I am estuding fertilizer use efficiency in oil palm
Rb can be used to mimic K. It is a good approximation but as it has a different hydrated radius to K then there can be some discrimination between K and Rb when K is preferred to Rb. Rb should only be used in low concentrations.
Depending on what you are trying to study, it may be possible to use radioactive K. It is not clear how you are going to define fertiliser use efficiency.
Please read the publication by Karim et al (1971). Rb86 as tracer for potassium. 1., Uptake of Rb and K by rice plant in nutrient solution. Plant and Soil 35, 179-182.
Rubidium is widely used as a tracer for potassium in many physiological studies because its physicochemical properties are similar to potassium. The usage of rubidium as tracer are often used with caution as several plant species were able to selectively acquire potassium over rubidium. However, its usage depends on the non-selective absorption of potassium and rubidium by the plant. Therefore a study to determine the absorption of potassium and rubidium by oil palm and measure the potassium uptake rate was conducted. Results showed that the uptake of potassium and rubidium was similar making rubidium a suitable tracer for potassium in oil palm. Prior to reaching potassium saturation in the root, the non-lignified “white”root tip segment were actively absorbing 86Rb at a rate of 194.9 cpm/g/h. The rate of 86Rb uptake would then correlate to rate of uptake at approximately 16 pM of potassium per gram per hour. As excised root tip were use, the root almost reaches it saturation phase after 8 h of uptake. The maximum activity of 86Rb absorbed by the excised root plateaued at 586 cpm g-1.
C.C. Sim and A.R. Zaharah, 2014. Potassium Uptake Kinetics by Oil Palm Root via Radiotracer Techniques. Asian Journal of Plant Sciences, 13: 195-197.DOI: 10.3923/ajps.2014.195.19
A radioactive uptake assay to measure ion transport across ion channel–containing liposomes by Crina M Nimigea , Nature Protocols 1, 1207 - 1212 (2006) doi:10.1038/nprot.2006.166
Abstract ; Here we describe a procedure for incorporating ion channels into lipid vesicles (liposomes) and functional characterization of the channel population by assaying radioactive isotope uptake into these proteoliposomes. The technique as described will work only for potassium channels but can be easily modified, as suggested in the text, for other ion channels and transporters. Purified ion channel proteins in detergent micelles are combined with solubilized lipids. Detergent is subsequently removed from protein-lipid complexes by gel filtration or dialysis into high potassium (high [K+]) buffer. After freezing-thawing and sonication, the resultant larger liposomes are passed over another gel-filtration column to exchange an extraliposomal high [K+] to a low [K+] buffer, thus establishing a large K+ gradient across the liposomal membrane. Trace 86Rb is then added to the extraliposomal space and the reaction begins. If the ion channel is permeable to K+, the K+ inside exits the liposomes down its concentration gradient and the 86Rb outside accumulates in the intraliposomal space until equilibrium is reached. The reaction time course is monitored by measurement of accumulated 86Rb after removal of external 86Rb over an ion-exchange column. The 86Rb flux assay takes 2–5 hours depending on the reaction rate and the number of desired time points
Please read the publication by Oliver R., Boaké K.. 1990. L'Agronomie Tropicale (1975), 45 (4) : p. 283-291.
Please find an interesting work...
Foliar application of microbial and plant based biostimulants increases growth and potassium uptake in almond (Prunusdulcis [Mill.] D.A.Webb)..PDF enclosed
Dr. Sidi. Pleace send me a copy of publication by Oliver
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