Effect of phytohormones on the activity of H+-ATPase and H+-pyrophosphatase of red beet root tonoplast Beta vulgaris L. under conditions of different buffer systems

The effect of phytohormones on hydrolytic activity of H+-ATPase (EC 3.6.1.34) and H+-pyrophosphatase (EC 3.6. 1. 1) of red beet root tonoplast (Beta vulgaris L.) was investigated. The effect of hormones (IAA, GA(3), ABA and kinetin) on hydrolytic activity of the enzymes in some instances was shown to depend on pH of buffers (tris and imidazole). In restrained terms, the effect of hormones on enzymatic activity at different pH of buffers (tris and imidazole) was directly opposed. The most profound hormone effect was recorded in the case of H+-ATPase and GA(3) (10(-6) M) and IAA (10(-8) M). The H+-ATPase activity was reduced by IAA (by 23% as the average) and was insensitive to GA(3) in the imidazole media. On the contrary IAA and GA(3) stimulated the activity of this enzyme (by 32% as the average) in the tris-containing media. GA(3) stimulated the activity of H+-pyrophosphatase (by 33% as the average) only in the imidazole media. The mechanism of hormone action is probably very sensitive and depends on some factors, that can be influenced by the ionic nature of pH buffers.