Comparative effects of summer and winter conditions on the growth of six species of pasture legumes subjected to various nutrient levels

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SummaryCalcium level in the substrate was found to have a very marked effect on the distribution of 45Ca in subterranean clover. Sites of initial accumulation of 45Ca included the vein endings along the distal margins of the leaflets, the lateral veins, and the proximal halves of the petioles.In plants with a normal calcium supply these sites were quickly saturated and the isotope became uniformly distributed in the lamina, which contained a higher concentration than its associated petiole. There was a positive correlation between leaf age and 45Ca concentration. In the petiole a somewhat higher concentration of 45Ca finally occurred in the distal when compared with the proximal half.Calcium-deficient plants differed in that, with the exception of the vein endings, the initial sites of accumulation of 45Ca were not rapidly saturated. In the lamina 45Ca moved into the interveinal tissues adjacent to the vein endings. Provided acute calcium-deficiency symptoms did not occur, there was finally a build-up of 45Ca in the distal half of the petiole. The concentration in the petiole was greater than in the lamina. Before runner-stem formation began there was not the same correlation in deficient plants between leaf age and nCa concentration as in nonnal plants, indicating that much of the newly absorbed 4SCa was acquired by young leaves of deficient plants at the expense of the oldest. This resulted in petiole collapse in old leaves due to the lack of build-up of calcium concentration in the distal halves of the petioles. The development of marginal necrosis of youngest leaves due to calcium deficiency was associated with a further disorganization of tSCa distribution. 4SCa accumulated in epidermal hairs and flowers.Translocation of 45Ca into new leaves and flowers produced up to 9 weeks after transfer from radioactive low-calcium solutions to non-radioactive normal· or lowcalcium solutions was demonstrated. This mobile calcium came mainly from root tissue.Cold water, hot water, hot 0'5N HCI, and hot 0'5% ammonium oxalate extracts were made of parts of leaves of different maturities from normal. and low-calcium plants sampled at two stages of growth, the first before and the second after the onset of -petiole collapse in the low-calcium plants. For all leaf parts, the cold water plus hot HCI extracts contained over 90% of the total 45Ca activity. For plants under normal calcium nutrition, the ratio of 45Ca soluble in cold water to that soluble in hot HCI was greater than 1, the ratio increasing with leaf age for all plant parts except the distal halves of the petioles. For plants under low-calcium nutrition, before the onset of deficiency symptoms, the above ratio, although lower in value, followed similar trends with leaf age as found in the normal-calcium tissues. Mter the onset of petiole collapse the ratio fell sharply to less than l.

Section: Introductionmentioning

confidence: 99%

Effect of Calcium Level in the Substrate on the Distribution of 45Ca in Subterranean Clover (Trifolium Subterraneum L.)

Millikan¹,

Hanger²

1964

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“…However, with the limited calcium supply the plants responded differently to the two nitrogen sources. Dry matter yields remained unaltered where ammonium plus nitrate were supplied, but with solely nitrate growth was depressed and the symptoms of petiole collapse developed (Millikan 1953). This symptom appeared prior to day 31, and failed to progress beyond the unifoliate and first trifoliate leaves.…”

Section: Resultsmentioning

confidence: 91%

“…This symptom did not appear in plants of comparable vigour grown on the other nitrogen sources under a low-calcium nutrition. It is of interest to note that the symptom of petiole collapse as described by Millikan (1953) and Millikan andHanger (1964, 1966) occurred in plants grown in nutrient cultures in which nitrate was the sole nitrogen source.…”

Section: Discussionmentioning

confidence: 99%

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Interaction Between Calcium Level and Nitrogen Source on Growth and 45ca Distribution In Subterranean Clover

Millikan¹,

Hanger²,

Bjarnason³

1969

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SummaryUsing either ammonium or nitrate as the nitrogen sources, dry matter yields were highest from plants grown on a normal calcium nutrition, whereas plants supplied with urea grew best at low calcium level. When ammonium and nitrate were added together, yields were independent of the calcium concentration in the substrate. Plants fed solely ammonium nitrogen made extremely poor growth.The main factor affecting 45Ca distribution within subterranean clover was the calcium concentration in the substrate. The percentage of 45Ca retained in the roots was greatest at the low calcium level. At this level it was also greatest in the plants fed ammonium and least in those fed ammonium plus nitrate. The concentration of 45Ca in plant tops was equal in the presence of ammonium plus nitrate or urea, and higher than with nitrate or ammonium. Between nitrogen sources the lamina:petiole, leaf edge:leaf centre, and petiole distal:petiole proximal ratios of 45Ca concentrations were different at the low, but not at the normal, calcium level.

“…Two experiments were conducted in which subterranean clover (Trifolium 8ubterraneum L.) plants were grown in non-radioactive complete nutrient solution, the composition of which was identical to that described previously (Millikan 1961). The plants were allowed to grow until they had at least seven trifoliate leaves, when the various radioactive doses as 65ZnS04 .7H20 detailed below were injected into old leaves by the method described by Millikan and Hanger (1965).…”

Section: Methodsmentioning

confidence: 99%

Effects of Chelation and of Various Cations on the Mobility of Foliar-Applied 65zn in Subterranean Clover

Millikan¹,

Hanger²

1965

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SummaryInjection of 65Zn of high specific activity into old leaves of subterranean clover (Trifolium 8ubterraneum L.) resulted in the virtual immobilization of the isotope in the laminae of the treated leaves. The addition of 30, 300, or 500 p.g respectively of non-radioactive zinc to the dose resulted in progressively increased ,movement of 65Zn into other parts of the plant.Movement of 65Zn from the injected leaf was also enhanced by the addition to the dose of either EDTA or one of various cations in amounts equivalent to 500 p.g Zn. This enhancement was comparable with that induced by 500 p.g Zn with EDTA, Cu2+, Mn2+, and Fe2+; intermediate with Mg2+ and Ca2+; and least with Na+ andK+.It is concluded that non-selective negatively charged sites of fixation occur in the leaf of subterranean clover.