Table 1. Changes of plasma membrane marker vanadate-sensitive ATPase activity in red beet cells incubated in sucrose or betaine for 24 h.

24 h
	Time 0	Betaine	Sucrose	% increase
Vanadate sensitive P-ATPase (*Units/ total ATPase in tonoplast fraction)	0.17 ± 0.03	0.23 ± 0.01	0.31 ± 0.02	20%

^*One unit defined as 1 nkat. Purified tonoplast fractions were isolated from fresh tissue and from tissue incubated in sucrose or betaine for 24 h. V-ATPase activity was measured in the presence and absence of vanadate.