An improved determination of ammonia in kjeldahl digests and acidic solutions with a buffered berthelot reaction

Reay, Paul

doi:10.1016/s0003-2670(00)81655-4

Cited by 9 publications

(4 citation statements)

References 5 publications

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“…The samples were digested with concentrated sulphuric acid at 200¡C for 2 days. Then the glass tubes were sealed and heated at 400¡C for 10 h, and ammonia determined (Reay 1985).…”

Section: Methodsmentioning

confidence: 99%

Chlorophylls, carotenoids and anthocyanin concentrations in the skin of ‘Gala’ apples during maturation and the influence of foliar applications of nitrogen and magnesium

Reay

Fletcher

Thomas

1998

J. Sci. Food Agric.

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‘Gala’ apple fruit were sampled over two growing seasons, to determine the effects of maturation, and of foliar applications of nitrogen and magnesium on pigment concentrations and colour development in maturing fruit. Treatments of urea and/or magnesium sulphate sprays were applied to the trees in a commercial orchard. The chlorophyll, carotenoid and anthocyanin concentrations in the fruit skin were determined for both the blush and back sides over 15 harvests in 1991–1992. In 1990–1991, the skin chlorophyll concentrations were determined only for the back side of the fruit. The fruit nitrogen, magnesium and sulphur concentrations were determined near maturity. The concentrations of chlorophyll and carotenoids in apple skin decreased from the first harvest in 1991–1992 as the fresh weight increased from 12 g, 40 days from flowering to 140 g, 138 days from flowering. Chlorophyll continued to decrease whereas carotenoid concentrations increased after 138 days and until at least 153 days. The average skin chlorophyll and carotenoid concentrations were higher on the blush side of the fruit than on the back. The total chlorophyll per fruit increased from the first harvest to a peak about 70 days after flowering in 1990–1991 and then decreased over the remainder of the period studied. The time of this peak was about 40 days later in the 1991–1992 season compared with the 1990–1991 season. The total carotenoid increased up to about 50 days after flowering in 1991–1992, fluctuated and then decreased up to 138 days when the amount increased again. The ratio of carotenoids to chlorophylls was highest for the first three harvests, fluctuated somewhat up to c 138 days after flowering after which the ratio increased rapidly. The anthocyanin concentrations were low and fluctuated up to 130 days from flowering and then increased markedly only on the blush side at 130 days, about 14 days before the carotenoids started to increase. The treatment of the tree canopy with urea increased the chlorophyll and carotenoid concentrations in the fruit skin, 14–20 days after the first application until after maturity, more so on the blush side than on the back side. These increased concentrations were maintained up to the harvest after which carotenoid concentrations increased. The urea treatment lessened the increase of anthocyanin concentrations in the blush side skin of the fruit, at maturity. At maturity, the nitrogen concentration of fruit from urea treated trees was higher than those from untreated trees. The magnesium sulphate treatment of the canopy increased the chlorophyll and carotenoid concentration on the back of the fruit within 20–30 days from commencing spraying. The ‘ground colour’ scores for the back sides of the fruit (used for fruit picking and grading) were greener for the urea treated fruit and reached an acceptable score about two weeks later than the untreated fruit. ©1998 SCI

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“…The samples were digested with concentrated sulphuric acid at 200¡C for 2 days. Then the glass tubes were sealed and heated at 400¡C for 10 h, and ammonia determined (Reay 1985).…”

Section: Methodsmentioning

confidence: 99%

Chlorophylls, carotenoids and anthocyanin concentrations in the skin of ‘Gala’ apples during maturation and the influence of foliar applications of nitrogen and magnesium

Reay

Fletcher

Thomas

1998

J. Sci. Food Agric.

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“…The acidity of diluted digests was neutralized with sodium hydroxide. The phosphorus content of aliquots was determined by the method of Murphy and Riley (1962) and nitrogen content by the method of Reay (1985).…”

Section: Methodsmentioning

confidence: 99%

“…Digestion mixture {0 35 ml) (Williams and Twine, 1967) was added to each aliquot and the solution digested at 315°C. It was then diluted to 25 ml and the nitro-gen content of an aliquot determined by the method of Reay (1985).…”

Section: Methodsmentioning

confidence: 99%

The effects of phosphorus and form of nitrogen supply on leaf cell size and nutrient content in Trifolium repens and Lotus uliginosus

Hart

Collier

1994

Grass and Forage Science

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White clover (Grasslands Huia) and lotus (Grasslands Maku) were grown in pots of soil at a range of phosphorus supply, and reliant on symbiotic nitrogen fixation (SN plants) or entirely on mineral nitrogen {MN plants). Shoots increased in weight with phosphorus supply. White clover MN shoots were bigger than those of SN plants except at the lowest level of phosphorus supply; lotus MN shoots were only bigger than SN shoots at the highest level of phosphorus supply. Leaf growth rate and size increased with phosphorus supply but were not significantly affected by the nitrogen treatments.Estimates of cell size were made by determining DNA concentration, by digestion of tissue followed by counting and by taking vinyl impressions of epidermal cell surfaces. Lotus cells are bigger than those of white clover. "Digested' cell sizes were not significantly afTected by changes in phosphorus supply. Epidermal cell size increased with phosphorus supply, but the relationship was weaker in SN than in MN plants. Methods which give values for 'average' cell size are capable of detecting large-scale diiTerences. but methods able to resolve cell heterogeneity are necessary for an accurate picture of the relationship between leaf growth and cellular nutrition.Average concentrations of total and inorganic phosphorus on a DNA basis did not differ between the species, contrary to concentrations on a dry weight basis, indicating that differences in phosphorus efficiency can be partly explained on

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“…The P content of diluted, neutralised digest was determined by the method of Murphy & Riley (1962) and the N content by that of Reay (1985).…”

Section: Methodsmentioning

confidence: 99%

Nodule phosphorus and nodule activity in white clover

Hart

1989

New Zealand Journal of Agricultural Research

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Rooted cuttings established from stolon tips of a genotype of Trifolium repens cv . 'Grasslands Huia' white clover were grown in batch nutrient solution at a range of phosphorus (P) supplies. Growth, the concentration of nitrogen (N) and P in plant parts, the concentration ofP fractions in leaves and nodules, and the rate of ethylene production by detached root systems were measured. Shoot and total plant dry weight increased over the whole range of P supply but root dry weight (including nodules) was saturated at the higher levels of supply. The total concentration of P in leaves and nodules increased with supply, it being always higher in the nodules than in the leaves especially at low levels of supply. The concentrations of all the P fractions in the nodules and leaves increased with P supply, and were higher in the nodules than in the leaves. Inorganic-P concentrations did not change over the lowe~ levels of supply bu~ then changed markedly, ShOWlOg greater overall lOcreases than the other fractions. At low levels of supply, lipid-P and residue-P appeared to be the main contributors to a rise in total P concentration in the nodules. The rate of ethylene production increased with P supply, the largest rise coinciding with the rise in phosphate concentration in the nodules. N fixation may be dependent on phosphate in the nodule cytosol, rather than on bacteroid P. The relatively high concentrations oflipid-P and residue-Pin the nodules may be a result of high concentrations of these compounds in the bacteroids.

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An improved determination of ammonia in kjeldahl digests and acidic solutions with a buffered berthelot reaction

Cited by 9 publications

References 5 publications

Chlorophylls, carotenoids and anthocyanin concentrations in the skin of ‘Gala’ apples during maturation and the influence of foliar applications of nitrogen and magnesium

Chlorophylls, carotenoids and anthocyanin concentrations in the skin of ‘Gala’ apples during maturation and the influence of foliar applications of nitrogen and magnesium

The effects of phosphorus and form of nitrogen supply on leaf cell size and nutrient content in Trifolium repens and Lotus uliginosus

Nodule phosphorus and nodule activity in white clover

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