Loss of Phosphorus-32 by Plant Roots after Foliar Application.

Emmert, Fred H.

doi:10.1104/pp.34.4.449

Cited by 25 publications

(6 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…When plants were allowed to deplete P from solutions, the P concentration in the medium dropped to about 0.15 micromolar within 24 hours and 0.05 micromolar within 60 hours. Results indicate that P efflux is a substantial component ofnet P accumulation at P concentrations normally found in soil solutions.Loss of P from plant roots to the ambient medium has been well documented (9,11,16,26). Conflicting opinions have been advanced, however, on the significance of P efflux in the P economy of plants.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Influx and Efflux of P in Roots of Intact Maize Plants

Elliott¹,

Lynch²,

Läuchli³

1984

Plant Physiol.

View full text Add to dashboard Cite

ABSTRACIRates ofP influx and effiux were determined in whole plants at ambient P co tions compamble to those found in soil solutions. Maize (Zea mays L. var NC+59) seedings were trimnmed (endosperm and adventitions roots removed) and grown in a greenhouse in solution cultures at P concentrtions of approximately.0A and 1.8 micromolar. Roots of intact phlts previously exposed to NP-labeled solutions at 0.2 and 2.0 micromolar P for 48 hours were riosed 10 minutes in P-free solution and exposed to 33P solutions at 0.2 and 2.0 micromolar for 10 minutes. Net depletion of 3P from and appance of 32p in the ambient solution were used to measure influx and efflux. The ration of32P efflux to 3P influx was about 0.68 at 0.2 micromolar and 0.08 at 2.0 micromolar. When plants were allowed to deplete P from solutions, the P concentration in the medium dropped to about 0.15 micromolar within 24 hours and 0.05 micromolar within 60 hours. Results indicate that P efflux is a substantial component ofnet P accumulation at P concentrations normally found in soil solutions.Loss of P from plant roots to the ambient medium has been well documented (9,11,16,26). Conflicting opinions have been advanced, however, on the significance of P efflux in the P economy of plants. Mazel' and Fokin (16) argue that P efflux is strictly a passive exchange phenomenon, and of little consequence for net P accumulation. Bieleski and Ferguson (4) suggest that P efflux is at least partially under metabolic control and is a component of the mechanism whereby P balance is maintained in plants. There is very little information on the magnitude of P efflux in relation to P influx. The limited data available come from studies with aquatic plants (4, 15), in which both roots and shoots absorb ions from the medium. In Spirodela oligorrhiza, the ratio of efflux to influx was approximately 0.08 in plants maintained in 1.0 mm P solutions. Both influx and efflux decreased as the ambient P concentration was lowered, but the decrease in influx was proportionally greater than the decrease in effiux. In plants transferred from 1.0 mM P to 1.0 AM P, the ratio of efflux to influx was 0.70.Indirect evidence for the importance of efflux in P accumulation comes from studies of P depletion from nutrient solutions. If decreasing ambient P concentration affects influx to a greater extent than efflux, then efflux and influx should be equal at some limiting ambient P concentration, i.e. there would be no net accumulation. Experiments with several maize genotypes have indicated that net P accumulation ceases at concentrations ranging from 0.04 to 3.7 ,uM (1, 2 tration range of bulk soil solutions (20). Thus, it appears that efflux may be nearly equal to influx at ambient P concentrations comparable to those experienced by roots of terrestrial plants.In the work with Spirodela (4, 15) influx and efflux were measured in separate experiments. Nitrate influx and efflux, however, were measured simultaneously using 14NO3 and 15NO- (12,14,17). The availability of two radioisotopes of P, 3...

show abstract

mentioning

confidence: 99%

“…Loss of P from plant roots to the ambient medium has been well documented (9,11,16,26). Conflicting opinions have been advanced, however, on the significance of P efflux in the P economy of plants.…”

mentioning

confidence: 99%

Influx and Efflux of P in Roots of Intact Maize Plants

Elliott¹,

Lynch²,

Läuchli³

1984

Plant Physiol.

View full text Add to dashboard Cite

show abstract

“…Since external Pi was necessary for P exchange during efflux (Weigl 1968), it is not surprising that rates of Pi efflux were underestimated. Subsequent studies included Pi in the 'wash' solutions and rates of Pi efflux were shown to be proportional to external [Pi], although the quantitative significance of Pi efflux compared with gross Pi influx was unclear (Emmert 1959;Weigl 1968;Maze1 and Fokin 1977). A knowledge of this relationship is necessary for a complete understanding of Pi influx.…”

Section: Introductionmentioning

confidence: 99%

PI Efflux and Influx by P-Adequate and P-Deficient Spirodela and Lemna

McPharlin¹,

Bieleski²

1989

Functional Plant Biol.

View full text Add to dashboard Cite

Net Pi influx by P-adequate ( + P ) and P-deficient (-P) Spirodela and Lemna plants was determined by gross Pi influx and Pi efflux. Rates of Pi influx (gross) and Pi efflux were sensitive to both internal [PI and external [Pi]. The different responses of these two fluxes to external [Pi] resulted in their rates converging at low external [Pi], from Pi efflux being 9-10% of gross Pi influx at 1000 p~ Pi to being over 70% at low (1 p~) external Pi in + P plants. At very low external Pi (0.34 p~, 0.22 p~ Pi for + P Spirodela and Lemna, respectively), rates of gross Pi influx and Pi efflux were assumed to be either equal or zero (referred to as the equilibrium [Pilext), such that net Pi influx was zero. There was assumed to be insufficient Pi diffusing to the carrier site on the root surface at very low external [Pi] (i.e. equilibrium [P,],,,) for the phosphate pump to operate and Pi influx was zero. P deficiency resulted in a simultaneous reduction in rates of Pi efflux and an increase in gross Pi influx such that the equilibrium [Pilext was reduced 3-4 times (0.8, 0.07 p~ Pi for -P Spirodela and Lemna respectively) compared with + P plants. Some of the limitations of Pi diffusion to the carrier sites in P-adequate plants are overcome as internal [PI decreases during P deficiency. As a consequence the ability of Spirodela and Lemna to extract Pi from solution during P deficiency was considerably greater than for plants with adequate P status.Inhibitors of metabolism (low temperatures, arsenate, azide, cyanide and CCCP) reduced rates of gross Pi influx but increased rates of Pi efflux such that net Pi influx was reduced. These findings are discussed in relation to previous work on the kinetics of Pi influx in -P versus + P plants and the role of changes in membrane potentials in the enhancement of Pi influx and reduction of Pi efflux capacity in P-deficient Spirodela and Lemna.

show abstract

“…In the normal functioning of shoot cells, a large number of compounds are produced of wlhiclh many may be classified as growth substainces (17 Endogenous meclhanismiis ha-e been showx n to cauise wide fluctuations in the intensity with whiclh cells accumulate mineral ions (3,28,32,43). Suclh accumlulation is known to depend oIn imletabolic activity (1,18,37,41 (27) and Emmert (13) An increase of atmospheric humidity promoted the shoot growth of warm-rooted but not of cool-rooted plants. When plants were growing in distilled water, a weak but significant promotion of shoot growth was observed in response to increased root temperature and increased humidity.…”

mentioning

confidence: 99%