Day-night Differences in the Accumulation and Translocation of Ions by Tobacco Plants

Wallace, A.; Soufi, S. M.; Hemaidan, N.

doi:10.1104/pp.41.1.102

Cited by 25 publications

(18 citation statements)

References 6 publications

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“…Similar restrictions have been noted in experiments with other species (19,23,24) and with other nutrient ions (7,8,35), suggesting nonspecific control. It can be reasonably assumed that stomatal adjustments and the associated changes in water flux through the root and the vascular system would be intimately involved in the regulation of NO3-translocation to the shoots.…”

Section: Sources Of No3-for Reductionsupporting

confidence: 81%

Endogenous NO₃⁻ in the Root as a Source of Substrate for Reduction in the Light

Rufty¹,

Volk²,

MacKown³

1987

Plant Physiol.

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ABSTRACIAn experiment was conducted to investigate the reduction of endogenOUS No3-, which had been taken up by plants in darkness, during the course of the subsequent light period. Vegetative, nonnodulated soybean plants (Glycine max [L]. Merrill, 'Ransom') were exposed to 1.0 millimolar I5N03-for 12 hours in darkness and then returned to a solution containing 1.0 millimolar 4NO3-for the 12 hours 'chase' period in the light. Another set of plants was exposed to 'I5NO3-during the light period to allow a direct comparison of contributions of substrate from the endogenous and exogenous sources. At the end of the I5NO3-exposure in the dark, 70% of the absorbed 15NO3-remained unreduced, and 83% of this unreduced NO3-was retained in roots. The pool of endogenous '5NO3-in roots was depleted at a steady rate during the initial 9 hours of light and was utilized almost exclusively in the formation of insoluble reduced-N in leaves. Unlabeled endogenous NO3-, which had accumulated in the root prior to the previous dark period, also was depleted in the light. When exogenous 15NO3-was supplied during the light period, the rate of assimilation progressively increased, reflecting an increased rate of uptake and decreased accumulation of NO3-in the root tissue. The dark-absorbed endogenous NO3-in the root was the primary source of substrate for whole-plant NO3-reduction in the first 6 hours of the light period, and exogenous N03-was the primary source of substrate thereafter. It is concluded that retention of NO3-in roots in darkness and its release in the following light period is an important whole-plant regulatory mechanism which serves to coordinate delivery of substrate with the maximal potential for NO3-assimilation in photosynthetic tissues. (14). The atom % 'sN of the NO3-fraction was determined by mass spectrometry using a nitric oxide procedure (34). The analysis of reduced N involved an initial removal of NO3-(20), followed by Kjeldahl digestion (17) and colorimetric determination of NH4' (2). The NH4' in the remaining digest was recovered by diffusion and the atom % '5N determined mass spectrometrically using a freeze-layer procedure (33).The tissue samples were analyzed for NO3-and soluble and insoluble reduced nitrogen. After being freeze-dried, weighed and ground, the tissue was extracted with methanol:chloroform:water (13:4:3). Following separation of the chloroform from the methanol:water fraction, the chloroform was added back to the tissue residue, with this constituting the insoluble reduced N fraction. Total nitrogen -and 'IN in the insoluble reduced N fraction were determined as described for exudate reduced N, omitting the NO3-removal procedure. The methanol:water fraction was analyzed for NO3-and soluble reduced N. After the methanol was evaporated, an aliquot was taken and NO3-and its '5N enrichment were determined as in the exudate analysis. Nitrate in the remainder of the sample was removed and the soluble reduced N and atom % '5N determined as in the analysis of exudate reduced N. All tissue "5N d...

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Section: Sources Of No3-for Reductionsupporting

confidence: 81%

Endogenous NO₃⁻ in the Root as a Source of Substrate for Reduction in the Light

Rufty¹,

Volk²,

MacKown³

1987

Plant Physiol.

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“…Difference significant at P <0.05 is denoted by* (Cochran "t" test). (3,33). In the present experiments (fig 1-3 (6,10).…”

Section: Methodssupporting

confidence: 52%

Relation Between Simultaneous Ca and Sr Transport Rates in Isolated Segments of Vetch, Barley, and Pine Roots

Hutchin¹,

Vaughan²

1968

Plant Physiol.

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Abstract. Root segments of vetch, barley, and pine were exposed to a nutrient solution containing 85Sr and 45Ca tracers. Translocation was measured from solutions containing stable ions at concentrations of 2.5 mM Ca, and at either 0.5 mM or 2.5 mM Sr. Polar transport was established between 12 and 18 hr in barley, and between 16 and 22 hr in vetch. Acropetal transport remained below 5 % of basipetal transport of tracer during these intervals. Transport in both vetch and barley usually deolined before an elapsed time of 24 hr unlike corn, which maintained its steady state beyond 24 hr. Pine was radically different in that it showed no difference between acropetal and basipetal transport rates and had very low rates. Sr transport in all plants studied to date paralleled that of Ca and the ratio Sr:Ca transported was equal to the ratio Sr:Ca in the nutrient. In vetch, stable Ca transport was reduced to one-fifth when Sr concentration was increased from 0.5 mM to 2.5 mM. Yet stable Sr transport did not change, indicating that the effect on transport was not due to competitive inhibition. A similar effect was less pronounced in barley, but could not be detected in pine. The magnitude of the transport rates varied considerably among the various species, corn having the greatest followed by barley, vetch, and pine in decreasing order. Transport did not correlate with root weight or surface area; it amounted to from 0.03 to 0.60 nanomoles per hr in these experiments as oompared to 7 nanomoles per hr previously established in corn (in all cases, 55 mm segments, sectioned 10 mm from apex).Several investigators have shown that the rates of translocation of strontium or calcium tracers from the roots can vary significantlv among different plants (11,18,20, 23,26,28,29 of competitive inhibition were studied also in corn (15). The purpose of the present studies was to compare vetch, barley and pine tunder the same conditions previously used for corn. Vicia sativa (common vetch) was cho-en as a representative dicotyledon, and its roots could be studied in the perfusion bridge previously described (10, 32). Also. since it is a common pasture plant. measurement of its strontium transport might be directly applicable to fallout contamination problems. Pinlts radiata was selected as a representative gymnosperm. Barley was included as an additional monocotyledon that has been widely studied. Materials and Methods

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“…Studies have been made of salt accuimulation and translocation in the daytime and in the nighttime for intact tobacco and bush bean plants (7). (1).…”

Section: Methodsmentioning

confidence: 99%

Day-Night Periodicity of Exudation in Detopped Tobacco

1967

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Summary. Exudate was collected periodically from the root systems of detopped tobacco plants. Volume, cations, and 42K or 88Rb transfer were measured. According to measurements of K by 42K and by the flame photometer, when concentrations of KCl and KN03 were lower than 10-2 M, the K in the exudate came mostly froni a pool in the plant rather than from the external solution. With higher external KNO3 solutions, within a few hours nearly all of the K in the exudate came directly from the external solutions. Studies with 86Rb lead to the same conclusion. In contrast the maximum proportion of K in the exudate that came from KCl in the external solution was reached usually in many hours after detopping and amounted to from 50 to 75 %. The higher the external concentration the faster it was reached. These data for KCl are indicative of the 42K passing through a K pool in the root cells. K and Rb from high concentrations of KNO3 and RbNO,, however, may not pass through such a pool. The addition of 10-2 M KNO3 into the external solution dutring exudation essentially eliminated the effect of periodicity at least for a period of time and under the conditions of the experiments. Hydrochloric acid, mercuric chloride, anaerobiosis, and 2,4-dinitrophenol had the same effect and each resulted in a massive final exudation that usually persisted for 1 to 3 days before stopping. These results all lead to a hypothesis that periodicity is regulated at the tonoplast.Detopped root systems of many plant species exhibit diurnal fItlctuations in exudation volume (2,3,4

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Day-night Differences in the Accumulation and Translocation of Ions by Tobacco Plants

Cited by 25 publications

References 6 publications

Endogenous NO₃⁻ in the Root as a Source of Substrate for Reduction in the Light

Endogenous NO₃⁻ in the Root as a Source of Substrate for Reduction in the Light

Relation Between Simultaneous Ca and Sr Transport Rates in Isolated Segments of Vetch, Barley, and Pine Roots

Day-Night Periodicity of Exudation in Detopped Tobacco

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Day-night Differences in the Accumulation and Translocation of Ions by Tobacco Plants

Cited by 25 publications

References 6 publications

Endogenous NO3− in the Root as a Source of Substrate for Reduction in the Light

Endogenous NO3− in the Root as a Source of Substrate for Reduction in the Light

Relation Between Simultaneous Ca and Sr Transport Rates in Isolated Segments of Vetch, Barley, and Pine Roots

Day-Night Periodicity of Exudation in Detopped Tobacco

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Endogenous NO₃⁻ in the Root as a Source of Substrate for Reduction in the Light

Endogenous NO₃⁻ in the Root as a Source of Substrate for Reduction in the Light