Potassium Absorption by Rice at Different Levels of Organization

Abstract

A study was made of the effects of temperature and calcium on the properties of K+ transport in rice roots (Oryza sativa L. cv. Dunghan Shali), in cell suspension culture of rice and in callus cultures. The rates of influx and efflux of K+ were measured by using 86Rb as tracer, and the net change in K+ content was determined by atomic absorption spectrophotometry. In roots of low salt status the K+ transport mechanism exhibits a positive temperature dependence and calcium exerts a stimulation. In cell and callus cultures a transport mechanism of this kind is lacking, and the K+ fluxes are inhibited by calcium and independent of temperature. Chilling‐induced K+ leakage is similar for both types of tissue, and can be characterized by a negative temperature‐coefficient and the inhibitory effect of calcium.

Influence of lecithin liposomes on chlorophyllase-catalyzed chlorophyll hydrolysis. Comparison of intramembraneous and solubilized Phaeodactylum chlorophyllase

“…Similar enzyme activations have been described for protein kinase [32], ATPase [33,34] and D-~-hydroxybutyrate apodehydrogenase [35]. With chlorophyllase, this would mean that the enzyme can be activated in two ways, either with Mg 2÷ + dithiothreitol or with lecithin.…”

A 86Rb BIOASSAY TO DETERMINE THE POTASSIUM STATUS OF TREES

“…However, many workers have shown the suitability of the rubidium isotope (®^Rb) as an analogue for K in studies of nutrient uptake by plants (Erdei & Zsoldos, 1977;Jensen, 1981;Berczi 696 H. E. JONES, A. F. HARRISON AND J. DiGHTON et al, 1982;Hannaway et al, 1984), particularly in short duration experiments in which K and Rb are taken up at approximately the same rate (Franklin & Snyder, 1965;Baligar, 1985).…”

Benzylaminopurine‐induced coupling between calmodulin and Ca‐ATPase in wheat root microsomal membranes

“…The relatively long 398 lag period ( fig. 3) for the manifestation of the hormonal effect indicates an action on gene or ribosomal level [21,24,25]. The c~modulin-binding sites or receptors can become a part of the ATPase complex, in accordance with an earlier scheme of the transport-ATPase 1151.…”

“…Changes in the properties of transport ATPase in auxin-pretreated rice seedlings were observed in [21], when the stimulation of K-influx and the ATPase activity by Ca apparently disappeared. Later [9] it was shown that calmodulin was involved in the ATP-dependent Ca-uptake in microsomes.…”