Through the continuous treatment with various solutions of ATP disodium salt the rotational streaming of the cytoplasma in barley root hairs has been stimulated about 1.2–1.7 times. With the concentrations employed the stimulation of the streaming did not depend on the external ATP supply, but on the initial rate of streaming. It is assumed that the main source of energy supporting the protoplasmic streaming is ATP. Therefore, the results obtained may be interpreted on the basis of variations in ATP content and its degradation products. The differences between initial rates of streaming are supposed to be due to variations of the endogenous ATP level. The ATP taken up probably stimulates the rotational streaming both through the supply of delivered energy and by lowering the cytoplasm viscosity. On the contrary, products of ATP hydrolysis increase the cytoplasm viscosity and induce a lowering or even cessation of the streaming.
The rotational streaming of cytoplasm in barley root hairs has been stimulated about 1.3–1.8 times through continuous treatment with various solutions of myo‐inositol. The stimulation attained the same level as after ATP administration and was dependent on the external myo‐inositol supply with the employed concentrations. The stimulation was cut off by simultaneous treatment with myo‐inositol and uranyl salts. By using uranyl acetate the rate of streaming was maintained about the value of the control. The uranyl chloride caused an inhibition in the rotational streaming and later made it to cease altogether. The simultaneous treatment with myo‐inositol and 2.4‐DNP (dinitrophenol) induced a quick inhibition in 60% of the root hairs. consecutively stopping rotational streaming.
It is assumed that the stimulation of rotational streaming is not due to the direct effect of myo‐inositol but to ATP formed in the reaction: inositol hexaphosphate ++ ADP ↔ ATP + inositol. According to the results obtained by testing with uranyl salts, the phosphorylation of inositol probably takes place at the cell surface. The effect of 2,4‐nNP points to the presence of two competitive metabolic processes involved in ATP consumption: the upkeep of rotational streaming and the uptake of substances by the plant cell.
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