The relationship between rubidium influx and potassium stimulated magnesium atpase activity in oat avena sativa cultivar brighton roots of different potassium status flexible coupling
Lundborg, T.; Jensen, P.; Kylin, A.
Physiologia Plantarum 59(2): 277-284
The relationship between Rb+ influx and microsomal ATPase activity stimulated by K+ and Mg2+ + K+ was investigated for roots of 7-day-old seedlings of oat (A. sativa L., cv. Brighton). Different concentrations of K+ in the roots, .**GRAPHIC**. were produced by cultivating plants in complete nutrient solutions of different dilutions and different K+ concentrations at various temperatures. Experiments were performed in both light and darkness. The range of the influx/ATPase ratios was large with a factor of 5 or more between the highest and lowest values. In most cases, the highest ratios were obtained at low .**GRAPHIC**. and at high temperatures, and the lowest at high .**GRAPHIC**. and at low temperatures. At high temperatures (20 and 25.degree. C) in the light, the influx/ATPase ratio was constant, independently of .**GRAPHIC**. if K+ in the medium was kept constant but the bulk of the nutrient solution diluted. If K+ was varied and the other components of the medium kept constant, the normal relation of decreasing influx/ATPase ratio at increasing .**GRAPHIC**. was found; thus, Rb+ influx appears regulated by both the internal and external potassium conditions. Also in darkness, at 15.degree. C and with K+ in the medium varied, the influx/ATPase ratio was independent of .**GRAPHIC**. but in the corresponding light experiments, ratio and .**GRAPHIC**. had the normal, inverse relationship. The difference between light and dark conditions appears to indicate that growth rate is of importance for the relationship between energy input and transport. The data lead to the concept of flexible coupling between transducer(s) of energy and ion carrier. Without exluding other possibilities, this may be one of the mechanisms for ecological adaptation to variations in the root medium.