Sodium as an Essential Micronutrient Element for Plants and its Possible Role in Metabolism

Brownell, P. F.

doi:10.1016/s0065-2296(08)60088-9

Cited by 86 publications

(56 citation statements)

References 120 publications

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“…Positive role(s) of Na+ was first suggested by Brownell and coworkers as an essential micronutrient in some C4 plants (3) and further confirmed (2,21). However, its exact role has not yet been clarified (2), although recent reports have suggested its role in NO3-uptake and metabolism (20,21) or metabolite transport (2). The Na+/ pyruvate cotransport demonstrated here in mesophyll chloroplasts of several C4 species could be one of the physiological roles of Na+ in C4 plants.…”

Section: Discussionmentioning

confidence: 67%

“…The Na+/ pyruvate cotransport demonstrated here in mesophyll chloroplasts of several C4 species could be one of the physiological roles of Na+ in C4 plants. It should be added that a significant discrepancy exists in the distribution of positive Na+ effects among C4 species between the present in vitro study of pyruvate transport and in vivo study on growth (2,3,21). The growth of P. miliaceum did not respond to the Na+ level in culture medium (21), while the growth of two NADP-malic enzyme type species, Kochia childsii and Portulaca grandiflora, responded to the Na+ level (3).…”

Section: Discussionmentioning

confidence: 75%

“…Na+ is usually found in plant cells at a high concentration but seems to be excreted through plasma membrane or sequestered into vacuole via Na+/H+ antiport (1,24). Positive role(s) of Na+ was first suggested by Brownell and coworkers as an essential micronutrient in some C4 plants (3) and further confirmed (2,21). However, its exact role has not yet been clarified (2), although recent reports have suggested its role in NO3-uptake and metabolism (20,21) or metabolite transport (2).…”

Section: Discussionmentioning

confidence: 88%

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Involvement of Na⁺ in Active Uptake of Pyruvate in Mesophyll Chloroplasts of Some C₄ Plants

Ohnishi¹,

Flügge²,

Heldt³

et al. 1990

Plant Physiol.

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An artificial Na' gradient across the envelope (Na+ jump) enhanced pyruvate uptake in the dark into mesophyll chloroplasts of a C4 plant, Panicum miliaceum (NAD-malic enzyme type) (J Ohnishi, R Kanai [1987] FEBS Lett 219: 347). In the present study, 22Na and pyruvate uptake were examined in mesophyll chloroplasts of several species of C4 plants. Enhancement of pyruvate uptake by a Na+ jump in the dark was also seen in mesophyll chloroplasts of Urochloa panicoides and Panicum maximum (phosphoenolpyruvate carboxykinase types) but not in Zea mays or Sorghum bicolor (NADP-malic enzyme types). In mesophyll chloroplasts of P. miliaceum and P. maximum, pyruvate in tum enhanced Na+ uptake in the dark when added together with Na+. When flux of endogenous Na+ was measured in these mesophyll chloroplasts preincubated with 22Na+, pyruvate addition induced Na+ influx, and the extent of the pyruvate-induced Na+ influx positively correlated with that of pyruvate uptake. A Na+/H+ exchange ionophore, monensin, nullified all the above mutual effects of Na+ and pyruvate in mesophyll chloroplasts of P. miliaceum, while it accelerated Na' uptake and increased equilibrium level of chloroplast 22Na+. Measurements of initial uptake rates of pyruvate and Na+ gave a stoichiometry close to 1:1. These results point to Na+/pyruvate cotransport into mesophyll chloroplasts of some C4 plants. for pyruvate, which was predominantly found in mesophyll cells, i.e. the gradient seemed to be against the supposed flow (28). This apparent contradiction could be circumvented if pyruvate in mesophyll cells is compartmented in subcellular organelle(s) making its cytosolic concentration lower. In fact, recent findings have demonstrated light-driven active uptake of pyruvate into mesophyll chloroplasts of maize (a NADPmalic enzyme type) (6) and Panicum miliaceum (a NADmalic enzyme type) (17, 18).Huber and Edwards (12) first showed the existence of a pyruvate carrier in the envelope of mesophyll chloroplasts of Digitaria sanguinalis, a NADP-malic enzyme type C4 species. Since they studied the transport only in the dark, the internal pyruvate concentration was always less than the external one. However, pyruvate uptake in C4 mesophyll chloroplasts was enhanced by illumination resulting in an active accumulation of pyruvate as noted above. The energy source of this lightdependent uptake seemed to be the pH gradient across the envelope, because light enhancement of pyruvate uptake correlated to some extent with the light-dependent stromal alkalization (18). However, an artificial pH gradient across the envelope did not enhance pyruvate uptake in mesophyll chloroplasts of P. miliaceum. In the course of such experiments, we found that an abrupt increase of [Na+]ex3 (a Na+ jump) enhanced pyruvate uptake remarkably in the dark, partially mimicking the light effect (19). Thus, a Na+ gradient across the envelope could be an alternative energy source for the active transport of pyruvate. In this paper we have examined 22Na' and pyruvate uptake in mesophyll ...

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Section: Discussionmentioning

confidence: 67%

Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 88%

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Involvement of Na⁺ in Active Uptake of Pyruvate in Mesophyll Chloroplasts of Some C₄ Plants

Ohnishi¹,

Flügge²,

Heldt³

et al. 1990

Plant Physiol.

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“…were used. The procedures for the germination and growth of plants under low sodium conditions have been described previously (5). The ..…”

Section: Methodsmentioning

confidence: 99%

“…Once a particular section was photographed on account of its distinguishable detail within the chloroplast, a minimum of 5 Atm was cut offthe face ofthe block to ensure that the same chloroplast was not photographed again. Generally, the block was entirely refaced prior to more ultrathin sections being cut.…”

Section: 'mentioning

confidence: 99%

Effect of Sodium Nutrition on the Ultrastructure of Chloroplasts of C₄ Plants

Grof¹,

Johnston²,

Brownell³

1989

Plant Physiol.

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Mesophyll chloroplasts from sodium-deficient compared to normal plants of the C4 species Kochia childsii and Amaranthus tricolor were found to have significantly less stacking in their grana. On the other hand, no marked difference of thylakoid arrangement between bundle sheath chloroplasts from sodiumdeficient and normal plants of A. tricolor were observed.Sodium is unique as a micronutrient for higher plants in that it is required only by plants possessing the C4' C02-concentrating appendage (6, 7). The mesophyll cells are implicated as the site of the lesion since increased ambient CO2 concentration alleviated the signs of sodium-deficiency without restoring the lower Chl a/b ratio, characteristic of sodiumdeficiency, to that of normal plants (13)(14)(15).Increased concentrations of alanine (9, 18) and pyruvate and decreased concentrations ofPEP, OAA, malate, aspartate, and 3-PGA (M Johnston, CPL Grof, PF Brownell, unpublished observations) have been found in leaves of sodiumdeficient compared to normal C4 plants, suggesting a limitation in the conversion of pyruvate to PEP.It is unlikely that this limitation is due to reduced activity of pyruvate orthophosphate dikinase, the enzyme catalyzing this reaction (4,8). The transport of pyruvate into the mesophyll chloroplast and its subsequent conversion to PEP may be limited by the supply of ATP from photosynthetic phosphorylation. Decreased Chl a/b ratios ( 13), and fluorescence ratios (10) observed in sodium deficiency are consistent with dysfunction of the light reactions. These differences between sodium-deficient and normal plants suggest that the ultrastructure ofmesophyll and/or bundle sheath chloroplasts may also be affected by sodium nutrition. MATERIALS AND METHODS Amaranthus tricolor L. (nonpigmented form) and

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Trace Element‐Deficient Soils

Schulin

Johnson

Frossard

2010

Trace Elements in Soils

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Sodium as an Essential Micronutrient Element for Plants and its Possible Role in Metabolism

Cited by 86 publications

References 120 publications

Involvement of Na⁺ in Active Uptake of Pyruvate in Mesophyll Chloroplasts of Some C₄ Plants

Involvement of Na⁺ in Active Uptake of Pyruvate in Mesophyll Chloroplasts of Some C₄ Plants

Effect of Sodium Nutrition on the Ultrastructure of Chloroplasts of C₄ Plants

Trace Element‐Deficient Soils

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Sodium as an Essential Micronutrient Element for Plants and its Possible Role in Metabolism

Cited by 86 publications

References 120 publications

Involvement of Na+ in Active Uptake of Pyruvate in Mesophyll Chloroplasts of Some C4 Plants

Involvement of Na+ in Active Uptake of Pyruvate in Mesophyll Chloroplasts of Some C4 Plants

Effect of Sodium Nutrition on the Ultrastructure of Chloroplasts of C4 Plants

Trace Element‐Deficient Soils

Contact Info

Product

Resources

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Involvement of Na⁺ in Active Uptake of Pyruvate in Mesophyll Chloroplasts of Some C₄ Plants

Involvement of Na⁺ in Active Uptake of Pyruvate in Mesophyll Chloroplasts of Some C₄ Plants

Effect of Sodium Nutrition on the Ultrastructure of Chloroplasts of C₄ Plants