Uptake of 24Mg by excised pine roots: A preliminary study

Abstract

Uptake of 24Mg by excised roots of Pinus sylvestris L. during up to 4 h long incubations in 99.9 atom % 24Mg (50/IM) was measured by ICP-MS. A rapid initial uptake phase (30 min) was followed by a slower uptake. This was interpreted as a shift from a phase dominated by saturable ion exchange (free space uptake), to a non-saturable phase, during which the rate of uptake was 0.077=t=0.0.012/~mol Mg g-~ (d.wt.) h -1. The metabolic uncoupler DNP (2,4-dinitrophenol) at 50/~M decreased the Mg uptake rate by 35% only, but the effect of DNP was significant (p<0.01). Several problems related to a high variability in the experimental material were encountered, and further refinement of this approach in studies of plant Mg uptake is suggested.

Use of stable isotopes to quantify nitrogen, potassium and magnesium dynamics in young Scots pine (Pinus sylvestris)

“…Similar results have been reported for the spring growth of Sitka spruce subjected to contrasting supplies of N (Proe & Millard, 1994) or P (Proe & Millard, 1995), where current nutrient supply had little effect on total tree biomass for several months. Uptake of Mg, in addition to that added in the nutrient solution was probably from sources in the sand at the start of the experiment, as has been reported by Hogberg et al (1995) when growing Scots pine seedlings in acid-washed sand. Provided that the distribution of #'Mg uptake reflected that for total Mg uptake, our estimates for uptake and remobilization of Mg to different tissues should remain valid.…”

“…Uptake of Mg, in addition to that added in the nutrient solution was probably from sources in the sand at the start of the experiment, as has been reported by Hogberg et al (1995) when growing Scots pine seedlings in acid-washed sand. Provided that the distribution of #'Mg uptake reflected that for total Mg uptake, our estimates for uptake and remobilization of Mg to different tissues should remain valid.…”

Growth, Mg nutrition and photosynthetic activity in Pinus radiata: evidence that NaCl addition counteracts the impact of low Mg supply

“…The uptake of Mg in roots is generally slow compared with uptake of other nutrients due to lack of a specific uptake and transport mechanism across plasma membrane (Mengel and Kirby 1987). The process is considered to be passive and operate through electrochemical gradients across the ion pores in the membranes, although an active uptake component was suggested to exist by a study using radioactive isotope 24 Mg (Hogberg et al 1995). The uptake of Mg has been found to be complex and relatively slow in Pinus taeda L. seedlings (Kelly and Barber 1991;Kelly et al 1992).…”

Root Methods

“…The ability of roots to take up nutrients may be estimated from isolated root segments by measuring either nutrient depletion from solutions (Cruz et al 1995), or nutrient accumulation in the roots (Hogberg et al 1995). The ability of roots to take up nutrients may be estimated from isolated root segments by measuring either nutrient depletion from solutions (Cruz et al 1995), or nutrient accumulation in the roots (Hogberg et al 1995).…”