Metabolic Effects on Ion Fluxes in Nitella Translucens I. Active Influxes

Abstract

SummaryThe effects, on the light-dependent active ion fluxes in Nitella translucen8, of interference with the normal patterns of photosynthetic electron flow and associated phosphorylation has been further studied. The results provide confirmatory evidence for the picture previously proposed.In conditions in which only cyclic photophosphorylation is possible, in far-red light, in C02-free nitrogen, or in the presence of low concentrations of dichlorophenyldimethyl urea, there is inhibition of the active chloride influx without any effect on the active potassium influx. In conditions in which the electron flow is uncoupled from phosphorylation, in the presence of ammonium ions, imidazole, or carbonyl cyanide m-chlorophenyl hydrazone, there is inhibition of potassium influx, but no effect, or even a marked stimulation, of chloride influx. It is necessary to postulate that these effects are on the active component of potassium influx rather than on the passive component.These results support the hypothesis that the potassium transport is dependent on ATP from photophosphorylation, but that the chloride transport is directly coupled to some electron transfer reaction, perhaps close to the second light reaction of photosynthesis, and is independent of ATP.

Kinetics and Energetics of Light-enhanced Potassium Absorption by Corn Leaf Tissue

“…The effect of these inh'ibitors is not limited to studies on cell particulates (chloroplasts and mitochondria). Algal eellts have been used (22,23,34) and virtuallly identical resullts were reported when these inhibitors were emnployed in light-dark treatments. Also similar resuilts have been repor'ted for tissues of aquatic angiosperms, tissues more highily organized than those o'f ailgae (21,41,42).…”

“…Respiration is sevierely restricted by maintaining external anaerobic conditions and inhibiting 0°evolution by tihe ad'dition of DCMU (39). This can be accoimiplished witiho-ut interfering with cyclic photophosphorylaition (1,14,22,23,34,39,40). The system was mad,e anaer,obic by buibbling CO-free nitrogen throutgh the system, 02 evolution anid oxidative phosiphorylaition were asstumed (to be inhibited, iand a considerable amount.…”

“…The demonstration of more than 1 ion-transport mechanism in higher plants (6,7,30,31) light is closely linked to ATP formed by cyclic photophoslphorylation (22,23,29). Cyanide and unoouplers of oxidative phosphorylation, DNP, mC4-CCP, or NaN3 (1,11,12,18,19,32), manifested their greatest effect in the dark when a large percenitage of ATP is probably formed by respiratory processes.…”

“…AlacRobbie (22,23) Calcitum w.as indluded in all experimenital 'sollutions becatuse of its essentiality for uinimipaired ion transport (4, 13).…”

“…Dich'lorouhenyl-1,1-dimet'hyl'urea is an inhibitor of photosynthettic 'reactions, particularly those involved in 02 evolution (1,15,23,39,40). givmes the results of an exiperiment in whioh abesorp- 1. exposed to anaerobic conditions for loniger was irreversibly injured.…”