this preharvest sprouting susceptible cultivar than in the resistant cultivar, Betta-DN, where the C6/C1 ratio remained above unity during the germination phase.

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“…Glutamine synthetase may be activated by products of photosynthesis such as ATP and NADPH (27). The pericarp is a photosynthetic tissue while the endosperm, although synthesizing ATP and NADPH via the glycolytic and pentose-P pathways (12), may maintain lower intracellular levels of these substances than the testa pericarp, in view of their requirement by the pathways of carbohydrate, lipid, and protein synthesis. Again, glutamine synthetase activity will be favored in testa pericarp.…”

Section: Resultsmentioning

confidence: 99%

“…Ammonium ion is certainly found in the endosperm during the early stages of grain development and could be utilized there by glutamate dehydrogenase. The equilibrium lies in favor of glutamate synthesis and the acceptor is a-ketoglutarate which, since respiratory processes are active (12) in developing endosperm, would be readily available. It may be that the supply of 2-oxoglutarate is itself regulated by ammonium ion concentration since it has been reported (3) that glycolysis, and hence the supply of carbohydrate for Krebs' cycle intermediate synthesis, may be activated by ammonium ions.…”

Section: Resultsmentioning

confidence: 99%

Metabolism of Ammonium Ion and Glutamate in Relation to Nitrogen Supply and Utilization during Grain Development in Barley

Duffus¹,

Rosie²

1978

Plant Physiol.

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(1), who showed that the dry matter entering the developing grain is derived mainly from photosynthesis after grain emergence. The nitrogen required for development in lupin seeds moves in the phloem (23), the major compounds present being similar to those found in maize xylem sap (15). Glutamate/glutamine and aspartate/asparagine were the predominant amino acids. In phloem, as in xylem (15), the relative amounts present of the various nutrients will no doubt depend on the physiological status and inorganic nutrition of the plant.The mode of incorporation of nitrogen into the amino acids of higher plants is also a matter of some controversy. Miflin (20) Under these conditions the period between anthesis and maturity took 60 days. The method used to determine the date of anthesis was that of Merritt and Walker (19). Immature grains were used either fresh from the ear or after storage at -18 C for periods of not more than 3 months.Extraction of Enzymes. A minimum number of 10 endosperms, embryos, or testa pericarps was used for each assay. Endosperms (including the aleurone layer) and embryos (including the scutellum) were dissected out by hand after removal of the grains from intact ears. As soon as possible after dissection the tissues were suspended in a minimum volume of the appropriate buffer at 4 C and homogenized completely using a Potter-type, hand-held, all glass homogenizer. Testa pericarps were similarly homogenized in a GrifTiths' ground glass hand-held homogenizer. The buffer to be used in the subsequent enzyme assay system was used as the extraction medium in each case. Homogenization was continued until tissue disruption was complete and soluble protein extraction maximal. Suspensions were centrifuged immediately at the speeds indicated in the assay methods or at l0,000g for 3 min on a Beckman microfuge. Since the object of this study was to measure enzyme activity as nearly as possible under in vivo conditions, the tissues were diluted as little as possible and no stabilizing factors were added to the homogenizing medium.Enzyme Assays. Glutamate-oxaloacetate transaminase (4) and glutamate-pyruvate transaminase (5) were assayed by standard methods. L-Glutamate dehydrogenase was assayed as described by Strecker (28)

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Carbohydrate Oxidation in Developing Barley Endosperm

Cited by 12 publications

References 21 publications

Enzymes of carbohydrate oxidation in developing wheat grains

Enzymes of carbohydrate oxidation in developing wheat grains

The possible role of the oxidative pentose phosphate pathway in seed dormancy in winter wheat cultivars

Metabolism of Ammonium Ion and Glutamate in Relation to Nitrogen Supply and Utilization during Grain Development in Barley

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