Effect of Vitamin K3 on plasma membrane-bound H+-ATPase and reductase activities in plants

Vitamin K-like compounds are widely diffused in plants, but their role and function are still partially unknown. Vitamin K1 - phylloquinone - is largely present in tylacoid membranes as electron carrier inside the PSI redox chain. More recently, it has been found that Vitamins K1 and K3 may also affect the plasmalemma-bound H+-ATPase and reductase activities. In this article we report the effects of Vitamin K3 treatment on the above activities in three different conditions: in the presence of Vitamin K3; after the addition of Vitamin K3 to the hydroponic solution; after sonication of plasma membrane in the presence of Vitamin K3 in the solution. Results showed that Vitamin K3 was able to improve both plasmalemma H+-ATPase and reductase activities at a concentration that is very well tolerated by the whole plant. Our findings support the hypothesis that Vitamin K is involved in plasmalemma activities of both mono and dicotyledonous plants.